version 3 - envco · 2014. 10. 4. · adc gas analysis ltd has a comprehensive range of analysers...

MGA3000 Multi-Gas Analyser Operation Manual Iss. 3.01

1

MGA3000C MULTI-GAS ANALYSER

OPERATION MANUAL Version 3.01


2

Health and Safety Information __________________________________________________________

Equipment Operation Use of this instrument in a manner not specified by ADC Gas Analysis Ltd may be hazardous.

Electrical Power Supply Before working on the electrical connections all of the electrical power lines to the equipment

must be isolated. All the electrical cables and signal cables must be connected exactly as

indicated in these operating instructions. If in doubt contact ADC Gas Analysis Ltd.

Face and Eye Protection Suitable face and eye protection must be worn when working on hot vessels and ducts!

Special safety measures must be taken when working on a high pressure duct.

Protective Clothing Protective clothing must always be worn when working in the vicinity of hot vessels or ducts.

Storage The instrument should be stored in its packaging, in a dry and sheltered area.

Unpacking Check all packaging for external signs of damage. Check the contents against the packing

note.

Return of Damaged Goods IMPORTANT

If any item has been damaged in transit, this should be reported to the carrier and to the

supplier immediately. Damage caused in transit is the responsibility of the carrier not the

supplier.

DO NOT RETURN a damaged instrument to the sender as the carrier will not then consider

a claim. Save the packing with the damaged article for inspection by the carrier.

Return of Goods for Repair If you need to return goods for repair please contact our Customer Service Department.

They will be able to advise you on the correct returns procedure.

Any item returned to ADC Gas Analysis Ltd should be adequately packed to prevent damage

during transit.

You must include a written report of the problem together with your own name and contact

information, address, telephone number, email address etc.

Lifting Instructions Where items are too heavy to be lifted manually, use suitably rated lifting equipment. Refer

to the Technical Specification for weights. All lifting should be done as stated in local

regulations.


3

Design and Manufacturing Standards __________________________________________________________

The Quality Management system of ADC Gas Analysis Ltd is approved to BS

EN ISO 9001 for the design, manufacture and on-site servicing,

environmental monitoring and non-contact temperature measuring

instrumentation.

The instrument complies with current European directives relating to

Electromagnetic Compatibility 89/336/EEC and Low voltage Directive

73/23/EEC.

Operation of radio transmitters, telephone or other electrical/electronic devices in close

proximity to the equipment while the enclosure doors of the instrument or its peripherals are

open, may cause interference and possible failure where the radiated emissions exceed the

EMC directive.

The protection provided by both CE and IP classifications to this product may be invalidated if

alterations are made to the structural, electrical, mechanical or pneumatic parts of this

system. Such changes may also invalidate the standard terms of warranty.

Dimensions

Unless otherwise stated, all measurements are given in millimetres and inches.

Copyright

This manual is provided as an aid to owners of ADC Gas Analysis products and contains

information proprietary. This manual may not, in whole or part, be copied, or reproduced

without the expressed written consent of ADC Gas Analysis Ltd

©copyright 2010 ADC Gas Analysis Ltd

Caution, risk of electric shock

Caution, attention to possibility of risk of damage to the product, processes or

surroundings. Refer to instruction manual.

Protective Conductor Terminal

Caution, hot surface

Observe precautions for handling electrostatic discharge sensitive devices

This item or material can be recycled


4

How to Get Further Assistance _________________________________________________________

If further assistance is required please contact your nearest Gas Analysis Led office the

following addresses or your local distributor (see our website for details http://www.adc-

service.co.uk)

United Kingdom

ADC Gas Analysis Ltd

Unit 35 Hoddesdon Industrial Centre

Pindar Road

Hoddesdon

Herts, EN11 0FF

Australia

Anri Instruments & Controls Pty Ltd

Unit 29

756-758 Burwood Highway

Ferntree Gully

Victoria, VIC 3156

Australia

United States of America

CEA Instruments Inc

160 Tillman Street

Westwood

New Jersey, NJ077675

France

Gruter et Marchand

22/24 Rue Lavoisier

92000 Nanterre

Fermanagh

Gas Monitoring Services

4 Second Street

Boksburg North 1459

South Africa

Macro Group Enterprise Co Ltd

Room 906

No 432 Keelung Road, Sec 1

Taipei

Taiwan

When contacting ADC please have the following information available:

Instrument Serial Number.......................

Instrument Part Number.........................

Instrument Name and Model....................

Power supply, voltage and frequency........

This information is found on the rating plate of each instrument.

ADC Gas Analysis Ltd has a comprehensive range of analysers and Environmental Monitoring

Instrumentation.

http://www.adc-service.co.uk/

http://www.adc-service.co.uk/


5

CONTENTS

Contents .............................................................................................................. 5

1. Introduction ...................................................................................................... 8

1.1 About the Instrument .............................................................................................. 8 1.2 Instrument Identification .......................................................................................... 8 1.3 The Display & Operating Controls .............................................................................. 8

1.3.1 The Display ...................................................................................................... 8 1.3.2 Design ............................................................................................................. 9 1.3.3 The Operating Controls ...................................................................................... 9

1.4 Electrical Outputs .................................................................................................... 9 1.4.1 Analogue Outputs ............................................................................................. 9 1.4.2 Alarm(trips) outputs .......................................................................................... 9 1.4.3 RS232 port ....................................................................................................... 9

1.5 Gas Path .............................................................................................................. 10 1.5.1 Gas Flow Diagram ........................................................................................... 10 1.5.2 Key to gas path figures .................................................................................... 11 1.5.3 Gas connections .............................................................................................. 11 1.5.4 MGA 3000 19” rack, infrared component with oxygen measurement .................... 12

1.6 Dimension drawings .............................................................................................. 13 1.7 Circuit diagrams (electric and gas connections) ........................................................ 14

1.7.1 RS-232C I/O (see section 2.4) .......................................................................... 14 1.7.2 Trip I/O(see section 2.6) .................................................................................. 14 1.7.3 Analogue Output(see section 2.5) ..................................................................... 15

1.8 Operating Principles ............................................................................................... 16 1.8.1 Infrared Absorption ......................................................................................... 16 1.8.2 The Optical Bench In Use ................................................................................. 16 1.8.3 The Oxygen Sensor in Use ............................................................................... 17

2. Installation ..................................................................................................... 19

2.1 Installation Arrangement ........................................................................................ 19 2.2 Location & Ambient Conditions ............................................................................... 19 2.3 Power Supply Setting & Connections ....................................................................... 19

2.3.1 Power Supply Setting ...................................................................................... 19 2.3.2 Power Supply Connections ............................................................................... 20

2.4 Serial I/O (RS232C) .............................................................................................. 20 2.5 Analogue Outputs .................................................................................................. 21 2.6 Alarm (Trip) Outputs ............................................................................................. 22 2.7 Gas Arrangements................................................................................................. 22

2.7.1 The Gas Circuit ............................................................................................... 22 2.7.2 The Sample Gas .............................................................................................. 23 2.7.3 The Span Gas ................................................................................................. 23 2.7.4 The Zero Gas .................................................................................................. 23 2.7.5 The Purge/bypass Gas ..................................................................................... 24 2.7.6 The Exhaust Gas ............................................................................................. 24 2.7.7 Gas Pump(s) .................................................................................................. 24

2.8 Use of Chemicals (certain models only) ................................................................... 24 2.8.1 Water Vapour ................................................................................................. 24 2.8.2 Carbon Dioxide ............................................................................................... 25 2.8.3 Precautions .................................................................................................... 25

2.9 Pre-operation Checks ............................................................................................. 25 2.10 General Advice .................................................................................................... 25

2.10.1 Use of Gas Cylinders ...................................................................................... 25 2.10.2 Gas Leaks ..................................................................................................... 26 2.10.3 Exhausting & Ventilation ................................................................................ 26


6

3. Setting Up ...................................................................................................... 27

3.1 Preview ................................................................................................................ 27 3.2 On Power Up ......................................................................................................... 27 3.3 Zero & Span Operations. ........................................................................................ 27 3.4 Display & Keypad .................................................................................................. 28

3.4.1 Display ........................................................................................................... 28 3.4.2 Function Keys ................................................................................................. 29 3.4.3 Menu tree ....................................................................................................... 30

3.5 Analogue (Chart) Outputs ...................................................................................... 31 3.6 Alarm (Trip) Outputs ............................................................................................. 31

3.6.1 Setting Alarm Outputs ..................................................................................... 31 3.7 RS232C Serial Port ................................................................................................ 32

3.7.1 Protocol.......................................................................................................... 32 3.7.2 Serial Port Settings .......................................................................................... 32

3.8 Measurement ........................................................................................................ 33

4. Calibration ...................................................................................................... 34

4.1 Initial Checks ........................................................................................................ 34 4.1.1 Warm Up........................................................................................................ 34

4.2 Zero Adjustment ................................................................................................... 34 4.2.1 Manual Zero ................................................................................................... 35 4.2.2 Auto Zero ....................................................................................................... 35

4.3 Span Adjustment .................................................................................................. 35 4.3.1 Setting Span ................................................................................................... 36 4.3.2 Auto Span ...................................................................................................... 36

5. Maintenance ................................................................................................... 38

5.1 Routine Checks ..................................................................................................... 38 5.1.1 Water Vapour ................................................................................................. 38 5.1.2 Dust .............................................................................................................. 38

5.2 Instrument Checks ................................................................................................ 39 5.2.1 Source Block Purge (when fitted) ...................................................................... 39 5.2.2 Filter Column (when fitted) .............................................................................. 39 5.2.3 Sample Flow ................................................................................................... 39 5.2.4 Throttles ........................................................................................................ 39

6. Optical Bench Descriptions ............................................................................... 40

6.1 Introduction .......................................................................................................... 40 6.2 GC Bench ............................................................................................................. 40

7. Electrical Specifications .................................................................................... 42

7.1 Power Supply ........................................................................................................ 42 7.2 Analogue Outputs .................................................................................................. 42

7.2.1 Set for current output ...................................................................................... 42 7.3 Alarm (Trip) Contacts ............................................................................................ 42 7.4 Serial (RS 232) Port .............................................................................................. 42

8. Spare Parts..................................................................................................... 43

9. „AK‟ Remote Control Protocol ............................................................................ 44

9.1 Introduction .......................................................................................................... 44 9.2 Protocol Overview ................................................................................................. 44 9.3 Address ................................................................................................................ 45 9.4 Commands and Parameters ................................................................................... 45 9.5 Response To Commands ........................................................................................ 45

9.5.1 Status Codes .................................................................................................. 46 9.6 Command descriptions........................................................................................... 46

9.6.1 Interrogation Commands ................................................................................. 46 9.6.2 Show model and version information ................................................................ 46


7

9.6.3 Show range information ................................................................................... 46 9.6.4 Show Calibration Information ........................................................................... 47 9.6.5 Show sample gas inlet ..................................................................................... 48 9.6.6 Show analyser gas flow and sample pump state ................................................. 48 9.6.7 Show Alarm and Valve States ........................................................................... 48 9.6.8 Show analyser's gas name(s) ........................................................................... 49

9.7 Remote Control Commands .................................................................................... 49 9.7.1 Set remote control mode ................................................................................. 49 9.7.2 Set local control mode ..................................................................................... 49

9.8 Measurement Enquiry Commands ........................................................................... 50 9.8.1 Get current readings........................................................................................ 50

9.9 Range Selection .................................................................................................... 50 9.9.1 Select active range .......................................................................................... 50

9.10 Gas Inlet Control Commands ................................................................................ 50 9.10.1 Select sample inlet ........................................................................................ 50 9.10.2 Select zero gas ............................................................................................. 51 9.10.3 Select span gas ............................................................................................. 51 9.10.4 Sample pump control .................................................................................... 51

9.11 Calibration Commands ......................................................................................... 51 9.11.1 Perform auto-zero ......................................................................................... 51 9.11.2 Set span gas concentration ............................................................................ 52 9.11.3 Perform span calibration ................................................................................ 52

10. Implementation notes .................................................................................... 54

11. Known Issues ............................................................................................... 55


8

1. INTRODUCTION

IMPORTANT

Before operating the Instrument for the first time, ensure all the relevant

installation checks have been carried out [refer to Section 2.9].

1.1 About the Instrument

The MGA3000C Series Instrument is designed for bench or rack mounting and provides a

measurement of gas concentration according to specific user requirements.

Single, dual, triple and 4 gas versions are available utilising one or more IRGA optical

benches and/or chemical cells.

Most instruments incorporate IRGA benches that generate a signal proportional to the

infrared absorption of the measured gas. Providing the gas concentration lies within the

designed range of the instrument, the signal is periodically compared with reference gas

(usually at zero and a convenient mid-span condition). Calibration is achieved manually via

simple front panel controls or fully automatically within the software configuration.

Some instruments may include a chemical cell which reacts with the specific gas and which

provides an electrical output in proportion to the reaction.

Gas concentrations are indicated on a front display panel together with both analogue and

digital signal outputs.

Gas connections to and from the instrument are via suitable fittings on the rear panel. The

gas flow is maintained via an internal sample pump.

The MGA3000's electrical supply can be with any voltage from 90-240V AC and 50/60Hz

1.2 Instrument Identification

Each Instrument is uniquely identified with a Serial Number. This is located on a label on the

rear panel alongside the Model Number for the particular Instrument.

Always quote the serial number and model number in any communications

requiring after sales support.

1.3 The Display & Operating Controls

1.3.1 The Display

The display is a LCD Graphic type that is illuminated

from behind to achieve good contrast and visibility.

Its primary function is to provide large character

readouts of the gas concentrations together with

sample flow status and key functions.

Figure 1 - An example main screen (Multi gas model)

HCL

NOX

CO

SO2

PP

M

PP

M

PP

M

PP

M

2.2

16.2

21.2

18.1

Range

Calib

Set Up

Stp.Pump

*Notes: Flow display can be optional with related flow

switch range (Currently, 200 ㎖/min is installed.)


9

1.3.2 Design

1.3.3 The Operating Controls

The operating controls are menu driven and accessed by the 4 keys on the keypad adjacent

to the LCD display. The individual functions of the keys are clearly labelled on the display.

Selecting a menu function (by pressing the appropriate key) will cause the function to be

selected, or the next menu to be displayed, as required. In general, the bottom menu key is

used to return to the previous menu, acknowledge a message, or cancel an operation.

1.4 Electrical Outputs

1.4.1 Analogue Outputs

MGA series analysers have up to four analogue outputs, numbered 1 to 4 for connection

purposes. One output is provided for each of the gas channels fitted. When fewer than four

gas channels are fitted, one or more outputs will be inactive or not connected.

1.4.2 Alarm(trips) outputs

Up to five alarm contacts are provided to indicate gas readings above/below/outside user set

concentrations

1.4.3 RS232 port

An industry-standard serial port is fitted to the rear panel to allow gas readings to be read

and zero to be set by a PC or other computer equipment.

Switch internal pump

on and off:

Pump flowrate adjustable via menu

CAL Key to start

AUTOCAL with ambient air or N2

Dimension freely selectable to

Program (PPM, ppm, mg/m3 )

Status display “AR” or OR”

Status display “Flow” Failure

Component for measured

value, dimension and

component name

*Notes: Flow display can be optional with related flow switch

range (Currently, 200 ㎖/min is installed.)

LCD Display Flowmeter in conjunction with sample pump for mounting the sample gas flow

Setting to component for

measured value, unit, cal

period, etc…

*


10

Figure 2 – Gas Flow Diagram

1.5 Gas Path

1.5.1 Gas Flow Diagram


11

1.5.2 Key to gas path figures

1.5.3 Gas connections

1. Inlet to sample gas

2. Inlet for AUTOZERO/ zero gas

3. Calibration gas

4. Gas outlet

5. Sample gas pump

6.

6. Solenoid valve for zero

7. Solenoid valve for span

8. Oxygen measuring cell(Option)

9. Sample flow sensor

10. Infrared measuring cell

11. Safety fine filter

▣ Gas connections: stubs 6.35mm or 1/4”

Sample gas Inlet Zero gas Inlet

Span gas Inlet

Sample gas Outlet

Analogue Output

RS-232 Serial output Trips(Alarm) output


12

1.5.4 MGA 3000 19” rack, infrared component with oxygen measurement

☞ Connections: 6.35mm or 1/4”

Power supply and fuse

9-pin socket

RS-232

Trips (Alarm)

Digital output

Relay output(N/C, N/O)

Gas outlet

Connections 6mm or 1/4”

Sample gas Inlet

1.0 ℓ /min, 0.3Bar

Zero gas Inlet/AUTOCAL gas

(Gas pressure above 0.3Bar / 5psig

will damage the instrument.)

Span gas Inlet

(Gas pressure above 0.3Bar / 5psig

will damage the instrument.)

Figure 4 – MGA 3000 19” Rear View


13

1.6 Dimension drawings

MGA 3000, 19” unit, dimension in mm

664 66 44 480

266


14

1.7 Circuit diagrams (electric and gas connections)

1.7.1 RS-232C I/O (see section 2.4)

Serial (RS232C) Port Connections SUB-D 9F

Pin Name Function

1 - no connection

2 Rx Received data (input)

3 Tx Transmitted data (output)

4 DTR Handshake for Rx (output)

5 Ground 0V (nominally chassis)

6 - no connection

7 RTS „true‟ whenever unit is powered

8 CTS Handshake for Tx (input)

9 - no connection

Notes:

1. DTR is normally „true‟

2. CTS is monitored only when „hardware handshake‟ is selected

3. Screened cables must be used for RS232 connections

1.7.2 Trip I/O(see section 2.6)

Trips(Alarm) Port Connections SUB-D 15F

Pin Name Function

1 Trip1 Trip 1 contact A




5 Trip5 Trip 5 contact n/o

6 Trip5 Trip 5 contact n/c

7 +25V Out +25V Output(500mA Max)






13 None (not connected)

14 +25V return 25V return

15 None (not connected)

Notes:

1. Screened cables must be used for “SUB-D 15” Female connections


15

1.7.3 Analogue Output(see section 2.5)

NOTES:

1. I is used to indicate pin functions when output is set to 4..20mA mode

2. Screened cable should be used for analogue output connections (screen to connector

shell).

Analogue Output Pin Connections

Pin Function

1 I output 4 sink

2 I output 3 +ve / I output 3 source


4 I output 3 sink

5 I output 2 sink



8 I output 1 sink

shell 0V (connected to chassis)


16

1.8 Operating Principles

1.8.1 Infrared Absorption

With the exception of Oxygen, the instrument measures gas concentrations using the effect

of infrared absorption.

All heteroatomic gases absorb (or transmit) light energy in the infrared region at specific

wavelengths that are dependent upon the chemical composition of each type of gas.

Furthermore, the level of absorption is proportional to the mass of the gas present. This

characteristic is utilised in infrared gas analysis (IRGA) benches.

The benches incorporate a source of infrared energy (usually in the form of a heated

filament), which is then optically filtered to reduce the radiation spectrum to that of the

absorption band of the gas being measured.

A pyro-electric detector is used to measure the difference in energy between a reference zero

(no absorption) condition and that after some absorption in the gas has occurred. By

calibrating the bench at the zero condition and a known span concentration, a reliable

measure of concentration over the span range is obtained.

To improve the stability and to assist in the detection process, the infrared source is

modulated mechanically at 3-18Hz depending on the type of bench being used.

The relationship between absorption and concentration is not linear. For this reason the non-

linear output from the detector is modified electronically to give a linear output to the chart

recorder and display outputs.

The performance of an IRGA bench is compromised by the presence of 'interference' gases in

the sample. Such gases, of which the most common is water vapour, have an overlapping

infrared response to that of the measured gas and their effects are minimised by careful

filtering and the selection of the absorption band.

The level of absorption measured is relative and therefore an IRGA provides a comparative

measurement, not an absolute one, against 'zero' and 'span' reference gases.

A 'zero' gas has no detectable concentration of the gas being measured. Depending on the

gas, fresh air, chemically stripped air or nitrogen may be used. A 'span' gas has a known

concentration of the measured gas and is used to set the gain (or span) of the analysis in the

mid-range region. Under normal circumstances, the concentration is equivalent to about 80%

of the displayed full-scale reading.

1.8.2 The Optical Bench In Use

In order to obtain and maintain the optimum performance from the instrument, a number of

guidelines are offered associated with the use of the instrument, and, in particular, those

elements under the control of the User.

The IRGA bench is essentially an optical system and can suffer some deterioration in the

performance if it is internally contaminated by the condition of the incoming gases.

The gas sample should be reasonably dry. If the presence of water vapour is or is not

expected it is recommended that the instrument is continuously switched 'ON' to prevent

condensation.

The flow rate of the gas sample affects the response time (to change) of the measurement -

the measurement being on average the mix of the sample flowing through the cell. In

practice a sample flow rate of nominally 500 ml/min1 provides satisfactory performance for


17

any instrument. The instrument is fitted with a flow sensor and the flow rate is indicated on

the display. There is a potentiometer and throttle fitted internally that allows this flow rate to

be reset if necessary.

Generally the sample gas will be pumped to achieve the required flow rate. An internal pump

is fitted in the instrument and can be switched on or off via the key labelled „pump‟ on the

front panel. It is recommended that the pump is switched 'OFF' if the sample lines are being

attended to or the condition of the sample gas is suspect (for example it contains water).

The sample rate is factory pre-set for sample gas at ambient pressure.

The installation of pressurised cylinders must include suitable pressure regulators and

carefully controlled to avoid damage to pump or flow sensor due to over-pressure.

The instrument must be allowed to 'temperature stabilise' after first being switched on. The

display will show a thermometer symbol until the associated bench has reached operating

temperature. The instrument's enclosure plays a role in temperature control as well as

providing protection and the enclosure (top and front) should be securely in place before use.

Unless the instrument is only used occasionally it is advisable to leave the instrument

switched on, particularly over-night when reduced temperatures may result in condensation.

In standby conditions the sample pump should be switched off'.

1.8.3 The Oxygen Sensor in Use

As oxygen does not absorb infrared (it is diatomic), it's measurement is via a choice of 3

technologies, chemical sensor, paramagnetic sensor and zirconia based Lambda sensor. The

choice of technology is generally made by the application.

Chemical oxygen sensor: This operates in a similar way to a battery in that a voltage is

generated between two plates immersed in electrolyte. The sample gas is passed over a

membrane which allows oxygen molecules to pass through it into the electrolyte, stimulating

the reaction, and resulting in a voltage proportional to the oxygen concentration.

Typically the sensor is calibrated by adjusting for zero reading with nitrogen applied, and for

span using a cylinder containing 20.9% O2, though fresh air can be used for a quick check.

Both span and zero adjustments are made via front panel controls.

The sensor fitted has a long operational life and is very stable. If the output falls (i.e. the gas

reading is low), the sensor should be replaced. Sensor lifetime depends primarily conditions

of use (e.g. average sample oxygen concentration, sample flow rate, temperature), and so

this part is excluded from the instrument warranty. For typical applications, ADC

recommends routine replacement of the sensor every two years as part of the maintenance

programme.

Paramagnetic oxygen sensor: This operates on the principle that oxygen molecules are

paramagnetic in nature and that exposing them to a high magnetic field induces alignment to

the field, creating a movement detectable by a simple infrared sensor reflecting on a mirror.

A very stable and long life sensor with high performance, this sensor offers the best results

for measurement in the range 0-25%. Replacement of the sensor is in excess of 10 years

Calibration of the sensor is identical to procedures used for the chemical oxygen cell

Lambda oxygen sensor: Primarily designed for use in the MGA to measure low levels of

oxygen down to 100ppb levels, the sensor uses a variation on the zirconia oxide ceramic

sensors developed by Nernst. The Lambda sensor and is in general use in motor vehicles.


18

Calibration within the MGA is similar to the other oxygen sensors, but this sensor does

require an annual service and calibration outside of the MGA to ensure continued use.

The sensor has a lifetime of around 2-4 years in use is small i

ADC Gas Analysis Ltd or their authorised local agents can supply replacement sensors with

the correct fittings and electrical characteristics. Fitting alternative parts may cause

problems and will invalidate the instrument warranty.


19

2. INSTALLATION

2.1 Installation Arrangement

The basic arrangement of the Instrument is a „3U‟ or „6U‟ high, 483mm (19”) chassis for rack

mounting, or alternatively, it may be supplied with a case for bench mounting.

In multigas applications because of restrictions of space a “double” 6U high case may be

used

All power input, output and gas connections are via the rear panel.

Power connection is via a standard three-way IEC power plug. A suitable plug and cable is

supplied.

Gas connection details are indicated in Section 1.5.3, 1.5.4, 2.7

RS232C, analogue and alarm contact outputs are detailed in sections 2.4, 2.5 and 2.6

respectively.

2.2 Location & Ambient Conditions

The location must provide firm support and access to the rear of the instrument when the

instrument is mounted in the normal attitude on its base. When installed in a rack, the use

of runners is recommended.

It is not necessary to force ventilate the enclosure to cool the unit, but free circulation of air

is necessary for accuracy and reliability.

Although it is not necessary to maintain a controlled environment during use, a reasonably

stable ambient temperature gives best results. Sudden changes in temperature will disturb

the IRGA bench(s), causing a shift in readings until the compensation recovers. If a drop in

temperature is expected, it is best to leave the instrument energised (switched 'ON'), to

avoid possible condensation of water in the optical bench. If not being used in this condition,

it is also better to switch off the sample pump as this not only prolongs the life of the pump,

but helps to reduce condensation.

In all cases the ambient conditions must comply with the specifications. High

ambient conditions will affect reliability.

IMPORTANT: The MGA series analysers are not certified for operation in hazardous

environments.

2.3 Power Supply Setting & Connections

2.3.1 Power Supply Setting

The instrument operates from single phase, 90-240 volts nominal AC, at 50 or 60 Hz.

The supply frequency is not critical.

Spare fuses are provided which are 20 X 5 mm ceramic HRC „T‟ (Time Delay) types.

Maximum Power consumption is 120VA.


20

2.3.2 Power Supply Connections

The power cable supplied must be connected to a suitable plug or distribution

board as follows:

BROWN - Line or High Voltage

BLUE - Neutral or Low Voltage

GREEN/YELLOW - Earth or Ground

For safety reasons the Earth connection MUST provide a low resistance to Ground.

Further protection is provided by making a direct Earth-Bonded connection to the chassis of

the instrument, via a 4mm screw. This bonding is just below the voltage selector.

The instrument is provided with an ON/OFF switch under the power socket.

WARNING

If the front, top or bottom sections of the enclosure are removed, BEWARE of

HIGH VOLTAGES near the power connector, switch and internal supply.

When REMOVING or REPLACING the enclosure sections ALWAYS disconnect the

mains supply FIRST.

Avoid touching the electronic boards. If these are removed for any reason -

SWITCH OFF the instrument FIRST.

DO NOT HANDLE without ANTI-STATIC precautions being taken.

2.4 Serial I/O (RS232C)

An industry-standard serial port is fitted which allows the analyser to be connected to a wide

range of computer equipment for logging and remote control.

The connector is similar to an „AT‟ style PC serial port allowing the use of standard cables.

The serial port is configured from the front panel – see section 3.7.2. The serial port protocol

is detailed in section 3.7.1.

Serial (RS232C) Port Connections

Pin Name Function

1 - no connection

2 Rx Received data (input)

3 Tx Transmitted data (output)

4 DTR Handshake for Rx (output)

5 Ground 0V (nominally chassis)

6 - no connection

7 RTS „true‟ whenever unit is powered

8 CTS Handshake for Tx (input)

9 - no connection

Notes:

1. DTR is normally „true‟

2. CTS is monitored only when „hardware handshake‟ is selected

3. Screened cables must be used for RS232 connections

In common with all RS232C ports, long cable runs can cause problems with data corruption

and noise. Keep cables as short as practicable – certainly no longer than 30 meters at 9600

baud. Route signal cables well away from power cables, switchgear and other noise sources.


21

For long cable runs, and in electrically noisy environments, optical RS232C cable extenders

are recommended. Contact ADC Gas Analysis Ltd. or their local authorised agents for advice.

2.5 Analogue Outputs

Analogue outputs are provided for connection to chart recorders, remote meters, analogue

logging equipment etc. Up to four outputs are available; one for each gas reading.

The outputs are arranged so that the reading shown at the top of the screen is presented on

analogue output 1, the reading on the next line down (if any) is presented on output 2 and

so on. Where there are fewer than four gas readings, unused analogue outputs will be

inactive or not fitted.

The analogue outputs are available via a circular „DIN‟ connector on the rear panel, labelled

„OUTPUTS‟. A suitable connector is provided in the kit with each instrument, and further

supplies are available from ADC Gas Analysis Ltd. or their authorised local agent.

Analogue Output Pin Connections

Pin Function

1 I output 4 sink



4 I output 3 sink

5 I output 2 sink



8 I output 1 sink

shell 0V (connected to chassis)

NOTES:

1. I is used to indicate pin functions when output is set to 4..20mA mode

2. Screened cable should be used for analogue output connections (screen to connector

shell).

Each output is set as standard

4 – 20mA - current mode

All outputs are non-isolated

Optional output cards can be specified to provide isolated mA, voltage and MODBUS RTU

Figure 3 – Analogue Output pin numbers


22

2.6 Alarm (Trip) Outputs

The alarm outputs are isolated relay contacts which can be set to operate at certain gas

levels, or on sample flow error. Up to five contacts may be available depending on the

specification of the instrument. The number actually available is shown on the trip set-up

screen (see section 3.6.1).

Alarm contact outputs are available via a 15 way “SUB-D 15 F” connector on the rear panel.

A suitable connector is provided in the kit with each instrument, and further supplies are

available from ADC Gas Analysis Ltd. or their authorised local agent.

The connector pin functions are printed on the rear panel adjacent to the connector, and the

pin numbering scheme is shown in Fig 4.

See section 7.3 for specifications.

A nominal 24 Volt (20%) DC supply is available at the

alarm connector which can be used to power larger relays,

sirens, indicator lamps etc. This power source is internally

fused at 1A and the maximum continuous load is 500mA.

The +24V DC supply is referenced to chassis ground.

2.7 Gas Arrangements

2.7.1 The Gas Circuit

The gas connections within the instrument are shown on the gas circuit enclosed with this

manual. The gas circuit is quite specific to a particular instrument and shows how the gas is

routed from the inlets to individual analysis bench(s). Gas connections are via 'entries' that

are located on the rear panel.

All external connections are made with 6.35mm (1/4'') pipe fittings. The type of piping used is

recommended to be either polythene for general use or polytetraflurothalene (PTFE) or

stainless steel for corrosive gases.

All entries are fitted with in-line filters that are intended to stop any foreign matter entering

the instrument as a last resort. Unless the gas is perfectly clean and dry, particulate

filters and / or driers must be fitted externally.

Contact ADC Analysis Ltd. or their authorised local agents for advice.

The requirements for particular gases vary with the application and therefore these and the

gas circuit are specific to the delivered Instrument. Some guidelines follow, but it is the

responsibility of the installer to ensure that all safety and other requirements are met.

The Instrument Specification accompanying the Instrument defines the specific requirements

and this must be referred to during installation.

WARNING

All Gases are potentially toxic and hazardous to health.

All gas lines and connections must be leak-tight. Joints can be checked by

applying water containing some liquid soap and looking for bubbles.

Exhaust lines must be properly vented and arranged to prevent blockage.

Ventilate the enclosure to prevent a build-up of gas in the event of a leak.

Figure 4 - Alarm connector pin numbers numbering


23

2.7.2 The Sample Gas

The gas to be measured is the 'sample gas' labelled 'GAS IN'. After passing through the gas

circuit the measurement gases are exhausted at the entry labelled 'GAS OUT'. The analyser

is designed to receive sample gas at nominally atmospheric pressure, using the internal

sample pump to control the flow. Alternatively external pumps may be used

The Sample Gas supplied to the Instrument must be relatively clean, cool and of low

moisture content. Samples containing dust or particulates must be filtered externally and the

filters serviced at regular intervals.

Hot Samples with high moisture content should be passed through a water trap or dessicator

after cooling.

To prevent the possibility of condensation in the Instrument if the Instrument is not in

continuous use, it is recommended that it is left Switched on with the Sample Pump Switched

off.

Samples may contain other gases which „interfere‟ with the gas being measured.

The extent to which known interferents can affect the measurement are defined in the

Instrument Specification.

Sample gas pipes shall be inert to and shall not contaminate the gas.

The response time for a change in concentration will be affected by the sample flow rate.

Instrument response times are normally quoted for the recommended 500ml min-1 flow rate,

ignoring the effect of sample pipe volume. Lower flow rates will increase the response time,

as will the volume of the sample piping. Higher flow rates will reduce the response time, but

excessive flow will pressurise the instrument which may cause damage or measurement

errors.

If it is necessary to draw higher flows than recommended (e.g. due to long sample gas lines),

it will be necessary to provide some means of bypassing the excess flow to exhaust.

2.7.3 The Span Gas

The Span Gas is used for calibration and is a known concentration of the measured gas -

usually between 10% and 80% of the full-scale range of the Instrument. The gas is usually

obtained specially mixed in a pressurised cylinder and this must be fitted with a 2-stage

pressure regulator, with an output pressure indication of 0 - 0.3 Bar (0-5psig).

The Regulator should be set to give a nominal output pressure of 0.2 Bar (3psig). This will

usually give a suitable gas flow during a span operation (i.e. flow indicator approximately

mid-position). If necessary, a small adjustment to the pressure will provide correct flow.

WARNING – Application of gas pressures above 0.3 Bar / 5 psig will damage the

instrument.

2.7.4 The Zero Gas

The zero gas is used to check/set the reading from the optical benches in the zero

concentration condition. Dry nitrogen is the preferred zero gas as it is cheap and readily

available.

The zero gas must not contain any significant traces of the gas measured or interferents. For

all types of instruments and gases measured, nitrogen (from a cylinder) is usually specified.

For some gases however, fresh air may be used (for example on high concentration CO and


24

CO2 Instruments). When fresh air is used, it shall be drawn from 'outside‟ air and away from

any possible contamination from such as Exhaust Ducts, Chimneys, etc.

In most respects fresh air should be treated in the same way as the sample gas with regard

to filtering, moisture content etc. See span gas, section 2.7.3.

2.7.5 The Purge/bypass Gas

For some instruments, multirange and oxygen separate inlets ports and outlets are provided

where fresh air is drawn into the analyser to allow unused gas cells to be purged of gases

2.7.6 The Exhaust Gas

Exhaust gas is the sample (or zero/span) gas that has passed through the analyser.

For hazardous gases (high concentrations, flammable or poisonous), exhaust gas must be

carefully routed to a safe venting point.

It is important to minimise „back pressure‟ at the GAS OUT port, as this will affect readings

and reduce the efficiency of the sample pump. Where long runs of pipe are necessary, larger

bore pipe should be used via a suitable adapter. Where the exhaust pipe is connected to a

forced air extraction duct, make sure that any suction is minimal.

2.7.7 Gas Pump(s)

Gas pumps fitted in the instrument are of the vibrating diaphragm type and are capable of up

to 1.0 I/min1 under pressures normally encountered.

The sample pump operates at fixed speed and at a flow rate of nominally 500 ml/m1n1.

If it should be necessary to adjust the flow, it can be set using the potentiometer VR2 on the

power supply board and / or the throttle (when fitted).

The internal sample pump is operated via the front panel 'PUMP' menu button.

Certain instrument configurations may be fitted with a second internal pump which is used to

circulate purge gas. This pump would be set to run continuously at a factory set rate.

2.8 Use of Chemicals (certain models only)

Certain instruments use chemicals to remove (or strip) certain gases from the air for zero

adjustment, or to purge the optics to prevent ambient air from affecting readings. These

chemicals must be replaced regularly to ensure efficient operation and hence good accuracy.

The chemicals are contained in glass „columns‟ which are accessible from the front of the

instrument to aid inspection and refilling.

The chemicals that may be used are listed below under the gas application.

2.8.1 Water Vapour

An indicating form of calcium sulphate (CaSO4) known as 'DRIERITE' is normally supplied

with new instruments and replacement supplies are available from ADC Gas Analysis Ltd or

their local authorised agents. In use, drierite changes from blue to pink as it becomes

exhausted, making it obvious when the container should be refilled with fresh chemical.

Drierite can be recovered by drying.


25

„Silica gel‟ is a good indicating drier, but can „hang on‟ to some gases, especially C02, giving

false readings, and is not generally recommended.

2.8.2 Carbon Dioxide

To remove C02, usually in a C02 Instrument, indicating „soda lime‟ is used. Soda lime

consists of about 80% calcium hydroxide ((Ca(0H)2)), 4% sodium hydroxide (NaOH) and

0.2% indicator (green to brown).

In use, soda lime changes from green to brown and must be changed when green is no

longer visible. It is not recoverable. Replacement supplies are available from ADC Gas

Analysis Ltd or their local authorised agents.

Other chemicals may produce corrosive by-products which can damage the instrument.

2.8.3 Precautions

Any chemical intended for use in the instrument is provided with it in a separate container,

labelled with international identification labels. Under normal use, the quantity supplied will

last for about 6 months to a year. Replacements can be obtained from ADC Gas Analysis Ltd

who will also advise on the use of chemicals obtainable by the User.

When handling chemicals, refer to the „Safety Letter‟ enclosed in the manual for precautions

against possible health risk. For all chemicals, avoid skin and eye contact and do not taste or

swallow them.

2.9 Pre-operation Checks

Before connection power to the instrument, check:

1. That gas connections are leak free

2. That the exhaust gas venting arrangements are safe for the gases in the sample

3. That the instrument is properly grounded (earthed).

2.10 General Advice

2.10.1 Use of Gas Cylinders

Before use, Gas Cylinders must be checked to ensure that -

the cylinders are securely located.

the cylinders are fitted with a two-stage regulator.

the cylinders contain the correct gas mixture for use.

the cylinders are connected to the correct „entry‟ on the Instrument.

the cylinder's Output Pressure regulator is 'OFF'.

During use, check -

• the Instrument is 'ON'.

• the Sample Pump is 'ON'.

• the Output Pressure regulator is set for 0.2 Bar.

After use, check -

• the Output Pressure regulator is turned 'OFF'.


26

• the cylinder tap is turned 'OFF'.

• if the Instrument is in „Standby‟, turn 'OFF' the Sample Pump.

Following a cylinder change, it is advisable to initiate a Span or Zero cycle a few minutes

after the supply is re-connected.

2.10.2 Gas Leaks

All external-piping connections must be checked for gas leaks, to ensure that no gases are

leaking to the local area (which may be a health hazard), and that no uncontrolled air or gas

is drawn into the Instrument (and so affect the measurement).

Applying water containing a mild soap solution can check connections under pressure. Do not

increase the pressure to check for leaks (or for any other reason), since this may damage the

Instrument.

Connections of pipes under nominally ambient pressure, such as the sample piping, are

difficult to check for leaks, but can be checked for tightness.

2.10.3 Exhausting & Ventilation

Because any gas is potentially toxic, and, some may be inflammable, the gas must be

exhausted to where it will be rapidly dispersed. For the same reasons, the Instrument and

its environment including the location of gas cylinders must be properly ventilated to

minimise the dangers of gas leaks.

If Span cylinders contain hazardous or inflammable gases, they must carry suitable warning

labels, and if inflammable, must be located in a suitable „Inflammable Store‟ when in use or

in storage.

In all cases the local safety regulations must be consulted and followed.


27

3. SETTING UP

3.1 Preview

This section describes the settings available from the front panel. Factory settings have been

chosen to suit the general application of the instrument, or in accordance with the particular

instructions specified previously by the user.

3.2 On Power Up

IMPORTANT: Before operating the Instrument, ensure all the relevant installation

checks have been carried out [refer to Section 2.9], and that if a filter column is

fitted, it is properly charged with the chemical supplied.

Immediately after power is applied, the display presents a screen for 10 seconds. This page

contains the software version number.

If the logo does not appear on the screen

within 20 seconds of applying power, try

adjusting the „LCD‟ control, using a 2mm flat

bladed screwdriver through the labelled hole in

the rear panel.

The next screen is the main display, which will show the measured value(s), units and the

Gas type, sample flow status and key functions.

The measured value is initially replaced with a

symbol of a thermometer until the instrument

has warmed up.

Pressing the key labelled „Set Up‟ displays a

second screen showing the gas(s) measured

together with the range and units.

Pressing „More‟ allows other gas measurement s present to be shown

3.3 Zero & Span Operations.

Before precise gas readings can be obtained, the analyser must be adjusted so that it reads

zero when there is no trace of the measured gas present, then, when a known concentration

of the gas is applied, the reading is adjusted to agree with this concentration.

These adjustments are known as „zero‟ and „span‟ respectively.

The gases used for zero and span adjustment are supplied through the inlets at the back of

the instrument (see section 2.7), and electrically operated valves are used to route the

HCL

NOX

CO

SO2

Range

Calib

Set Up

Stp.Pump


28

Figure 7 - screen contrast adjustment

Figure 5 – Set-up Automatic Zero

appropriate gas in place of the sample automatically when zero or span adjustment is

selected using the front panel controls.

'How often' to Zero or Span varies with each instrument. The interval required depends on

how much re-adjustment is being carried out: this can be established by noting the

discrepancy of the displayed value prior to resetting.

If the discrepancy is less than 0.5% of full scale, the intervals can be increased, or if this is

not accurate enough, decreased. Generally Zeroing is required more often than Spanning, so

that typically a daily Zero, with weekly Span is

adequate.

The instrument can be set to automatically adjust

zero or span on a periodic basis.

The period can be set from 1 hour to 250 hours for

zero and 1-99 zeros between spans.

The normal operating layout is shown in Fig 5

See section 4 for details.

3.4 Display & Keypad

3.4.1 Display

The normal operating layout is shown in Fig 8, but

note that this is an example; the gases shown will

vary with the specification ordered.

On the left of the screen are the gas names,

followed by the current reading(s). A thermometer

symbol indicates that the analysis bench is warming

up – readings will be shown when warm-up is

completed.

On the right, adjacent to the four „function‟ keys, are the key labels.

These describe the functions of the keys at any time, and the labels change as different

options are selected.

Between the gas readings and the function key labels, is the sample flow indicator, which is

designed to mimic a float flowmeter. Normally, the flow, as indicated by the „float‟, should be

around the centre of the indicator. If the float is in a shaded region, the flow is too high or

low and a warning triangle is shown.(Flow display can be optional with related flow switch

range(currently, 200 ㎖/min is installed))

Flow fail and alarm trips are indicate at the bottom

of the display.

The LCD display is affected by ambient temperature

and viewing angle. A contrast control is provided to

adjust the display to give the best contrast under all

viewing conditions.

To adjust the contrast, Select the following menu

functions: Set Up , Display

The contrast screen is displayed. Use the lighter

and darker controls to get the best display. The

bar shows the amount of contrast adjustment. If it is not possible to get good contrast within

Figure 6 - Example Main Screen (4 gas)

HCL

NOX

CO

SO2

PP

M

PP

M

PP

M

PP

M

2.2

16.2

21.2

18.1

Range

Calib

Set Up

Stp.Pump


29

Figure 8 – Main Overview

HCL

NOX

CO

SO2

PP

M

PP

M

PP

M

PP

M

2.2

16.2

21.2

18.1

Range

Calib

Set Up

Stp.Pump

the range of the bar, press the „Default‟ key, then, using a 2mm flat-bladed screwdriver,

adjust the „LCD‟ control through the labelled hole in the back panel for best display. Note

that the rear panel control has a wide range and the display will not be visible for extreme

settings.

3.4.2 Function Keys

The instrument is operated using the four function keys to the right of the display screen.

The keys are labelled on the display, allowing the functions of the keys to change dynamically

as options are selected.

Range

Measuring gas is the range selectable

Manual and Automatic range

Calib

Zero & Span adjustment

Auto Zero & Span setting of the time

period

Manual calibration & Auto calibration

Set Up

Sample flow is adjustment

Setting by Trips(Alarm), Key click,

Warming Beep, Decimal point, Serial port, etc..

Stp.Pump

Sample Pump Start /Stop

▣ Function key button by select “Push”


30

Figure 8 – Menu tree

3.4.3 Menu tree


31

Fig. 8 shows the menu „tree‟, starting from the main screen showing the sample gas

readings.

Sub-menus provide routes to more detailed functions, until the operator is required to 'DO'

an action. At this point, the display will present instructions, or more information, appropriate

to the action required.

For example, pressing the function key 'Zero adj' on the main menu, presents a Sub-menu

with the function keys on the right hand side of the display and instructions on the bottom of

the screen.

3.5 Analogue (Chart) Outputs

An analogue output is provided for each gas measured (up to 4 channels). The outputs are

available from a circular DIN type connector on the rear panel. Outputs are set for 4-20mA

at the factory, a operator interface in the menu is included to allow adjustment where

required, and test at See section.

The outputs are arranged so that the gas shown on the top line of the screen is presented on

analogue output 1. The gas shown on the second line of the screen (if any) is presented on

output 2 and so on.

Analogue output scaling is fixed and corresponds to the full scale measurement range of the

associated gas. Analogue outputs do not indicate negative or over-range conditions.

3.6 Alarm (Trip) Outputs

The MGA analyser features up to five electrically isolated alarm contact outputs. The alarms

can be set up individually from the front panel to indicate gas readings above or below a set

value, inside or outside a set range, or to indicate sample error.

The number of trip contacts fitted may vary depending on the specification ordered.

For connection information, see section 2.6.

3.6.1 Setting Alarm Outputs

The alarm outputs are not set at the factory.

To set or check the alarm settings from the main

screen, press the „Trips‟ function key. The screen

will list the settings for each trip fitted. If no alarms

are fitted, a warning message will appear before

returning you to the main screen.

Use the and keys to highlight a trip then press:

„Test‟ To temporarily set a trip to the alarm state –

allowing connected equipment to be tested.

„Change‟. To modify settings for the selected trip. The screen will display the selected trip,

and the function keys now offer items to change. From this screen use:

„Gas‟ to select the gas for which this trip is active, or alternatively select „not set‟ (trip not

used) or „flow error‟ (active if sample flow out of range).

Figure 9 - Trip settings screen


32

„Lo point‟ to set a gas value below which the trip is active. If there is no reading shown

under this column on the display, or if the „Off‟ key is used when setting the low point, this

trip will not respond to low readings.

„Hi point‟ to set a gas value above which the trip is

active. If there is no reading shown under this

column on the display, or if the „Off‟ key is used

when setting the low point, this trip will not respond

to high readings.

Note: setting both high and low trip points

will give a range indication.

„Contacts‟ to swap between normally-closed („n/c‟)

and normally-open („n/o‟) contact modes to suit externally connected equipment. In

normally-closed mode, the trip is fail safe in that power failure, disconnection or trip

becoming active will all open the circuit, generating the alarm.

„Done‟ to save any changes made and return to the previous screen.

Repeat the settings above for each trip to be set.

3.7 RS232C Serial Port

A serial port is available on the rear panel (labelled „RS232C‟), to which a PC, VDU or other

computer equipment can be connected. The port provides a way of monitoring the readings

remotely, and triggering auto-zero.

For connection information see section 2.4.

3.7.1 Protocol

Please refer to the Section 9.

3.7.2 Serial Port Settings

The serial port is configured from the front panel. To check or change the serial port

settings, select:

Set Up , Ser. Port

From the main screen menu.

The screen will show current settings.

Press the „Baud‟ key to cycle through the available

port speed options

Press the „Handshk.‟ key to cycle through the

available flow control / handshaking options.

The „Done‟ key will store any changes before returning

to the previous screen.

Note that the data format is fixed at 8 bit data, no parity, 1 stop bit.

Figure 10 - Setting up a trip

Figure 11 – Serial port setting


33

3.8 Measurement

The gas ranges, display format and units of measurement are factory set to order, and no

changes are possible. If changes to ranges or gases are required, contact ADC (Sales &

Service) Ltd. or their local authorised agents for a quotation.

Units of measurement are normally „by volume‟ or „ppm‟ though other options are possible to

order (e.g. mg m-1).

The display uses up to four digits, with values up to 3 decimal places, depending on range,

gas etc.

The symbols shown in place of the readings are as follows:

Over-range – the reading is too high. Normally this indicates a gas concentration that

is above the measuring range.

Under-range – the reading is too low. Normally, zero adjustment will correct the

problem.

Warming up – the associated analysis bench is stabilising.

readings will be shown when warm-up is completed.

The measured value is initially replaced with a symbol of a thermometer until the instrument

has warmed up.

HCL

NOX

CO

SO2

Range

Calib

Set Up

Stp.Pump

Figure 12 – Initialize Screen


34

4. CALIBRATION

Gas readings made using IRGA optical benches are relative rather than absolute.

Before precise gas readings can be obtained, the analyser must be adjusted so that it reads

zero when there is no trace of the measured gas present, then, when a known concentration

of the gas is applied, the reading is adjusted to agree with this concentration.

These adjustments are known as „zero‟ and „span‟ respectively.

Routine calibration is important, not only to verify measuring accuracy, but also to spot

changes over time that may indicate problems.

Note: because the instructions will vary slightly from gas to gas, the instructions given here

are fairly general. ADC Gas Analysis Ltd. or their authorised local agent will be pleased to

answer any questions.

4.1 Initial Checks

It is assumed that the instrument is correctly installed and all gas connections are correctly

made – if not, refer to section 2.

Before operating the Instrument, ensure all the relevant installation checks have

been carried out [refer to Section 2.9], and that if a filter column is fitted, it is

properly charged with the chemical supplied.

As one of the first operations concerns Zeroing and Spanning the Instrument, ensure that

external Zero and Span Gas supplies are available for connection to the Instrument.

If gas cylinders are used, check the Pressure Regulators are set correctly.

Make sure that the Power Settings [on the Rear Panel] are correct for the supply used [refer

to Section 2.3]

4.1.1 Warm Up

If previously removed for any reason, re-fit and secure the enclosure's front or top covers to

the Instrument. The covers are necessary to ensure that the internal temperature stabilises.

Switch on the Instrument via the Rear Panel mounted Power ON/OFF switch, and allow the

instrument about 30 to 60 minutes to warm up.

Until the instrument has reached operating temperature the display will indicate a symbol

which represents a thermometer. This symbol will be replaced by the gas measurement

when the correct temperature has been achieved.

4.2 Zero Adjustment

Before a zero adjustment is made ensure that the gas cylinder is connected and

that the correct pressure is set.

See section 2.7.4.


35

Figure 13 - Zero screen (Multi gas model)

4.2.1 Manual Zero

1. Select 'Zero Adj. ' on main menu, which will

display the zero screen and apply zero gas to

the analyser bench(s).

2. Verify that the flow meter shows adequate

flow – zero adjustment cannot be made if the

flow is incorrect. If necessary, make small

adjustments to zero gas pressure to correct

the flow.

3. Wait for the gas reading to stabilise,

allowing any error to be noted.

4. If the reading(s) are satisfactory, press „< Main‟ to return to the main screen without

making changes. – or ->

5. When the readings have stabilised, select the key labelled with the gas type you wish to

zero.

6. The microprocessor will then reset the reading to zero. If the change is to great and the

processor is unable to reset the zero, a warning message will appear on the screen.

Depending on the bench type, the message will either warn of failure, or offer to set

„coarse zero‟.

7. Before selecting to perform coarse zero adjustment, double check that the zero gas is

correct – coarse zero cannot be cancelled and may take a few minutes.

4.2.2 Auto Zero

MGA series analysers can set zero automatically at user set intervals, or by command from

the RS232 port. Automatic zero does not require

user intervention, but it will „freeze‟ the analogue

output voltages temporarily.

Auto zero is set by selecting the following from the

main screen:

Set Up , Auto Z.

The screen shows the current setting, and, if a time

period is set, the time until the next zero

adjustment.

The interval for auto zero can be set in 1 steps selecting the + or - key until the required

time is set. Press „Off‟ to disable auto zero, and „< Back‟ to save settings and return to the

previous screen.

When an Auto Zero takes place the analyser will go through the same procedure as for a

manual Zero, but the processor will automatically reset the gas reading to Zero.

Auto zero will attempt adjustment for all gases, but will not initiate a coarse zero adjustment

if the standard zero fails.

When using Auto Zero the zero gas cylinder must be connected at all times

4.3 Span Adjustment

Before a Span adjustment is made ensure that the gas cylinder is connected and

that the correct pressure is set. See section 2.7.3.

Figure 14 - Auto zero set-up screen.

Zero Adj.

Span Adj.

Aut. Span

Aut. Zero

Main

HCL

NOX

CO

SO2

PP

M

PP

M

PP

M

PP

M

0.0

Zero gas selected ? purging

0.0

0.0 0.0


36

Before a Span adjustment is made ensure that the analyser is set to the higher or

maximum range for multirange analysers.

It is recommended that zero adjustment is done immediately prior to adjusting span.

For multi-gas analysers, it is convenient if the span gas used is a mixture containing an

accurately known concentration for each of the gases measured. If this is not practicable,

then the span process must be repeated for each gas in turn, using the appropriate span gas.

4.3.1 Setting Span

Select 'Span Adj.' on the main menu. The span screen will be displayed, and the span gas

will be connected to the analyser(s). The readings will change to reflect the span gas.

Verify that the flow meter shows adequate flow – span adjustment cannot be made if the

flow is incorrect. If necessary, make small adjustments to span gas pressure to correct the

flow.

Wait for the gas reading(s) to stabilise.

If the readings are satisfactory, press „< Main‟ to return to the main screen without making

changes. – or ->

Press the key labelled with the appropriate gas. The

display will ask you to set the correct gas value. The

value offered is that last used, but if necessary use

the Gas + and Gas - keys to set a value that agrees

closely with the span gas concentration.

Press „Set Span‟. The microprocessor will then

reset the reading to the value entered. If the change

is to great and the processor is unable to reset the

span, a warning message will appear on the screen.

If the span adjustment fails, carefully check the span gas cylinder. If possible, verify the gas

concentration on a second analyser, or try another bottle of span gas. If the span fails and

the span gas is correct, contact ADC Gas Analysis Ltd., or their local authorised

agents for service.

4.3.2 Auto Span

MGA series analysers can set span automatically at user set intervals, or by command from

the RS232 port. Automatic span does not require user intervention, but it will „freeze‟ the

analogue output voltages temporarily. Users may choose the gases to be included in the

autospan operation

Auto span is set by selecting the following from the

main screen:

Set Up , Auto S.

The screen shows the current setting, and, if a time

period is set, calculated by number of zero‟s entered,

the time until the next span adjustment.

The interval for auto span can be set in 1 steps

Figure 16 - Auto span set-up screen.

Figure 15 – Setting the span gas


37

selecting the + or - key until the required interval is set. Press „Off‟ to disable auto span, and

„< Back‟ to save settings and return to the previous screen.

When an Auto Span takes place the analyser will go through the same procedure as for a

manual span, but the processor will automatically reset the gas reading to the entered span

gas values. Auto span will attempt adjustment for all gases.

When using Auto Span the span gas cylinder must be connected at all times


38

5. MAINTENANCE

5.1 Routine Checks

Problems with the Instrument can be avoided if the installation is maintained regularly,

especially with regard to parts used to pre-condition or route the various gases, and in

particular the sample gas.

The User should be aware of any constituents of the gas that may directly or indirectly affect

the optical components within the instrument as described in Section 2.7.2.

If Water Traps and/or Particulate (dust) Filters are included in the installation these must be

periodically inspected and maintained to avoid overflows or blockage.

5.1.1 Water Vapour

If, during the initial installation of the Instrument, the presence of high water vapour content

was not expected (and therefore means of trapping it was not included) signs of it should be

looked for during routine maintenance, particularly during the first few weeks of operation.

If transparent piping was used, water can often be seen in droplets on the inside walls or

collecting at a low point in the piping arrangement. With opaque or steel pipes, disconnect

them at a low point to see if water drips out.

If signs of water are found, it may eventually block the pipes or result in amounts being

drawn into the instrument which may affect the pumps, solenoids etc., as well as the optics.

In this case, it is recommended that some form of Water Trap be fitted, such that the

contents can be easily seen and regularly inspected.

If the Sample does contain water vapour, leave the Instrument switched on if it is not in use,

and with the Sample Pump off. This will help to prevent condensation within the instrument.

A service visit is advisable in cases of water ingress, so that the optics can be cleaned. Dirty

optics will reduce performance.

5.1.2 Dust

Long term problems may occur if dust is in the sample. Usually this cannot be „seen‟, but

over a period of time it can build up and affect all parts of the gas path. Dust may also block

the particulate filters fitted in the inlets of the Instrument and may therefore result in a

blockage or a reduction in flow.

As part of the maintenance routine, inspect the Inlet Filters for signs of dust. If there is any

sign of dust, the sample line must be fitted with a suitable filter (down to 1O microns) and

the filter elements regularly replaced.

Where dust has penetrated the instrument, arrange for a service visit so that the optics can

be cleaned and full performance restored.


39

5.2 Instrument Checks

The instrument requires little maintenance, other than the filter column (if fitted), source

block purge (if fitted), sample flow adjustment (if necessary), and zero and span adjustment

(see section 4).

5.2.1 Source Block Purge (when fitted)

Certain instruments fitted with the „SB‟ type IRGA bench have a CO2 trap to remove traces of

the gas from the source block. The trap is a glass jar which protrudes through the front

panel of the instrument, filled with indicating soda lime (see section 2.8.2). The colour of the

soda lime should be checked regularly, and the contents replaced when only the very end of

the jar remains green. The jar is removed by unscrewing.

When replacing or handling chemicals, avoid physical contact and wash hands

afterwards.

Dispose of chemicals carefully and in accordance with any local Health & Safety

requirements.

5.2.2 Filter Column (when fitted)

If a Filter Column is fitted, regularly check the condition of the chemical it contains. The

characteristic to look for when the chemical is exhausted depends on that used and is

described in Section 2.8.

Replace the chemical before it is completely exhausted to avoid subsequent „hang-up‟. If it is

used in an exhausted state it may cause unstable operation of the Instrument.

When replacing or handling chemicals, avoid physical contact and wash hands

afterwards.

Dispose of chemicals carefully and in accordance with any local Health & Safety

requirements.

5.2.3 Sample Flow

Once set, sample flow should not require adjustment unless it moves near the shaded areas

on the flow meter. Before adjusting flow internally, check sample and exhaust piping for

obstruction, state of filters etc.

If the flow continues to fall off over a period of time, it may indicate that the lines are

becoming blocked, as indicated in the previous section.

5.2.4 Throttles

The sample and zero gas flows are normally set in the instrument with external throttles, as

indicated in the Gas Circuit. These paths can also become affected by blockages and they (or

some other reason) may require some re-adjustment.

Readjustment is not a routine procedure – always check span and zero gas bottles, regulator

pressures etc. before attempting adjustment.


40

6. OPTICAL BENCH DESCRIPTIONS

6.1 Introduction

This section describes the basic construction and operation of the various types of bench that

may be fitted in an instrument. All the infrared types rely on a characteristic of heteroatomic

gases to absorb energy at specific wavelengths in the infrared spectrum, and, follow the

operating principles described in Section 1.8.1.

Each bench type makes use of a different technique. To recommend a type of bench best

suited to the requirements will generally relate to the type of gas measured and/or the

accuracy and sensitivity of measurement.

6.2 GC Bench

The GC (Gas Correlation) infrared bench is a non-dispersive single beam analyser in which

the gas to be measured is passed through an optical cell continuously. Although the

instrument output is in terms of gas concentration, this type of analyser operates as a

comparator. That is, its output is not absolute, but is established by standardising with a

known gas mixture at a point on the calibrated scale. See section 4.

A typical GC Bench layout is shown in Fig. 18. This reflects a „single‟ analysis cell. Variations

on this will be on the length of cell or the number of cells.

The length of the cell is dependent on the concentration of the sample measured and may

vary from 1mm (at very high concentration) up to about 250mm (at low concentration).

Motor

Sensor Filter Wheel

Source

Lens

Optical Filter

Window Window

Gas Entries Lens

Analysis Cell

Detector

Figure 17 - The Gas Correlation optical bench


41

Infrared (heat) radiation from a small source is directed through a rotating filter wheel, a

collimating lens, an optical (Thin-Film) filter, the sample cell, a focussing lens and on to a

solid state detector. The wheel is rotated at 1100 RPM, to give a modulation frequency of

18.3 Hz.

Each cell element is sealed at both ends by a window that does not optically interfere with

the radiation.

The heart of the analyser is the gas filter wheel, which contains a sealed sample of gas of the

type to be measured, and a non-absorbing gas. As the wheel rotates it provides a ratio of

sample and reference signals, in a sequence detected by a wheel position sensor. The ratio

signals, together with the selective transmission of the optical filter, sensitises the analyser to

respond to that region of the infrared spectrum corresponding to the measured gas in the

sample.

When the gas to be measured enters the analysis cell, it absorbs some radiation, and alters

the ratio of the sample and reference signals. It is this change in energy level that is

amplified to give the output signal.

The optical path between the source and the first cell window, and between the last window

and the detector, will normally contain room air, or a gas from which any interfering gases

have been stripped. This air is referred to as „Purge‟ air, and if a chemical stripper is used, it

will be shown on the gas circuit. As Purge air has the properties required for the Zero Gas, it

may be used as such.

Whilst the bench can be stripped down to individual parts and parts replaced, this process will

require re-calibration of the bench and possibly some re-adjustments in the Pre-amplifier

and/or amplifier associated with the detector. Since this requires special training and

equipment, the User should not undertake re-calibration unless such training and equipment

has been approved.


42

7. ELECTRICAL SPECIFICATIONS

For specifications relating to gas measurements, refer to the Certificate of Conformity.

7.1 Power Supply

Voltage: 90-240V AC

Frequency: 47 – 63Hz

Maximum Power Consumption: 120VA

7.2 Analogue Outputs

Outputs are not isolated.

7.2.1 Set for current output

Output at zero gas: 4mA 1%

Output at full scale: 20mA 1%

Source resistance: > 1M

Maximum loop voltage: 25V

Voltage drop (at 20mA) 0.5V maximum

Current output sink is connected to chassis (nominally ground).

7.3 Alarm (Trip) Contacts

Contact rating: 1A (non inductive)

Voltage rating: 30V DC / AC peak

Max. Voltage with respect to chassis: 30V DC / AC peak

Auxiliary 24V output: 24V DC 20% at 500mA maximum.

Auxiliary supply has negative rail connected to chassis.

7.4 Serial (RS 232) Port

The port signal levels correspond nominally to RS232C specifications, however the output is

approximately 9V into 7k.


43

8. SPARE PARTS

The following table lists some of the more common spare parts. ADC (Spares & Service)

Limited provided total parts support and can quote for any item not listed – just contact us or

our authorised local agent.

Description ADC Part Number

MGA 3000 series Operation Manual MGA-MANUAL

MGA 3000 series Technical Manual MGA-TECMAN

Inlet filter FIL-131/A

In line filter (flowmeter protection) 630-508

Infrared Source (GC bench) after Serial No. 3175 MGA-021

Shutter Motor (GC bench) MGA-R-017

Sample Pump PVU-024

Sample Pump Repair Kit 676-456

Fuse 5x20mm, 1A T 022-256

Fuse 5x20mm, 1A F (aux 24V output) 022-556

Fuse 5x20mm, 500mA F (analogue output) 022-656

Connector for the alarm output, 14 way MGA-B-040

Connector for the analogue output, circular 8 way MGA-B-041

Trimming tool, long 867-056

Mains lead assembly, with UK plug, 5A fused. 052-661

Always quote the Serial Number and Model Number in any communications

requiring spares or after sales support.


44

9. „AK‟ REMOTE CONTROL PROTOCOL

9.1 Introduction

The MGA 300 has extensive remote control functionality using a variant of the widely used

„AK‟ protocol.

This document details the commands, allowing full remote control and monitoring of the

analyser.

Before starting, ensure that the serial port speed, handshake mode and analyser address are

set as required to match the AK host, using the „Serial‟ option from the „Set Up‟ menu.

9.2 Protocol Overview

Commands are sent to the analyser as AK „packets‟, which consist of the following parts:

Start code

Address character

Command name

Parameters appropriate to the command, as and when required

End code

Note: spaces are not allowed between the start code, address and command.

A typical command might look as follows: <S>1SEGA 0 1 0.768<E>

Note: In the examples shown, text show in Courier font represents literal characters (i.e.

what you would see if you printed a command), and <S>, <E> represent individual special codes, which are not visible ASCII characters. Any space characters are shown explicitly in the examples. Optional parameters are show in [square brackets].

In this example, the parts are as follows:

<S> Start code, a single STX character (2 hex, or ^B)

1 Address, a single digit between 0 and 9, or a „*‟

SEGA Command name.

For the MGA 3000 all commands have four capital letters.

(one or more spaces)

0 Parameters (3 in this example) 1 These are specific to the SEGA command

0.768 Each parameter is separated by a one or more spaces

<E> End code, a single ETX character (3 hex, or ^C)

The command packet is processed on receipt of the end

code.


45

9.3 Address

The address character is used to distinguish different pieces of equipment. The MGA will only

respond to a command if the address digit in the command matches the address set in the

analyser (in the serial port set up screen). If the command address is „*‟ however, the MGA

will always respond.

9.4 Commands and Parameters

The MGA will respond to the commands detailed later. Zero, one or two parameters will be

expected, depending on the command.

For example, the command SREM (set remote control mode) requires no parameters, while

SEGA (set span gas concentration) requires three (channel, range, span gas). In general,

the MGA analyser ignores unexpected parameters.

All commands recognised by the MGA analyser for remote control use consist of four upper

case letters. Case is important.

9.5 Response To Commands

After the analyser receives and processes a command, it sends a reply „packet‟ using a

similar format. Here is an example:

<S>1GRAN 0 77 3000 2.06<E>

<S> <E> Are the start and end codes as before.

1 The analyser address, as set on the serial set up screen.

GRAN An „echo‟ of the command sent.

This will be ???? if the command was not recognised.

0 Status code, a single hex digit, containing status flags.

See below.

77 3000 Returned parameters (if any) appropriate to the command.

etc.

Certain commands require that the analyser is set for „remote control‟ mode, or cannot be

used while calibration is in progress, for example. If a command is inappropriate or badly

formed, it will be ignored, and the reply will contain a fault code in place of any parameters.

Here is an example:

The error indications are as follows:

SE Syntax error; bad, missing or illegal parameter values.

NF Not fitted; command addresses a channel, range or

option that is not fitted. CAL In calibration; this command is not allowed while

calibrating. WMUP In warm-up; this command is not allowed while the analyser

Is warming up. SMAN Manual; this command is not allowed while analyser is

in local control mode. Use the SMAN command first.


46

Do not confuse ‘SMAN’ when used as an error indication, with a response to a valid SMAN command. Error indications are parameters, and appear after the command echo.

9.5.1 Status Codes

The status code digit indicates certain error conditions. It consists of four flag bits summed

into a single hexadecimal digit as follows:

Bit Weight Indication when set

0 1 One or more analyser channels indicate failure

1 2 Sample flow error (too high or low)

2 4 Last zero attempt failed

3 8 Last span attempt failed

Since it is possible for more than one error to be indicated, the code displayed is the sum of

the weights of the active indications.

Examples:

Error code digit Error(s)

2 Sample flow error

A Sample flow error & last span failed

B Last zero failed & last span failed

Both zero and span fail indications remain set until a successful zero/span has been

completed, or the analyser is reset.

The flow error indication is set whenever a warning triangle would be shown under the flow

meter on the analyser display.

Analyser failure indication normally indicates that service attention is required.

9.6 Command descriptions

9.6.1 Interrogation Commands

Used to determine the analyser type and the gases and ranges fitted. These commands can

be sent at any time; remote control mode is not a prerequisite.

9.6.2 Show model and version information

Command: GRAN

Parameters: none

Data returned: <model> <version>

Where: <model> is always 77 3000

<version> is firmware version, and of the form x.yy

Example reply: <S>1GRAN 0 77 3000 2.06<E>

9.6.3 Show range information

Returns information about a specific channel and range. Poll all possible channel/ranges to

get full details for the analyser.

Command: GRRD

Parameters: <channel> <range>

Where: <channel> is an integer 1..4 selecting possible channel

(which equates to a specific gas)

<range> is an integer 0 or 1;


47

0 = least sensitive or only range

1 = more sensitive range, if fitted

Data returned: <full_scale> <units> 1 <dec_places> <gas> <active>*

or, if channel or range not present: NF

Where: <full_scale> full scale reading as a decimal number

<units> number representing the ASCII code for a character indicating gas

units:

112 = („p‟) ppm (parts per million)

118 = („v‟) vpm (volume per million)

103 = („g‟) mg/m3 (milligrammes per cubic metre)

37 = („%‟) percent concentration

<dec_places> number of decimals readings are shown

to on analyser screen.

<gas> number representing the measured gas:

1: CO - Carbon Monoxide

2: CO2 - Carbon Dioxide

3: O2 - Oxygen

4: SO2 - Sulphur Dioxide

5: SF6 - Sulphur Hexafluoride

6: NO - Nitric Oxide

7: N2O - Nitrous Oxide

8: NH3 - Ammonia

9: CH4 - Methane

10: C2H2 - Acetylene

11: C2H6 - Ethane

12: C3H8 - Propane

13: C4H10 - Butane

14: C5H12 - Pentane

15: C6H14 - Hexane

16: C6H6 - Benzene

17: C6H5CH3 - Toluene

18: HCL - Hydrogen Chloride

19: ratio - Ratio of gas 0 to gas 1

<active> (only returned by version 2.07 or later)

1 = this is the range currently selected for this gas

0 = this range is not selected

Example replies: <S>1GRRD 0 100.0000 37 1 1 2<E>

range reads 0.0 .. 100.0% CO2 <S>1GRRD 0 1000.0000 118 1 0 7<E>

range reads 0 .. 1000vpm N2O

9.6.4 Show Calibration Information

This command is supported by firmware version 2.07 and later.

This command returns the calibration factors used by the MGA analyser. By reading these

factors before and after a calibration, it is possible to see by how much the calibration has

„moved‟ the zero/span. Factors are held separately for each range and gas.

Command: GRCL


Where: <channel> is an integer 1..4 selecting possible channel


48

(which equates to a specific gas)




Data returned: <span_factor> <zero_offset>

Where: <span_factor> Is an integer representing the span

factor multiplied by 10000.

e.g. a value of 10000 represents a span factor of 1.0, the

nominal value.

<zero_offset> Is an integer representing the zero offset

9.6.5 Show sample gas inlet

Sample switching varies depending on options fitted. Most models are fitted with gas

switching for zero and a single span gas. Multi inlet options cover 2, 8 or 16 sample inlets.

Note that inlet numbering as shown on the analyser screen is 1 higher (i.e. numbering starts

at 1).

Command: GRMW

Parameters: none

Data returned: <I>

Where: <I> is a number representing the analyser gas as follows: -1 = zero calibration gas

-2 = span calibration gas

0 = first or only sample inlet

1 .. 15 = other sample inlets (as options fitted)

9.6.6 Show analyser gas flow and sample pump state

The flow reading comes from a mass flow meter which is in series with the analyser cells.

The flow reading is non-linear, for guidance only. Flow readings vary from 0 (no flow) to

1023 (maximum flow), and a reading of 800 approximates to a sample flow of 600 ml min-1,

the recommended nominal sample flow for most applications.

Command: AFLO

Parameters: none

Data returned: <flow> <pump>

Where: <flow> is the sample flow, 0 .. 1023 (see above) <pump> is sample pump state: 0=off, 1=on

Example reply: <S>1AFLO 0 800 1<E>

sample flow is approx. 600ml min-1, pump is on

9.6.7 Show Alarm and Valve States

This command is supported by firmware version 2.07 and later.

The MGA has eight „ports‟ which may be used for trip relays or gas switching valves. The

assignment of relays and valves to ports depends on the specification of the specific analyser.

Normally, ports 1 to 4 correspond to trips 1 to 4 (as fitted). Where trip 5 is fitted, this

corresponds to port 8.

When using this command to interrogate the state of trips, bear in mind that a trip can be

configured to make the relay operate either when the trip condition is met, or when it is not

met. The trip setting will therefore determine whether a port state of 1 means tripped, or

not tripped.


49

Command: GRTP

Parameters: none

Data returned: <p1> <p2> <p3> <p4> <p5> <p6> <p7> <p8>

Where: <px> is the state of port „x‟

0 = relay not operated or valve closed

1 = relay operated, valve closed Example reply: <S>1GRTP 0 0 1 0 0 1 0 0<E>

ports 3 and 6 are in the active state.

9.6.8 Show analyser's gas name(s)

Example1 command: *GNME 1 Response 0GNME 2 CO2 (shows 1st gas name is CO2) Example2 command: *GNME 2 Response 0GNME 2 CH4 (shows 2nd gas name is CH4)

9.7 Remote Control Commands

The MGA analyser has two modes:

Remote control mode – front panel controls are ignored, all appropriate AK commands

accepted.

Manual control mode – front panel controls are available, only interrogation AK

commands are accepted.

The two modes avoid conflict between commands from front panel and remote control, as

only one can be in control at any time.

9.7.1 Set remote control mode

This command disables the front panel controls and enables all appropriate AK commands. It

can be sent to the analyser at any time. Command has no effect if the analyser is currently

in remote control mode.

Command: SREM

Parameters: none

Data returned: none

9.7.2 Set local control mode

This command enables the front panel controls. Setting AK commands are no longer

accepted. It can be sent to the analyser at any time. Command has no effect if the analyser

is currently in local mode.

Command: SMAN

Parameters: none

Data returned: none


50

9.8 Measurement Enquiry Commands

These commands are not accepted during calibration.

9.8.1 Get current readings

Command: AKON

Parameters: none

Data returned: <r1> [<r2> [<r3> [<r4>]]]

Where: <rx> is current gas reading, as a fixed point decimal

number without units or gas name.

<r1> is always present, <r2> only if a second gas is fitted

<r3> if a third, etc.

The reading is for the currently selected range in each case.

Example reply: <S>1AKON 0 2.1234 45.1223<E>

This example is from a dual gas analyser. Use the GRRD command to get details of full scale, gas and units. Note that the first reading comes from the lowest numbered channel present, and that missing channels are simply skipped.

9.9 Range Selection

Only permitted when in remote control mode, and not calibrating.

9.9.1 Select active range

Error NF is returned if the selected range is not fitted.

Command: SEMB


Where: <channel> is an integer 1..4 selecting gas / channel

<range> is an integer, 0 or 1;



Data returned: none

9.10 Gas Inlet Control Commands

These commands are only accepted in remote control mode, and will be rejected during

calibration.

9.10.1 Select sample inlet

Multi inlet options cover 2, 8 or 16 sample inlets. Valid parameters for inlet are 0 through

[number of inlets – 1]. Inlet 0 is always present. Command: SMGA

Parameters: <inlet>

Where: <inlet> sample inlet number as an integer.

If multiple inlets are not fitted, this must be zero

Error NF is returned if the selected inlet is not fitted.

Data returned: none

Note: inlet numbers displayed on the analyser screen start at 1, not zero. e.g. if SMGA

command is used with inlet parameter „2‟, the analyser screen will show the inlet as „3‟.


51

9.10.2 Select zero gas

This command switches zero gas through the analyser, to allow for zero check. Calibration is not attempted - concentrations can be read as normal. Error NF is returned if a zero gas

switching valve is not fitted.

Command: SNGA

Parameters: none

Data returned: none

9.10.3 Select span gas

This command selects span gas through the analyser, to allow for span check. Calibration is not attempted – concentrations can be read as normal. Error NF is returned if a span

switching valve is not fitted.

Command: SEGA

Parameters: none

Data returned: none

9.10.4 Sample pump control

Controls the analyser‟s internal sample pump. Note that error NF is returned if an internal

sample pump is not fitted.

Command: SRPS

Parameters: <on_off>

Where: <on_off> an integer to control the pump

0 to turn off the pump, <>0 to turn it on

Data returned: none

9.11 Calibration Commands

Again, these commands are only accepted in remote control mode, not when calibration is in

progress. Zero and span commands are only accepted after warm-up for all channels in

complete.

9.11.1 Perform auto-zero

Firmware version 2.07 and later offer two zero modes; „instant‟ and „automatic‟, specified by

an optional parameter. Earlier firmware allows only „automatic‟ zero.

For either case, zero is performed for all gasses and ranges simultaneously.

An automatic zero calibration executes as follows:

Freeze analogue output(s)

If a zero gas switching valve is fitted, switch to zero gas

Wait for a preset purge time interval

Attempt to set zero for all fitted gasses and ranges

Switch to sample gas (using previously set inlet)

Wait for preset purge interval

Release analogue output(s)

Automatic zero may take a few minutes to complete, depending on the gasses and ranges

fitted. Automatic zero cannot be aborted once started.

An instant zero calibration attempts to set zero using the current contents of the measuring

cells. There are no gas circuit changes or delays. It is assumed that the analyser is fully


52

purged with zero gas before sending an Instant zero command. Instant zero completes in 1-

2 seconds.

No error is given if the zero adjustment fails for any gas. Perform a zero check to verify if necessary. The SATZ command is not acknowledged until the zero cycle is completed.

Error WMUP is returned if this command is attempted while any channel is warming up.

Command: SATZ

Parameters: [<instant>]*

Where: <instant> is a letter „I‟, and, when present causes an instant

zero calibration.

This parameter is ignored prior to firmware 2.07.

Data returned: none

9.11.2 Set span gas concentration

This command is used to set the expected span gas concentration for a given gas channel and range and is used prior to performing a span adjustment. Error NF is returned if the

given channel or range is not fitted.

Command: SPGA

Parameters: <channel> <range> <conc>





<conc> is a real value specifying span gas concentration

as a proportion of the full scale range.

Accepted values are from 0.5 to 1.0. Values can be set to three decimal

places.

Data returned: none

Example command:

Range 1 on channel 2 is 5% CO2 full scale. We wish to set the analyser to expect 4.17%

span gas:

<S>*SPGA 2 1 0.8340<E>

9.11.3 Perform span calibration

This command causes the MGA analyser to calibrate the given gas and range immediately,

using the current gas measurement.

Before sending this command, ensure that:

Correct span gas has been applied to the analyser

Analyser cells have been purged with span gas

Reading has stabilised

Failure to verify any of these prerequisites may result in inaccurate span!

Only the selected range and channel is calibrated. The status of the calibration is reported. Error NF is returned if the given channel or range is not fitted. Error WMUP is returned if this

command is attempted while any channel is warming up.

Command: SATS





53



Data returned: none *

* Note: error ERR is returned if the calibration failed.


54

10. IMPLEMENTATION NOTES

The following provides guidance when writing software to communicate with the MGA

analyser.

1) The MGA analyser can handle only one AK packet at a time. Do not send a second

command until the reply is received from the first.

2) There may be a delay in processing commands at certain times (e.g. during calibration).

If the analyser is set to perform automatic zero periodically, it may be minutes before

responding.

3) There may be some delay between receiving the first part of the reply packet and the

end code. This delay may be some seconds for certain (notably calibration) commands.

4) The gas concentration readings are calculated every 800mS approximately. There is no

advantage in polling for readings at a rate faster than this.

5) The number and position of spaces in AK packets is important; each parameter must be

preceded by a one or more spaces. Any spaces following the last expected parameter

are ignored. There are no spaces between the <S>, address and command.

6) Where a real (or fractional) parameter value is expected, number strings with zero up to

four decimal places are accepted, as are leading zeroes. The decimal point is optional.

Scientific format (exponent) number strings are not accepted.

7) Where an integer numeric parameter is expected an arbitrary number of leading zeroes

are accepted. Decimal points are not allowed in integer parameter values. See

command descriptions for parameter details.

8) The MGA returns real number values formatted as fixed point with four decimal places.

9) Performing a „soft reset‟ allows remote control mode to be cancelled without using the

serial link. Pressing the top and bottom soft keys together performs a soft reset – the

analyser will perform a warm start and return to local control.


55

11. KNOWN ISSUES

This list is comprehensive as of the date of printing.

When switching to remote control using the SREM command, ensure that the main results

screen is displayed. Other screens may appear corrupted by remote control commands.

Sample gas may be restored on setting the analyser back to local control if span or zero gas

was previously selected.

Analyser fail indication (bit 0 in status code digit) is not yet implemented – all other

indications work as described.


56

Authorised Local Agent:

ADC Gas Analysis Limited

Unit 35, Hoddesdon Ind. Estate

Pindar Rd, Hoddesdon

Herts, EN11 0DB

United Kingdom

Tel: +44-1992478600 Fax: +44-1992478938

Email: [email protected]

Web: http://www.adc-gas.com

mailto:[email protected]

http://www.adc.service.co.uk/

version 3 - envco · 2014. 10. 4. · adc gas analysis ltd has a comprehensive range of analysers...

Documents