ISOL

ATOR

SHIGH ACCURACY / 0.05%

SMALL SIZE / HIGH PACKING DENSITY

INPUT AND OUTPUT POWER VERSION

VERY LOW COST VERSION

SIGNAL SPLITTING VERSION

LOOP BOOSTERS FROM A SINGLE SUPPLY

52-215-2091-02

Green Lane Tewkesbury Gloucestershire UK GL20 8DE Tel: 01684 853300 Fax: 01684 293746Email - sales@status.co.uk Web site: http://www.status.co.uk A RICHTEC PLC GROUP COMPANY

PROCESS SIGNAL ISOLATORSSEM1000 SeriesDESCRIPTIONThe SEM1000 series of loop powered analogue signalisolators comprises versions that are suitable for mostapplications, regardless of whether the loop power is availableat the input or output side of the isolator. There is also a loop'splitter' which produces two completely isolated outputs from asingle input.

Various special applications can be realised such as loopboosting and driving into 900 ohms from a barrier protectedIS circuit, using the SEM1020 low cost version.

The small size of the SEM1000 series enables many moreunits to now be installed in the same physical space.

Their high accuracy permits the addition of isolation tosystems without significantly degrading the overall systemperformance. The zero and span adjustment potentiometerscan be used to remove any system errors.

SPECIFICATION @ 20°CGENERALIsolation 1000V AC RMS (Flash tested to 3KV)Accuracy 0.05% (Including Hysteresis and Linearity)Stability 100 ppm/°CAmbient 0 to 70°C; 10 to 95% RH Non-condensing Time Constant 0.1Sec (to 63% of final value)Cable Size 4mm2 Solid / 2.5mm2 StrandedMaterial Polyamide (Grey)Flammability To UL94-VO VDE 0304 Part 3 Level IIIAMounting Top Hat rail to DIN EN 50022-35Adjustments Front entry Zero and Span potentiometers

APPROVALS EMC All versions are tested to:IEC 801-2 Susceptibility to electrostatic dischargeIEC 801-3 Radiated SusceptibilityIEC 801-4 Susceptibility to conducted interferenceEN 55022 Radiated emissions

GROUND OR EARTH LOOPS. What are they and how can they be removed?

APPLICATIONS

SEM1000Most analogue loops are grounded at a single point, indeed wiringstandards often specify that loops should be grounded at a singlepoint. Problems occur when there is more than one grounding pointbecause earth potentials are never the same, and earth currentsflow between the two points causing errors, noise or erratic signals.

Eliminating multiple grounds can be difficult or even impossiblebecause of system requirements or if the particular instrumentationto be used has multiple non-isolated inputs. In other applications,there may be a safety requirement to earth through, say, Zenerbarriers. Even when the system has been designed to have a singleearthing point, sometimes leakage, through, for instance, mineralinsulated thermocouple probes can give an unexpected path toearth and cause unwanted errors.

A simple way to ensure the removal of ground loops is to use signalisolators. These isolators accurately transfer the analogue signalwhilst at the same time effectively blocking the DC continuitybetween the input and the output of the isolator.

Isolators can be loop powered, i.e. they do not require any externalpower source, or externally powered. Loop power obviously has anadvantage in that no external power supply is required, however inorder to work they require some power which is supplied in the formof a loop voltage drop i.e. there is some voltage required for theisolator and hence less voltage available for other devices in theloop. Some isolators also double as signal convertors such that avoltage signal can be isolated and converted to a 4-20 mA signal inthe same device.

The choice of isolator often comes down to whether power isavailable on the input side or the output side of the isolator, and alsoif there is sufficient voltage available in the loop to power a looppowered isolator.The SEM1000 series provides a complete family of small highaccuracy isolators to suit almost every application.

ISOLATING INPUTS INTO A PLCPLCs or similar systems often have high level non-isolated inputs.

Inserting the SEM1000 into an existing powered 4-20mA loopprovides a simple low cost means of providing complete signalisolation. Use a resistor in the output loop to provide a voltagesignal

DRIVING TWO EARTHED LOOPSA field transmitter and control room device can often have differentearths.

Inserting the SEM1000 into the loop enables both earths to beconnected to the signal lines without the introduction of earth loops.

A SYSTEM WITH MULTIPLE INPUTSMany systems have a number of inputs that require isolation. Usingconventional isolators, a separate power supply is required for eachloop in order to completely isolate each input from each other.

By using the SEM1010 a single power supply at the system sideproduces a separate isolated power supply for each fieldtransmitter as well as isolating and repeating the transmitter signal.

LOOP BOOSTING (Non-isolated)In certain applications there can be a number of devices in a loop, eachrequiring some volts from the loop. Often there is a requirement formore volts than the loop can supply.By using the SEM1020 low cost isolator, connected as shown, anadditional load up to 900 ohms can be driven from a single 24Vsupply.*NB. Input and output loads can be driven from separate suppliesto maintain isolation.

UP TO 900 OHM DRIVE FROM IS CIRCUITSWhen field transmitters are in hazardous areas, they are normallyprotected by the inclusion of a zener barrier. Zener barriers have atypical series resistance of approximately 300 ohms and so it canbe difficult on occasions to provide sufficient drive capability forseveral safe area devices.

The SEM1020 provides an economic means of creating anadditional drive capability, of up to 900 ohms, from a single 24Vsupply.

SIGNAL SPLITTINGIn modern control systems there are frequent requirements to send acommon signal from a field transmitter to two different pieces ofequipment e.g. a control system and a recorder. Because of earthloop effects or because the designer wants to ensure that any fault atthe recorder has no effect on the control system, both signals shouldbe isolated from each other.

The SEM1200 is designed to satisfy this requirement, taking asingle 4-20 mA loop and providing two identical isolated 4-20 mAoutputs.

SUBTRACTOR (Non-isolated)It is a frequent requirement to provide a different output from two 4-20 mA transmitters. The circuit shown enables each transmitter tobe used independently and at the same time produce a 4-20 mAoutput signal proportional to the difference between the two signals.4-20 mA = A – B*NB. Input and output loads can be driven from separate suppliesto maintain isolation.

ADDER (Non-isolated)In a similar way to the Subtractor outlined above, the adder circuitenables the outputs from two 4-20 mA transmitters to be usedindependently whilst providing an isolated output proportional to thesum of the two signals.4-20 mA = A + B*NB. Input and output loads can be driven from separate suppliesto maintain isolation.

Every effort has been taken to ensure the accuracy of this specification, however we do not accept responsibility for damage, injury, loss or expenseresulting from errors and omissions, and we reserve the right of amendment without notice.

ORDER CODE DEVICE SUMMARYINPUT OUTPUT CASE POWER NOTES

REQUIREMENTS *Mechanical details page 1SEM1000 4-20 mA 4-20 mA A INPUT Replaces SEM100SEM1010 4-20 mA 4-20 mA B OUTPUT Replaces SEM101SEM1015 ±0.1-100V 4-20 mA A OUTPUT Voltage to current conversionSEM1020 4-20 mA 4-20 mA A INPUT & OUTPUT Low costSEM1200 4-20 mA 4-20 mA C INPUT & OUTPUT 1 x input, 2 x outputs 4-20 mA

BLOCK DIAGRAMS and CONNECTION DETAILSSEM1000The SEM1000 is designed to be inserted in an existing 4-20 mA loopand provides an isolated 4-20 mA signal driving into a load up to500 ohms.Loop volt drop = 5V Typical 5.5V Max (plus load)If output load =250ohm. Volt Drop =5+(0.02+250�)=10V

SEM1010The SEM1010 provides isolated power for a field transmitter fromthe 4-20 mA output. It requires a single DC power supply (Vs) onthe output.

(Max Load R1) = Vs-5 – Tx Volts K ohm20Vs is 24V nominal or 30 Max. Loop volt drop @ 24V = 5V

SEM1015This series provides an isolated 4-20 mA output from a voltage input.They require a single DC power supply (Vs) on the output.

(Max Load R1) = Vs-8 K ohm20Vs is 24V nominal or 30 Max.SEM1015 Vin = ±0.1V to 100V (user selectable)(note: current inputs can be monitored by use of external resistors)

SEM1020The SEM1020 is a low cost isolator that requires power on bothsides of the isolation barrier. This must of course be provided by twosupplies isolated from each other to maintain isolation.Loop volt drop = 2.7V Load R1 = 900 ohm @ Vs = 24V

Load R1 = 1200 ohm @ Vs = 30VVs is 24V nominal or 30 Max

SEM1200The SEM1200 is an isolator that provides two isolated 4-20 mAoutputs from a single 4-20 mA input. It requires power for all loops.Loop volt drop = 5V Load R1 =900 ohm @ Vs = 24V

Load R1 =1200 ohm @ Vs 30VLoads must be >250R for ambients >50 CVs 30V max(For best stability keep max volt drop across outputs to <15V)

DIN RAIL PRODUCTSALSO AVAILABLE

SEM1100 MAINS POWERED PROCESS ISOLATOR/CONVERTERSEM1401/2 LOOP POWERED TRIP AMPLIFIERSSEM1300 24V POWER SUPPLY 90-240VAC INPUTSEM1500 PT-100 & T/C SIGNAL CONDITIONERS

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