how to create a set file

7/26/2019 How to Create a SET File

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TRAINING REPORT

MBK408 Hardware and Rejust-It Software

Chamari Deshika


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Table of Contents

1. INTRODUCTION ......................................................................................................... 3

2. MBK408 HARDWARE ................................................................................................. 3

3. REJUST-IT SOFTWARE ................................................................................................ 4

4. BRIDGE AND TC ADJUSTING REJUSTOR ...................................................................... 4

5. OFFSET ADJUSTING REJUSTOR ................................................................................. 13

6. SPAN ADJUSTING REJUSTOR .................................................................................... 17


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1. INTRODUCTION

This document describes the guidelines for designing SET files of Rejustors. Rejust-it

software is designed to adjust the resistance of the Rejustor in the application circuit. The

circuitries use mainly three types of rejustors from Micro Bridge Technologies. There are,

Bridge and TC Adjusting Rejustor

Offset Adjusting Rejustor

Span Adjusting Rejustor

2.

MBK408 HARDWARE

Basically this hardware comprises of ADC channels and DAC channels. ADC channels

are to make measurements of the analog voltages of the sensor in use. DAC channels areto send heating pulses to the heater pins of the Rejustors. This is fully controlled by

Rejust-It software in a PC via a USB connection. The functional block diagram of the

hardware is shown below.

Figure 01: Functional Block Diagram of MBK408


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3.

Rejust-it SOFTWARE

This is a National instruments LabVIEW based software in which MicroBridge has

implemented all the necessary algorithms to perform trimming or rejusting in their

terminology. Key to the successful trimming is the appropriate *.set file which can

closely represent the system behavior of the sensor. How to create a *.set file is detailed

below.

4.

BRIDGE AND TC ADJUSTING REJUSTOR

This Rejustor is known as eTC bridge rejustor in the sense its temperature coefficient

(TC) can be adjusted electrically as well as its resistance. MBT303 type rejustor is

selected for the further explanation.

MBT303

This is coming in a QFN package and having two resistors in a bridge which are meant to

be connected in parallel with strain gauges of a bridge as shown in Figure 02. Each

resistive element is having 30k of as manufactured value and their resistance can be

trimmed down to 30% of that value - up to 21k.

One arm of the bridge has a single resistive element. One resistive element (one Arm of

the bridge) comprises two separate resistive elements having positive & negative

temperature coefficients (TC) respectively. This can be shown as follows.

Figure 02: MBT 303 Schematic


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The final resistance is the addition of the resistance of two elements and same applies for

the TC. So if the A element is trimmed, the resistance is reduced and so is the

modulus value of the TC. As a result the overall resistance is reduced and the TC

becomes more positive. If theBelement is trimmed the resistance is reduced and so

is the modulus value of the TC. As a result the overall resistance is reduced and the TC

becomes more negative.

Creation of the *.set file used for Rejustor MBT303

a) Create *.tf file using Transfer Function Editor.exe (TFE) coming with the

MicroBridge 408A Hardware driver CD.

C: Program Files Rejust_It_eTC Open Transfer Function Editor.exe

Figure 03: eTC Rejustor Resistive Element

Figure 04: Screen shot of file path


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b) The List of Schemes displays. Select the eTC divider 1 (Ratio) from the

Adjustment scheme type

c)

List of Schemesshows sample circuit and equation of the eTC divider 1 (Ratio).

Figure 05: Screen shot of List of Schemes

Figure 07: Sample circuit of eTC_dividerFigure 06: Strain Gauges Bridge


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Figure 06 is shown the arrangement of the Strain gauge Bridge and the MBT303

bridge rejustor.

R1, R2, R3 and R4 are representation of Strain gauges (5k)

R7 and R8 are rejustor resistance value (30k) R5 and R6 are parallel with rejustor (22k)

Figure 07 is shown the sample circuit of eTC divider 1 (Ratio). According to the

equation,

Figure 08: Second stage Amplifier Circuit


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The sensor transfer function is represented the following equation.

[ ]

- The mV/mV output of the strain gauge bridgeThe gain of the first stage instrumentation amplifierThe gain of the second stage amplifierThe nominal offset voltageThe bridge excitation voltage

{ }

Comparing with above equation (1) and (2)

( )


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d) The required parameters for the eTC divider 1 (Ratio) is shown below. Only the

parameters marked with red are to be changed as shown. Others are left as defaults.

Once parameters have been set click on Drawbutton will give the output relationship

of the strain gauge bride arrangement with the EAR network.

Parameters Value Remarks

Rpar1 & Rpar2 5000Parallel Resistance with rejustor (Strain gauge

Resistance)

Rser1 & Rser2 22000 Series Resistance with rejustor

Rj1 and Rj2 30000 Resistance of one arm of the Rejustor

Xmax 0.4 Maximum trim down fraction allowed

Offset 0.5 Calculated value

Gain -7030000 Calculated value

Figure 09: Screen shot of eTC divider (Ratio)

Table 01: Parameters of eTC divider 1 (Ratio)


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e) File Save transfer function Select location (Application Circuit folder of

Rejust_It_eTC) Save

f) Load the Circuit Configuration Editor.exe (CCE) and create the *.set file. The

parameters are shown in the below.

1: Only one adjustable parameter which is the sensor output is used in rejusting

MBT303.

2: The adjustable parameter name can be anything of interest

3: The adjustment type is Bridge_TC because MBT 303 is a bridge type rejustor

4: DAC channels of the MBK 408 hardware connecting to heater pins of the MBT303

5: The *.pow file corresponding to the rejustor type connected to the respective heater

pin- whether A type or B type as described in the above section. This file is

coming with the Rejust-It software installation.

Figure 10: Circuit Configuration Editor


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MBK DAC .pow file Rejustor Type

2 MBT303B B1

3 MBT303B B2

4 MBT303A A1

5 MBT303A A2

6: The *.tf file created in first should be introduced to the CCE. Click onImport

Data From Fileand select the *.tf file created.

7: Click on a DAC channel on the above table and select the respective type A or

B from the drop down menu of Rejustor Type and assign transfer function

parameters. It is represented in Table 02. Do same for all the DAC channels.

8: Notice the CCE screen changes as in Figure 10.

9: Since only one parameter (Sensor output) is being looked at only one ADC channel

is required. Enter 3 after checking V1.

g) Next click on How to Measure Adjustable Parameter and Rejustor Conditions

screen pops up as shown in Figure 11.

Table 02: Parameters of DAC

Figure 11: Rejustor Conditions Screen


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h) Leave the conditional check box unchecked. Since the adjustable parameter (sensor

output) is directly related to the bridge outputs, the measurement of the sensor output

is not needed to be manipulated before read by Rejust-It software. So the

coefficients are set (A1=1 & B0=1) such that one to one reading is read by the

software. Once coefficients are set click on Set Condition button and close the

window.

i)

Once all the above steps are completed click on Save Settings button. And save the

*.set file with a preferred name. That file is shown as follow.

Figure 12: Created SET file


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5.

OFFSET ADJUSTING REJUSTOR

MBD-103-ES

The MBD 103 is a QFN package and having two resistive elements (1:9 dual resistors).

Each resistive element is having 10K and 90K; theirresistance can be trimmed down

to 30% of that value up to 7Kand 63K respectively. The package schematic is shown

below.

R1ADJ & R2ADJ are heater pins used for adjustment and are connected to MBK408

hardware. These rejustors are used in adjusting the offset voltage.

Creation of the Offset_Down.set file used for Rejustor MBD103

If the bridge is balanced and offset rejustor is sitting at its as manufactured value the

output is approximately equal to Voffset (Voffset 0.5V).

a)

The transfer function is defined as follows accordance the Figure 14.

The Operational Amplifier is configured for unity gain.

Figure 13: MBD 103 Schematic


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b) Output variation for the fractional change of the resistance of the rejustor can be

determined.

Eg: Trim down fraction = 0.05

Resulting values are shown below.

Trim down

Fraction

Voffset_Down

(mV)

0 400

0.05 382

0.1 364

0.15 345

0.2 326

0.25 308

0.3 289

0.35 269

0.4 250

Figure 14: Reference Buffer Circuit

Table 03: Voffset_Down with Trim down fraction of Rejustor


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c) This table can be used directly in CircuitConfigurationEditor.exe (CCE). The

CCE is same as above and the parameters are shown below.

Select the correct Rejustor Type (*.pow file) to connected to the respective heater pin.

d)

Using the

How to Measure Adjustable parameter

is exactly same as the abovecase. After all the necessary parameters are entered the *.set file can be created by

clicking theSave Settingsbutton.

Figure 15: CCE for Creating Offset_Down.set


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Creation of the Offset_Up.set file used for Rejustor MBD103

a) Output variation for the fractional change of the resistance of the rejustor can be

determined.



b) This table can be used directly in CircuitConfigurationEditor.exe (CCE). The


Trim down

FractionVoffset (mV)

0 400

0.05 4190.1 440

0.15 462

0.2 488

0.25 516

0.3 548

0.35 584

0.4 625

Fiure16:CCEorCreatinO

setU.set


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c) Using theHow to Measure Adjustable parameteris exactly same as the above

case. After all the necessary parameters are entered the *.set file can be created by


6. SPAN ADJUSTING REJUSTOR

MBD-903-AS

The MBD 903 is a QFN package and having two resistive elements. Each resistive

element is having 90K; their resistance can be trimmed down to 30% of that value up to

63K respectively. The package schematic is same as the above Figure 13.

Creation of the Span_Down.set file used for Rejustor MBD903

a) The output voltage is defined as follows accordance the Figure 17.

First stage output is,

Second stage output is

- The mV output ofthe strain gauge bridgeThe gain of the first stage instrumentation amplifierThe gain of the second stage amplifierThe nominal offset voltage

( )


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( )

Figure 17: MBD 903 Schematic


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This table can be used directly in CircuitConfigurationEditor.exe (CCE). TheCCE is same as above and the parameters are shown below. Select the correct

Rejustor Type (*.pow file) to connected to the respective heater pin.

Trim down


0 3001

0.05 2963

0.1 2920

0.15 2878

0.2 2828

0.25 2776

0.3 2720

0.35 2656

0.4 2590

Figure 18: CCE for Creating Span_Down.set


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b) Using theHow to Measure Adjustable parameteris exactly same as the above

case. After all the necessary parameters are entered the *.set file can be created by


Creation of the Span_Up.set file used for Rejustor MBD903

a) The output voltage is defined as follows accordance the Figure 17.

First stage output is,

Second stage output is

( )

Eg: Trim up fraction = 0.05


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b) This table can be used directly in CircuitConfigurationEditor.exe(CCE). The


Trim down


0 3001

0.05 3035

0.1 3053

0.15 3073

0.2 3096

0.25 3120

0.3 3150

0.35 3183

0.4 3223

Figure 19: CCE for Creating Span_Up.set


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c) Using the How to Measure Adjustable parameter is same as the above case.

After all the necessary parameters are entered the *.set file can be created by clicking

theSave Settingsbutton.

how to create a set file

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