Siemens sitrans tr200, Operating Instructions Manual

Page: 45 / 78

Functions
8.14 Current sensor calibration (digital-to-analog trim)
SITRANS TR200/TR300
Operating Instructions, 04/2007, A5E01071992-01
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8.14 Current sensor calibration (digital-to-analog trim)
This function allows you to calibrate the current output by the transmitter irrespective of the
process circuit. This function allows compensation of inaccuracies in the process chain
downstream from the transmitter. The trim can only be performed as follows:
●
SITRANS TR200: at 4 mA and at 16 mA
● SITRANS TR300: at 4 mA and at 20 mA
The "Sensor calibration: Example of 4 to 20-mA output" diagram shows an example of the
principle of calibration for a 4 to 20 mA current output.
Application example: Current output calibration at 4 mA and 20 mA
The current is to be measured as a voltage drop from 1 to 5 V at a resistance of 250 Ω +/-
5%. To trim the tolerance of the resistance, set the current sensor so that the voltage drop at
4 mA is exactly 1 V and at 20 mA is exactly 5 V.
NOTICE
The multimeter used must have a higher accuracy class than the transmitter.
Trim at 4 mA:
1.
Use the menu item D/A trim to assign 4 mA output to the transmitter.
2. Read the measured value at the voltmeter.
3. Calculate the current value from the measured value.
4. Enter the calculated current value using the operating software.
The transmitter uses this value for offset correction of the current.
Trim at 20 mA:
1.
Use the menu item D/A trim to assign 20 mA output to the transmitter.
2. Read the measured value at the voltmeter.
3. Calculate the current value from the measured value.
4. Enter the calculated current value using the operating software.
The transmitter uses this value for gradient correction of the current. The value for 4 mA is
not affected by this.