B872-200 Calibration
(Original Document)
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Principle
The analog output module is calibrated at the factory prior to shipment. To ensure the module's accuracy, you should calibrate the trim-pots for each output regularly. Calibration is recommended at 12 month intervals for operation between 25-45 °C, and at 6 month intervals between 0-60 °C.
Required Tools
The following tools are needed to calibrate an analog output module:
1) A programming panel
2) A precision voltmeter, with an accuracy of +/-0.0001 volts on a 10 volt scale
3) A 1/4 inch Phillips screwdriver
4) A 1/8 inch standard screwdriver
Calibration Procedure
The following table shows the steps to calibrate the B872-200 module:
Step
Action
1
Remove the two screws and the label located on the front panel of the analog output module. This allows you access to the trim-pots. There is one trim-pot per output. The first trim-pot is for output number one, the second set is for output two, etc. The trim-pots adjusts the range's total magnitude (full scale). Refer to the figure below.
Note The 0.1% tolerance is the maximum FSR accuracy achievable thru calibration for any volt range. Calibrating any range to the 0.1% tolerance throws the other slightly off; i.e., tolerances for the remaining ranges available to that channel cannot be assumed better than +/- 0.25% FSR.
2
Open the analog output module handle to expose the connectors and terminals.
3
Connect the voltmeter minus lead (-) to the channel 1 (Analog Common CH1) and the plus lead (+) to the channel 1 (Analog Output CH1) terminal. Refer to the voltmeter connections diagram below.
Note Field wiring may remain connected during calibration.
4
With the desired voltage range already selected. Manually program a data value of 4095 into the output register for channel two. Compare channel output voltage with anticipated voltmeter reading given in the table below.
5
Adjust the (full scale calibrate) trim-pot for corresponding channel to get desired voltmeter reading.
6
Repeat steps 3 through 5 for remaining channels.
7
After the calibration procedure is complete, disconnect the voltmeter, return all connections to their original state, close the module handle, and replace the front label that covers the trim-pots.
END OF PROCEDURE
Location of Trim-Pots
The following figure shows the location of the Trim-Pots on the B872-200 Module.
Voltmeter Connections
The following figure is the voltmeter connections diagram for the B872-200 module.
Data Value to Output Channel
The following table gives data value to output channel, for the B872-200 module.
Selected Voltage Range
Data Value
Voltmeter Reading
-5 to 5 V
4095
4.9976
-10 to 10 V
4095
9.99951
0 to 5 V
4095
4.9988
0 to 10 V
4095
9.9976