- Assume the valve is a 4-20mA operated pneumatic valve. It also has a 4-20mA valve position feedback output.
- Connect the universal calibrator (or source) to the input of the valve.
- Connect the multimeter at the valve position feedback output as shown in above the setup figure.
- Select the Source function in universal calibrator and the knob will help to vary the mA (4 to 20mA).
- Select 4mA in the calibrator (also called as source meter). The control valvewill show a 0% valve position. We can verify the valve position on the scale provided on the control valve.
Also, the valve has 4 – 20mA output which indicates valve position feedback. We connected a multimeter to measure this valve position feedback. The valve position feedback range is 0 to 100 percent which is equivalent to 4 to 20mA. In this case, the multimeter will show 4mA.
- Now increase the current (mA) in the calibrator from 4mA to 8mA. Now the valve will travel from 0% to 25%. The multimeter will show 8mA valve travel position feedback (25%).
- Now increase the current (mA) in the calibrator from 8mA to 12mA. Now the valve will travel from 25% to 50%. The multimeterwill show 12mA valve travel position feedback (50%).
- Now increase the current (mA) in the calibrator from 12mA to 16mA. Now the valve will travel from 50% to 75%. The multimeter will show 16mA valve travel position feedback (75%).
- Now increase the current (mA) in the calibrator from 16mA to 20mA. Now the valve will travel from 75% to 100%. The multimeter will show 20mA valve travelposition feedback (100%).
- Now we tested the control valve from 4mA to 20mA upward direction. Now repeat the same in downward direction i.e. from 20mA to 4mA in steps.
- Note: While sourcing you can view the Feedback on multimeter these will be nearby reading to source mA.
- Now we completed the upward test from 4mA to 20mA. Repeat the same steps in a downward direction also i.e. from 20mA to 4mA in steps.
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