• ## Diaphragm Seal and Instrument Assembly

Calibration procedure – Displacer type level transmitter

Procedure:

*Ask panel man to put the controller in manual mode for control loop and to put it on MOS for ESD loop.
*Hook up HART Communicator and verify some parameters by refer to data sheet. Typical parameters are, tag number, PV, LRV and URV.
*Isolate the instrument from the process.
WARNING – If the process is hazardous, please unsure proper flushing is done to remove the entire hazard.
Remove isolation drain valve and open the vent flange
*Connect water pump to drain line and line up the reference tube
*Calculate the new measurement to get equivalent up trust force with S.G and length
*Mark on the chamber for reference calibration
*Hook up a multimeter in series with the signal to the DCS to measure current signal.
*Apply water level until 0% marking on chamber
*Multimeter should show 4mA
If not, do zero adjustment at transmitter using HART Communicator
Apply water level until 100% marking on chamber
*Multimeter should show 20mA
*If not, do span adjustment at transmitter using HART Communicator
*Verify the linearity by increasing and decreasing the pressure (0%,25%,50%,75%,100%,75%,50%,25% and 0%of range)
*After completion of the job ask panel operator to put loops back in normal mode or normalize the MOS

Example Calculation:
Low S.G=0.802
High S.G= 0.992
A= 810mm (measurement length)
0%    = (A x Low S.G)
= (810 x 0.802)
= 649.42 mm
100%     = (A x High S.G)
= (810 x 0.992)
= 803.52 mm

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## 1 thought on “How to calibrate Displacer level transmitter”

1. I have a displacer level transmitter which must work at 4-20ma for 0-400mm level changes.

when I change level from 400mm(at the top of displacer) to 300mm, current will reduce from 20ma to 16ma. when we reduce level more, the current not only reduce but also increase! so we haven't range from 0-300mm.

How can we solve this problem? we have a HART COMMUNICATOR as a calibrator tools.

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