v  Equipments required


  • Pressure transmitter,
  • Multimeter,
  • HART communicator,
  • Hand-held test pump (pressure source).

 

 


v  Procedure OF Pressure Transmitter online calibration

  • Isolate the Pressure Transmitter from the Process.
  • Slowly open the vent plug and the vent valve to release the pressure.
  • Connect the multimeter with the transmitter and ensure that the output is 4ma when 0% pressure is applied.
  • Connect the hand held test pump (pressure source) to the transmitter. Ensure there is no leak.
  • Apply pressure range at 0%, 25%, 50%, 75%, and 100% and check if there is any error.
  • If there is any error calibration should be done.

    If the transmitter is analog transmitter

  • Apply 0% pressure as per LRV with hand-held test pump and check multimeter if it is not 4ma adjust the zero pot in the transmitter and correct transmitter output to 4ma
  • Apply 100%pressure as per the URV and correct 20ma in multimeter by adjusting span pot in the transmitter
    • NOTE: Repeat these steps to rectify error.

In case of SMART Transmitter



We have to use a HART communicator. Connect the communicator with the transmitter and select the HART Communicator Menu for lower range value trim and upper range value trim using these steps:


  • HART communicator will automatically calibrate the transmitter
  • Restore the process connection
  • Take the transmitter on line. Ensure there is no leak

NOTE: Small example of five point calibration is given below:

Low range value          =          0psi Upper range value        =          200psi

PERCENT OF RANGE (%)

INPUT PRESSURE

OUTPUT CURRENT (IDEAL)

0%

0 PSI

4.00 mA

25%

50 PSI

8.00 mA

50%

100 PSI

12.00 mA

75%

150 PSI

16.00 mA

100%

200 PSI

20.00 mA

75%

150 PSI

16.00 mA

50%

100 PSI

12.00 mA

25%

50 PSI

8.00 mA

0%

0 PSI

4.00 mA