Calibration Procedure : Differential Pressure Flow Transmitter

How to calibrate flow DP transmitter 

Material

Data sheet

Pressure calibrator (std)

Multimeter (std)

Hart communicator

Step

*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.

*Release both pressure and drain low and high side liquid throughout manifold drain.

*Connect pressure calibrator to high side of manifold

*Expose the low side to atmosphere

*Hook up a multimeter in series with the signal to the DCS to measure current signal.

*Apply pressure as per data sheet LRV (normally 0mmH2O)

*Multimeter should show 4mA

*If not, do zero adjustment at transmitter using HART Communicator

*Apply pressure as per data sheet URV

*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

Fill the calibration form and file it for future reference.

Example calculation

Instrument calibrated range: 0 – 2500 mmH2O

Process calibrated range: 0 – 105000 Nm3/h

Q =K  P

0%  0 mmH2O = ( 0/2500) x 105000

= 0 Nm3/h 

50%  1250 mmH2O = ( 1250/2500) x 105000

= 7424.6 Nm3/h 

100%  2500 mmH2O = ( 2500/2500) x 105000

= 105000 Nm3/h