How To Calibrate Differential Pressure Transmitter

How To Calibrate Differential Pressure Transmitter/Procedure for Differential Pressure Transmitter Calibration.

Types of equipment required:-

1. 24 VDC power supply
2. Multimeter digital
3. Pneumatic hand pump
4. Low-pressure hand pump
5. High precision digital test gauge
6. HART communicator

The procedure For DPT transmitter bench Calibration:-

1. Remove the differential pressure transmitter from the process
2. Make sure the equalizing valve manifold is closed.
3. connect the transmitter with the calibration equipment as shown in fig
4. Apply the LRV pressure with the handheld test pump and check the multimeter reading
5. If it is not 4ma then calibration is required.

If the transmitter is an analog transmitter:-

1. By applying 0% pressures by test pump adjust the zero pot in
2. transmitter to get 4ma output in a multimeter.
3.  Apply 100% pressure and adjust span pot to get 20ma in a multimeter.
4. Check for 25%, 50%, and 75%.
5.  Repeat the process to ensure that no error occurs

In case of SMART Transmitter:-

We have to use the HART communicator, connect the communicator with the transmitter select the HART Communicator Menu for lower range value trim and upper range value trim.

1. Basic Set up – Calibration – Zero Trim/Sensor Trim —Lower/Upper range value trims.
2.  HART communicator will automatically calibrate the transmitter.
3.  Restore the process connection
4. Take the transmitter on line. Ensure there is no leak

Calibration of DP Transmitter in the field.

Transmitter range = 0-2 kg/cm2

LRV = 0 kg/cm2

URV = 2 kg/cm2.

Note: Capillary flange at the same elevation

Equipment required:-

1. Data sheet,
2. Pressure calibrator,
3. Hart communicator.
4. Multimeter,

The procedure of DP Transmitter Calibration:-

Select the controller in manual mode for the control loop and to put it on MOS for the ESD loop. Hook up HART Communicator and verify some parameters by referring to the datasheet. Isolate the instrument from the process.
Open vent valve at drip ring and open plug at the top of the drip ring(if available) to release the process pressure. Clean the liquid inside the drip ring and put back the plug for the high side. only (if available) & Expose the low side to the atmosphere. Hook up a multimeter in series with the signal to the DCS to measure the current signal. In this condition, both capillary flanges will be atm pressure at difference high. Multimeter should show 4mA and PV at HART communicator should show 0 (LRV). If not, do zero adjustments at transmitter using HART Communicator. Connect pressure calibrator to high side flange (drip ring). Apply pressure depends on the datasheet span (URV). Multimeter should show 20mA and PV at HART communicator should show the same with URV. 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.