Calibration of Differential Pressure Transmitter Capillary Tubes

When you use capillaries you need to do the calibration completely differently from normal, so be careful when using capillaries in level application.

Information Needed

Data sheet

Equipment Needed

Pressure calibrator (std.)
Multimeter (std.)
Hart communicator (used in this example).

Steps to Calibrate

  1. Ensure that the control valve is isolated from the process if working on live system or newly installed system. “IMPORTANT USE LOCK OUT TAG OUT Procedures”

  2. Make sure the controller is in manual mode for the control loop.

  3. Verify steps 1 and 2 are done a second time to insure safety of yourself and others that may not be involved in the process being worked on.

  4. Open vent valve at drip ring and open plug at the top of the drip ring (if available) to release the process pressure.

  5. Clean the liquid inside the drip ring and put back the plug for high side only (if available).

  6. Expose the low side to atmosphere.

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

  8. In this condition both capillary flange will be atmospheric pressure at difference high.

  9. Multimeter should show 4mA and PV at HART communicator should shows 0 (LRV).

  10. If not, do zero adjustment at transmitter using HART Communicator.

  11. Connect pressure calibrator to high side flange (drip ring).

  12. Apply pressure depend data sheet span (URV).

  13. Multimeter should show 20 mA and PV at HART communicator should shows same with URV.

  14. If not, do span adjustment at transmitter using HART Communicator.

  15. Verify the linearity by increasing and decreasing the pressure (0%, 25%, 50%, 75%, 100%, 75%, 50%, 25% and 0%of range).

  16. After the calibration and it has been verified put loops back in normal mode or normalize the MOS.

  17. Document all work having been done on standard calibration form and properly log in system used and update any job books required by company.