How to calibrate capacitance level transmitter?

Field Instrumentation Calibration
1

Procedure of capacitance type level Transmitter calibration:

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  • Remove the level transmitter from the system (tank).

  • Check whether the transmitter shows zero reading by connecting with multimeter otherwise release the pressure.

For a smart transmitter:

  • Connect 475 hart communicator and multimeter to the transmitter.

  • Put Multimeter to ma.

  • Fill in the correct density of the corresponding liquid and record the readings. Fill fluid in ascending and descending orders at 25%, 50%, 75% and 100% and write down the measurements.

  • Check for errors if there is zero and span adjusts should be done.

For zero calibration:

  • Drain the liquid and check the multimeter if not 0, then go to the HART sensor trim option and go to zero trim and the HART communicator automatically trim the sensor to zero.

For span calibration:

  • Fill 100 percent and wait a while for the sensor to be trimmed and pick the length cut in the HART communicator.

  • After completing zero and span trimming, check the reading again at 0%, 25%, 50%, 75% and 100%.

In case of non smart capacitance type transmitter:

Connect a multimeter and rotate the zero pot and stop when multimeter shows 4ma. Fill the chamber to maximum liquid level and rotate the span screw to 20ma.

Repeat these steps and check all readings

2

Calibrating a capacitance level transmitter involves the following steps:

1. Preparation

  • Isolate the Transmitter: Ensure the transmitter is isolated from the process and powered off to prevent interference.
  • Check Equipment: You’ll need a standard calibration tool such as a signal generator, multimeter, and a calibrated reference level.
  • Inspect Wiring: Verify that all wiring and connections are intact and correct.

2. Zero Calibration (Empty Tank)

  • Empty the Vessel: Ensure the vessel or tank is at its lowest level (preferably empty).
  • Adjust Zero: Apply power to the transmitter. Using the calibration interface (either buttons or software), set the zero point by adjusting the transmitter to output the corresponding signal for an empty tank (e.g., 4 mA for a 4-20 mA transmitter).

3. Span Calibration (Full Tank)

  • Fill the Vessel: Now, fill the tank or simulate a full tank condition.
  • Adjust Span: Adjust the transmitter’s span to the output signal for a full tank condition (e.g., 20 mA for a 4-20 mA transmitter).

4. Midpoint Calibration (Optional)

  • Partial Filling: Optionally, you can check a mid-point calibration by filling the vessel to a known percentage (e.g., 50%) and verifying that the transmitter outputs the corresponding signal (e.g., 12 mA for a 50% level).
  • Adjust as Necessary: Fine-tune any adjustments based on deviations from expected outputs.

5. Final Check

  • Verify Zero and Span: Once adjustments are made, recheck the zero (empty condition) and span (full condition) points.
  • Document Results: Record calibration results, ensuring they are within acceptable error limits.

6. Reinstallation

  • Reintegrate into the System: After completing calibration, reinstall the transmitter into the system, ensuring all connections and fittings are secure.

Tips:

  • Avoid Electrical Noise: Capacitance transmitters are sensitive to electrical interference. Make sure the environment is as noise-free as possible during calibration.
  • Temperature Compensation: Some transmitters require temperature compensation. Ensure you follow the manufacturer’s guidelines regarding environmental conditions during calibration. Refer the below link for the detailed step by step procedure for [Calibration of capacitance type level transmitter