Calibrating a displacer level transmitter involves verifying its output signal response to changes in liquid level and adjusting it to match the desired measurement range. Here's a general procedure for calibrating a displacer level transmitter:

1. Gather Equipment:

   • Obtain a reference measurement device such as a sight glass, dipstick, or another level transmitter with known accuracy.
   • Ensure you have a pressure source or control valve to vary the liquid level in the vessel.
   • Prepare a multimeter or loop calibrator to measure the output signal of the displacer level transmitter.

2. Isolate the Transmitter:

   • Disconnect the displacer level transmitter from the process to avoid interference during calibration.
   • Ensure that the liquid level in the vessel is stable and not subject to sudden changes during calibration.

3. Establish Calibration Points:

   • Identify the desired calibration points, including the minimum and maximum levels to be measured by the displacer level transmitter.
   • Use the reference measurement device to verify the actual liquid levels corresponding to these calibration points.

4. Apply Test Pressure:

   • Adjust the liquid level in the vessel to the minimum calibration point.
   • Measure the output signal of the displacer level transmitter at this level using the multimeter or loop calibrator.
   • Record the measured output signal and the corresponding liquid level from the reference measurement device.

5. Adjust Zero Point:

   • If necessary, adjust the zero point of the displacer level transmitter to match the measured output signal at the minimum calibration point.
   • Some displacer level transmitters have zero adjustment screws or potentiometers that can be used to fine-tune the zero point. Follow the manufacturer's instructions for adjustment.

6. Apply Test Pressure for Span Calibration:

   • Adjust the liquid level in the vessel to the maximum calibration point.
   • Measure the output signal of the displacer level transmitter at this level using the multimeter or loop calibrator.
   • Record the measured output signal and the corresponding liquid level from the reference measurement device.

7. Adjust Span:

   • If necessary, adjust the span of the displacer level transmitter to match the measured output signal at the maximum calibration point.
   • Some displacer level transmitters have span adjustment screws or potentiometers that can be used to adjust the span. Follow the manufacturer's instructions for adjustment.

8. Verify Calibration:

   • After adjusting the zero and span, repeat the calibration process to verify that the displacer level transmitter accurately measures the liquid level within the desired range.
   • Ensure the output signal of the transmitter corresponds correctly to changes in liquid level.

9. Finalize Calibration:

   • Once satisfied with the calibration results, finalize the process by documenting the calibration procedure, including the calibration points, measured output signals, adjustments made, and any observed deviations.
   • Label the displacer level transmitter with the calibration date and any relevant information.
   • Reconnect the transmitter to the process and ensure it operates correctly under normal conditions.

10. Regular Maintenance:

    • Schedule regular inspections and calibrations of the displacer level transmitter to ensure continued accuracy and reliability.
    • Monitor the performance of the transmitter over time and recalibrate as necessary to maintain proper operation.

By following these steps, you can effectively calibrate a displacer level transmitter to ensure accurate and reliable level measurement in your process or application. If you're unsure about any steps or require assistance, consider consulting the transmitter manufacturer or a professional calibration service.