Calibrating a Differential Pressure Transmitter (DPT) level transmitter in the field involves verifying and adjusting its output signal to accurately measure the level of a liquid or gas in a tank or vessel. Here's a step-by-step guide on how to calibrate a DPT level transmitter in the field:

1. Gather Equipment:

   • Obtain a pressure calibrator or a reference pressure gauge with a known accuracy that covers the range of the DPT level transmitter being calibrated.
   • Ensure you have the necessary adapters, fittings, and hoses to connect the DPT level transmitter to the reference standard.

2. Isolate Transmitter:

   • Isolate the DPT level transmitter from the process by closing any isolation valves and ensuring that the process conditions are stable.

3. Zero Adjustment:

   • If the DPT level transmitter has a zero adjustment screw or trim potentiometer, ensure it is set correctly to read zero when no pressure is applied. Use the process zero reference point, typically atmospheric pressure, to zero the transmitter.

4. Apply Test Pressure:

   • Apply a known test pressure to the high-pressure side of the DPT level transmitter using a pressure calibrator or hand pump.
   • The test pressure should correspond to the height of the liquid or gas in the tank or vessel being measured by the transmitter.
   • Connect the pressure calibrator or reference pressure gauge to the low-pressure side of the transmitter.

5. Record Readings:

   • Record the pressure readings displayed on both the DPT level transmitter and the reference pressure gauge. Note any differences between the two readings.

6. Adjustments (if necessary):

   • If there is a significant difference between the readings of the DPT level transmitter and the reference pressure gauge, adjustments may be required.
   • Use the zero and span adjustment screws or trim potentiometers on the transmitter to adjust the output signal until it matches the reference pressure gauge.

7. Perform Multiple Points Calibration:

   • Repeat the calibration process at multiple points across the DPT level transmitter's range to ensure accuracy and linearity.
   • Apply different test pressures corresponding to various levels in the tank or vessel and adjust the transmitter's output signal accordingly.

8. Verify Zero (Optional):

   • After calibration, verify that the DPT level transmitter returns to zero when no pressure is applied. This ensures that the zero point is accurate and stable.

9. Document Calibration:

   • Document the calibration process, including the test points, readings obtained, adjustments made (if any), and any other relevant information.
   • Prepare a calibration certificate or report that includes all calibration details. This documentation serves as evidence of the DPT level transmitter's accuracy and compliance with standards.

10. Label and Store:

    • Once calibrated, label the DPT level transmitter with the calibration date and any relevant information.
    • Store the transmitter in a suitable location where it is protected from damage and contamination.

11. Regular Maintenance:

    • Schedule regular calibration and maintenance intervals for the DPT level transmitter to ensure continued accuracy and reliability.
    • Follow manufacturer recommendations and industry best practices for instrument maintenance and calibration.

By following these steps, you can effectively calibrate a Differential Pressure Transmitter (DPT) level transmitter in the field and ensure accurate and reliable level measurements in your process or application. If you're unsure about any steps or require high-precision calibration, consider consulting a professional calibration service.