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

1. Gather Equipment:

   • Obtain a reference pressure source capable of generating differential pressures within the desired range.
   • Prepare a pressure gauge or pressure calibrator to measure the differential pressure applied to the transmitter.
   • Ensure you have any necessary tools for adjusting the zero and span of the transmitter.

2. Isolate the Transmitter:

   • Disconnect the differential pressure transmitter from the process to avoid interference during calibration.
   • Ensure that the pressure source and pressure gauge or calibrator are connected to the high and low-pressure ports of the transmitter securely.

3. Establish Calibration Points:

   • Identify the desired calibration points, including the minimum and maximum differential pressures to be measured by the transmitter.
   • Use the pressure gauge or calibrator to verify the actual differential pressures corresponding to these calibration points.

4. Apply Test Pressure for Zero Calibration:

   • Adjust the pressure source to the minimum differential pressure calibration point.
   • Measure the differential pressure using the pressure gauge or calibrator and record the reading.
   • Note the output signal (current or voltage) of the transmitter and record it.

5. Adjust Zero Point:

   • If the transmitter output does not match the expected value at the minimum calibration point, adjust the zero point as needed.
   • Some differential pressure transmitters have zero adjustment screws or potentiometers that can be used to adjust the zero point. Follow the manufacturer's instructions for adjustment.
   • Incrementally adjust the zero point and repeat the calibration process until the transmitter output matches the expected value at the minimum calibration point.

6. Apply Test Pressure for Span Calibration:

   • Adjust the pressure source to the maximum differential pressure calibration point.
   • Measure the differential pressure using the pressure gauge or calibrator and record the reading.
   • Note the output signal (current or voltage) of the transmitter and record it.

7. Adjust Span:

   • If the transmitter output does not match the expected value at the maximum calibration point, adjust the span as needed.
   • Some differential pressure transmitters have span adjustment screws or potentiometers that can be used to adjust the span. Follow the manufacturer's instructions for adjustment.
   • Incrementally adjust the span and repeat the calibration process until the transmitter output matches the expected value at the maximum calibration point.

8. Verify Calibration:

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

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 differential pressure 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 differential pressure 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 differential pressure transmitter to ensure accurate and reliable measurement of differential pressures 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.