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How to Calibrate a Pressure Gauge Transmitter & Switches

Calibrate a pressure gauge transmitter and switch with the use of a hand pump with a PSI gauge and a digital pressure calibrator. Digital pressure calibrators are multimeters that are designed to measure electrical currents and calculate pressure set points for pressure gauges, which are instruments attached to processing plants that work with gasses and liquids. They control safety devices installed at the plant that keep it working properly and prevent workplace injuries. Calibrating a pressure gauge ensures that the gas or liquid pressure in a plant is maintained at safe levels.

Things You'll Need

  • Digital pressure calibrator
  • Hand pump with PSI gauge
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Instructions

  1. Calibrate Transmitter

    • 1

      Depressurize or purge the system on which the pressure switch transmitter is located. Connect the NPT pressure-port cable to the transmitter. Attach the hand pump to the transmitter.

    • 2

      Connect the positive red lead of the digital pressure calibrator to the normally open electrical switch contact -- which is marked NO -- and the black negative lead to the normally closed -- or NC -- electrical switch contact.

    • 3

      Turn on the digital pressure calibrator. Open the vent on the digital calibrator. Press the "Zero" button on the calibrator and then close the vent. Select "PSI" units on the calibrator.

    • 4

      Open the bleed valve of the digital calibrator and then push the "Zero" key. Shut the bleed valve. Select "+" for the pressure/vacuum valve setting on the calibrator to set it to read positive pressure.

    • 5

      Gently squeeze the hand pump in half-pump strokes until the PSI gauge of the pump reads 3 PSI. Turn the fine-adjust knob on the pump to get the reading as close to 3.00 PSI as possible. Record the PSI and mA reading on the digital device by pressing the "Hold" key.

    • 6

      Use the digital calibrator to calculate the "error" point of the pressure switch. Enter "Error= ([(i-4)/16]-[(P-3)/12])*100" into the calibrator. If the number is equal to or less than the manufacturer's listing for the pressure switch's tolerance range, the transmitter has been calibrated properly.

    Calibrate Switch

    • 7

      Depressurize or purge the system on which the switch is located. Connect the NPT pressure-port cable to the transmitter. Attach the hand pump to the transmitter.

    • 8

      Turn on the digital pressure calibrator. Turn the vent valve to open it. Press the "Zero" button on the calibrator. Close the vent by turning it in the opposite direction.

    • 9

      Select the "Switch Test" mode on the digital calibrator. Squeeze the hand pump in half-pump strokes until the PSI gauge of the pump reaches the switch's set point, as provided by the manufacturer. Turn the "vernier" adjuster until the switch opens and the digital calibrator display reads "Open" for an open circuit.

    • 10

      Slowly release the air pressure with the "vernier" adjuster until the digital display reads "RCL." Push the "Switch Test" button on the digital calibrator to read the switch-opening and switch-closing values. Clear the test results and test the switch again.

    • 11

      Turn the pressure switch adjuster until it the switch opens and closes at the proper pressure.

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