How to Calibrate a Pressure Gauge ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How to Calibrate a Pressure Gauge

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In the plant, pressure gauge calibration is often taken for granted probably because they seem to be everywhere in the plant that one just assumes that some how the gauges are accurate even when they are out of calibration. A pressure gauge can be calibrated with a standard pneumatic calibrator, a dead weight tester or any other suitable calibrator.
There is no standard way to calibrate a pressure gauge.  The way a gauge is calibrated depends on the way the gauge is used. Here an outline is given on how a pressure gauge could be calibrated with any type of calibrator.

Pressure Gauge Calibration Procedure:

Verify that the calibrator has been currently calibrated in accordance with manufacturer’s specifications. If the calibration is not current, it should be performed before using the calibrator for this calibration procedure otherwise you might just be calibrating your pressure gauge with a calibrator that is already out of calibration. The result would be that your calibration exercise will not be reliable. Connect the calibration setup as shown below and follow steps 1 -7:

Step 1
Before applying any pressure to the gauge, set the pointer to read zero on the scale.

Step 2
Apply the full range pressure to the gauge.  Adjust the linkage so that the pointer is at the maximum reading on the scale, (full scale deflection).

Step 3
Reduce the pressure to zero and check that the pointer reads zero on the scale.  Adjust the pointer if necessary.

Step 4
Repeat steps (2) and (3) until both readings are correct.

Step 5
If the Pressure gauge has a linearizing adjustment, set the applied pressure to 50% of the maximum scale reading.  Adjust the linearizing adjustment so that the pointer reads at 50% of the maximum scale reading.

Step 6
Check the Pressure gauge reads correctly at 0, 50% and maximum scale reading.  You may need to adjust the gauge many times before the gauge is correct.  You must be patient and careful.

Step 7
When step (6) is completed, write down the reading on the gauge for the applied pressure readings on a calibration sheet.

Step 8(Optional)
Draw a graph of the gauge readings and the applied pressures (increasing and decreasing).This is important if you are doing a bench calibration and intend to generate a calibration certificate after the calibration exercise. In a plant environment, a simple calibration is just enough

With a dead weight tester as shown below, the pressure is applied to the gauge using calibrated weights. Please see How to Calibrate a Pressure Gauge with a Dead Weight Tester for a detailed guide.

For more information on Pressure Gauges, checkout:

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