Calibrating a Guage using Deadweight Tester
Calibrating at the bench with a deadweight tester
A deadweight tester (DWT) is a method of pressure calibration that is done in bench applications especially when accuracy and reliabilityis required. Calibrations are performed at the bench for convenience and to maintain reference conditions. Reference conditions are necessary to achieve the reference accuracy of the device under test and the calibration standards. Reference accuracy may be required to maintain the necessary test uncertainty ratios (TUR).
To perform the test:
- The pressure gauge should be mounted in the same orientation (vertical or horizontal) as in the process.
- Measurement points should be distributed uniformly over the calibration range.
- Calibrated weights are placed on the instrument corresponding to the measurement points.
- Pressure is added with an internal pump or screw press until the piston holding the weights begins to float.
- The piston and weight are spun by hand to minimize friction.
- While the piston is floating the reading on the device under test is compared to the pressure corresponding to the sum of the selected weights.