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What Is a Dead Weight Testers & How it works for Pressure Calibration?

20 Apr , 2021 Dead Weight Testers

What is a Dead Weight Tester?

Dead Weight Tester (DWT) is a pressure measurement instrument that calibrates pressure based on the weight of force divided by the area the force is applied.

DWT provides high accuracy in pressure gauge calibration and prevents the occurrence of an error in pressure reading.

It is used in calibration of various pressure measuring instruments such as pressure gauges, sensors, transmitters, and transducers.

Dead Weight Testers’ stability, accuracy, and repeatability have made them a universally accepted primary standard for pressure measurement.

Let’s find out how it works:

Pressure Calibration how it works

The above diagram depicts a deadweight tester along with a Pressure Gauge. The following are its components:

1. Handle
2. Screw Pump
3. Resorviour
4. Piston and Cylinder
5. Weights
6. Pressure Gauge (DUT)

For priming the entire systems valves A & B are opened and the oil from the reserviour (3) fills the system. The weights (5) are loaded on to the piston (4) corresponding to the pressure range of the device under test. The pressure is generated via a mechanical or manual handle (1) until the loaded measuring piston (5) is activated. DUT (6) is fixed on the gauge stand. To test the instrument under test, valve B is closed keeping valve A open, the screw pump (2) is rotated in clockwise direction till the handle (1) becomes stiff to rotate.

For high pressure testing, once the handle rotation becomes stiff, valve B is closed and Valve A is opened. The pressure transfer medium can be oil or gas in the cylinder. and starts rising and floating on the fluid (Pneumatic or Hydraulic). The weight moves the piston downwards by creating a pressure P on the fluid. The spinning of the piston maintains the system pressure. The pressure generated by the piston during its application on the fluid can be calculated with the formula P = F/A. The pressure value is calibrated through the fluid pressure P indicated by the pressure gauge. The pressure value shown by the calibrator equals the pressure P applied. In case there is a value difference, the gauge can be adjusted.

The amount of pressure a deadweight piston can generate is based on the mass of the piston. Deviation in the piston area can significantly impact the results of pressure reading. Factors such as local gravity and buoyancy in the piston’s force and the temperature of the piston, and the pressure surrounding the piston affect the optimal result in pressure calibration. Also, excessive friction between piston and cylinder can cause measurement error.

However, using high-quality material in the manufacturing of the Dead Weight Tester and controlling certain environmental factors can minimize the chances of error in pressure reading, leading to better pressure calibration. Dead Weight Testers come with a calibrator unit and can detect all ambient parameters and make real-time accuracy changes.

The essential advantage of using a Dead Weight Tester instrument is that it helps to precisely control and measure an instrument’s pressure. Plus, when it comes to calibrating secondary pressure devices or measure unknown pressure where a high degree of precision is required, the Dead Weight Tester provides the most accurate and cost-effective solution. If you have any query, Get in Touch with Us!

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