Short Answer:
A dead weight tester helps in calibration by providing a highly accurate and stable pressure reference using known weights and a piston-cylinder system. It applies a specific pressure by placing calibrated weights on the piston, which balances the fluid pressure inside the system.
This method is commonly used to calibrate pressure gauges, transmitters, and sensors. Since the applied pressure depends on physical quantities like mass and gravity, a dead weight tester gives reliable and traceable pressure values, making it ideal for high-accuracy calibration in electrical and mechanical systems.
Detailed Explanation:
Dead Weight Tester in Calibration
In both electrical and mechanical measurements, precise pressure calibration is very important, especially when pressure sensors or transmitters are involved. One of the most accurate instruments used for this purpose is the dead weight tester. It operates based on a simple physical principle — applying a known weight over a known area creates a known pressure. This makes it a primary standard device used widely in calibration laboratories and industries.
Working Principle of a Dead Weight Tester
The dead weight tester works using a piston-cylinder assembly and a set of calibrated weights. The basic idea is that when a known weight is placed on the piston, it creates a downward force. This force is distributed over the cross-sectional area of the piston, generating a known pressure in the fluid (usually oil or air) inside the system.
Formula Used:
Pressure (P) = Force (F) / Area (A)
Where:
- Force (F) = mass × gravitational acceleration
- Area (A) = cross-sectional area of the piston
By adjusting the weights, different pressures can be generated and applied to the instrument under test.
How It Helps in Calibration
- Accurate Pressure Generation
A dead weight tester generates pressure based on physical constants (mass and gravity), so it provides very accurate and stable pressure readings. This is essential when calibrating instruments that measure pressure. - Direct Comparison with Device Under Test
The instrument to be calibrated (like a pressure gauge or sensor) is connected to the same pressure system as the piston-cylinder. The pressure from the dead weight tester is applied, and the readings of the test instrument are compared against this known pressure. - Traceability and Standard Reference
The weights used in the tester are calibrated and traceable to national standards. This ensures that the pressure values generated are recognized and accepted globally. - Repeatability and Reliability
The system provides consistent results when repeated, making it ideal for testing and adjusting the accuracy of pressure-measuring instruments. - Used in High-Accuracy Applications
Since dead weight testers provide pressure with high precision, they are widely used in calibration laboratories, industries, research labs, and quality control departments.
Advantages of Using a Dead Weight Tester
- High accuracy and stability
- No dependence on electronic systems (purely mechanical)
- Long service life if maintained properly
- Excellent for calibration of pressure devices like:
- Pressure gauges
- Pressure transducers
- Pressure switches
- Manometers
Precautions While Using
- The piston and cylinder must be clean and free from dust.
- The weights must be handled carefully to avoid damage.
- The system must be level and vertical for correct force distribution.
- Use in a temperature-controlled environment for best accuracy.
Conclusion
A dead weight tester is a reliable and accurate tool used in the calibration of pressure-measuring instruments. It works on basic physics principles and provides traceable pressure values using known weights and piston area. Because of its simplicity, stability, and precision, it plays an important role in ensuring the accuracy of devices used in electrical and mechanical systems. When properly used and maintained, a dead weight tester can serve as a trustworthy primary pressure calibration standard.