Calibrating pressure or differential pressure measuring instruments accurately is one of the greatest challenges faced by instrument engineers. Deadweight pressure calibrators often provide an economical solution for industries in Singapore.Ā
This document outlines methods for selecting and using deadweight testers and gauges:
Precision Pressure Standards
Primary pressure standards, like deadweight testers and U-tube manometers, are generally more accurate than secondary standards. Primary standards rely on fundamental units of mass and length, ensuring high precision. Their accuracy is measured as a percentage of the reading. In contrast, secondary standards, such as precision pressure gauges, sensors, and transducers, have their accuracy measured as a percentage of the full-scale reading. In Singapore, electronic pressure testers are often used as an alternative to deadweight pressure testers for instrument calibration due to their affordability and portability. However, deadweight testers offer distinct advantages. They do not require a power source, generate stable and precise output pressures, and are less affected by environmental temperature variations. For applications requiring high accuracy, deadweight testers provide lower uncertainties (measured as a percent of the reading) compared to electronic calibrators, making them a valuable investment despite potentially higher costs.What qualities do you need to look for in a deadweight tester?
When selecting a deadweight tester, the following considerations are essential:- Required Accuracy: The testerās accuracy should match the applicationās needs. Deadweight testers typically have accuracy expressed as a percent of the indicated reading, offering greater precision compared to devices measured as a percent of full scale.
- Test Fluid Compatibility: The test fluid must be compatible with the process fluid of the instrument being tested to avoid contamination. Common test fluids include instrument-grade oil, distilled water, and clean, dry air or nitrogen gas.
- Pressure Range: The testerās pressure range must exceed the highest pressure of the instruments to be tested. Dual-range testers or a combination of pneumatic and hydraulic testers can cover a broad range of pressures.
- Portability and Application: For testing fixed instruments, portability is crucial. High-performance tasks may require custom-designed testers, while frequent testing can benefit from dual-column testers for quicker range adjustments.
Using Deadweight Testers: A Guide by Unitest Calibration
When using a deadweight pressure calibrator in Singapore, technicians should follow these guidelines for safe and effective use:- Thoroughly read and understand the instruction manual.
- Avoid operating the tester above its rated pressure.
- Ensure tubing and fittings exceed the testerās pressure rating.
- Never connect the tester to a pressurised source.
- Verify all pressure fittings are tight.
- Use compatible test fluids to prevent contamination or damage to the instruments.
- Clean the piston and cylinder before use.
- Stack weights appropriately, ensuring they do not exceed the maximum pressure.
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