Process calibration tools for pressure
By G van Rooy, Comtest
Electricity+Control, October 2013 (pages 46 – 47)
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The full article on Process calibration tools for pressure can be downloaded in PDF format.
The need to achieve consistent results is one of the most important reasons for pressure calibration. Accuracy is an important feature of a calibrator. You may need a particular level of accuracy to comply with standards that specify a test accuracy ratio (TAR) or test uncertainty ration (TUR). For example, many standards require a 4:1 ratio between the specified tolerance of the device under test (DUT) and the accuracy or uncertainty of the calibration equipment.
Accuracy is also important because when accurate standards are used most of the time, downtime only needs to be long enough to verify that the instruments are still in tolerance. However, with inaccurate calibration standards, more borderline and out-of-tolerance indications are found. This means that a routine verification turns into an additional adjustment procedure and a final verification at each of the test points to prove the ‘as left’ condition is in tolerance. This more than doubles the downtime and the technician time involved in completing the calibration - inaccurate standards tend to not be consistent with each other causing us to make more adjustments to correct phantom errors.
- Process calibration tools enable calibration of industrial instruments.
- No instrument can be used without being calibrated – and maintained.
- Properly calibrated equipment can save money.