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There are many error indexes in pressure calibration. How to distinguish them?
Truth value refers to the physical quantity which exists objectively and cannot be obtained with absolute accuracy. In practice, the value obtained by the standard instrument with high enough precision is often taken as the truth value. When the pressure calibrator is used as a standard, the measured value is considered to be true.
The reference error is generally used to describe a method of performance characteristics of the instrument. In pressure calibration, the pointer and digital pressure gauges are expressed in this way and are calculated according to the full range of the instrument.
For example, for the digital pressure calibrator of 10MPa and 0.05 level, the allowable error at all points is ±10MPa×0.05%=± 0.005mpa.
The reading error is another representation of the error, which is used by the piston manometer in the pressure calibration work and is calculated on the basis of the check point. For example, the allowable error of (1~60) MPa at the point of 60MPa is ±60MPa×0.05%=±0.030MPa, while the allowable error at the point of 10MPa is ±10MPa×0.05%=±0.005MPa.
The return error, also called the return error, is the absolute value of the difference between the measured data at the same check point in the upper and lower stroke of a verification cycle.