A Master LoadCell also called a calibrator is the reference Load Cell used for calibration of the loadcell located in the testing Machine.
Force is applied on the Testing Machine in which both the factory loadcell and the Master Loadcell read results.
We often read on Standard Calibration Certificates, a Measuring Device Limits Specs covering Accuracy, Repeatability, Reversibility, Zero f0, Relative resolution.
But what do they mean and why are they important?
When we speak about the accuracy of a measuring device we will be pointing the correctness of the measurements values. In other words, we are comparing the obtained measurement values to the exact/absolute value of a physical quantity or a standard device. So the measuring device accuracy increases when the shift decreases between the exact/true value and measurement value.
Repeatability is one of the factors that give us an idea about the measuring device quality. It can be verified easily. After measuring the same quantity (temperature, pressure, length…, etc.) several times, the measurement values obtained are compared to each other. The more consistent and close to each other the measurement values are, the higher the repeatability will be.
Reversibility is directly related to the “Hysteresis” error. As a definition, Hysteresis Error is the maximum difference between load cell output signals for the same applied load. The first measurement can be obtained by decreasing the load from the rated output down to zero and the second by increasing the load from zero up to the rated output. So the lower the difference is, the better the reversibility will be.
Resolution can be defined as the smallest difference that can be shown or noticed by a measuring device when the measured quantity varies. In other words, the measuring device won’t notice or show a difference in measurement if the measured quantity variation is smaller than the resolution.
Zero error can be noticed when a measuring device is displaying a load value when there is no load input. In general, this kind of error can result in an offset of the measurement values which can be easily adjusted by taking this error into consideration when drawing the calibration curve of the sensing device or by simply pressing the zero button found on most of the weighing scales and balances and many more testing devices.
Error is the shift between the true/exact value of a measurement (physical aspect being measured e.g.: temperature, pressure, length…) and the measurement value given by the Master Load Cell.
While uncertainty specifies the interval of values within which the exact value of the measurand lies with a certain level of confidence
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