What Is a Calibrator?
A calibrator is a device or instrument used to calibrate a measuring instrument.
Calibration is the process of comparing the accuracy of a measuring instrument to a standard and ascertaining the deviation from the value that should be indicated. The deviation is called “instrumental error”, and the instrumental error is like the individual difference of measuring instruments. As with any measuring instrument, there is a small amount of deviation, so it is important to understand the deviation.
Instrumental error also fluctuates depending on the environment and deterioration. Therefore, it is necessary to perform calibration on a regular basis. Calibration ensures the reliability of the results measured by the calibrator.
Principle of Calibrators
Calibration is performed by measuring the characteristics of the calibrators itself (eg, mass and dimensions) or the output from the calibrators (eg, current) using the calibrators to be calibrated. For example, an electronic balance weighs a weight or a micrometer measures a block gauge.
The difference between the measured value and the calibrator’s assigned value is the instrumental error. Calibration is completed when the instrumental difference is known. Properly calibrated calibrators are the basis of the calibration operation.
Uses of Calibrators
Calibrators are used to determine the condition of the measuring instruments to be calibrated. Calibration is usually performed periodically.
However, the calibrators themselves also needs to be calibrated. Since it is burdensome to maintain calibrators, one option is to outsource periodic calibration to a specialist. On the other hand, there are cases where calibrators are used for self-inspection of measuring instruments, although this has a different meaning from the original calibration.
While daily inspections are conducted to ensure that there is no significant loss of accuracy, formal calibration can be conducted once every six months or so. In this case, the calibrators should still be calibrated on a regular basis.
Other Information on Calibrators
1. Calibrators and Traceability
Calibrators are standards used to calibrate measuring instruments. As a standard, it needs a reference to indicate the standard (proper value). That is, calibrators must be calibrated by a superior standard.
The higher level standard is then calibrated to another higher level standard, and so on, culminating in the highest standard in the country.
This connection to standards is called “traceability”. This makes it possible to compare the results of the same type of measurement anywhere in the country. Each country confirms the interchangeability of its standards with the International Committee of Weights and Measures and other organizations.
2. Accuracy of Calibrators
Calibrators should be more accurate than the equipment to be calibrated. This is because it allows for more appropriate and practical control. In other words, if the magnitude of the discrepancy is determined with low accuracy, it will not be useful for measurement at the accuracy that the equipment to be calibrated can originally demonstrate.
3. Example of Micrometer Calibration
As an example of calibration, let the micrometer be the measuring instrument and the block gauge be the calibrators.
- Measuring instrument: Micrometer
- Calibrator: Block gauge
The smallest unit of a micrometer is 1μmm => “1/1000 mm of 1 mm”. Since the condition of calibrators are to have higher accuracy than a measuring instrument, the smallest unit of a block gauge is 0.1μmm => “1/1000th of 1mm”.
In this way, the calibrators, the block gauge, will have a higher accuracy. By calibrating the micrometer with the block gauge before and after measurement, the error can be known. Performing this before and after measurement provides the most reliable calibration results.
Depending on your measurement control policy, you may wish to calibrate your micrometer periodically instead of every measurement, and keep a record for reference. Periodic calibration allows for estimation of conditions during that period.
On the other hand, if measurements are taken without any calibration at all, the measured values are unreliable because the errors are not known. In addition, it is necessary to calibrate the block gauge, which serves as a calibrators, using calibrators that is even more accurate than the block gauge.