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4 Methods of Calibration Period Method Determination

2020-11-01 16:00


statistical law



The measuring instruments can be classified according to the different conditions of the structure, reliability and stability of the measuring instruments, and then the calibration cycle can be determined according to the calibration procedure. And count the number of out-of-tolerance or other unqualified instruments and equipment within the specified period, and count the ratio of these instruments to the total number of qualified instruments in the group.
When determining the unqualified measuring instrument, the damaged and returned instrument shall be replaced. If the proportion of unqualified instruments is high, the calibration period should be shortened.
When the proportion of non-conforming instruments is very low, it may be economically reasonable to extend the calibration cycle. However, if it is found that the instruments of a certain group (or manufactured by a certain manufacturer or a certain model) cannot work normally with other instruments in the group, the group shall be classified as other groups with different periods.



time method


When confirming the calibration cycle, it is indicated by the actual working hours. When the indicator reaches the specified value, the instrument is returned to calibration. The main advantage of this method is that the cost of instrument calibration is proportional to the time of use and the time of use of the instrument can be checked.
For example, some instruments can be directly checked how long they have been used continuously, which is beneficial to management.
However, this method has the following disadvantages in practice:
(1) This method should not be used when the measuring instrument drifts or is damaged in storage, handling or other circumstances;
(2) The installation of the timer will increase the cost, and the need to carry out under supervision due to user interference will increase the cost.



comparative method


When each measuring instrument is calibrated according to the specified calibration cycle, the calibration data is compared with the previous calibration data. If the calibration results of several consecutive cycles are within the specified allowable range, its calibration cycle can be extended. If it is found to exceed the allowable range, the calibration cycle of the instrument should be shortened.



chart method


In each calibration of the measuring instrument, select the same representative calibration point, draw their calibration results according to time, draw a curve, calculate the effective drift of the instrument during one or several calibration cycles according to these curves, and calculate the optimal calibration cycle from the data of these charts.


Metrological calibration is an important link to improve the efficiency of the laboratory, and determine the calibration cycle is a key link in the measurement work, plays a very important role in product quality and service quality, in determining the calibration cycle of measuring instruments, to the actual use of measuring instruments after scientific analysis of the evaluation decision.