1. The meaning of verification and calibration
JJF1001 defines verification as: the procedure to find out and confirm whether measuring instruments meet legal requirements, including inspection, marking and (or) Issue a calibration certificate. In addition to the determination of whether the measuring instrument is qualified, a very important piece of information on the calibration certificate is the calibration period, which is the validity period of the calibration. This validity period can only mean that the measuring instrument is legal to use during this period, but it does not mean that the measuring characteristics of the measuring instrument meet the specified requirements during the validity period. Even if a qualified measuring instrument is within the validity period, the loss of control during daily use, maintenance, etc. will still cause the measurement characteristics of the measuring instrument to change, resulting in inaccurate measurement. The internal calibration certificate is not enough.
The validity period of the verification can only represent a legal technical measure and the legal maximum time interval under normal maintenance conditions and normal use. Therefore, the laboratory should be based on the frequency of its own use. , the operator's skills, the use environment and other factors to formulate a calibration cycle that meets its own requirements and is no less than the legal requirements.
Calibration is different from verification. There are no statutory verification procedures. Some measuring equipment may not even be calibrated, and some may never have national calibration specifications. Therefore, calibration has its flexibility and changes. There is a large implementation space. At the same time, the calibration laboratory also bears corresponding risks. The recommendations for the next calibration on the calibration report are also based on the calibration laboratory. Generally, they are based on the design principles, structure, and Measurement characteristics, etc. are expected to be valid under standard conditions of use, and laboratories using different equipment will have their own particularities, such as the frequency of use, the operator's level of care for the equipment, the service period of the equipment, and the use of supporting projects. Quality (stability of power supply, stability of reference materials, quality of consumables, quality of easily worn accessories), it is completely necessary for the testing laboratory to establish a suitable equipment verification and calibration validity period control system. Therefore, it is absolutely necessary for the proposed calibration The required laboratory must be able to discern whether the calibration fees we pay are commensurate with the services we receive.
2. Conclusion
It can be seen that the phenomena mentioned at the beginning of this article are normal. Neither verification nor calibration can guarantee that the equipment within the validity period will always meet the quantitative requirements. Likewise The values ??of the two pieces of equipment that have obtained the certificate are not necessarily the same. For example, if the same two pieces of equipment have two levels of measurement ranges, it may happen that the values ??of the low range of equipment A and the high range of equipment B are in compliance with the traceability requirements. , then when both use low ranges at the same time, there may be a large deviation in the measurement data; for example, even if the two ranges of the two devices meet the value requirements, the measurement may be performed by two different people or the same person. If the process is not completely consistent, large deviations in measurement data will also occur.
Therefore, the period of equipment that requires mandatory calibration must not be longer than the requirements of the prescribed procedures, and the period of calibration equipment can be determined by itself according to the specific conditions of the laboratory. In order to ensure that the value of the equipment meets the requirements, the period of calibration must be The most effective method is to carry out necessary inspections and maintenance during the validity period.