Qualified calibration means "calibration" is carried out in accordance with the "Calibration Procedure" "under legal conditions", and the result is within the specified error range of the measurement value. As for whether it can be used directly on site, it also depends on the following points:

If the error exceeds the use requirements, but a stable real value can still be obtained through numerical correction, then it can continue to be used, but the correction value must be marked, and the correction value must be recorded when reading, and the final real value is obtained through conversion. Of course, it would be better if it can be adjusted, repaired, and put into use until the error reaches the use requirements. If it cannot be adjusted,

Within the error range, adding the correction value is also acceptable, as long as the correction value is stable or linear, or there is a regular calculable error. Calibration can also be divided into calibration under specified conditions and online calibration. If it is calibration under specified conditions, it is still necessary to remember that "measurement confirmation" is required under actual use conditions, otherwise it may not be accurate at all.

If it is online instrument calibration, it is basically accurate. Therefore, we still need "online calibration". Of course, it is best to perform "online calibration and measurement confirmation" after verification and offline calibration. Verification is the legal basis for judging the quality and performance of the instrument itself. Offline calibration is also for judging the accuracy and error performance of the instrument itself. Therefore, online calibration and measurement confirmation after installation are the basis for judging whether the instrument can be put into production.