Calibration process and requirements of gas detectors
The calibration of the gas detector refers to placing the instrument in the test gas of the corresponding known concentration, and comparing the detection result of the gas detector with the gas concentration to know the accuracy of the gas detector. For example, n-hexane will burn and explode at 1.1% VOL. When the 10% alarm is set on the hexane detector, the alarm should be triggered when the hexane concentration reaches 0.1%. For a catalytic combustion sensor, this concentration is quite low. The alarm value of toxic gas is much lower than that of combustible gas. For chlorine gas, its threshold alarm value is only 0.5ppm.
The difference between the measurement results of the recalibrated gas detector and the measured gas concentration is generally not more than 10%, and the instrument can continue to be used without calibration. For example, if an ammonia gas detector detects 50ppm of standard ammonia gas, if the measurement result of the instrument is 46ppm, then it can be considered that the detection accuracy of this ammonia gas detector is qualified and does not need to be re-calibrated, because 46ppm is at 50±10%X50 The result is between 45~55ppm. Similarly, if the detection result of this ammonia gas detector is 44ppm, then this detector needs to be recalibrated before it can be used.
The calibration of the gas detector is an important way to detect the sensitivity of the instrument and restore the accuracy of the instrument. At the same time, through testing and calibration, we can also judge whether the sensor of the gas detector has failed. Therefore, regular instrument calibration is very necessary. In general, calibration is a very simple and convenient process, requiring only two steps:
1. Zero the instrument in "air" that does not contain the gas to be tested.
2. Calibrate the instrument in a standard gas containing a known concentration.
For small partners in the security industry, portable detectors must be accurate and reliable, and there is no room for sloppiness. Correct and regular calibration and maintenance of the detector is an essential method, which shows how important calibration is. In fact, both the detector manufacturer and the national regulations also have provisions for calibration, which are usually divided into two categories:
Equipment manufacturers will require regular calibration, usually once within 2-6 months, to ensure that the instrument can work normally and effectively. The manufacturer recommends that qualified users, dealers or service personnel authorized by the manufacturer can calibrate the instrument.
Metrology regulations require that the number of calibrations should not be less than once every 12 months, and this calibration must be carried out in the measurement department specified by the state, that is to say, it needs to be calibrated in a third-party measurement institute.
