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How to calibrate a gas detector?
2024-10-12
Gas detectorIt is an instrumentation tool for gas leakage concentration detection, including portable gas detectors, fixed gas detectors, etc. It mainly uses gas sensors to detect the types of gases present in the environment. Gas sensors are used to detect the composition and content of gases.
The gas detector can detect the leakage of gas, and remind people to take safety measures such as evacuation, forced exhaust, shutdown equipment and so on by sending out alarm signals such as sound and light. It is an indispensable instrument in industrial production and daily life.
However, the gas detector is not always able to accurately measure the gas concentration, just like our watch needs regular and standard time proofreading, the gas detector also needs regular correction to ensure the accuracy of the detection, and the correction process is called "calibration".
Why do 1. need calibration?
The accuracy of the combustible gas alarm is an important prerequisite for detection and alarm, and its accuracy depends on the built-in combustible gas sensor, whether it is an electrochemical sensor or a catalytic combustion sensor, it will be affected by some substances in the environment during use, and gradually change or even poisoning failure. Only after timely maintenance and correction, the accuracy of the results detected by the instrument can be guaranteed.
In actual use, many factors will affect the accurate value of the alarm. Regular calibration is to minimize the error of the detection results and achieve the highest accuracy.
2. which situations require calibration
2, the oxygen concentration is too high or too low
The detection of combustible gas in the atmospheric environment with insufficient oxygen may cause the concentration of combustible gas to be lower than the actual concentration; on the contrary, when the detection is carried out in the environment with excessive oxygen, the detected concentration may be higher than the actual concentration.
In this case, it is necessary to calibrate the detector to achieve the purpose of accurate measurement.
2. Re-calibration of combustible gas detector
When the gas concentration is too high and the combustible gas detector displays "over-range", it needs to be calibrated again. For example, in the process of using combustible gas detector, the measuring range of the instrument is 0-200% LEL, and the actual concentration is higher than 200, which will cause the phenomenon of over-range. At this time, the gas detector needs to be calibrated again.
The water vapor or other known impurities of the silicone compound may affect the normal operation of the combustible gas detector, causing its reading to be lower than the actual gas concentration. If the instrument has been used in the water vapor environment of silicone compound, to ensure the accuracy of the measurement, the instrument should be calibrated again before the next use.
3. how to perform calibration
According to the lower explosive limit of each detection gas, we need to carry out targeted calibration.
Take the hydrogen alarm, we must first complete the production of hydrogen standard gas, the gas sensor or application products in the rated working conditions of power aging for a period of time (generally not less than 2 hours, preferably more than 24 hours) so that the component resistance is fully stable. Put the gas sensor or application product of the detector into the test chamber, and inject the gas or liquid to be tested into the test chamber with a sampler (medical syringe can be used) according to the volume requirements to form a calibration gas sample. Adjust the circuit preset mechanism such as variable resistor on the application product to make the application product just trigger (such as alarm). Exhaust the test gas from the test chamber with an exhaust fan and repeat 2-4 times to confirm that the application is just triggered.
Precautions for 4. calibration
Gas detector in the calibration should pay attention to the following matters:
2. Calibrate the environmental conditions. The gas alarm is an electronic instrument, and the error in its verification mainly comes from the verification environment. It is required to be well ventilated and will not be interfered with during calibration. Its environment and temperature need to reach a certain value.
2. Calibration flow control. Since gas alarms are mostly catalytic combustion sensors, the size of the flow directly affects the accuracy of the verification results, so it is necessary to control the flow. Flow is too large, or too small, will affect the calibration results.
3. The main controller does not match the indication of the field detector during calibration. When the gas concentration of the gas detector in the environment reaches or exceeds the preset alarm value, the main controller sends out an alarm to remind the personnel on duty to take safety measures, so as to ensure the safe production of the enterprise.
4. Calibration cover for calibration. When calibrating combustible and toxic gas alarms, calibration covers will be used. Each manufacturer has its own special calibration covers. When calibrating, it is better to use the original calibration covers, and the calibration results will be more accurate. In addition, in order to ensure the accuracy of detection, gas alarm calibration at least once a year.
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