How is the gas detection alarm calibrated?

1、 To determine the environmental conditions, the gas detector is an electronic instrument, and the calibration error mainly comes from the environment at the time of calibration 1 Good ventilation is required for the diffusion and escape of open combustible gas In the absence of good ventilation conditions, it is easy to make the combustible gas content in the air of a certain part close to or reach the lower explosion limit concentration, resulting in inaccurate verification results 2 In the verification process of ambient temperature, the change of temperature before and after detection will significantly change the activity of molecules, and the increase of temperature will increase the risk The temperature has no direct influence on the gas detector itself, but when the temperature is below 0 ℃, the inertia of the standard gas increases, and the molecular activity of the standard gas is not active When the temperature is low, the display value of the instrument will have a great error, and when the temperature is below 0 ℃, it is not suitable for the verification work 3 The components tested without interference shall be protected against electromagnetic interference during the verification of gas detector The influence factors of electromagnetic environment on gas detector are as follows: human static electricity, narrow pulse group of power supply and other input and output lines, and electromagnetic interference in the air 2、 During verification, the indication of main controller and field detector is not consistent In general, the gas detector is connected by the main controller and the detector in a split line system The detector is distributed in multiple nodes The main controller controls multiple monitoring nodes in a centralized way, and the gas concentration of each detector is displayed independently When the gas concentration of the detector in the environment reaches or exceeds the preset alarm value, the main controller will send an alarm to remind the personnel on duty to take safety measures, So as to ensure the safety of production 3、 In the verification process of verification flow control, because most of the gas detectors are catalytic combustion sensors, the magnitude of the flow directly affects the accuracy of the verification results The alarm can keep high sensitivity in a certain flow range, too high or too low will have a greater impact on the sensitivity When the flow rate is less than the measurement requirements, the original surface of the sensor will not reach the true concentration After combustion of combustible gas, no new gas can be added in time, combustion can not continue, so the sensitivity is very low When the gas flow rate increases, the thermal effect increases correspondingly, and the sensitivity increases gradually When the gas flow rate continues to increase, the excessive air flow will increase the heat dissipation of the element, but reduce the sensitivity When the flow rate is greater than the measurement requirements, the accuracy decreases When the general instrument is designed, the manufacturer has selected the gas flow rate through repeated tests 4、 Calibration cover for verification It is stipulated in the verification regulation that the diffusion instrument should have a special calibration cover, and each manufacturer has its own special calibration cover However, in the actual verification, the verifier will replace it with self sealing bag and self-made calibration cover It is better to try to use the original special one for verification, because the response time and indication error of the calibration cover's internal air and air intake mode (bottom air intake and side air intake) to the instrument are the two factors The indicators still have a certain impact Of course, no matter what kind of calibration cover is used in the calibration of gas detector, a principle must be adhered to, that is, it is strictly prohibited that the calibration cover is too tight and there is no positive pressure produced by overflow port, which will affect the calibration results It is also prohibited to loosen too much, which will lead to the entry of external gas, so that the actual value of standard gas is too small, affecting the verification results Gas detection and alarm instrument is a kind of precision instrument, which has strict requirements on all aspects of production, and different requirements on the use environment and installation mode We should be careful in the use process and often maintain the instrument.