Verification and calibration of various gas detectors
Multiple gas detectors are used to detect the concentration of combustible gas, toxic and harmful gases in the environment. They belong to safety detection equipment and are mandatory calibration measuring instruments. They are widely used in fields such as petroleum and petrochemical, aviation, chemical engineering, metallurgy, and civil safety detection. Gas detection alarms have a variety of types, a wide range of applications, short sensor component life, and significant performance differences. The performance and quality of gas detection alarms are directly related to the personal safety of employees in the workplace, and are one of the guarantees of safe production. Therefore, adopting scientific and reasonable testing methods for different instruments is an important measure to ensure personal safety, property safety, and production safety. Multiple gas detectors are generally composed of detection systems, amplification circuits, alarm systems, and display button modules. Main working principles; Convert the signal detected by the gas sensor into an electrical signal, and then convert the electrical signal into the concentration of the measured gas.
Calibration of various gas detectors
Multiple gas detectors belong to safety testing equipment. To ensure the safety of users, they need to be verified or calibrated before use. Currently, there are various types of gas detectors on the market, and the verification and calibration methods are different. Therefore, before calibration, it is necessary to carefully read the instructions and verification regulations, and adopt the correct method to calibrate the instrument. For example, the Japanese New Universe 302M requires a USB data cable to be connected to a PC equipped with calibration software to calibrate each gas separately. For the UK Ion Science FIRSTCHECK+calibration, the ISLPC data transmission software, infrared link device, and data cable are required to set the concentration of the calibration gas, transfer the setting data to the instrument and save it, and then calibrate the instrument.
Verification conditions: According to regulations, the ambient temperature needs to be maintained at (0-40) ℃, relative humidity is less than or equal to 85%, and there is no electromagnetic interference. The gas flow controller needs to meet the instrument verification requirements, and the pump suction type needs to be equipped with a bypass flow meter to ensure that the bypass flow meter in the flow controller has flow venting. To control the gas flow rate well, ensure that the intake flow rate is consistent with the pump suction flow rate of the instrument. The flow rate of the diffusion type should be according to the requirements of the instrument manual. If there are no clear requirements in the instrument manual, it is generally controlled within the range of (250 ± 50) mL/min. Precautions: For different detectors, a suitable standard gas cover should be used. A suitable standard gas cover has a significant impact on the verification and calibration results. For semiconductors and catalytic combustion, the bottom gas of the standard gas needs to be air, with a calibration concentration. The instrument has a fixed calibration point, and corresponding standard gas needs to be prepared according to the fixed standard gas concentration of the instrument for calibration, such as Industrial Scientific's M40, which has a fixed calibration value, The calibration point for combustible gases is 25 or 50% LEL, the calibration point for carbon monoxide is 100ppm, and the calibration point for hydrogen sulfide is 25ppm. Some gas detectors have adjustable calibration points within a certain range, such as the Delge X-am 2000, combustible: (40-100)% LEL, oxygen: (10-25) vol%, carbon monoxide: (20-999) ppm, and hydrogen sulfide: (5-99) ppm. For gas detectors with adjustable calibration points, calibration should be carried out according to the calibration concentration required by the regulations.
A common problem is that some instruments have a calibration cycle set. When the instrument is used for more than the calibration cycle, it will alarm or display a malfunction. In this case, the instrument needs to be recalibrated, such as GasAlertMicroClip from BW Company; If the measurement range is exceeded or negative drift occurs, a fault will be displayed. When the oxygen concentration is below 10 vol%, a combustible gas may display a fault. For gases outside the measurement range, the sensitivity of the gas may temporarily increase. It is necessary to wait for the instrument to recover for a certain period of time before calibrating or calibrating it; A gas detector that displays "- -" when turned on usually has a sensor failure or needs to be recalibrated, such as X-am 2000; After starting up, a gas channel displays a malfunction, the sensor is not installed properly or the sensor is malfunctioning.
