Can the sensor of a portable gas detector be replaced?

Don’t be fooled by the “modular design and user replaceable” written in the instructions. I think changing the sensor is as simple as changing the battery of the remote control. After so many years in the front line, I have seen too many cases in which a good detector was finally turned into a “time bomb” because I changed the sensor blindly.

First of all, you have to understand that the sensor is not a light bulb. If it is broken, it will light up if it is replaced with a new one. It is more like an “old Chinese doctor” with a temper, and the “constitution” of each sensor is different. You can buy the same model from the internet, or disassemble it from another old machine and install it. The instrument can be turned on and the screen can display numbers, but only God knows whether that number is true or not. Why? Because the Sensitivity Factor of each sensor is slightly different when it leaves the factory, the “fingerprint” data of the old sensor is stored in the memory chip in the circuit board. You changed a new “organ” and didn’t give it a “brain match”, so the number it read was wrong. In the security business, reading is not allowed to be more terrible than not reading at all, because it will give you a false sense of security and make you swagger into the poisonous gas.

Let’s talk about the “calibration” link, which is the death gate of changing sensors. Many people think that putting on a new sensor and pressing the “zero” button in fresh air will be enough. All wet! Zeroing just tells the instrument that “it is clean air here now”, but you have to “feed” it with a standard gas bottle and tell it that “you should display 100 when you encounter 100ppm of hydrogen sulfide”. This is called Span Calibration. If you don’t have a certified standard gas, a pressure reducing valve and a ventilation hood in your hand, then you are completely deceiving yourself by changing the sensor. Some old masters try to save trouble by measuring combustible sensors with the gas of lighters and carbon monoxide with the smoke of cigarettes. The data calibrated by this wild way can kill people at critical moments.

There is also a small detail. Many novice hands are too “dirty” when changing sensors. Sweat on your hands, grease from hand cream, and even fiber dust on your clothes, as long as they touch the air inlet film of the new sensor, this sensor will basically be wasted by half. The film of electrochemical sensor is as thin as cicada’s wing, and the catalytic combustion type is afraid of silicon poisoning, while the infrared type is afraid of dirty lenses. You must wear clean gloves when changing, and your movements should be as light as changing a baby’s diaper. I have seen someone directly squeeze the sensor head into it with their hands. As a result, within two days, the reading began to drift, and no school could come back. Finally, the whole machine had to be returned to the factory, which was time-consuming and expensive.

The most realistic question is, who will endorse it after you change it yourself? In a regular factory or high-risk industry, the instrument has a “hukou”, and every calibration and maintenance must be recorded and supported by a qualification certificate. You secretly changed one yourself, and the safety inspection will come tomorrow. When you see that the calibration label is you from last month, but the serial number of the sensor doesn’t match, or the calibration record can’t be found directly, this instrument will be sealed immediately. If there is an accident, it will be enough for you to drink a pot and even bear legal responsibility to investigate the responsibility and replace key components without permission.

Therefore, my suggestion is straightforward: Do not touch that sensor unless you are a professional maintenance person who has been strictly trained by the manufacturer, has a full set of standard gas and calibration equipment in hand and is authorized by the company. If it is broken, it will be repaired. When the service life is up, it will be sent back to the manufacturer or find a qualified service provider. Don’t gamble with yourself and your workmates’ lives on “if it works” in order to save a few hundred dollars in working hours, or for temporary convenience. In the matter of gas detection, professional things must be handed over to professional people and equipment, which is the real responsibility.