The reason why the gas detector reading is negative
A gas detector is a type of equipment equipped with high sensitivity sensors, which can sensitively sense small amounts of harmful gases, combustible gases, etc. that are commonly present in the air. It is currently a type of equipment that needs to be assembled in various fields of industrial production. The use of precision gas detectors can always remind of the risk of gas exceeding standards, ensuring the safety of operators. But in the use of gas detectors, sometimes negative readings may occur. So what is the reason for negative readings on gas detectors?
1. Zero reading in polluted atmosphere:
The situation where negative sensor readings are more common is when the instrument is "zeroed" when there is a small amount of target gas from the sensor in a polluted atmosphere. When the instrument is later placed in a clean air environment, the sensor will display a negative reading, corresponding to the pollutant concentration at the time the device is reset to zero. For example, when the sensor is reset to zero, if the carbon monoxide concentration is 5 PPM, the reading will be -5 PPM when the sensor returns to clean air.
2. Negative cross interference:
When the sensor is placed in a gas that generates negative cross interference, negative readings may also occur. If the sulfur dioxide sensor typically has -100% cross interference with nitrogen dioxide and is placed in 2PPM of nitrogen dioxide, the sulfur dioxide reading on the instrument will be -2 PPM.
3. Pressure changes:
If the pressure changes significantly (such as when passing through the gas plug), the gas detector reading may experience temporary fluctuations, which may cause the detector to sound an alarm. When the oxygen volume percentage remains stable at around 20.8% and the overall pressure drops significantly, the oxygen used for breathing in the environment may become a danger.
4. Humidity change:
If there is a significant change in humidity (such as when entering an outdoor humid air environment from a dry environment with air conditioning), the water vapor in the air will drive away oxygen, causing the oxygen reading to drop by up to 0.5%. The gas detector is equipped with specialized filters to eliminate the impact of humidity changes on gas readings. This effect will not be immediately detected, but it will gradually affect the degree of oxygen after several hours.
5. Temperature changes:
The gas detector is equipped with temperature compensation, however, if the temperature fluctuates violently, the gas detector reading may experience drift. The instrument should be calibrated at the work site to minimize the impact of temperature changes on readings.
