What is the reason of negative number in gas detector?
The gas detector is an instrument tool for detecting the concentration of gas leakage. It mainly uses sensors to detect the types of gases existing in the environment. The gas detector is a sensor used to detect the composition and content of gases. So why is the gas detector negative?
First, the reading is zero in the polluted atmosphere
Negative sensor readings often occur when the instrument is in a polluted atmosphere and there is a small amount of sensor target gas, so the instrument is "zeroed". When the instrument is placed in a clean air environment later, the sensor will display a negative reading, corresponding to the pollutant concentration at that time when the equipment returns to zero.
For example, when the sensor returns to zero, if the concentration of carbon monoxide is 5 PPM, when the sensor returns to clean air, the reading will be-5 ppm;
Second, negative cross interference
Negative readings may also occur when the sensor is placed in a gas that produces negative cross-interference. If the sulfur dioxide sensor usually 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;
Third, pressure changes
If the pressure changes sharply (such as when passing through an air plug), the reading of the gas detector may fluctuate temporarily, which may cause the detector to give an alarm. When the volume percentage of oxygen is kept at about 20.8% and the whole pressure drops greatly, the oxygen for breathing in the environment may become dangerous;
Fourth, the humidity change
If the humidity changes obviously, such as entering the outdoor humid air environment from a dry environment with air conditioning, the water vapor in the air will drive away oxygen, which may cause the oxygen reading to drop by up to 0.5%.
The gas detector is equipped with a special filter to eliminate the influence of humidity change on gas reading. This effect will not be found immediately, but it will gradually affect the degree of oxygen after several hours;
V. Temperature changes
The gas detector is equipped with temperature compensation. However, if the temperature fluctuates sharply, the reading of the gas detector may drift. The instrument should be calibrated at the work site to minimize the influence of temperature changes on readings.
