4 Characteristics of Gas Detectors
1. Stability
Stability refers to the stability of the basic response of the sensor throughout the working time, depending on the zero drift and interval drift. Zero drift is the change in sensor output response throughout the operating time in the absence of target gas. Interval drift refers to the output response change of the sensor continuously placed in the target gas, which is manifested as the decrease of the sensor output signal within the working time. Ideally, a sensor should have a zero drift of less than 10% per year under continuous operating conditions.
2. Sensitivity
Sensitivity is the ratio of the change in sensor output to the change in the input being measured, and is largely dependent on the technology used in the sensor construction. Most gas sensors are designed using biochemical, electrochemical, physical and optical principles. The first consideration is to select a sensitive technology that is sensitive enough to detect the percentage of the valve limit (TLV-thresh-oldlimitvalue) or lower explosive limit (LEL-lowerexplosivelimit) of the target gas.
3. Selectivity
Selectivity is also known as cross sensitivity. It can be determined by measuring the sensor response to a certain concentration of the interfering gas. This response is equivalent to the sensor response produced by a certain concentration of the target gas. This characteristic is very important in the application of tracking multiple gases, because the cross-sensitivity will reduce the repeatability and reliability of the measurement, and the ideal sensor should have high sensitivity and high selectivity.
4. Corrosion resistance
Corrosion resistance refers to the sensor's ability to be exposed to high volume fractions of the target gas. When a large amount of gas leaks, the probe should be able to withstand 10 to 20 times the expected gas volume fraction. Sensor drift and zero correction values should be as small as possible when returning to normal operating conditions.
The basic characteristics of gas sensors, namely sensitivity, selectivity and stability, etc., are mainly determined by the choice of materials. Select appropriate materials and develop new materials to optimize the sensitive characteristics of gas sensors.
