Gas Sensor

Stability
Stability is the stability of the basic response of the sensor throughout the operating time, depending on zero drift and interval drift. Zero drift is the change in the output response of the sensor throughout the operating time in the absence of the target gas. Interval drift is the change in the output response of a sensor continuously exposed to a target gas, as indicated by a decrease in the sensor output signal over the operating time. Ideally, a sensor should have a zero drift of less than 10% per year under continuous operating conditions.

Sensitivity
Sensitivity is the ratio of the change in the output of a sensor to the change in the measured input, and is largely dependent on the technology used in the construction of the sensor. Most gas sensors are designed using biochemical, electrochemical, physical and optical principles.

Selectivity
Selectivity is also known as cross-sensitivity. It can be determined by measuring the response of the sensor produced by 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 important in applications where multiple gases are being tracked because cross sensitivity reduces the repeatability and reliability of the measurement and the ideal sensor should have high sensitivity and high selectivity.

Corrosion resistance
Corrosion resistance is the ability of the sensor to be exposed to high volume fractions of the target gas. In the case of large gas leakage, the probe should be able to withstand the desired gas volume fraction 10 to 20 times. On return to normal operating conditions, sensor drift and zero calibration values should be as small as possible. The basic characteristics of a gas sensor, i.e., sensitivity, selectivity, and stability, are determined primarily by the choice of materials. Selection of appropriate materials and development of new materials optimize the sensitive characteristics of gas sensors.