Measuring method for semiconductor gas sensor based on alternating-current impedance

A measuring method for a semiconductor gas sensor based on alternating-current impedance, comprising the following steps:

• a first step, connecting the semiconductor gas sensor to a capacitor in parallel, wherein alternating-current impedance features are formed after the semiconductor gas sensor is connected to the capacitor in parallel, and the alternating-current impedance features comprise the following nine features,
• Y:
• a modulus value, obtained by alternating-current impedance measurement, of admittance,
• X1:
• a reciprocal of a modulus value, obtained by alternating-current impedance measurement, of a real part of the admittance,
• G:
• a modulus value, obtained by alternating-current impedance measurement, of the real part of the admittance,
• Z:
• a modulus value, obtained by alternating-current impedance measurement, of impedance,
• Z1:
• a modulus value, obtained by alternating-current impedance measurement, of a real part of the impedance,
• Y1:
• a reciprocal of the modulus value, obtained by alternating-current impedance measurement, of the real part of the impedance,
• Y2:
• a reciprocal of a modulus value, obtained by alternating-current impedance measurement, of an imaginary part of the impedance,
• phase:
• a phase obtained by alternating-current impedance measurement, and
• P:
• a reciprocal of the phase obtained by alternating-current impedance measurement;
• a second step, connecting an alternating-current impedance measuring device to the semiconductor gas sensor and the capacitor, wherein the semiconductor gas sensor measures a target type of gas with a known concentration according to the following way:
• combining measuring parameters under measuring frequencies within a first preset range and parallel capacitance values within a second preset range, and measuring a certain type of gas with the known concentration according to each of the nine features under each combination;
• after each measurement is ended, obtaining a feature value corresponding to the known concentration under a currently selected certain feature in the nine features;
• traversing all parameter combinations and all the nine features to obtain a plurality of feature values corresponding to the same gas concentration under each feature;
• in the case that the linearity and signal-to-noise ratio of each of the feature values of all kinds of the features and the known concentration are simultaneously taken into consideration, the linearity is enabled to be greater than or equal to a first threshold and the signal-to-noise ratio is enabled to be greater than or equal to a second threshold:
• selecting measuring frequencies within a third range adopting a frequency range formed by corresponding frequency values, wherein a lower limit of the third range is the minimum frequency in the corresponding frequency values, and an upper limit of the third range is the maximum frequency in the corresponding frequencies,
• selecting parallel capacitance values within a fourth range adopting a capacitance range formed by corresponding parallel capacitance values, wherein a lower limit of the fourth range is the minimum capacitance value in the corresponding parallel capacitance values, and an upper limit of the fourth range is the maximum capacitance value in the corresponding parallel capacitance values,
• selecting a certain or several of the corresponding features, and
• taking the selected measuring frequencies within the third range, the selected parallel capacitance values within the fourth range and the selected certain or several of the corresponding features as finally selected measuring parameters for measuring an unknown gas concentration;
• and
• a third step, measuring the type of gas with an unknown concentration based on the measuring parameters.