| 摘要 |
A gas sensor which works according to the principle of thermal conductivity is functionally tested. In the method, a calibration cycle is conducted in which a membrane of the gas sensor is immersed in a fluid calibration medium having a known concentration of a target gas. After the calibration cycle, a measurement chamber of the gas sensor is purged with a purging gas. Then, a measuring cycle is conducted, using a thermal conductivity sensor to measure the target gas in the measurement chamber. Using a calibration baseline established from the calibration cycle and a measurement baseline in the measurement cycle, a baseline comparison value is obtained and compared to a predetermined baseline threshold value. An error message, indicating a malfunction in the purging gas supply, is generated when the baseline comparison value exceeds the predetermined baseline threshold value. |
| 主权项 |
1. A method for functionally testing a gas sensor operating according to the principle of thermal conductivity, the gas sensor designed to sense the presence of a target gas in a fluid medium, the gas sensor comprising a measurement chamber with a connection to a supply of a purging gas, a thermal conductivity sensor, disposed in the measurement chamber, for determining one or more measurement values, a temperature sensor, and a membrane that separates the measurement chamber from the fluid medium during operation, the membrane being permeable to the target gas; the method comprising the steps of:
performing a calibration cycle, comprising the steps of:
immersing the membrane of the gas sensor in a calibration medium that is a fluid medium with a known concentration of the target gas;conducting a purging procedure, comprising purging the measurement chamber with the purging gas;conducting a measuring procedure after the purging procedure, the measuring step comprising the step of using the thermal conductivity sensor to take a plurality of measurements of the gas in the measurement chamber, obtaining a plurality of time-related measurement values; anddetermining a calibration baseline from the plurality of time-related measurement values; performing a measurement cycle, comprising the steps of:
immersing the membrane of the gas sensor in a measurement medium that is a fluid medium with an unknown concentration of the target gas;conducting a purging procedure, comprising purging the measurement chamber with the purging gas;conducting a measuring procedure after the purging procedure, the measuring step comprising the step of using the thermal conductivity sensor to make a plurality of measurements of the gas in the measurement chamber, obtaining a plurality of time-related measurement values; and
determining a measurement baseline from the plurality of time-related measurement values; calculating a baseline comparison value taking account of the calibration baseline and the measurement baseline; and comparing the baseline comparison value to a predetermined baseline threshold value, and, if the baseline comparison value is greater than the baseline threshold value, generating a first error message, indicating a malfunction in the purging gas supply. |
