Temperature calibration methods and apparatus for optical absorption gas sensors, and optical absorption gas sensors thereby calibrated

摘要

An optical absorption gas sensor has an LED light source and a photodiode light detector, a temperature measuring device for measuring the LED temperature and a temperature measuring device for measuring the photodiode temperature. The sensor is calibrated by measuring the response of photodiode current at zero analyte gas concentration and at a reference analyte gas concentration. From these measurement, calibration data taking into account the effect of photodiode temperature on the sensitivity of the photodiode and, independently, the effect of changes in the spectrum of light output by the LED on the light detected by the photodiode with LED temperature can be obtained. Calibration data is written to memory in the gas sensor and in operation of the gas sensor, the output is compensated for both LED and photodiode temperature. The LED and photodiode can therefore be relatively far apart and operate at significantly different temperatures allowing greater freedom of optical pathway design.

主权项

1. A method of calibrating an optical absorption gas sensor for detecting an analyte gas, the sensor comprising a gas sample receiving chamber, a light emitting diode (LED) and a photodiode having an output signal sensitive to the amount of light received by the photodiode, the method comprising measuring the photodiode output signal at a first concentration and a different second concentration of the analyte gas within the gas sample receiving chamber, and thereby determining photodiode calibration data and determining LED calibration data based on the measured photodiode output signal at the first concentration and the different second concentration of the analyte gas within the gas sample receiving chamber.