Oxygen Sensor
This sensor measures the amount of Oxygen (O2) gas in air.
UNDERSTANDING OXYGEN IN AIR
We have developed a PDF called "Understanding Oxygen in Air" (PDF) that discusses the following topics, some of which are summarized below:
~ Absolute and Relative Gas Concentration
~ Effect of Barometric Pressure on the
Output of the Apogee Oxygen Sensor
~ Example of Pressure Correction
~ Effect of Temperature on the Output of
the Apogee Oxygen Sensor
~ Example of Temperature Correction in Soil
EFFECT OF BAROMETRIC PRESSURE: The sensor is not pressure compensated so changes in barometric pressure change the mV output of the sensor. Barometric pressure changes are relatively small and they do not occur rapidly so it is not always necessary to measure and correct for pressure.
At sea level, the pressure averages 101.3 kPa and ranges ± 2%. The pressure extremes are uncommon. Barometric pressure varies less than ± 1% on about 90% of the days of the year. When the sensor is in air the reading could change from about 20.7 to 21.2 % over a period of several weeks, assuming typical pressure changes.
EFFECT OF TEMPERATURE: In a constant oxygen atmosphere, the mV output of the sensor would change in proportion to a change in the absolute temperature. Since room temperature is about 300 K, a 3 degree Celsius temperature change would change the output by 1% (from 20.9 to 20.7%).
However, this unit has a temperature compensation circuit that corrects for about half of the temperature effect. For exact measurements, the sensor has either a thermistor or a type-K thermocouple inside that can be used to calibrate and more precisely correct for the effect of temperature.
$259
$30
Model SO-110:
Model AO-001:
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