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Optional Hardware and Software Teledyne API M100E Analyzer Operation Manual
66
Table 5-9: CO
2
Sensor Specifications
Accuracy at 25˚C 0.02% C
O
2
+ 2% of reading
Linearity 0.5 % of full scale
Typical Temperature
Dependence
-0.1% FS / ˚C
Long Term Stability <+15 % FS / 2 years
Response time 20 seconds
Warm up time 5 minutes
Power consumption 2.5 watts
5.9.2.2. THEORY OF OPERATION
NDIR MEASUREMENT OF CO
2
The optional CO
2
sensor is a silicon based Non-Dispersive Infrared (NDIR) sensor. It uses a single-beam, dual
wavelength measurement method.
An infrared source at one end of the measurement chamber emits IR radiation into the sensor’s measurement
chamber where light at the 4.3 μm wavelength is partially absorbed by any CO
2
present. A special light filter
called a Fabry-Perot Interferometer (FPI) is electronically tuned so that only light at the absorption wavelength of
CO
2
is allowed to pass and be detected by the sensor’s IR detector.
A reference measurement is made by electronically shifting the filter band pass wavelength so that no IR at the
CO
2
absorption wavelength is let through.
Figure 5-11: CO
2
Sensor Theory of Operation
The sensor computes the ratio between the reference signal and the measurement signal to determine the
degree of light absorbed by CO
2
present in the sensor chamber. This dual wavelength method the CO
2
measurement allows the instrument to compensate for ancillary effects like sensor aging and contamination.
04515F DCN6048