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Principles of Operation Teledyne API T801 NDIR CO2 Analyzer Operation Manual
204
Figure 12-1. 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 of measuring CO
2
allows the instrument
to compensate for ancillary effects like sensor aging and contamination.
12.2. OPERATION WITHIN THE T801 ANALYZER
Operationally, the CO
2
sensor is transparently integrated into the core analyzer
operation. All functions can be viewed or accessed through the front panel.
The gas concentration reading is viewable in the upper right-hand corner of the
display screen.
Test functions for the slope and offset are also viewable in the display screen,
along with the analyzer’s other test functions.
Calibration is performed via the front panel keypad under the CAL button. See
Section 9 for more details.
Stability valu
es can also be viewed in the display screen (see Section 9).
12.2.1. ELECTRONIC OPERATION OF THE CO
2
SENSOR
The CO
2
PCA is powered by 12 VDC from the analyzer via the relay card, which
outputs a 0-5 VDC analog signal to the analyzer’s CPU via the motherboard that
corresponds to the concentration of CO
2
measured by the probe.
07274B DCN6418