Carbon Dioxide; Ndir Measurement Of Co; Figure 12-8: Co 2 Sensor Principles Of Operation - Teledyne t100 Operation Manual

Teledyne API - T100 UV Fluorescence SO
12.3. CARBON DIOXIDE (CO
OPERATION
12.3.1.

NDIR MEASUREMENT OF CO

06807F DCN7335
Analyzer
2
2
The CO sensor probe measures the concentration of carbon dioxde in the sample gas; a
2
Logic PCA conditions the probe output and issues a 0-5 VDC signal to the analyzer's
CPU, which computes the CO
and CO _OFFSET recorded during calibration
2
The CO sensor assembly itself does not have any serviceable parts and is enclosed in an
2
insulated canister.
The optional CO sensor is a silicon based Non-Dispersive Infrared (NDIR) sensor. It
2
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 present. A special light filter called a Fabry-Perot Interferometer
2
(FPI) is electronically tuned so that only light at the absorption wavelength of CO
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
IR Light
Source
Sample
In
Figure 12-8: CO
The sensor computes the ratio between the reference signal and the measurement signal
to determine the degree of light absorbed by CO
dual wavelength method the CO
ancillary effects like sensor aging and contamination.
) SENSOR PRINCIPLES OF
concentration by scaling the values of the CO
2
2
absorption wavelength is let through.
2
Sample
Out
Sensor Principles of Operation
2
measurement allows the instrument to compensate for
2
Principles of Operation
IR
Detector
(NDIR)
Signal
Out
FPI
(Measure Phase)
Signal
Out
FPI
(Reference Phase)
present in the sensor chamber. This
2
_SLOPE
2
is
2
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