SICK GM35

15
8009441/YN36/V3-0/2015-08| SICK OPERATING INSTRUCTIONS|GM35
Subject to change without notice
PRODUCT OVERVIEW
2.3.2 Signal evaluation
The optimized algorithms of the GM35 evaluation electronics process the measurement
signals of the receiver elements together with the associated parameters in accordance
with the correlation procedure with optical filters for CO
2
and H
2
O and with cells filled with
CO or N
2
O.
Fig. 4: Evaluation of absorption spectrums for sample gases with the GM35
2.3.3 Automatic check cycles
To ensure a consistently high level of measuring precision, the GM35 SR-unit performs a
regular automatic check cycle in an adjustable interval (standard: Every 2 hours). In this
check cycle, the zero point is first determined by swiveling a zero point reflector into the
CO
CO
2
H
2
O
2000 2500 3000 3500 4000
λ
[nm]
4500 50001500
18001600 2000 2200
Ref. 2 H
2
OCO
2
Ref. 1
Absorption
H
2
OCO
2
46004400 4800 5000
CO
N
2
CO
4600 4800 4600 4800
CO
2
and H
2
O measurement in
the range of 1600–2200 nm
CO measurement in the range
of approx. 4500–4900 nm
Cell wheel
N
2
/CO
Absorption CO
≈ measured value
Absorption CO
= 100%
Filter wheel for
CO
2
and H
2
O
Reference filter for determining the
background absorption, free of cross-
sensitivities with other gas components
The CO or N
2
O measured values are
determined from the signals at the
detector with absorption by the sample gas
and with a cell filled with the component to
be measured. Interference is eliminated.
Transmission
characteristic line
of the CO
measurement filter
Absorption