GM35 Operating Instructions
Probe Model
Product overview
18 © SICK MAIHAK GmbH • Germany · All rights reserved 8009389/07-2006
2.2.2 Signal evaluation
The optimized algorithms of the GM35 evaluation electronics process the measurement
signals from the receiver elements along with the associated parameters in accordance with
the correlation procedure with optical filters for CO
2
/H
2
O and with gas-filled cells for CO.
Fig. 6 Evaluation of absorption spectrums for measured gases with the GM35
2.2.3 Automatic check cycles
To ensure a consistently high level of measurement accuracy, the GM35 SR unit carries out
a regular automatic check cycle. In this check cycle, the zero point is first determined by po-
sitioning a zero-point reflector in the beam path. Reference filters are then moved into posi-
tion to calculate the check point. If the check cycle reveals that the system is not functioning
in accordance with the specifications, the GM35 measuring system outputs the appropriate
error or warning messages.
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
Absorpt
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 1600 to 2200 nm
CO measurement in the
range approx. 4500 to
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 measured value is determined from the
signals at the detector with CO absorption by
the measured gas and with 100% CO
absorption (CO cell). Interference is eliminated.
Transmission
characteristic
of the filter for the
Absorption
To Next Page
Loading...
