Vaisala GMM20W - Manual

GMM20W CO
2
module
Sensor Systems Division U300en-1.1
1999-11-16
INTRODUCTION
Vaisala’s GMM20W module uses a
completely new sensor technology. The
silicon based CARBOCAP

sensor
provides for excellent stability and
reliability. The GMM20W module
requires almost no maintenance: the
recommended calibration interval is five
years. This combined with the high
performance makes the GMM20W
modules an ideal choice for OEM
applications related to ambient CO
2
measurement.
72 mm
74
m
m
Figure 1 Dimensions
ELECTRICAL CONNECTIONS
The nominal 24 V supply must be
connected between terminals + and - on
the mother board. The analogue output is
available at remaining terminals. The
common wire is connected to terminal 0
and the other wire either to terminal V
(voltage output) or to terminal mA
(current output). The current output is
chosen with the jumper 0/4mA (see
Figure 3): 4...20mA is chosen by
connecting the jumper (default) and the
0...20 mA is chosen by disconnecting the
jumper. If the relay output of display
models is used, note that the wiring is
done at the back of the display board.
The default relay trigger point has been
set to 1000 ppm. This can be changed
with the optional software kit 19222GM.
For further details, contact your local
Vaisala representative.
Figure 2 Electrical connections and
leds V7, V10
Note that during normal operation the
green led (V10) at the lower righthand
corner is blinking. In case the self-
diagnostics procedure comes across some
abnormality, the red led (V7) lights up
(see Figure 2 above).