Vaisala GMM20W User Manual
GMM20W CO
Sensor Systems Division U300en-1.1
module
2
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
measurement.
72 mm
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
2
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.
74 mm
Figure 1 Dimensions
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 selfdiagnostics procedure comes across some
abnormality, the red led (V7) lights up
(see Figure 2 above).
1999-11-16
GMM20W CO
Sensor Systems Division U300en-1.1
module
2
SERVICE AND MAINTENANCE
The GMM20W module has an excellent
stability and requires almost no maintenance. A full after sales calibration and
service facility is naturally provided by
Vaisala and its distributors.
In case the user prefers to do the calibration himself, calibration gases and
equipment are also available. Vaisala's
portable CO2 meters together with the
Calibration Kit provide for easy and
convenient on-site calibration checks
(see the corresponding manuals for
detailed instructions).
GMM20W should be adjusted if the
reading differs too much from the
reference value during checking (note
that in any case, only slight differences
are expected). For this purpose, we
recommend Vaisala’s Software Kit
19222GM which includes a floppy disk
and a serial COM adapter.
Connect the cable to the connector
marked “Serial Com” on the main PCB
of the module and to the connector A on
the serial COM adapter (see Figure 3).
In order to achieve full accuracy, the
module has to be calibrated against
accurate and traceable calibration gases
in stable environmental conditions
(temperature, pressure). Accurate calibrations are usually performed in laboratories; in these calibrations, temperature
and pressure corrections have to be
made. For further details, consult your
local Vaisala representative.
1999-11-16
Figure 3 Connection of the serial communication cab le
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