MSA Chemgard - Remote Gas Sampling Channel

Chemgard Infrared Gas Monitor
Appendix C, RS-232 Output
C-3
Table C-3. Data Logging
Table C-4. Alarm Logging
RS-232 Output
The RS-232 output broadcasts certain information
about the Chemgard Infrared Gas Monitor
(TABLE C-3). This output conforms to the
specification for RS-232 signal levels and is
capable of driving its signal up to 200 feet (61 m)
when using low capacitance RS-232 cable. See
FIGURE C-1 for RS-232 connector location.
Connection to the RS-232 output is via a 25-pin
sub "D" female connector. See FIGURE C-2 for
the wiring defini
tion. To enable this
communication, pins 4 and 5 on the sub "D"
connector must be connected. FIGURE C-2
shows the connector and wiring as it is wired to a
computer. FIGURE C-3 shows the rear view
wiring of the connector.
When connecting RS-232 cable to the instrument:
• The strain relief cover or shell on the 25-pin
sub "D" connector must be removed. It is not
possible to use a pre-wired or molded cable
because its shell or strain relief is not
removable. The connector’s shell or strain
relief does not fit within the instrument
.
• It may be necessary to remove the metal
covers from the printed circuit boards to
attach the 25-pin sub "D" connector to its
mate on the unit. If the metal covers are
removed, replace them when the cable’s
connector is mated to the connector on the
printed circuit board.
Remote Gas Sampling
Channel Identification
Chemgard Infrared Monitors have two analog
outputs:
• 4-20 mA and
• 0-10 Volts.
The voltage output can be programmed to
correspond to the channel presently being
sampled. The front panel screen indica
tes:
1V/PT IF OUT = 1-10V
(1 volt per point if output equals one to 10 volts).
When enabled and the unit is monitoring from:
• channel 1, the voltage output is one volt
• channel 2, the voltage output changes to
two volts.