MSA Chemgard - General Description

Section 1, General Information
Chemgard Infrared Gas Monitor
1-4
Figure 1-5. Chemgard Gas Monitor with Optional Beacon
General Description
The Chemgard Unit:
• Monitors gases from parts-per-billion (ppb)
to % level
• Operates on the photo-acoustic principle,
allowing gas concentration measurement in
a
comp
lex mixture of background gases
• Allows gas detection in applications where
contaminants or interferants preclude use of
other techniques
• Provides a digital display; if it is a multi-point
monitor, it also shows the point number
currently being sampled by the unit
• Is also used for applications requiring
long-term stability and low maintenance
• Is factory-calibrated to the full scale value of gas
• Is compensated for the relative humidity of the
gas to give excellent zero stability.
• Operates over a wide temperature range
• Has front-panel windows for viewing:
- Gas concentration
- Diagnostics
- Alarm Conditions
• Is highly selective to enable operation in:
- Areas with varying humidity
- Areas containing other contaminants.
• Comes standard with:
- Four sets of relay contacts
- Two com
pletely i
ndependent outputs:
0-10 V
4-20 mA
• One input: 4-20 mA, assignable to the
ALARM relay.
• RS 232 output (see Appendix C for more
informati
on).
The Internal Multipoint Sequencer Unit:
• Allows a single Chemgard unit to monitor up
to four or eight areas or locations, if equipped