Teledyne 1220 - Multipoint flammable gas and vapor detection system - Manual (Page 11)

2-1
Multi-Channel Combustible Monitor Operational Theory 2
Teledyne Analytical Instruments
Operational Theory
2.1 Introduction
The Model 1220 combustible gas analyzer is composed of four com-
ponents:
1. System Chassis
2. Control Unit
3. Channel Modules
4. Combustible Sensors
The System Chassis provides structural support and electrical inter-
connection for a Control Unit and up to eight Channel Modules. Each
Channel Module can monitor one or two sensors (dual-sensor option).
2.2 System Chassis
All electrical connections are located on the rear of the system chassis.
The nine terminal strips constitute one each for the Channel Modules and
one for the Control Module.
2.3 Control Unit
The Control Unit provides control of electrical power to the channel
module, audio alarms and external alarms through the common alarm
relays.
Alarm signals from any Channel Module trigger the corresponding
relays in the Control Unit. For example, “high” alarm signals from any
channel trigger the “high” alarm relay in the system control module. There
are three such relays in the Control Unit, one each for high, caution and
failure alarms. The failure alarm relay in the Control Unit is operated
“fail-safe”; however, the gas level alarm relays can be optionally connected
Control Unit - Front Panel