Detcon DM-700 - Manual (Page 6)

Model DM-700
DM-700 Instruction Manual Rev. 4.0 Page 2 of 48
Figure 2 Construction of Galvanic Cell
1.2 Sensor Electronics Design
Intelligent Transmitter Module
The DM-700 Intelligent Transmitter Module (ITM) is a fully encapsulated microprocessor-based package that
is universal in design and will accept any Detcon intelligent plug-in electrochemical gas sensor. The ITM
design uses an internal intrinsically safe barrier circuit that lifts the requirement for use of flame arrestors to
achieve Class 1, Division 1 (Zone1) area classification. This facilitates fast response times and improved
calibration repeatability on highly corrosive gas types. The ITM circuit functions include extensive I/O circuit
protection, on-board power supplies, internal intrinsically safe barrier circuit, microprocessor, LED display,
magnetic programming switches, a linear 4-20mA DC output, and a Modbus™ RS-485 output. Magnetic
program switches located on either side of the LED Display are activated via a hand-held magnetic
programming tool, thus allowing non-intrusive operator interface with the ITM.
Calibration can be
accomplished without declassifying the area. Electrical classifications are Class I, Division 1, Groups B C D
and Class I, Zone 1, Group IIC.
Figure 3 ITM Circuit Functional Block Diagram
I/O
Circuit
Protection
RS-485
4-20mA
Display
Micro-
Processor
Intrinsically
Safe Barrier
Analog 4-20mA Out
Modbus™ RS-485 Output
Power In
Power Supply
Intelligent
Plug-In
Sensor