Detcon 700 Remote Sensor/Alarm Relay Module - Manual (Page 14)

700 RAM I.M.
3.5 Signal Output Check
Signal Output Check provides a simulated 4-20mA output and RS-485 Modbus™ output. The simulation
allows the user to conveniently perform a functional system check of the entire safety system, and can be
initiated at the RAM. This signal output simulation aids in performing troubleshooting of signal wiring
problems.
This menu item appears as: “Signal Output Check”.
From the “Signal Output Check” text scroll, hold the magnet over PGM1 (©) or PGM2 (ª) until the arrow
prompt appears and then hold continuously for an additional 3 seconds. Once initiated, the display will
continuously scroll “Simulation Active” until the function is stopped. During simulation mode, the 4-20mA
value will be increased from 4.0mA to 20.0mA (in 1% of range increments at a 1 second update rate) and
then decreased from 20.0mA to 4.0mA. The same simulation sequence is applied to the Modbus™ output
gas reading.
NOTE: Signal Output Check stays active indefinitely until the user stops the function. There
is no automatic timeout for this feature.
To end simulation mode, hold magnet over PGM1 (©) or PGM2 (ª) until the arrow prompt appears and
then hold continuously for an additional 3 seconds. The display will revert to either the prior menu item or
the next menu item respectively.
The user can then choose to either: 1) move to another menu item by executing a momentary hold, or 2)
return to Normal Operation via 15 second automatic timeout.
4. RS-485 Modbus
™
Protocol
The RAM module provides a Modbus™ compatible communications protocol and is addressable via the
program mode. This Modbus™ output is exactly repeated from the specific Model 700 sensor that is
attached. Communication is two-wire, half duplex RS-485, 9600 baud, 8 data bits, 1 stop bit, no parity, with
the sensor set up as a slave device. An RS-485 Master Controller up to 4000 feet away can theoretically poll
up to 256 different RAM’s. This number may not be realistic in harsh environments where noise and/or
wiring conditions would make it impractical to place so many devices on the same pair of wires. If a multi-
point system is being utilized, each RAM must be set for a different address. Typical address settings are:
01, 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10, 11…etc.
Successful Modbus™ communications between the RAM and an RS-485 Master Controller is indicated by a
blinking “CAL” LED. If the Modbus™ communication between the RAM and the 700 Gas Sensor is not
functioning, the RAM will display “COMM” and the “FLT” LED will be illuminated.
NOTE: The 700 Gas Sensor must be set to Serial ID = 01 for proper communications set-up
with the RAM.
RS-485 ID numbers are factory default to 01. These can be changed in the field via the Operator Interface
described in Section 3.3, Set Serial ID.
NOTE: Refer to the Model 700 Gas Sensor Instruction Manual for details on the Modbus™
protocol registers.
700 RAM I.M. Rev. 1.0 Page 10 of 13