Detcon 700 Series Remote Sensor/Alarm Relay Module With HART Interface - Manual (Page 9)

700 HART-RAM I.M.
The recommended cable for remote sensor separation is Belden 1502P (18AWG unshielded pair for power
and 22AWG shielded twisted pair for serial Modbus™ communications). The mA signal return is not
required.
NOTE: Only the 2-wire power cable (mA signal return is not required) and the 2-wire
Modbus™ serial communications cable are required when remote wiring between the HART-
RAM and the 700 Gas Sensor.
NOTE: The same recommended cables should be used for the connection between a
Modbus™ master control device and the HART-RAM. However, if only the 4-20mA/HART
signal is being used by the master/host controller, then Belden 8770 is recommended.
2. Operator Interface
The operator interface of the HART-RAM is very similar to the Model 700 Gas Sensor. It uses the identical
LED display, same programming magnet, and has the same magnetic programming switches (PGM1/ZERO
and PGM2/SPAN). The main difference is that the 700 HART-RAM has LED indicators for the 3 relays
(ALM1, ALM2 and FAULT) and a CAL LED to indicate when the 700 sensor is in calibration.
The gas reading, gas units, and fault status reported by the HART-RAM will mimic that of the 700 Gas
Sensor.
NOTE: If the Model 700 Gas Sensor is directly connected to the HART-RAM and junction
box, then the gas sensor operation should be exercised through the 700 Gas Sensor (and not the
HART-RAM). This is the recommended practice since the HART-RAM contains only a
limited number of sensor operational control functions. If the HART-RAM and 700 Gas
Sensor are separated, then normal remote gas sensor operation should be exercised through the
HART-RAM.
The operating interface is menu-driven via the two magnetic program switches located under the target
marks on the HART-RAM faceplate. The two switches are referred to as “PGM1” and “PGM2”. The menu
list consists of three major items that include sub-menus as indicated below. (Refer to the complete Software
Flow Chart Figure 8)
Normal Operation
Current Reading and Fault Status
Calibration Mode
AutoZero (if applicable)
AutoSpan
Program Mode
View Sensor Status (representative of whichever Model 700 Gas Sensor is attached)
Set AutoSpan Level
Set Serial ID
Alarm 1 Settings
Alarm 2 Settings
Fault Settings
Signal Output Check
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