3.1
Physical Installation
Location
The mounting location for the Remote RTD Module should be chosen to give easy
access to the RTD wiring as well as providing a location to mount the power supply.
The Remote RTD Module is specifically designed to be mounted close to the
equipment it is monitoring. This eliminates long RTD wire lengths which save time
and money on installation and wiring.
Site Requirements
The installation location must meet the following specifications;
•
Temperature: -40
o
C to 60
o
C.
•
Humidity: up to 95%, non-condensing.
Mounting
The Benshaw Remote RTD Module is designed to mount on industry standard 35mm
wide by 7.5mm deep DIN rail. The Remote RTD Module should be mounted in a
location that allows access to the control terminals and visual inspection of the
indicator LEDs.
Modbus Address
Set the rotary switch on the top of the Remote RTD Module to the desired Modbus
address.
3.2
Power Wire Connections
Power Connections
The 24VDC power source is connected to the following terminals.
•
24VDC –
- Negative connection to 24VDC power supply
•
24VDC +
- Positive connection to 24VDC power supply
•
g
- Chassis ground connection
3.3
RS-485 Wiring
RS-485 Communications
The RS-485 communications wiring should use shielded twisted pair cable. The shield
should only be terminated at one end. The connections are as follows;
•
A (–)
- RS485 negative communications connection.
•
B (+)
- RS485 positive communications connection.
•
Com
- RS485 common connection.
RS-485 Cable Specification
The RS-485 communications cable should conform to the following specification;
•
Conductors - 2 twisted pair (one pair signal plus one for signal common).
•
Gauge - 16 to 24 AWG stranded, tinned copper.
•
Impedance - 100 to 120 Ohms.
•
Capacitance - 15.5pF/ft. or less.
•
Shield - Overall Shield.
RS-485 Topology
The RS-485 network should be wired in a daisy-chain configuration. Avoid using star
or stub configurations.
RS-485 Shielding
The RS-485 shield should be terminated at only one point in the network, preferably
at the master device. Do not connect the RS-485 shield to the RTD shield terminals.
RS-485 Termination
A 120
W
resistor may optionally be installed between the A(-) and B(+) terminals if the
Remote RTD Module is the end device on the RS-485 network. The terminating
resistor may be necessary if the RS-485 cable is extremely long. Do not install a
terminating resistor if the Remote RTD Module is not the end device on the network.
There should never be more than two terminating resistors on the network.
8
3. INSTALLATION OF THE REMOTE RTD MODULE
