2.4
MS-2101
Chapter 2
Installation
You must install the RTD sensor on the pipe surface or
thermal well before the pipe insulation to ensure proper
thermal contact. The RTD position should be 180° from
the electric heat trace cable which is the coldest spot of
the pipe. The RTD sensor may be secured to the pipe by
fiber-glass tape. If additional wiring is required for the
RTD, shielded 3-lead wire sized 18 or 20AWG must be
used for the RTD sensor to minimize the effects of noise
pickup. A typical RTD installation is shown in
Figure 2.4
.
Communication Wiring
The MS-2101 is equipped with a communication port that
provides continuous monitoring and control from a
remote computer, SCADA system or PLC. Communica-
tions protocol is Modicon Modbus as discussed in the
communications chapter.
Communication is RS-485 mode where data transmission
and reception are done over a single twisted pair with
transmit and receive data alternating over the same pair of
wires.
Shielded twisted pair such as Belden cable 9841 or
equivalent is recommended to minimize error from noise.
You must observe polarity. For each MS-2101 controller,
you must connect A+ terminals together and B- terminals
together. The shield terminal (labelled SHD) connect to
shield wire of the cable.
To avoid loop currents, the shield should be grounded at
one point only. Connect between controllers in daisy-
chain fashion. The total length of this daisy-chain should
not exceed 4,000 feet. The maximum number of devices
connected is 32 to avoid exceeding driver capability. You
can use commercially available repeaters to increase the
number of devices over 32. Avoid star or stub
connections.
Terminate the first and last device in the daisy-chain loop.
Each controller is equipped with a termination jumper as
shown in
Figure 2.2.
The controller comes unterminated from the factory
(JP401 and JP402 in
OUT
position). If the controller is
the first or last device, it can be terminated by moving the
two jumpers (JP401 and JP402) to the
IN
position.
The communication port is powered by an isolated power
supply with opto-coupled data interface to eliminate noise
coupling. In addition, surge protection devices are
employed at the front end of the port to protect against
lightening strikes and ground surge currents. These may
cause large, momentary voltage differences between
devices on the data highway.
Alarm Wiring
The MS-2101 has one passive (mechanical) alarm contact
and one active alarm output for driving an LED alarm
indicator. The alarm contact is software configurable for
normally open or closed. The alarm LED output is
software configurable for alarm on, alarm off or flash
during alarm. Refer to
Figure 2.
7 for alarm output termi-
nals.
The mechanical (dry) alarm output is rated 30Vdc/10mA,
250Vac/0.5A Max.
The alarm LED output is rated 5Vdc, 50mA. It can drive a
6Vdc LED indicator. Alarm output is designed for interface
to annunciator, panels, PLC or DCS.
Figure 2.5
Communication Wiring
