MASTERTRACE
F.1
Appendix F
Wireless and Wired RTD
RTD is the main temperature sensor in MasterTrace
TM
heat-tracing controllers. Each heater in a MasterTrace
TM
heat-tracing control module has at least one RTD input.
For RTD wiring, the conventional way is to mount one
end of the RTD, the probe, on the pipe and connect the
other end of the RTD, 3 wires, to the RTD input terminals
on the controller. If the distance between the pipe and the
controller is longer than the RTD wire, extension wires
must be added. This could be very costly. In order to re-
duce the wire resistance, a special RTD wire such as Beldon
cable 8770 must be used as the extension wire. Also, to
meet the industrial standard, the RTD wire must go through
aluminium conduit. For every foot of RTD extension wires,
at least $22 is added to the installation cost.
To reduce the installation cost and add more conven-
ience and flexibility to the RTD wiring process, 4 RTD
wiring configurations, as shown in Figure F.1-F.4, are cre-
ated for MasterTrace
TM
heat-tracing controllers. They are:
(1) On-Board RTD Wiring; (2) Transmit RTD Measure-
ment via RS485 Cable; (3) Transmit RTD Measurement
via Wireless RF-Modem; (4) Transmit RTD Measurement
via 18 AWG wire.
The RTD BOARD function (msg. S3-14) is created to
give customers the flexibility to choose their desired RTD
wiring configuration. Its selectable choices are: RTD Sam-
pler 0, ..., RTD Sampler 15, On Board, and RTD Trans-
mitter.
(a) If the option “On Board” is selected, the control
module uses the RTD board directly mounted on itself to
measure heater temperatures.
(b) If the option “RTD Sampler x” is chosen, the con-
trol module uses the temperature measurements from “RTD
Sampler x” to control heaters. Here, x is the address of the
RTD Sampler.
The RTD Sampler is an independent temperature-meas-
urement device and is usually located far away from the
control module. The address of an RTD Sampler can be
set to a value between 0 to 15 by positions of the dip
switches on board. An RTD Sampler can measure either
10 or 20 RTD temperatures depending on the setup. The
temperature measurement from the RTD Sampler is trans-
mitted to the control module via either RS485 cable or RF
Modem. The communication from the RTD Sampler to
the control module is in a manner of continuous broadcast
transmission. The communication message includes not
only the temperature measurement but also the address of
the RTD Sampler. This means that any numbers of control
modules can use the same RTD Sampler as long as their
designated RTD Sampler addresses match.
(c) If the option RTD Transmitter is selected, the con-
trol module uses the temperature measurement signal re-
ceived from the RTD Transmitters to control heaters.
The RTD Transmitter is another independent tempera-
ture-measurement device. The actual RTD sensor is to be
locally wired to the RTD Transmitter. The RTD transmit-
ter is connected to the Xmitter terminals on RTD Trans-
mitter board on the control module through two 18 AWG
wires. Refer to Figure 5.7 in Chapter 5 and Figure MS-
10ADIN2X in Appendix D for the wiring details between
the RTD Transmitter and control module. Each control
point requires a dedicated RTD Transmitter for its tem-
perature measurement. Since the RTD Transmitter only
uses two 18 AWG wires to transmit its temperature meas-
urement to the control module in a form of 4-20mA dc
current, the actual RTD sensor can be located up to 7km
away from the control module. This creates a great deal of
flexibility to the RTD wiring process.
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