Watlow Series D8 - Manual (Page 116)

Chapter 4: Operation and Setup Series D8 User’s Guide
98 Watlow Anafaze Doc. 0600-3120-2000
Typical uses include data logging to analog recording sys-
tems, and long distance transmission of the primary signal to
avoid signal degradation. The retransmitted signal can also be
used as an input to other types of control systems such as a
PLC.
Any available heat or cool output may be used as a retransmit
output. Any process variable may be retransmitted, including
the input from the same loop.
To get a 4 to 20 mA or 0 to 5 Vdc signal, the controller output
signal must be connected to a Serial DAC.
How to Set Up Process Variable Retransmit
1. Configure all of the setup parameters for the primary
loop (the loop whose input signal will be retransmitted).
2. Choose an unused control output to retransmit the input
signal. This output may be on the primary loop or on a
different loop.
3. On the secondary loop (the loop whose output will re-
transmit the signal):
•
Set up the parameters in the PV retrans menu. See
Process Variable Retransmit Menu on page 148.
• Enable the loop’s output and configure it to meet the
requirements of the application.
4. If the signal is being retransmitted to another controller,
configure the input of that controller to accept the linear
output signal produced by the retransmit output.
Process Variable Retransmit Example: Data Logging
The D8 controls the temperature of a furnace. The thermocou-
ple in one of the zones is connected to the controller and is
used for closed-loop PID control. An analog recorder data
logging system is also in place, and a recording of the process
temperature is required. The recorder requires a linear 4 to 20
mA input signal, which represents a process variable range of
0 to 1000° F.