Watlow Series 988 - Manual (Page 148)

WATLOW Series 988 User’s Manual 9.11 Enhanced Software Features, Chapter 9
Enhanced Software
Sample Application
The system outlined above uses a three-way valve for heating and cooling
a fluid sample. Coils surround the container holding the fluid. When the
temperature needs to be raised, the signal to the valve will be between 12
and 20mA, sending hot water through the coils. When cooling is required,
the signal will be between 12 and 4mA, sending cold water through the
coils.
Figure 9.11 - Fluid
sample container
with duplex control.
TL TL W W W WA A
PROCESS
L1 L2 L3 L4
DEV
% OUT DISPLAY
MODE
AUTO
MAN
SERIES 988
input 1 output 1
hot water
cold water
temperature
transmitter
Fluid S a mple Cont a ine r