Watlow PM PLUS™ 6 • 94 • Chapter 8: Features
Differential Control
The PM can be configured for Differential Control with two inputs and enhanced firmware. After configuring
the appropriate inputs and their associated internal functions Differential Control allows the PM to drive an
output based on the difference between those analog inputs. See
Application examples.
Ratio Control
The PM PLUS can be configured for Ratio control with two inputs and enhanced firmware, especially useful
in applications that mix materials. Ratio control is commonly used to ensure that two or more flows are kept
at the same ratio even if the flows are changing. See
Application examples.
Duplex Control
Certain systems require that a single process output controls both heating and cooling outputs. A PM PLUS
with a process output can function as two separate outputs.
With a 4 to 20mA output the heating output, for instance, will operate from 12 to 20mA (0 to +100%) and
the cooling outputs will operate from 12 to 4mA (0 to -100%). In some cases this type of output is required
by the device, such as a three-way valve that opens one way with a 12 to 20mA signal and opens the other
way with a 4 to 12mA signal. This feature reduces the overall system cost using a single output to act as two
outputs.
Motorized Valve Control
A motorized valve is used is to regulate the flow of fluid which in turn impacts the loop process value. A
valve is opened or closed by closing contacts to drive the value in the intended direction.
Timer Function
Applicable on models with a countdown timer. Check your product label to confirm the configuration code shows
T in the 4th digit: PM _ T _ _ _ - _ _ _ _ _ _ _.
hot water
cold water
temperature
transmitter
Fluid S ample Cont ainer
Input 1 Output 1
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