Watlow PM LEGACY™ Limit Controller • 8 • Chapter 1 Overview
Figure 3: Output Wiring Example
(Overview Continued)
Internal Functions
The controller will use input signals to calculate
a value and then perform an operation. A sample
of some functions may be as simple as:
• Detect a failure of the primary sensing device
and trip a contactor to remove power from the
heating element.
• Reading a digital input to set a state to true or
false.
• Evaluate an incoming temperature to determine
an alarm state (on or off).
• Compare an input value to the set point and
calculate the optimal power for a heater.
To set up a function, it’s important to define the
source, or instance, to use. For example, if the
control is equipped with DIO they can be con-
figured to respond to an alarm. If configured
as such, the digital output must be tied to the
desired alarm instance (1 to 4). Using this as
an example, the Function for the digital output
would be defined as an Alarm where the Instance
would be selected as 1, 2, 3, or 4 corresponding
to the alarm instance that will drive the output.
Keep in mind that a function is a user-pro-
grammed internal process that does not execute
any action outside of the controller. To have any
effect outside of the controller, an output must be
configured to respon
Outputs
The Output Wire Terminals are located on the
back side of the controller. See Figure 3. The
Outputs properly wired and configured can
perform various functions or actions in response
to information provided by a function such as,
removal of the control voltage to a contactor;
operating a heater, turning a light on or off, un-
locking a door, etc.
Assign a Function to any available output on the
Setup Page within the Output Menu or Digital
Input/Output Menu. Then select which instance
of that function will drive the selected output.
For example, you might assign an output to
respond to alarm 4 (instance 4).
You can assign more than one output to re-
spond to a single instance of a function. For ex-
ample, alarm 2 could be used to trigger a light
connected to output 1 and a siren connected to
digital output 5.
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