Watlow PM PLUS™ 6 • 11 • Chapter 1 Overview
PM PLUS™ Operational Overview
The PMPLUS receives Information from an input, performs an internal function as a response to that input,
then causes a resulting output. All of these - the inputs, the internal functions, and the outputs - are
configurable. A single PM PLUS™ can carry out several functions at the same time, such as PID control, check-
ing for a limit condition, monitoring for several alarm situations, etc.
You may configure up to four profiles to automate a sequence of up to ten steps per profile, to further
customize and extend the application of the device.
Inputs
Inputs provide the information a programmed procedure can act upon. A basic example is a sensor monitoring
the temperature of a part being heated or cooled. Each analog input typically uses a thermocouple or RTD to
read the process temperature or the volts, current or resistance from various devices.
Optional digital input/output (DIO) hardware can be used as either an input or an output. Each DIO must be
configured as either an input or output. A digital input allows for a specific function to occur. The Function Key
can also be programmed to allow for a specific function to occur.
Internal Functions
A function is a user-programmed internal process that uses input signals to calculate a value and then perform
an action, i.e.:
• Compare an input value to the set point and calculate the optimal power for a heater
• Detect a failure of the primary sensing device and trip a contactor to remove power from the heating
element
• When a digital input signal changes, allows for a specific function to occur.
• Evaluate an incoming temperature to determine an alarm state (on or off)
Each internal function is associated with one source, or instance. For example, a control equipped with DIO,
can be configured to respond to one of the four alarms.
Outputs
Outputs are functions or actions configured to respond to information provided by an internal function. Some
output examples are: removal of the control voltage to a contactor; operating a heater, turning a light on or off,
unlocking a door, etc.
You can assign outputs to any input, and may assign more than one output to respond to a single instance of a
function. For example, alarm 2 could be used to trigger a light connected to output 1 and a siren connected to
DIO 5.
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