The flexibility of the PM’s software and hardware allows a large range of configurations. Acquiring a better understanding of the controller’s overall functionality and capabilities while at the same time planning out how the controller can be used will deliver maximum effectiveness in your application.
It is useful to think of the controller in three parts: inputs; procedures; and outputs. Information flows from an input to a procedure to an output when the controller is properly configured. A single PM controller can carry out several procedures at the same time, for instance
Inputs
The inputs provide the information that any given programmed procedure can act upon. In a simple form, this information may come from an operator pushing a button or as part of a more complex procedure it may represent a remote set point being received from another controller.
Each analog input typically uses a thermocouple or RTD to read the temperature of something. It can also read volts, current or resistance, allowing it to use various devices to read humidity, air pressure, operator inputs and others values. The settings in the Analog Input Menu (Setup Page) for each analog input must be configured to match the device connected to that input.
Each digital input reads whether a device is active or inactive. A PM with digital
The Function or EZ Key on the front panel of the PM also operates as a digital input by toggling the function assigned to it in the Digital Input Function parameter in the Function Key Menu (Setup Page).
Functions
Functions use input signals to calculate a value. A function may be as simple as reading a digital input to set a state to true or false, or reading a temperature to set an alarm state to on or off. Or, it could compare the temperature of a process to the set point and calculate the optimal power for a heater.
To set up a function, it’s important to tell it what source, or instance, to use. For example, an alarm may be set to respond to either analog input 1 or 2 (instance 1 or 2, respectively).
Keep in mind that a function is a
Outputs
Outputs can perform various functions or actions in response to information provided by a function, such as operating a heater; turning a light on or off; unlocking a door; or turning on a buzzer.
Assign an output to a Function in 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) or to retransmit the value of analog input 2 (instance 2).
You can 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 digital output 5.
Input Events and Output Events
Input events are internal states that are set by the digital inputs. Digital input 5 provides the state of input event 1, and digital input 6 provides the state of input event 2. Wait for Event steps in profiles are triggered by these events. The setting of Digital Input Function (Setup Page, Digital Input/Output Menu) does not change the relationship between the input and the event, so take care not to configure the function in a way that would conflict with a profile that uses an input event. An input will still control the input event state, even if Digital Input Function is set to None.
Output events are internal states that can only be set by profile steps. Outputs 1 through 4 can be configured to respond to output events.
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