Range High

Output Scale

Range Low

Scale Low

Retransmit Source

Scale High

 

 

Set the range of the process output with Scale Low [`S;Lo] and Scale High [`S;hi]. Scale the retransmit source to the process output with Range Low [`r;Lo] and Range High [`r;hi].

When the retransmit source is at the Range Low value, the retransmit output will be at its Scale Low value. When the retransmit source is at the Range High value, the retransmit output will be at its Scale High value.

Cool Output Curve

A nonlinear output curve may improve performance when the response of the output device is nonlinear. If a cool output uses one of the nonlinear curves a PID calculation yields a lower actual output level than a linear output would provide.

These output curves are used in plastics extruder applications: curve 1 for oil-cooled extruders and curve 2 for water-cooled extruders.

100

Power

80

 

 

 

 

Output

60

 

 

 

 

Actual

 

Linear

40

Curve 1

Curve 2

 

 

 

 

20

 

 

 

 

0

 

 

PID Calculation

 

 

Select a nonlinear cool output curve with Cool Output Curve [`C;Cr] (Setup Menu, Loop Menu).

Control Methods

Output Configuration

Each controller output can be configured as a heat output, a cool output, an alarm output or deactivat- ed. No dependency limitations have been placed on the available combinations. The outputs can be con-

figured in any combination. For instance, all three could be set to cool.

Heat and cool outputs use the set point and Operations parameters to determine the output value. All heat and cool outputs use the same set point value.

Heat and cool each have their own set of control pa- rameters. All heat outputs use the same set of heat control parameters and all cool outputs use the same set of cool output parameters.

Each alarm output has its own set of configuration parameters and set points, allowing independent operation.

Auto (closed loop) and Manual (open loop) Control

The controller has two basic modes of operation, auto mode and manual mode. Auto mode allows the controller to decide whether to perform closed-loop control or to follow the settings of Input Error Failure [FAiL] (Setup Page, Loop Menu). The manual mode only allows open-loop control. The EZ-ZONE®PM controller is normally used in the auto mode. The manual mode is usually only used for specialty applications or for troubleshooting.

Manual mode is open-loop control that allows the user to directly set the power level to the controller’s output load. No adjustments of the output power level occur based on temperature or set point in this mode.

In auto mode, the controller monitors the input to determine if closed-loop control is possible. The controller checks to make certain a functioning sensor is providing a valid input signal. If a valid input signal is present, the controller will perform closed-loop con- trol. Closed-loop control uses a process sensor to determine the difference between the process value and the set point. Then the controller applies power to a control output load to reduce that difference.

If a valid input signal is not present, the controller will indicate an input error message in the upper display and [Attn] in the lower display and respond to the failure according to the setting of Input Error Failure [FAiL]. You can configure the controller to perform a “bumpless” transfer [bPLS], switch power to output a preset fixed level [MAn], or turn the output power off.

Bumpless transfer will allow the controller to transfer to the manual mode using the last power value calculated in the auto mode if the process had stabilized at a ±5 percent output power level for the time interval of Time Integral (Operations Page, Loop) prior to sensor failure, and that power level is less than 75 percent.

Watlow EZ-ZONE®PM Integrated Controller

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Chapter 9 Features