Watlow Electric Integrated Controller User Manual Rev C EZ-ZONE PM - Manual (Page 61)

Wa t l o w E Z - Z O N E ® P M I n t e g r a t e d C o n t r o l l e r • 5 9 • C h a p t e r 9 F e a t u r e s
Retransmit Source
Output Scale
Range High
Range Low
Scale High Scale Low
Set the range of the process output with Scale
Low [`S;Lo] and Scale High [`S;hi]. Scale the re-
transmit 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.
Actual Output Power
0
20
40
60
80
100
PID Calculation
Linear
Curve 1
Curve 2
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 Oper-
ations 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 configura-
tion 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 con-
troller to decide whether to perform closed-loop con-
trol 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 appli-
cations 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 con-
troller 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 de-
termine 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 control-
ler 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 out-
put 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.