Watlow ez-zone pm - On-Off Control

Watlow EZ-ZONE
®
PMI Controller • 194 • Chapter 9 Features
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 or 10 seconds, (whichever is
longer) prior to sensor failure, and that
power level is less than 75 percent.
Reverse Bumpless functionality will take
effect when the control is changed from
Manual to Auto mode. The control will
preload the Manual Power value into the
Integral and Proportional Terms, which
will allow for a bumpless transition. The
normal PID action will then take over to control the output to the Set Point value.
Note:
Reverse bumpless ignores the transition from Off to Auto.
Input Error Latching i.Er (Setup Page, Analog Input Menu) determines the controller’s re-
sponse once a valid input signal returns to the controller. If latching is on, then the con-
troller will continue to indicate an input error until the error is cleared. To clear a latched
alarm, press the Advance Key ‰ then the Up Key ¿. If latching is off, the controller will
automatically clear the input error and return to reading the temperature. If the control-
ler was in the auto mode when the input error occurred, it will resume closed-loop control.
If the controller was in manual mode when the error occurred, the controller will remain in
open-loop control. The Manual Control Indicator Light % is on when the controller is operat-
ing in manual mode.
You can easily switch between modes if the Control Mode C.ЛЏ parameter is selected to ap-
pear in the Home Page.
To transfer to manual mode from auto mode:
1. Press the Advance Key ‰ until C.ЛЏ appears in the lower display. The upper display will
display aUto for auto mode.
2. Use the Up ¿ or Down ¯ keys to select ЛЏan. The manual set point value will be re-
called from the last manual operation.
To transfer to auto mode from manual mode:
1. Press the Advance Key ‰ until C.ЛЏ appears in the lower display. The upper display will
display ЛЏan for manual mode.
2. Use the Up ¿ or Down ¯ keys to select aUto. The automatic set point value will be re-
called from the last automatic operation.
Changes take effect after three seconds or immediately upon pressing either the Advance
Key ‰ or the Innity Key ˆ.
On-Off Control
On-off control switches the output either full on or full off, depending on the input, set
point and hysteresis values. The hysteresis value indicates the amount the process value
must deviate from the set point to turn on the output. Increasing the value decreases the
number of times the output will cycle. Decreasing hysteresis improves controllability. With
hysteresis set to 0, the process value would stay closer to the set point, but the output
would switch on and off more frequently, and may result in the output “chattering.” On-off
Time
Temperature
40%
Sensor
Break
2 minutes
Locks in
Output
Power
0%
Set Point
Actual Temperature
Output Power
Power
100%