96VTR Datasheet, PDF (10/15 Pages) Extech Instruments Corporation. – 1/4 DIN Process Controller

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Table III - Programmable Auto Tune Initialization Modes
Auto Tune Initialization Modes
Autotune can only be initiated manually with the Setpoint (SV) not equal to the
Process (PV)
Autotune can only be initiated manually with the Process (PV) equal to the
Setpoint (SV)
Autotunes automatically when the controller is FIRST powered up if the PV < SV
Autotunes automatically when the controller is FIRST powered up if the PV = SV
EVERY time the controller is powered up the autotune process begins
automatically if the PV < SV
EVERY time the controller is powered up the autotune process begins
automatically if the PV = SV
9.2.2 Auto Tune Procedure
Note: For Auto Tune to be effective, the controller must be connected in line with
the working application. The process must be running as close to expected
operation as possible.
a. In order to automatically set the Tuning parameters of Level 2 which are ‘Pb’
Proportional Band, ‘ti’ Integral time (also known as Reset), and ‘td’ Derivative time
(also known as Rate), first adjust the controller's setpoint (SV) to a value which
closely approximates your application.
b. Make sure that the value for Proportional Band (Pb) is NOT zero (zero initializes
ON/OFF control).
c. To initiate Auto Tune, press and hold the SCROLL key for at least 5 seconds until
the 'AT" status LED lights.
d. When Auto Tune is complete, the 'AT' status LED will extinguish. The new Tuning
values will now be stored in nonvolatile memory. Adjustments can be made
manually if desired in programming level 2.
e. To abort an Auto Tune process, simply press and hold the RETURN key for 5
seconds until the 'AT' LED extinguishes. Be careful not to hold it longer than it
takes for the 'AT' LED to extinguish otherwise you will access the MANUAL output
control mode inadvertently.
AUTO TUNE NOTE: The Auto Tune process can last from several minutes up to
several hours depending upon each individual process. However, if the Auto Tune
process does take an inordinate amount of time in a fast responding process, it is
recommended that the Auto Tune session be aborted by powering the controller down.
Check all physical connections as well as the controller programming to ensure that the
controller is properly configured in the system before trying another Auto Tune session.
10. AUTOMATIC AND MANUAL OUTPUT CONTROL
AUTOMATIC CONTROL
Automatic Control is the normal mode of controller operation and does not require
keystrokes or special menus to access. In automatic control mode the controller
automatically adjusts the percentage of both the Heating (Primary) and the Cooling
(Secondary) outputs so that the PV = SV.
MANUAL CONTROL
Manual control allows the user to manually drive the Primary and Secondary output
percentages from 0.0 through 100.0% (for testing purposes). To use this feature you
first have to unlock it. Press and hold the DOWN and RETURN keys until the display
flashes. Press and hold the RETURN key for 5 seconds to access the Manual Mode.
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96VTR Ver. 2.0 11/99