Automatic Tuning - Extech Instruments 48VTR User Manual

Automatic Tuning

The Auto Tune feature automatically sets the tuning parameters for the 2
parameters ('Pb' Proportional Band, 'ti' Integral time a.k.a. Reset, and 'td' Derivative time,
a.k.a. Rate). The controller must be wired and functioning in the application at hand for
Auto Tune to work correctly.
1. Adjust the controller's setpoint (SV) to closely approximate your application.
2. Ensure that the value for Proportional Band (Pb) in the 2
(zero is used for ON/OFF control only – Auto Tune does not apply to ON/OFF
control).
3. Press and hold the SCROLL key for at least 5 seconds until the right-most decimal
on the PV display begins flashing.
4. When Auto Tune is complete, the right-most decimal will cease flashing. The new
Tuning values will now be stored in nonvolatile memory. The controller is now
ready for use.
5. To abort an Auto Tune session, simply press and hold the SCROLL key again for 5
seconds until the decimal stops flashing.
NOTE: The Auto Tune process can last from several minutes up to two hours. If an
Auto Tune session tops the 2-hour mark, the session should be aborted and the
controller manually tuned by qualified personnel.
Auto Tune Initialization Modes
The Controller can also start an Auto Tune session automatically. If this is desired,
select the condition, from the Table below, whereby an Auto Tune session will
automatically begin. Change the setting in the 'tune' parameter in the 4
match the mode below. The controller defaults to a setting of '0'.
'Tune' Setting
0 (default) Auto Tune can only be initiated manually with the SV not equal to the PV
1 Auto Tune can only be initiated manually with the PV equal to the SV.
2 Auto Tunes automatically when the controller is FIRST powered up if the PV < SV.
3 Auto Tunes automatically when the controller is FIRST powered up if the PV = SV.
4 EVERY time the controller is powered up the auto tune begins if the PV < SV
5 EVERY time the controller is powered up the auto begins automatically if the PV = SV
Auto Tune Initialization Modes
Mode
21 Model 48VTR - Version 5.0 – January 2006
nd
Menu Level
nd
Menu Level is NOT zero
th
Menu Level to