Extech Instruments 48VTR Instruction Manual page 10

Table III - Programmable Auto Tune Initialization Modes
Auto Tune can only be initiated manually with the SV not equal to the PV
0
Auto Tune can only be initiated manually with the PV equal to the SV.
1
Auto Tunes automatically when the controller is FIRST powered up if the PV < SV.
2
Auto Tunes automatically when the controller is FIRST powered up if the PV = SV.
3
EVERY time the controller is powered up the auto tune begins if the PV < SV
4
EVERY time the controller is powered up the auto begins automatically if the PV = SV
5
11.2 Auto Tune Procedure
a. In order to automatically set the Tuning parameters in Level 2 ('Pb' Proportional Band,
'ti' Integral time or Reset, and 'td' Derivative time or 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. Press and hold the SCROLL key for at least 5 seconds until the right-most decimal
point on the PV display begins flashing.
d. When Auto Tune is complete, the right-most decimal will cease flashing. 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 SCROLL key again for 5
seconds until the decimal stops flashing.
NOTE: The Auto Tune process can last from several minutes up to several hours,
depending on each system's parameters.
12. AUTOMATIC AND MANUAL OUTPUT CONTROL
12.1 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 control output percentage so that the PV = SV.
12.2 Manual Control
Manual control allows the user to manually drive the output percentage from 0.0
through 100.0% (usually used for testing purposes). To access the Manual Mode, you
must first unlock it. Press and hold the DOWN Arrow and RETURN keys until the
display blinks. The feature is now unlocked. Now, press and HOLD the RETURN key
for approximately 5 seconds. The controller's output percent automatically will appear
on the SV display preceded by an 'H" for Heating or a 'C' for Cooling (depending upon
how the action of the controller is configured under the parameter 'act'). The rightmost
decimal will flash while in Manual mode. To manually adjust the controller's output, use
the UP and DOWN arrow keys. To return to normal operation, press the RETURN key
again. To re-lock the feature, press and hold the UP Arrow and RETURN keys until the
display blinks.
48VTR English 9/00
Auto Tune 'Initialization Modes'
Ver. 2.7
9