Dwyer 16A - Manual (Page 16)

Page 16
Operating of Self Tune Function
Self Tune allows automatic selection of the necessary parameters to achieve best
control operation from your 16A2 & 16A3 Series control. If you are using the con-
trol output as a simple on-off function (
0ut 1 set for 0n0F ), none of the following
will apply.
Theory of Operation
The Self Tune function calculates the Pb1 , rES , and rtE parameters under the Pid
tunE selection, and the Fbnd and FrtE parameters, as shown in the Secondary
Menu. These values are determined by measuring the response of the process con-
nection to the control. While in this mode the control measures the overshoot and
undershoot of the process, and the period of the process (the time from peak value
to the next peak value). These measurements are collected over a period that lasts
three periods of overshoot and undershoot. The data collected over this time is effect
of Fuzzy Logic on the process is still controlled by the
Fint (fuzzy intensity) setting.
If Fint is 0 , the Fbnd and FrtE will be calculated, but will have no effect. The calcu-
lations for the PID values are the same as used in the standard Ziegler - Nichols
equations that have been recognized as standard for decades.
The only modification to the application of the Ziegler - Nichols equations is con-
trolled by the
dFAC menu item. This menu item controls the amount of rate (deriva-
tive) that is applied. A dFAC setting of 3 (factory default) or less allows for less damp-
ing. A dFAC setting of 4 allows for critical damping as set forth in Ziegler - Nichols. A
dFAC setting of 5 or more allows over damping of the process.
Program Setup and Operation
Do not cool the process or add heat while the tuning is occurring. In the secondary
menu set
tunE to SELF . Skip LErn and check to make sure that dFAC is set to the
desired value. Back up to LErn and set to YES . The control will begin the Self Tune
function. While the Self Tune function is active, the right hand decimal point on the
lower display will blink. When Self Tune is complete, the blinking will stop.
After Self Tune is complete, the tunE setting automatic switches to Pid . This allows
examination and/or modification of the values calculated. We recommended that you
do not change the calculated values unless you have a firm understanding of the
parameters involved and their function.
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