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Page 15
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 4allows for critical damping as set forth in Ziegler - Nichols.
A dFAC setting of 5or more allows over damping of the process.
Program Setup and Operation
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 blink-
ing will stop.
After Self Tune is complete, the tunE setting automatically switches to PID. This
allows examination and / or modification of the values calculated. We recommend
that you do not change the calculated values unless you have a firm understanding
of the parameters involved and their function. For more information on PID tuning,
please contact your supplier.
Option C4, Serial Communication.
The serial communications option allows the control to be written to and read from
a remote computer or other similar digital device. Communication is allowed through
a RS-485 (Option C4) port.
Wire the communication lines as shown on Page 6. Wiring for the RS-485 is run
from control to control in a daisy chain fashion with a termination resistor (120 ohms)
across the transmit and receive terminals of the last control in the chain.
Select the control address and communication baud rate with the Addr and bAUd
menu items in the Secure Menu. THE BAUD RATE AND ADDRESS MENU ITEMS
WILL TAKE EFFECT ON THE NEXT POWER UP OF THE CONTROL. BE SURE TO
POWER CYCLE THE CONTROL BEFORE USING THE NEW BAUD RATE AND
ADDRESS.
In operation, you have the option of preventing a write command from the host com-
puter. To prevent the host from writing to the control change the LOrE menu item in
the Secondary Menu to LOC. To allow the host to write commands to the control
set LOrE to rE. (The host does have the ability to change the LOrE state, but it is
not automatic.)
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