"tieback" PID in RSLogix5

Guys,

Anybody here knowing what's function of "tieback" in PID instruction in RSLogix5?
What value that I should fill it? and what happend if I fill it with the zero value?
Thanks in advanced

Warm regards,
Deer

in basic terms ...

if you put a ZERO in the entry you'll disable (and not use) the Tieback feature ...

suppose you put a location such as N7:55 instead ...



suppose that you have an analog input module which delivers a signal to N7:55 ... the signal ranges from 0 to 4095 as an operator turns a potentiometer up and down ... now suppose that you put the PID into the "Manual" mode ... note: this is NOT the same as the "Set Output Mode" ... now when the operator turns the potentiometer up and down, the output of the PID (the CV signal) will "follow" the potentiometer's signal ... this will give the operator manual control of the system ...

note that the Tieback signal can be taken from an HMI instead of a potentiometer ... but in most cases, it needs to be scaled from 0 to 4095 for optimum operation ...

Thanks Ron, more question...if we set the PID to the manual mode,and we set the output % value to the any value, and in the same time we turn the potensiometer up and down, what's happend with CV, following values from potensiometer or value from that we set on the output % value? because as I knew in manual mode, output CV will follow from the value that we write in output % value.
And is it right function of tieback is use for bumpless transfer from manual to the auto mode to avoid any transient from manual to the auto mode?

when both "Manual" (Tieback) mode and "Set Output" mode are selected at the same time, the output (CV) will follow the Tieback signal - and just ignore the Set Output signal ...

yes, "Bumpless Transfer" is one of the reasons for using the Tieback feature ...

have you studied the PID section in the PLC-5 Instruction Set Reference Manual? ... I'm glad to answer your questions, but there's a lot of basic information in the book that you might find useful ...

hope this helps ...