Hi all,
Came across some examples today of PID instructions in an SLC 5/04 with the Setpoint (SMax) & Setpoint (SMin) both set to zero.
In addition the PV and SP were both scaled 0-1000 (in logic before the PID).
My understanding of these two parameters is they simply apply a scaling factor to the PV, so that you can specify a SP in a meaningful engineering unit. If that's the case, does it therefore apply no scaling when both are zero? If the PID instruction is expecting values in the range 0-16383, is leaving these at zero the same as manually setting a Smax of 16383?
Therefore, with my PV & SP only ever reaching a max of 1000, has the PID control been stuck operating in the bottom sixteenth of the range (which would explain a lot actually)?
I've since altered the PV & SP to be scaled 0-16383 pre-PID, and set the SMax to 16383 to avoid any unexpected behaviour, it just got me wondering that's all...
Came across some examples today of PID instructions in an SLC 5/04 with the Setpoint (SMax) & Setpoint (SMin) both set to zero.
In addition the PV and SP were both scaled 0-1000 (in logic before the PID).
My understanding of these two parameters is they simply apply a scaling factor to the PV, so that you can specify a SP in a meaningful engineering unit. If that's the case, does it therefore apply no scaling when both are zero? If the PID instruction is expecting values in the range 0-16383, is leaving these at zero the same as manually setting a Smax of 16383?
Therefore, with my PV & SP only ever reaching a max of 1000, has the PID control been stuck operating in the bottom sixteenth of the range (which would explain a lot actually)?
I've since altered the PV & SP to be scaled 0-16383 pre-PID, and set the SMax to 16383 to avoid any unexpected behaviour, it just got me wondering that's all...