pid factors and offsets in siemens

Can you tell me when and where do we use
PV_FAC and PV_OFF used in PV NORM block in PID loop in FB41 of siemsns S7? and similarly LMN_FAC and
LMN_OFF in LMN NORM block.What are practical applications of using
these factors and offsets in these blocks.what are their uses?what are they for?

Hello ravilal;

It is a scaling function for the PV input; I've had to use it once to work with a PV that only ranged up to 40%; using the factor and offset for the PV I brought the signal to 0-100% (almost). But noise was also increased. If I had to do it again, I would work on the input transducers instead.
Hope this helps,
Daniel Chartier

Another good one is if you make pb negative it acts as reverse controller