"Thom Stewart" wrote in message
...
Doug,

I think you have Reset & Deviative mixed up but maybe not.
Proportional Band limits the amount of response to the original Off Set
or a proportional amount.

PB will keep cycling down but has a tendancy to "Droop" Not return to
its original value. RESET will make additional correction to return to
original point but with a new correction force.

Deviative (Like Pepper) needs to be added carefully. It is a ampilifier
of the original off set. It forces the PB to a greater correction force.

Doug, that is a rather quick and dirty explaination. If you want more
contact me off line

Thom,
you just reminded me of an old Croydon boy I worked at LBH with. He was a
carpenter but when things were slow in his area, he'd be my helper with the
HVAC controls. We had lots of pneumatics. We later converted the controls to
digital but left the pneumatic actuators in place (to save some cash). When
I left LBH and went to Rohm and Haas, he went to a local school district for
a job. He reported back to me that they wanted to know if he knew anything
about troubleshooting and calibrating pneumatic controls. He said, "I can
usually play with the settings enough to get them working." That was not
the answer they wanted to hear! Needless to say, he didn't get the job.
Scout