Yes Doug,
---------------------------------------------
Have you worked on control systems that cycled or hunted? An example of
how difficult it can be to get forces to equalize smoothly?
-------------------------------------------------
That is why PB, Reset, & Dev have been added to those systems




http://community.webtv.net/tassail/ThomPage

Thom Stewart wrote:
Yes Doug,
---------------------------------------------
Have you worked on control systems that cycled or hunted? An example of
how difficult it can be to get forces to equalize smoothly?
-------------------------------------------------
That is why PB, Reset, & Dev have been added to those systems


Proportional Band also known as Gain

Reset rate can be a very effective way of stopping the
system from hunting, but can also be over done so that the
system is either too fast or too slow... ask Bobsprit which,
after all I've been busted for talking gibberish.

Get him to explain what Dev stands for and what it does too.
I'd like to read that myself.

Regards
Doug King

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




http://community.webtv.net/tassail/ThomPage

"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

Scout wrote:
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.

Cool... he already had a hammer

.... We had lots of pneumatics. We later converted the controls to
digital but left the pneumatic actuators in place (to save some cash).

Everybody did that. Saved cash plus the first & second
generation digitally controlled linear actuators sucked. The
ones they make now are pretty good but don't trust their
power ratings or their power consumption specs.

The funny thing is that a lot of people justified the switch
in order to save on LP air system & compressor maintenance.


... 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.

That's where better test-taking skills would have made the
difference. If he'd tossed around a lot of words like
"setpoint" and "proportional band" he'd have been all set.

Regards
Doug King

"DSK" wrote in message
.. .
Scout wrote:
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.

Cool... he already had a hammer

.... We had lots of pneumatics. We later converted the controls to
digital but left the pneumatic actuators in place (to save some cash).

Everybody did that. Saved cash plus the first & second generation
digitally controlled linear actuators sucked. The ones they make now are
pretty good but don't trust their power ratings or their power consumption
specs.

The funny thing is that a lot of people justified the switch in order to
save on LP air system & compressor maintenance.


... 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.

That's where better test-taking skills would have made the difference. If
he'd tossed around a lot of words like "setpoint" and "proportional band"
he'd have been all set.

True!
He probably shouldn't have mentioned kerf when discussing cut-in and cut-out
setpoints.
Scout

Scout wrote:
He probably shouldn't have mentioned kerf when discussing cut-in and cut-out
setpoints.

Or said that he used a coping saw for those difficult
calibration jobs.

DSK

Doug,
1/4 wave reduction probably done the trick also:^)




http://community.webtv.net/tassail/ThomPage