Thanks for the reply, I had begun to figure this out from the thread.  I
can see how this would be useful anywhere there is a response time lag,
such as in motion control, due to inertia, and in temperature control, due
to the time required for the temperature to respond to heat input.  I guess
anywhere you would like the controlled system to respond quickly when there
is a gross error, and more gently as the error difference narrows.

Again, thanks for the response.  I found the thread very interesting, but
that TLA was bugging me.


CIAO - Martin R. Green
elimar@bigfoot.com

----------
From:   Eric van Es[SMTP:vanes@ILINK.NIS.ZA]
Sent:   Wednesday, September 03, 1997 3:56 PM
To:     PICLIST@MITVMA.MIT.EDU
Subject:        Re: PID Temperature Controller for SMD reflow oven

Martin R. Green wrote:
>
> OK, I finally have to ask...
>
> What's PID?
>
> Ignorantly yours,
> Martin R. Green
> elimar@bigfoot.com
>
Wow! Big thing to explain!

What it is: A summing amp (if you like) with and proportional, integral
and derivative input. It adds them to obtain the desired effect.

Note: PID is feedback control! It is a controller that conditions your
input to the plant, moter, etc.

P: Output is proportional to the input. Basically an amplifier.
I: Integrates the output of the system's error and applies a signal that
will (theoretically) remedy this.
D: Output is proportional to the rate of change of the error on the
output of the system.

This really is a major field of study - actually impossible to explain
by e-mail! Maybe you could take a short course on control systems!

Sorry I can't help more! AND I stand corrected on all of the above!
--
Eric van Es               | Cape Town, South Africa
mailto:vanes@ilink.nis.za | http://www.nis.za/~vanes
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