Controlling Slow Processes

BillRobinson

Member

Join Date

Oct 2006

Location

Sydney, Nova Scotia

Posts

185

• Jul 5, 2012

• #1

Any tips on controlling slow processes. For example, a large well that has a level that will change slightly over a few days. If I use PID should I use a really small gain and large reset?

 

Mickey

Lifetime Supporting Member

Join Date

May 2003

Location

Palmdale,Ca

Posts

10,659

• Jul 5, 2012

• #2

Can you tolerate a little offset and use proportional only?

Some PID instructions have a deadband setting where nothings happen as long as the PV stays within the deadband.

 

Last edited: Jul 5, 2012

Tom Jenkins

Lifetime Supporting Member

Join Date

Apr 2002

Location

Milwaukee, WI

Posts

6,301

• Jul 6, 2012

• #3

In situations like that I don't use PID - just a simple thermostat type control.

 

John M

Member

Join Date

Mar 2004

Posts

85

• Jul 6, 2012

• #4

In my experience a large reset(meaning lots of reset or integral action) on a slow process = major oscillations. Stick with enough Proportional control and only use reset if you cannot tolerate any deviation from setpoint.

 

shooter

Member

S

Join Date

Sep 2002

Location

duketown

Posts

2,711

• Jul 7, 2012

• #5

Only use the P action
or make it FUZZY controlled