Auber 2352 - Cycle Time

[jbsengineer]

Ok, why is "t" set to 24 on my setup? If I set it to "2" for my SSR's the temperature reading go wacko (571 degrees).

I set it to 2 before the AT and AT set it to 24. Whenever the output is triggered it is on for at least 1 second. I would figure this would pulse with short bursts of heat.

What am I missing?

 

[JRems]

I never messed with the t setting. I just auto tuned it and I use it that way.

 

[jbsengineer]

I never messed with the t setting. I just auto tuned it and I use it that way.

Does your cycle time seem appropriate? In my setup for keeping a 152 degree mash more often than not the element will be on for 2-3 seconds at a time.

 

[JRems]

It depends. Sometimes it's a one second blip and sometimes it's a few seconds. I don't know how the little gnome living in the pid figures out stuff. I just let him do his job.
Are you having overshoot problems?

 

[jbsengineer]

After autotune I dont have the 1 second blips, it's always or consistently lengthy which causes overshoots. I seem to always be hovering 1 or maybe 2 degrees above target.

I toyed with the PID last night. Bringing the set value of "P" down under 1000 from ~2500 the temperature reading would be correct when I set the cycle time back to 2.

Also, from my reading in the manual I don't see any mention of AT changed the "t" value. I emailed Auber support for there take. I also had a suggestion to try my boil kettle pid and see how autotune reacts with that. I might try that tonight.

 

[JRems]

Good luck. Let is know what happens. My pid only overshoots by a degree or two when changing temp. When it's set at one temp it usually holds it within one degree.

 

[jbsengineer]

I emailed Auber support and received a response within a couple hours (nice!).

"The auto-tune will increase the cycle rate if the system response is too slow. This happens when the large water tank at low temperature because it will take forever to cools down during the auto-tune. Water has the highest heat capacity amount the commonly used liquid. Once temperature passed the set point, it will take long times to goes down if it is very close to the ambient. It is correct that if the P is >900, the display will show wrong temperature. If the auto-tune can't get good result, you can try P=250, I =100 and D=5. That is the number we got from a low temperature water tank."

I tested with P=250, I=100, D=5, and T=2 with good success. I was able to keep 152 degrees for about 80%-85% of the time of test batch with water. The other 15%-20% it would be at 153.

I have a follow up question on what is considered a "large" water tank.