PID settings

[a1149913]

Hey guys, so i took my PIDs for their maiden voyage today however i'm having some troubles with maintaining the set temperature.

I set my HLT to 66.6C and the PID would overshoot the temperature at least a degree. It was hitting 68 before i had to manually turn it off. I think it may have something to do with the "cool" setting. Standard setting was 10, (heating, with alarm suppression, display in Fahrenheit). I have it set at 2 as the manual says "To change from Fahrenheit to Celsius display, set COOL=2"

I decided to change it back to 10 and it had no issues in holding at 66.6 "154F"

any ideas?

also i haven't auto tuned yet, however i find it weird that it can hold in F but not in C

J

 

[Adr_0]

what is the make of your PID controller? is there an option in there for heating, alarm suppression, display in Celcius? it may still have the setpoint in fahrenheit... pretty silly if it does but you never know.

 

[dave81]

Alarm setpoint hsve nothing to do with the pid control of the pid, just switches the alarm output.
I have a couple of sestos which I did auto tune both are within a 1.c of what a rtd table suggests theu shoukd be and overshoot about 1.c max whils maintaining temp.
What pid are u using? (As aksed)
What probes rtd thermocouple etc

 

[a1149913]

sorry, they're auber

 

[Adr_0]

It looks like setting the 'cool' to 2 is correct.

What type of thermocouple are you using?

Have you changed the P-SL and P-SH limits at all? If this range is brought in for e.g. it means that the error would be multiplied somewhat. Normally 1°C on a -50 to 1300°C K-type is basically 0.04% of the input scale, which then gets multiplied through the PID gains. If you re-ranged the celcius for e.g. you would end up with a much higher gain and it would overshoot.

Did you end up figuring it out?

 

[a1149913]

Hey, i'm running the auber PT-100 thermocouples. I havent managed to check them since. I'll run the auto tune this weekend before brewing and see how i go.

J

 

[Adr_0]

Cool. Although it's a bit weird, the solution is more important which would be to tune it. You may benefit from lowering the control timeaas well as they say in the manual. Since you were fine in Fahrenheit I would say your control time is ok, but there may have been a slight difference in how the error was measured and the corresponding output with the different temp units.

Good luck...