[ATR142] Control heating process in PID with SSR output

[user497]

Hello,

so, i made a test:

Pb=12
TI=600
Td=150
Tune: disabled

But the same problem.
In data, temperature are little bit higher, because it is closer to heater.
But the same problem with overheat!!!
The red dot line is alarm temperature : + 38C ( + 37,5 + 0,5 C ).



P.S.
We use ATR121-B

[Pixsys tecnico 1]

Ok, so set:

Pb: 15
Ti: 800
Td: 200
rEg: H.o.o.

[user497]

Here it is!
Not 2 hours, because it was already working day evening, but still overshoot is to big, over 40C.
Is there some more options to do?

[Pixsys tecnico 1]

With ATR121 we are so limitating in PID parameters so try:

Pb: 20
Ti: 999
Td: 500
rEg: H.o.o.

The first overshoot there will still be, but after that it would be more stable.

[user497]

Hello, thank You, i will try this on next working day.

But is it possible to do with ATR142?
I can still change it, because in this case it is more important to disable that overshoot!

Thank You.

[Pixsys tecnico 1]

With ATR142 we can use softstart to avoid overshoot when reaching the sepoint

[user497]

Hello,
so i tested it and now it is better, but still just little bit to high (max was ~ 38C, Setpoint: 37.0) (The red dot line is alarm line( 38C) - in attachment)
we need just a little bit less : max 37,5.
Can i try to change something more: bigger td ????

For information:
And in ATR142 case i need to change output power limit? or other parameter?

[Pixsys tecnico 1]

With ATR142 you will use 51 [GrAd] parameter to reach the setpoint slowly.

Now, with ATR121 you can try to increase Pb to 25 and Td to 600.

[user497]

Hello, so i changed controller to ATR142-ABC
Reg = Ho.o
Pb = 25
Ti = 999.9
Td = 600
tc = 1.0
tune = disabled
oPNo = PrcY
Grad: 10.0

Now its almost good, but still as You can see in graph, it is with bigger overshoot as it must be!
Setpoint: 37C ( +- 0,5C ) , but here max is 38C!
Is there some other parameter, which we can change?

[Pixsys tecnico 1]

Try limit the output power to 80% with parameter P22 [o.Po.L] as "80".

You have to leave [oPNo] = "cont" if you use only [Grad] parameter (we are not using pre-programmed cycle but only a fixed gradient to reach the setpoint).

[user497]

Hello,
i did it with 80% of power, but still in second "wave" it is going over max temperature. I think, it is because of time, what it need to heat up again the heater, and it has some small inerce, after 36,5 it heats up and reach some 1,5C inerce.
Maybe the reason is that reg type: ho.o ? (Over setpoint zero output)?
Beause it takes a lot of time, when it goes under setpoint and to heat up it again, mahes some small inerce again, but if already, when its comming down from 37,5 it starts to heat it already , so it does not go so low and do not need to give so long heat time to heat it up in second "wave".

Here is attachment with last log. As You can see, second wave is now problem!

[user497]

Today i did new test, and the results are:

Almost good, but still some small overshoot, but in second and third "wave"!!
AS You can see in attahcment ( 1 - overview ; 2 - detailed view of waves! )
Parameters:
A.c.t.t = H.o.o.S
P.b = 30
t.i = 999,9
t.d = 600,0
t.c = 1,0
O.Pol = 80
Grad = 10.0


Do You have some idea?

[Pixsys tecnico 1]

Hi,
try to set [Td] as "250".

[user497]

Ok, i changed t.d to 250.

But the same,
Sorry, SEtpoint was this time 35.8C. So as You can see, when it goes over Setpoint, it turns on and goes some ~ 1C over it! Maybe try to set output power to 50% ?

[Pixsys tecnico 1]

Hi, what is the resolution of the datalogger/graphic? We always see 0.5°C steps (maybe the real temp. overshoot of setpoint is 0.2 - 0.3 °C).

Set [O.Po.l] = 50