Hello. I have two high temperature furnaces that I am controlling using ramp/soak PID controllers. The first furnace is maintained at 1000 deg C using the SYL-2352 controller with an N-type thermocouple. After using the auto-tune step, the system is very stable: +/- 1 deg at the setpoint.
The second furnace is heated to 1400 deg C using the SYL-5352 controller with an R-type thermocouple. With the default PID parameters (P=0, I= 500, D=100) and with the cycle time set to 2 s, the furnace temperature oscillates ~ +/- 6 deg after reaching the setpoint (1400). In this case, however, the temperature oscillation gets worse (+/- 10-15 deg) after running the auto-tune step. The PID parameters after auto-tuning are P=8, I = 2283 and D = 2. Any help would be greatly appreciated.
Thanks, Joe
Your auto-tune result seems strange to me.
You can set the PID back to the default value (P=0, I= 500, D=100) then run auto-tune again.
Before you start the auto-tune, change your step 1 and 2 as the following.
r01 = 2000, t01 = 0, C01 = 100
r02 = 1, t02 = 60, C02 = 1400 (your most important temp in your profile).
Restart the program then start auto-tune.
Kkane, thanks for your quick response.
Is the very short r02 of 1 minute required? We have to be careful that we don't thermally shock the heating elements (silicon carbide) in our furnace
Joe
No, you can use any none-zero number as R02. If you set R02 to 0, the controller will bypass this step, so I put 1 here. If you like to slow down the ramp up rate to protect your element, you can use a large number there.
The rule is, the auto-tune is based on your set temperature and also your oven, so it is recommended to run the auto-tune at your most important temp in your profile. If you run auto-tune at a different temp, the result may not be good.
I just updated my previous reply. Once the program is restarted and running, you can start the auto-tune. You don't need to wait until the temp is 1400.
Kkane OK thanks I will give this a shot. Joe