HOW DO I RESET 2404 CONTROLLER TO DEFAULT CONFIGURATION

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hello,
I am using Eurotherm 2404 for controlling temperature in a box type furnace with following specifications
Heating element : SiC
Temperature sensor : (Pt/Rh) R-type thermocouple .
Continuous operating Temperature : 1300 deg C and max 1400 deg C
Accuracy : +/- 1 deg C

For the Following set of PID values found using "auto-tune" at 1000 deg C
Pb= 50, ti = 129 , td = 21.

1 . the control below 260 deg C is oscillating in nature (fig attached). what may be the reason ?

(the PV becomes greater than the value displayed at SP , then the controller gradually decreases the output to bring it below SP and same sequence of oscillation continue until 260 C)

2 . We could here in principle use the "gain schedule" option provided with 2404
and use two sets of PID values below and above 260 deg C by setting 260 deg C as the "G.SP" value.

That is my next question ,

3 . does the "auto-tune" decide the PID values that are good for only some temperature range ? I mean, looking at control below 260 deg C it is quite obvious that set of PID values calculated by 2404 is not correct .

4. Do we always need to auto tune for correct PID value.

thank you.

Hello Neeraj,

The auto tune parameters are just for one temperature range.
You could use Gain Scheduling and tune at 260deg C, then apply both sets of PID values at different temperatures.

Also perhaps applying holdback may help.

Hello Bob,

I did try setting two different PID values by first auto tuning below 200 deg C (at 200 deg C) and then above 200 deg C (at 1000 deg C) ,
I SET THE "G.SP" AS 200 Deg C, HOLDBACK = OFF
But the controller seems to return PID values which is not correct between 200 deg C to 260 deg C.
between 200 to 260 deg C the control is still oscillating.

Hello Neeraj,

Perhaps you should try auto-tuning again but with a lower output high limit.
Looking at the graph I wonder if your heating is too fierce causing this oscillating.

So perhaps using 70%-80% rather than 100% may help.

Hello Bob

That does not help , i started "auto-tune" from room/ambient temperature , aiming to auto-tune at 1000 deg C .
With this maximum power ( 75 % ) the maximum attainable rate (of change of temperature ) is around 6 deg C /min and the time required to reach that auto-tune is much greater than 2 hours returning "tune-error" .

Thank you ,

Hello Neeraj,

Try auto-tuning one set of PID values at 210 deg C where the oscillation occurs.
You could then run the program to see if this is better with the original PID set for 1000 deg C.

From your last comment it should still be able to acheive your ramp rate of 2 C /min.