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eurotherm 3208 controlling issue

Hi,

 

For past couple of weeks, im trying to use Eurotherm 3208 temperature controller to control my 2000W resistive heater. I dont have a active cooling system, as i would like to go upto 500˚C. I use a solid state relay to power my heater. I use a type K thermocouple to read the temperature.I am using the example VI that was available in National instrument website. 

 

 I am able to write the setpoint and also read out the measured temperature value. but im not able to control it. For an example, when i set the set point to 50˚C. it switches on the relay, for couple of seconds, the temperature rises steadily. and the relay is tuned off when it reaches little more than 50˚C. but, the problem is, since the heater is really fast (ramp is really really steep) the even for couple of seconds of power to this heater, it reaches more than 100˚C.. the heater shoots up really fast and the PID is not able to read this steep ramp. how do i make the PID to understand the ramp and make the switching rate fast?. 

 

i was also trying to change manually, the integral time and also the differentiate time. I can see some changes in the way it manages the PID.. but im not able to find the allowable range that i can use for these values. please help me out in this. i need to finish this project in a month..:(.. 

 

thanks in advance. 

 

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Hi parthi1987,

 

 

do use the iTools software from the producer to configure the temperature controller? How do you communicate with the controller? Why do you use a controller and LabVIEW?

I have worked with the 3504 controller. The controller allocates several parameters via OPC-Server to any clients. It's possible to start the config-mode via the iTools-software. With this tool you're able to change all parameters. I don't exactly know in which mode it is permissed to change the PID parameters.

In every case the control of the closed loop is done by the controller.

If the controller is in the config-mode, the controller disables the control. In this case it is possilbe to set the outputs (relay/SSD relay) manually with the iTools-software. I can't say if it's possible to set the parameters in this mode by other programs than iTools. Reading is possible. Like this it is possible to control the closed loop by LabView. But this is very circuitous.

I think your main problem ist the thermocouple measurement.

The control is done by the controller. And if the SP is reached the controller switch-off the relay. I don't know, if it's possible to use a delay but it won't solve the problem.

Can you put the thermocouple at another place?

 

 

 

Regards

 

Philipp

(AE)

National Instruments

 

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Unfortunately i can't place the thermocouple in another place. I'm using lab view to automate the whole process of measurement.. like i need to take a snapshot at every set point. i will change the set point for every 15 min.. 

 

Finally yesterday i triggered a simple way to control the PID.. there is a option called autotune built in to the PID.. and LABVIEW program gives me to enter the auto tune setting.. but the main problem here is that, i need to switch on auto tune for every measurement. 

 

auto tune basically calculated the ramp and changed accordingly. so every time when i start the lab view program with auto tune on. it heats up and calculates.. but doesn't save these data i guess.. because when i restart my PID with auto tune off, PID behaves the same way like before.. but if i restart with pid on, controlling is perfect.. 

 

can anyone please let me know, how can i make the setting after auto tune to be the default one?…

 

thanks in advance.. 

 

Regards

Parthiban 

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I have not worked with the 3208 controller. I have done a lot of work with other models of the Eurotherm controllers.

 

Our solution (we were running furnaces up to 900°C), was to set the Eurotherm itself to autotune and then save its settings internally. It will work out its own PID parameters for the system. It takes a long time to settle and work out the parameters, but once you save them, you never have to do it again.

 

Find if there is are autotune and save commands for your Eurotherm controller.

 

     Rob

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Thanks for the reply.

 

I found a way yesterday evening :)...

 

set the autotune on.. use read PID parameters (i used a number indicator to display). then typed in these values in to the set basic PID parameters.. its working fine..

 

Thanks for your help guys..

 

If someone need the vi.. post, i can send it.. 

 

regards

parthiban

 

Message 5 of 7
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Hi Parthi1987,

I am facing the same issue with the Eurotherm 3208, i am working with a PT100(RTD) sensor and need to control a Electric heater. i tried to set all the parameters but when i start the device it is showing the Input temperature value but with an Alarm 4. don't know where i have gone wrong. i have been using both on device set up and iTools software to configure the device. but the same error is showing up everytime. 

 

 

could you please help me out with this, thanks in advance.

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Hi.

 

There is an issue when you use the EUROTHERM VI's, once you enter the Config Mode some settings that you don't want to change , change.

 

My recommendation is to work with the EUROTHERM controller alone, go to the Config Mode and compare each Parameter against the values recommended in the Controller User's Manual. 

 

It happened to me, that the Range Max was set to 110 degC and therefore I had an Alarm everytime the furnace starts to heat up.

 

Good luck

 

C

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