PID Controller vs Compactlogix

Hi
We are looking to replace the temp control system on our main oven.
we currently run a eurotherm 2416 PID Controller with a single TC but are looking at running off 2 TC to get better consistency.
At the same time i want to upgrade the main electrical control system to a compactlogix 5370 L3.
To save on money and make it simpler i would like to use the new compactlogix with PID to control the oven temp instead of purchasing an additional temp controller.
My question is though are plc's able to handle temp control as well as a designated temperature controller?
I look forward to your reply

Hey Breadman,

The PLC should be able to provide as good or better temperature control than your dedicated PID controller. However, how well it performs is solely dependant on how you program it. You will have much more control over the process, but if you aren't comfortable with programming, it could end up being worse.

Breadman said:

but are looking at running off 2 TC to get better consistency.

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How do you propose to use 2 thermocouples to get better ’consistency’? What constitutes consistency?

rupej said:

Hey Breadman,The PLC should be able to provide as good or better temperature control than your dedicated PID controller.

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I don't see how this statement can be justified.
I would be I could do better with a motion controller than either the temperature controller or a PLC. Update rate has nothing to do with it.

However, how well it performs is solely dependent on how you program it.

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Yes!!!! However the types of PID and how they are implemented must be taken into account too.


Two sensors can be averaged to reduce noise or consider rates of change in load. It depends on the placement.


If the product is going through the oven on a conveyor then knowing the rate of product that is going through the oven will be a big help in predicting the load.


Technique and skill is more important than equipment.

Peter Nachtwey said:

I don't see how this statement can be justified.

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Well, it's a modern PLC. I'm confident it has better resolution on the analog inputs, and can be programmed to do anything the inexpensive single loop controller can do, and yet so much more. To me, that's "as good or better."

Thank you all for your help
This all came about from 1 person who i regard as being quite good at their job said that a plc will never be as good as a PID controller.
Then a second person who i regard as being quite good their job said why not, a plc has the ability to be.
It is good to get everyone's opinion.
Thank you

rupej said:

Well, it's a modern PLC. I'm confident it has better resolution on the analog inputs, and can be programmed to do anything the inexpensive single loop controller can do, and yet so much more. To me, that's "as good or better."

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Doubt it on the analog input front. Most PLC's have 14 bits as "special" precision, so a device that does one function wouldn't gain much by having less than that.

It's disingenuous to say a basket of fruit is better than an orange...

cardosocea said:

It's disingenuous to say a basket of fruit is better than an orange...

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Come on man, this is PLCtalk.net. A basket of fruit when filled by a skilled fruit picker is as good or better than the moldy pesticide-soaked orange you'll find in the cheap section of your local grocer.