# Help with muffle furnace controls



## lowlife (Feb 6, 2017)

Have a thermolyne muffle furnace that the controls went south. Not sure what happened but when I disassembled it I saw an old tube like a tube type TV. I think now may be the time to upgrade but I'm kinda in over my head as far as controls.
 I've run across what is called a pid but not sure what I need. The furnace goes to 2000 degrees. Taking it apart it seems all I really need is 220 1 pH in 220 1 pH out to the furnace controlled by a thermocouple. Not sure if that would cover it or not.  I would just like to be able to control the temp on and off don't think I need much more as its an efficient furnace and it's used mainly for melting and the occasional tempering etc. Thanks as always.


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## brino (Feb 6, 2017)

Could you post a picture of the old dead controller?

PID means Proportional/Integral/Derivative controller. It is a type of closed-loop control system. You can read about them here:
https://en.wikipedia.org/wiki/PID_controller

That kind of controller is high-end and should be able to produce a fairly tight temperature range, by adjusting for thermal mass to avoid overshoots, etc.

There was a great old thread that I found recently on some of this......looking, looking........here:
http://hobby-machinist.com/threads/heat-treat-oven.9929/

That (longish) thread lists some controllers used by other members building/upgrading their ovens/furnaces.

Good Luck! and please let us know how you make out.
-brino


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## jim18655 (Feb 6, 2017)

Post the tube type you need and I'll look through my stock for a replacement.


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## lowlife (Feb 6, 2017)

Thx for the threads Im just looking for info not afraid to put in the work necessary.

Wow you still have some tubes ? I remember my dad had 2 testers and he used to sit in the basement for hours testing tubes. Come to think of it he was probably getting away from my mom. I will check tomorrow after work, not sure if it's the tube or not though it is a simple system. I have to manually engage the relay so something controlling the relay is whacked.

Interesting, the last photo on page 3 of the above thread is the same exact controller I have. Do you still need a Picture? Thx


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## JimDawson (Feb 6, 2017)

This should work for you

https://www.automationdirect.com/ad...ers/1-z-16_DIN_Size_(SL4848_Series)/SL4848-RR


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## lowlife (Feb 18, 2017)

Thx uys always appreciate the help. Got a bit side tracked hooking up the new to me harig sg. Got it going whisper quiet. Now back to our previously scheduled problem


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