Temperature PID loop.

[ptonsparky]

I want to set up a small heating PID loop. Used only for my edification. I would like to use a budget friendly 0-10 volt or 4-20 ma for temperature input because I have that readily available. Any suggestions?

 

[ptonsparky]

NM.

Amazon for less than $40. If it works at all, it’s good enough.

 

[Jraef]

Complete kit, $28. Can’t beat it. Unlikely UL listed, but for your purpose, it’s probably fine.

https://a.co/d/3SSCp5o

Note that it says 100-240V in one place, then 220V in another (typical Chinese sellers). I would just assume it needs 240V.

 

[ptonsparky]

Well, for the price I shouldn’t expect destructions.
I had already pulled the trigger before reading post 3.
Anyone know which wires go where?
I have a pretty good hunch on the -+.

 

[Hv&Lv]

View attachment 2571074

Well, for the price I shouldn’t expect destructions.
I had already pulled the trigger before reading post 3.
Anyone know which wires go where?
I have a pretty good hunch on the -+.

https://support.tibbo.com/hc/en-us/articles/4407183163929-RTD-PT100-sensor-probe-Temperature-Transmitter-Tibbit-43-1

 

[ptonsparky]

Red Red White
I think.

 

[ptonsparky]

Works.
I test drove it via 3 - 9 volt batteries and my Fluke 87.

Applied voltage is closer to 28.5 vs the 24 volt suggested. How much does that affect my mA ?

Freezer checked at 2.84 mA.

 

[rlundsrud]

If you are getting less than 4 ma it isn't working. This is a two wire application so you need to wire it one of these two ways. More than likely, it's the first one or PNP sourcing. Pos/Neg is the 24 volt supply.

PNP Sourcing sensor
Sensor wired to positive terminal
Input wired to negative terminal

Sensor Input
(Pos)------- +● ●- -----------● ●------------ (Neg)



NPN Sinking sensor
Input wired to positive terminal
Sensor wired to negative terminal

Input Sensor
(Pos)-------● ●------------● ●------------ (Neg)

 

[ptonsparky]

Connected to my shop CLICK with 4-20ma input. Temperature scaled out correctly. The blue conversion unit is 0-200 C. Ice pack from the shop fridge gives me 32 degrees F via math. Right now the shop is a toasty 70. I did not check the ma.

 

[TwoBlocked]

Red Red White
I think.

Yes, I expect it is a 3 wire RTD (Resistance Temperature Detector). Red to red should be 0 ohms. Either red to white is probably about 1000 ohms.

Resistance thermometer - Wikipedia

en.wikipedia.org

 

[kwired]

Red Red White
I think.

Yes, I expect it is a 3 wire RTD (Resistance Temperature Detector). Red to red should be 0 ohms. Either red to white is probably about 1000 ohms.

Resistance thermometer - Wikipedia

en.wikipedia.org

A three wire RTD would have two of the leads connected to same side of the "RTD", and would be the two reds in this case. The resistance change would only occur between the white and (either) red as temperature changes. The reason for the third wire tied to same point as one other one is for certain processing equipment set up for a third wire. Those are self correcting so to speak as they can measure resistance between the two common conductors and automatically adjust the registered value for cable length instead of needing to calibrate for cable length or even temp changes of the cable would be self correcting as well.

 

[ptonsparky]

Worked out pretty well. My ‘oven‘ was a Grainger parts box heated with left over good parts of a Heat/vent/light. Blower & element. A SSR cycled the element.

MDSW wanted to know what I was going to do with it now. I told her it’s going on the shelf with my other good stuff so my heirs can go “WTH is this!?” That was not met with humor.