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  #26  
Old 10-16-2019, 04:12 PM
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Quote:
Originally Posted by Ted Trower View Post
Just finished the test Pete suggested. Kiln did come to the desired 850 with the extension wire removed from the circuit.
****
So if I understand you, the kiln will perform as expected IF you remove the extension wire. I would suggest using a completely different wire. The one you are using may actually have a defect hidden under the insulation.
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  #27  
Old 10-16-2019, 04:18 PM
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Quote:
Originally Posted by Rick Kellner View Post
Only took a quick peek at the Twidec controllers on Amazon. Very inexpensive.

The ones I found seemed to have an input rating for a PT100 temperature sensor. Did you get one compatible with a type K thermocouple, or are you able to select among a variety of thermocouple options in the parameters?

Maybe this has something to do with it?
Unit has multiple thermocouple input options. Is set to type K
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  #28  
Old 10-16-2019, 04:22 PM
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Quote:
Originally Posted by Pete VanderLaan View Post
****
So if I understand you, the kiln will perform as expected IF you remove the extension wire. I would suggest using a completely different wire. The one you are using may actually have a defect hidden under the insulation.
Thank you. Will give that a try.
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  #29  
Old 10-17-2019, 10:01 AM
Shawn Everette Shawn Everette is online now
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So I'm not going to argue that it works, just trying to figure out the why.

Whenever I've had issues with a thermo wire I've gotten a faulty reading of some kind. I can understand a bad or incorrect wire giving a wrong temp, but this situation seems odd since it's maintaining a roughly correct temp reading, but limiting the controller. If it were a short then I would expect signal loss, temp jumps, or an incorrect reading.

Last edited by Shawn Everette; 10-17-2019 at 10:16 AM.
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  #30  
Old 10-17-2019, 10:51 AM
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well, if I understand Ted correctly, it seems to work if the wire is removed but not when it's present. I could see that the simply act of changing it out allowed a connection that was marginal to temporarily appear better but I would be at a loss as well as to why this would occur.

I just want to see the issue isolated and since the wire appeared to be at the core of the problem in the first place, it seemed worth finding out if the wire was indeed the issue. I'm still not clear about it.

I have been impressed in the past just how far up into the insulation that decay can occur coming entirely from the ends. We had that at one point with the wire on the Direct TV lines. It went back two feet- astounding. The outer insulation appeared perfect.
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  #31  
Old 10-17-2019, 12:03 PM
Shawn Everette Shawn Everette is online now
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I get the deductive reasoning pointing to the wire, it's just never a symptom I've come across before. Having a faulty wire or connection give a false reading makes sense to me, having it limit the controller doesn't. Especially with a bare bones chinesium pid, though that may actually be the issue at hand.
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  #32  
Old 10-17-2019, 12:11 PM
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Well, the differences between having it there and not having it there at least make you scratch your head. I agree that it doesn't seem to make sense, but there you are. As I suggested just by removing the connector may be cleaning up the connection and making it better.
Controllers have gotten sort of weirder. Everything in sales wants to avoid human contact which I used to rely on. I really hate the Aubers. I am coming to hate Dwyer. I have a box of controllers that are a struggle to use. It shouldn't be like that. ..and I don't want to hear about the digitry.
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  #33  
Old 10-17-2019, 01:15 PM
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Re-reading your original post, 6ft is a rather long run for what is a very low voltage sensor signal.

As you've stated:
- wired up with 6ft extension wire, furnace won't go to temp.
- wired up without 6ft extension wire, furnace will go to temp.

So Pete's correct, it would seem the extension wire is the issue.

However, the wire may be fine, just 'too long'. Why not try 3ft of extension wire?

It could be the el-cheapo controller simply isn't sensitive enough to read the TC with the 6ft signal drop. It could also be the extension wire is either faulty or incorrect type. (you said they sold you K compatible wire, but maybe they made a mistake?).

Solid wire is also very prone to the kind of miserable breakage where the wire breaks but the insulation keeps the two ends in "kind of" contact. It may read OK with a DVM, but the signal gets so degraded through the break that it doesn't work in the application.

I have all my thermocouples on 4-5ft wires (similar solid TC wire) going into Fuji controllers and haven't had any real problems.
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  #34  
Old 10-17-2019, 02:15 PM
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Increasing the gauge diameter might help. Stranded wire might help.
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  #35  
Old 10-17-2019, 03:41 PM
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Was reading on some electrician forums that in industrial environments, these runs of thermocouple extension wire are sometimes in the hundreds of feet.

I doubt it's the length per se, but perhaps one of the other variables you cite. I think my extension wire is in the ballpark of six feet long as well, but it's been just fine.

Definitely worth trying an alternate cable, although I'm still not entirely convinced that this setup wouldn't run with a different PID controller hooked up.
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  #36  
Old 10-17-2019, 06:17 PM
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well, sure, if you throw out the tooling and get all different stuff, I think it to be likely that would work.
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  #37  
Old 10-19-2019, 06:02 PM
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I think I've got it figured out.

Ok - First off thank you everyone who has taken the time to address this question. I've spent the last two days running a variety of kiln cycles and configurations.

It seems that my problem was based upon the false assumption that the infrared thermometer would read the interior kiln temp in the same manner as the thermocouple. My tests seem to have confirmed that the non-contact infrared thermometer reads the temperature of the kiln brick while the thermocouple reads the temp of the kiln contents. There appears to generally be about 100 to 200 degrees F difference in these readings at the temperatures I'm running. Scanning my vacuum plate in the kiln it will read the desired temp while aiming at the adjacent kiln brick will read lower.

My test without the extension wire also happened to be the first time I read the temp of the kiln contents and the not the kiln walls/floor. I'm guilty of not recognizing the difference / significance on the first occasion.

So in essence, everything is actually working properly but I did not recognize that fact.

Again thank you.
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  #38  
Old 10-21-2019, 11:03 AM
Shawn Everette Shawn Everette is online now
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D'oh. Ok that explains something. I think most of us here were on the assumption that you were giving us the reading off of the controller, not a secondary source. Hence me thinking it was a controller issue. Still doesn't explain the difference between the two wires, but as Pete said, if it works, it works.
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  #39  
Old 10-21-2019, 12:38 PM
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Or, as Roseanna Rosanadana said: "Nevermind"
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