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Thread: PID thermocouples

  1. #1

    PID thermocouples

    I bought a used pid recently and the thermocouple has apparently quit. Question I have is does it matter the length of probe?
    The one on mine is 8 inch. In looking for a new one I find them most in 4 inch. Is it going to make a difference if the top end of probe is close to the pot maybe getting it to hot and not lasting as long? I have a Lee 4/20 pot 4 inch deep.
    What lengths does everyone use? And possibly a US source rather than an overseas source.
    I'm not in a hurry as I just had shoulder surgery and won't be in the shop for a bit.... but want to get one ordered so it is here when I can get it set back up.


    Sent from my SM-G920V using Tapatalk

  2. #2
    Boolit Master

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    the ones I have found are 6" probes, I can keep that about 1/2" from the bottom of the pot.

  3. #3
    Boolit Master

    Beagle333's Avatar
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    I like an 8" probe. It allows me to mount it above the rim of the pot with the tip about 1/2" from the bottom.
    I don't have a good US source though. I order them in a 6-pack from China.
    Colt 1860, it just feels right.

  4. #4
    Boolit Master
    Mike W1's Avatar
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    Auber has 6" ones. Offhand I think it is a WK-191 that I've used with no problems. If you order there they were installing the little male plugs for a $1 bill. Well worth that. It's a WRNK-191.
    Mike

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  5. #5
    Boolit Master OS OK's Avatar
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    If I have learned this right...those probes have a temp. max rating.

    You should PM HATCH he knows about this newfangled stuff.
    a m e r i c a n p r a v d a

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  6. #6
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    JonB_in_Glencoe's Avatar
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    There are different types of Probes...Most of us use a K type probe.
    Be aware, if you don't know what type of probe you have, you may have to change the Parameters in the PID for your new probe.

    I use a 4" probe and have it positioned so the Tip is right next to the spout, so it's way in the melt...I haven't had any issues with heat on the top end of the probe.

    I order mine from a Hong Kong source, where I have ordered many other items...while they say an order can take 30 days, I usually have my orders in hand in a week, or 10 days max. I think they use the 30 days, in the rare case the items get held up in customs.

  7. #7
    Boolit Master
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    Same as above. I always order 2 or 3 (maybe more ?) On occasion i have had one show up DOA

  8. #8
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    HATCH's Avatar
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    You want k-type
    Keep in mind most TC are listed by C instead of F.
    400c = @750f
    I would get one rated at least 600c
    Length of probe doesn't matter but 4 inch is standard.

    I order my probes in from overseas because is cheaper then buying them from the instock USA suppliers.

  9. #9
    Thanks for all the info.
    I know mine is k type, pid came up showing 0 - 1200 on temp range.
    Does the pid need to be set to match the temperature of the new TC when I put in on.
    I might give the 4 incher a shot and see how they work since they seem to be more available than the others in multi packs. I might even move the holder over next to the spout, right now it is on opposite side.

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  10. #10
    Boolit Master
    Mike W1's Avatar
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    Quote Originally Posted by AzElkhunter View Post
    Thanks for all the info.
    I know mine is k type, pid came up showing 0 - 1200 on temp range.
    Does the pid need to be set to match the temperature of the new TC when I put in on.
    I might give the 4 incher a shot and see how they work since they seem to be more available than the others in multi packs. I might even move the holder over next to the spout, right now it is on opposite side.

    Sent from my SM-G920V using Tapatalk
    Usually, the PIDs come factory set for K type. Depending on the make/model the warmup screen sequence might show it or you can go into the parameters and see how it's set. Not sure what you mean by matching the temperature but there is also a parameter whereby you can correct it a bit closer by doing the ice water test. It's called different things by the 3 makes I'm somewhat familiar with. Other than that you only have to set the temperature you want. SV
    Mike

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  11. #11
    Boolit Master
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    Type K for the range we use.

    Remember ONLY the tip of the TC reads the temp. It can be 4 feet long but only the welded junction at the very end inside the jacket reads the temp. Use whatever length works best for you.

    I make my own using type K wire and welding the ends of the bi-metallic wires together. That tiny "bead" junction at the end does the measuring.

    Banger

  12. #12
    That makes sense.
    I thought you might have to tell it what temp rating the actual TC is like 0 - 900 or 0 - 1200. Etc...

    Sent from my SM-G920V using Tapatalk

  13. #13
    Quote Originally Posted by bangerjim View Post
    Type K for the range we use.

    Remember ONLY the tip of the TC reads the temp. It can be 4 feet long but only the welded junction at the very end inside the jacket reads the temp. Use whatever length works best for you.

    I make my own using type K wire and welding the ends of the bi-metallic wires together. That tiny "bead" junction at the end does the measuring.

    Banger
    So can the one I have be taken apart and fixed if it has only burnt that connection at the tip. or are they done for at this point.

    Sent from my SM-G920V using Tapatalk

  14. #14
    Boolit Master dikman's Avatar
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    Probably not worth messing around with it (unless you've got nothing better to do). I use 4", which is the most common size I've found in HK/China, rated to 1300*. The PID has a menu to select the type of probe, but if yours already had a K then it should be just a plug-n-play. I haven't had one fail (yet) but I try to keep at least one spare on hand.

  15. #15
    Boolit Master OS OK's Avatar
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    Quote Originally Posted by AzElkhunter View Post
    So can the one I have be taken apart and fixed if it has only burnt that connection at the tip. or are they done for at this point.

    Sent from my SM-G920V using Tapatalk
    I think all you have to do is re-cut the wire at the end and silver solder it back together with a tiny little connection then slip the wire back into the thermocouple housing and 'bada-bing'...use it. Heat causes the two dissimilar wires to conduct a minuscule current across that junction and it creates a voltage the PID sees, computes and reads out to you as a temperature.

    "I think?"
    a m e r i c a n p r a v d a

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  16. #16
    My problem is I can't stand not knowing how things work and figure if it's already broke I can't hurt it anymore.
    When I can use both hands again I think it's time to tear it apart and see how it works just to do it. If that's all it needs is to be re soldered might be worth a shot.
    If it works I will let you all know and it might be a quick fix for someone without a spare....lol

    Sent from my SM-G920V using Tapatalk

  17. #17
    Boolit Master OS OK's Avatar
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    This technician uses something I've never seen before to weld the wire back together....gosh it's been decades since I was in electronics school but it seems like they told us back then it was a silver solder...can't remember!

    https://video.search.yahoo.com/video...&fr=aaplw&tt=b
    a m e r i c a n p r a v d a

    Be a Patriot . . . expose their lies!

    “In a time of deceit, telling the truth is a revolutionary act.” G. Orwell

  18. #18
    Boolit Mold
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    These higher temp.thermocouples are actually designed to be used in the Thermowell, which is a sleeve of another material or metal with a coating.
    The couple is inserted into this sleeve bottomed out or touching this sleeve to transfer the heat to the couple, it is isolated from the actual process. That being said cheap China couples probably will never last long. I'd try a better industrial American couple I get mine from my work supplier they seem to last pretty well. In the "old days" we made our own using the correct wire for the different types, we had a machine that welded the ends together not silver soldered, inserted through ceramic sleeves they lasted forever it seemed.
    The temp. ranges mentioned are oprerating temps for the couple itself, the pid range is independent of this normally can be set anywhere in this range,i.e. 0-500 or 0-1000.

  19. #19
    Boolit Mold
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    One more thing if using the small diameter couples try the larger quarter inch ones that's what I use.

  20. #20
    Boolit Master
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    Quote Originally Posted by OS OK View Post
    I think all you have to do is re-cut the wire at the end and silver solder it back together with a tiny little connection....."I think?"
    RAther than silver solder it would be better to actually melt the two wires a tad so they are welded at the tip using the same material. Silver solder puts a 3rd material at the sensing end where there should be only the two dissimilar materials.

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