Ping Karl!

Karl..Ive dug out the thermocouples for you.
They are 100 ohm Platinums with leads at least 5' long
Will your controller deal with 100 ohm platinum thermos?
If it will..they go out in an envelope later today.
I have others types if need be.
Gunner
--
"The danger to America is not Barack Obama but a citizenry
capable of entrusting a man like him with the Presidency.
It will be far easier to limit and undo the follies of an
Obama presidency than to restore the necessary common sense
and good judgment to a depraved electorate willing to have
such a man for their? president.. Blaming the prince of the
fools should not blind anyone to the vast confederacy of
fools that made him their prince".
Reply to
Gunner Asch
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OOps, those are Platinum resistance temp. detectors, NOT thermocouples.
Jon
Reply to
Jon Elson
Don Foreman has the equipment to help here. I'll ask him and email you.
Karl
Reply to
Karl Townsend
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A thermocouple is a twin-lead junction of two dissimilar metals that generates a voltage differential as a function of temperature changes ("the thermoelectric effect").
A resistance temperature detector (RTD, commonly) is a single material/alloy whose resistance varies w/ temperature.
In the former one measures the generated voltage; in the later one measures resistance. Each then uses a calibration curve to relate the output to temperature.
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Reply to
dpb
Further, a great many temperature controllers will accept multiple types of sensing elements with appropriate configuration.
Reply to
Pete C.
Do you have more of the platinum ones? It would be good for me to swap that in (or at least have it on hand to swap in when the type K burns out.)
Thanks, DoN.
Reply to
DoN. Nichols
Most reasonably modern temperature controllers will use those. Yes, they are not thermocouples, which need a junction of two dissimilar metal alloys -- such as Chromel and Alumel, or Iron and Constantan. I'm not sure whether either of those may be what is called Type-K, but I think that the first may be.
Yes Platinum are variable resistors, not true thermocouples. But a good controller should be configurable for many types of temperature detectors. And the Platinum resistance ones are (I believe) the best for life at high temperatures. (So my just posted question still stands, even though I missed that you called them thermocouples instead of thermo-sensors. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
Thermocouples are made of a welded junction of two dissimilar metals, and generate a tiny voltage proportional to absolute temperature.
Resistance temperature detectors are resistors whose value changes with temperature, so you have to put some current though one and measure the voltage resulting from that current to know the temperature. No problem, most modern controllers can handle either type, only requiring reconfiguration of a parameter in some interminable menus. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
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Yes Type-K is chromel-alumel. They're good to the Curie point of about 350 C.
Platinum is the premier RTD material for almost all purposes...
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Reply to
dpb
I pretty much switched to rtd's in r&d due to their better accuracy and stability. I had thermocouples drift a few degrees/year in extruder service with daily temperature cycling to 200+ C. There are two main rtd calibrations that I am aware of, European or American. There is a slight difference in temperature coefficient between the two. You need to know which you have when you set up your controller.
Pete Keillor
Reply to
Pete Keillor
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If they're Pt, they're RTDs as J--
Reply to
dpb
Platinum RTDs are best for moderately high temperatures (maybe up to 600°F-800°F), but especially for around room temperature up to a couple hundred C. They tend to have relatively pokey reponse times and are more fragile than thermocouples, but for applications such as plastic extruders, the better stability can be worth it- getting better than a few degrees with a thermocouple is not so easy/cheap.
Almost everyone uses the Euro standard (alpha = 0.00385) RTD these days. I have not seen the old US style 0.00392 type in ages).
There's not much platinum in an RTD these days, well under $1, since just a thin film is generally used (sealed under a glass passivation).
Platinum (actually Platinum/Platinum-Rhodium alloy) THERMOCOUPLES are such as type R and S are best for very high temperatures (over 2000°F). They are about useless for low temperatures, mostly because the output is so very low (about 1/10 that of a type K and 1/100 that of an RTD). Platinum thermocouples are made with platinum (alloy) wire so they tend to be pricey, even if fine wire is used.
Reply to
Spehro Pefhany
Yeah, seems like I standardized on 385's about 15 years or so before I retired. However, if Jon's are old stock, it would be important to know their calibration. Back then, my controllers could handle either. Don't know if that's still the case or not.
Reply to
Pete Keillor
Gunner Asch on Tue, 29 May 2012 23:22:20 -0700 typed in rec.crafts.metalworking the following:
Sure some wasn't Misc? Not to be confused with "Misc Stuff". Or Assorted Stuff, which of course is different than Unsorted Stuff, Various Stuff, and Unlabeled Stuff .
I think I may still have boxes from three moves back marked "desk stuff". And one marked "It's 3 AM, who knows?"
Reply to
pyotr filipivich
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What about some of these, maybe????
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Reply to
dpb
Sent via private e-mail. Let me know if you don't get it for whatever reason (which may be that my message never reached you, or vise versa) -- and proably best via a message here, since sometimes emails which I've expected to you have vanished in mid-transfer.
Thanks, DoN.
Reply to
DoN. Nichols
You appear to have the variable resistor type. Most controllers should handle them. The voltage generator type would need some other metal as half of the sensor element.
Not much that I can trim in this followup and keep the context for other readers. Sorry.
Good Luck, DoN.
Reply to
DoN. Nichols
Hi Pete Keillor and/or anyone on RCM
Recently I've sent a couple of messages to RCM to test the waters, so to speak. If anyone sees this test post of mine, please respond through a a normal RCM post. Thanks.
Bob Swinney
Yeah, seems like I standardized on 385's about 15 years or so before I retired. However, if Jon's are old stock, it would be important to know their calibration. Back then, my controllers could handle either. Don't know if that's still the case or not.
Reply to
<judybob
Hi, Bob.
Pete Keillor
Reply to
Pete Keillor
I see it. I trimmed all the unrelated quoted material in this followup.
Enjoy, DoN.
Reply to
DoN. Nichols

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