Inexpensive handheld thermistor probes?

Question

I have a handheld thermistor probe. It's a pretty standard 10k NTC thermistor in a stainless body with a plastic handle and some cable leading to banana plugs. It came for free with a Radio Shack DMM years ago and is perfectly functional.

I'd like to get some more similar to it. I thought they would be trivial to find and cost $10. This has not proved to be the case. In fact, I have had great difficulty finding any whatsoever.

I have found a lot of industrial ones designed to be permanently mounted and costing upwards of $50, neither of which are properties I want. There are also a great lot of thermocouples, and thermocouples are very nice, but I don't want them for this - I don't need the range and too many components are required to amplify the signal. It's also easy to get thermistors, but I have no desire to put my own bodies and handles on them, either.

Does anybody know where I can get maybe a dozen of the right thing for under $20 each? If it costs much more than that, I can buy prebuilt handheld thermometer units and throw out the display.

I am located in the United States.

Lostgallifreyan · Accepted Answer

Terran Melconian wrote in news:slrneqqdcn.832.te_rem_ra_ove_an_forspam@There-Are-Many- Things.consistent.org:

As far as I know, the cheap probe thermometers you mention are also thermocouples, not thermistors. Mine are, anyway.

Joerg · Answer

The ones I took apart over the years had mundane diodes.-- Regards, Joerg

Terran Melconian · Answer

Interesting. I would have thought that per-unit calibration would be too costly for a $20-$30 consumer device, but so would opamps with a low enough input offset voltage to avoid the need for it. Do you recall how they measured the thermocouple voltage? Perhaps they have some smart technique I can steal... er, borrow. :)

Lostgallifreyan · Answer

Terran Melconian wrote in news:slrneqqmlc.9ik.te_rem_ra_ove_an_forspam@There-Are-Many- Things.consistent.org:

I think it's likely I was wrong and Joerg is right. Without destroying one, I can't get at its innards enough even to test it. I was seeing just the wires to the probe, one is enamelled copper, the other is in what seems to be a teflon sheath, giving the impression of dissimilar metals. The range is -50C to +300C, which is definitely NOT a diode, maybe, or even a thermistor, unless it be PT100 type.

I'd still lay odds on it being a thermocouple, even though I can't prove it. If you want to buy one to mutilate, go for it. :) They're on eBay, they're very good for the money, even without yielding their dark secrets.

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(eBay listing. I was the buyer on that one.)

There are others similar, many sellers, but I chose these after careful comparison, and I think I got the best deal by far.

(Off-topic, but I'll take this shameless chance to suggest that if anyone's looking for an ITX computer, or an FS1R synthesizer (Yamaha), I'm selling them to raise money for a laser project. ITX machine will go up tomorrow night, is 1.2 GHz, tiny machine, built to keep, but I really need money fast to get some optics that won't wait around. I'll say no more here, it's not the place, but if anyone wants, they can post a question via a listing..)

Inexpensive handheld thermistor probes?

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