Help with digital thermometer and thermocouples.

So I find myself in need of buying a thermometer and thermocouple so that I can try benching on ln2 at the end of July. I am looking for something cheap as I do not want to make a large investment due to the fact that it may be awhile before I can play with ln2 again.

So I have been shopping around and found some cheap units on eBay and Amazon but I do not know if they will be good enough to get me by until I can invest more heavily. See example below.

https://www.amazon.com/gp/aw/d/B014..._m=ATVPDKIKX0DER&pf_rd_r=EEXSMV95029CTGXNHV5Z

This unit claims it is good down to -200c but it does not come with the right probes for this temperature which leads to the second part of this post.

What type of thermocouple is best for ln2 benching and where can I source them. Once again would like to stay on the low end of the cost spectrum if possible.

I understand I will be giving up some accuracy and repeatability but I am willing to live with that for the current situation.

Unfortunately my background with thermocouples is limited to working on the high end for furnaces were we are more worried about if the thermocouple can withstand the temperature and if the cladding will withstand the hostile environment.


So I'm hoping someone can give me some suggestions for what to look for or just an outright product link that will get me what I need. I'm sure there are things I'm not considering do please educate me and I will try to send any questions as they arise.

Thanks in advance.

http://www.ebay.com/itm/Digital-K-J...obes-2192-F-/181350835140?hash=item2a395a23c4

Is what I own and has done well enough. It may not be quite as accurate as a Fluke but is much less expensive.

That's what I used on Janus' recommendation a couple years back!

Does the thermocouple that come with this operate down to ln2 temps or did you have to source other ones.

The ones I got with mine went all the way down

Priller has his Fluke for sale here.

Edit: Temps are based on type. The K-type is good down to -200C. Source.

Blaylock said:

Priller has his Fluke for sale here.

Edit: Temps are based on type. The K-type is good down to -200C. Source.

Click to expand...

Thanks for the heads up on that fluke. Unfortunately it looks like he traded it already.

I thought the same thing about the k type thermocouple but when checking the spec sheets on the ones readily available online they list a lower temperature of -50, hence my confusion. See example below.

https://www.amazon.com/gp/aw/d/B0083T29PE?psc=1

Something's up with them then. They don't fall in any of the catagories listed.

My guess is they're just listed incorrectly. They look exactly like mine.

Janus67 said:

The ones I got with mine went all the way down

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Yep, same here. I saw -190 or so.

remember, pinpoint accuracy isn't exactly a requirement (though nice and I certainly understand why you want it!!). If your unit says a CPU is CBB at -110C so long as you use that same device, that same CPU is going to CBB at the same temp regardless if a more expensive/accurate model says it does so with more accuracy at a different temp.

I agree with that Ed I'm not to concerned about accuracy as long as the repeatability is good. We run into this at work a lot. I am not to concerned with the actual temperature it is just a value As far as I'm concerned as long as it reads the same value each time.

I like the unit Janis listed but I'm worried about the delivery time in it. Might do some shipping and see if I can find something similar worth a better delivery time.

Might also pick up a few different thermocouples of of Amazon and hopefully at least one will respond as expected.

Lochekey said:

I agree with that Ed I'm not to concerned about accuracy as long as the repeatability is good. We run into this at work a lot. I am not to concerned with the actual temperature it is just a value As far as I'm concerned as long as it reads the same value each time.

I like the unit Janis listed but I'm worried about the delivery time in it. Might do some shipping and see if I can find something similar worth a better delivery time.

Might also pick up a few different thermocouples of of Amazon and hopefully at least one will respond as expected.

Click to expand...

If you need to borrow one for the party (unfortunately I won't be attending) shoot me a PM and if you pay the shipping to/from me you can borrow it. Or if Joe plans to go still he can pick it up before driving out, whichever works.

Hey Janus thanks for the offer. I will let you know what I'm gonna do after a little more research. If I don't find one in the next week or so I will pm you so wet can work details out.

I will let you guys know if I go or not.. still on the fence.