LN thermometer..?

[Russ Andrews]

Anyone here have a source for a BASIC thermometer

for monitoring temps down to -324f...?

 

[logem]

It seems as if a digital thermometer with K-Type thermocouples should do the trick. I don't use liquid nitrogen or have a need to measure this low of temperature so I am not answering with first hand experience, but you should be able to find a used Fluke thermometer with K-Type wires on Ebay for not too much cash.

Here's what a quick internet search found:

Type K Thermocouple (Nickel-Chromium / Nickel-Alumel): The type K is the most common type of thermocouple. It’s inexpensive, accurate, reliable, and has a wide temperature range. The type K is commonly found in nuclear applications because of its relative radiation hardness. Maximum continuous temperature is around 1,100C.

Type K Temperature Range:

Type K Thermocouple Grade WireThermocouple grade wire, –454 to 2,300F (–270 to 1260C)


Type K Accuracy (whichever is greater):

Standard: +/- 2.2C or +/- .75%
Special Limits of Error: +/- 1.1C or 0.4%

Good luck,

Mike L.

 

[Russ Andrews]

Mike L....will check into that.....Thanks

 

[silver_pilate]

I'm curious as to the reason? If the nitrogen is still liquid, it's below -321F. But yeah, an appropriate thermocouple should do the trick.

--nathan

 

[jdm61]

Russ, why are you worried about that? The "air" space above the liquid is at leas twice as cold enough for anything that we need to do assuming you have a good seal. Are you trying to breed you some eta carbides?

 

[timgunn1962]

I'm also not clear exactly what you want to measure or why, but I've just put a calibrator on a TM902C and it will measure down to -200 degC (-328 degF) and up to 1370 degC (2498 degF). Display is degC only.

An ebay search for TM902C should find several at under 5 bucks delivered (albeit not fast).

I've had a lot of these, with several different ranges marked on the front. All have been good to 1370 degC with a suitable (type K) thermocouple, regardless of the marked range.

I've had the calibrator on them and their accuracy has been as good as that of recognized brands at 20 times the price.

I've never bothered to check the lower range before. The bead-type thermocouple it comes with is glass-fiber-braid-insulated and is good to around 400 degC (750 degF). It is thin and flexible enough to go through a typical oven or kiln door seal for checking/measuring tempering temperatures. It looks like it will work down to -200 degC, but you'll have to work out whether it's suitable for measuring in your application.

Obviously an appropriate thermocouple is needed for higher temperatures than about 400 degC.

I've always felt that no knifemaker should be without one.

 

[Russ Andrews]

Joe.... yes...
I mean to build a cold box for cryogenic processing, and allow for the monitoring/control
of the rate of temp drop/rise.

timgun1962....Thanks....will try one of those...

 

[ron_m80]

The "T" thermocouple is more suited for those temperatures than the K thermocouple. The K couple has a wider range and won't be as accurate.

Thermocouples would be the preferred method of measurement. However I suspect the temperature will be constant, as LN2 at ambient temperature and pressure is always evaporating.