Which sensor to use for measuring extremely cold temperatures with arduino

Using Arduino Project Guidance
1

Hi. I am using liquid nitrogen for cooling my experimental setup (it's a thermal based project). So, I was wondering what sensor I can use for measuring temperatures as low as -196 C?

(I know from theory it can be a T type thermocouple; but on searching online, I am not able to find it or any other sensor)

Please help.

2

That is really strange! I just did a Google search and found pages of type T thermocouples for sale.

3

Check Adafruit or Sparkfun.

4

Platinum RTD

https://www.ist-ag.com/en/sensor-finder?f[0]=category%3A7&f[1]=category%3A37

https://dwyer-inst.com/en/products/temperature/sensors/series-rtd-resistance-temperature-detector.html?utm_feeditemid=&utm_device=c&utm_term=go_cmp-17818943407_adg-_ad-__dev-c_ext-_prd-RTD-6418_mca-10700261_sig-Cj0KCQjwpompBhDZARIsAFD_Fp9gEtHqdN4-XVDu18kIoFInuV-WJ5s27XZCzwcBj-5Qg3WEPvnpJ4caAvuHEALw_wcB&utm_campaign=PMax:+Smart+Shopping+-+9%2F10&utm_source=google&utm_medium=cpc&hsa_acc=4712969374&hsa_cam=17818943407&hsa_grp=&hsa_ad=&hsa_src=x&hsa_tgt=&hsa_kw=&hsa_mt=&hsa_net=adwords&hsa_ver=3&utm_content=undefined&gclid=Cj0KCQjwpompBhDZARIsAFD_Fp9gEtHqdN4-XVDu18kIoFInuV-WJ5s27XZCzwcBj-5Qg3WEPvnpJ4caAvuHEALw_wcB

1 Like
5

If the liquid nitrogen is open and boiling , won’t temperature be constant? It’s boiling point at atmospheric temperature. ??

6

Hey. Like I guess I'm using google India, so all the sensors available in Indian market is being shown. Also, for some T type thermocouples, the minimum temperature is nowhere near -196 C.

7

Yeah... but it's like the liquid nitrogen is being used to cool down a system, but I need to see what exactly is the final temperature of cooled air at some distance from this cooling chamber.

8

hey.. thanks a lot!!! I thought a T-type thermocouple would be required... but seems K type would work the best here....

9

I have very limited experience with thermocouples...

But my concern would be getting a usable-stable reading. At lower temperatures you get lower voltage and noise (signal-to-noise) might be a problem.

The thermocouple itself should be fine... it's just physics... but you need a low-noise instrument (or amplifier) rated down to around -200 C.

10

We used thermocouples in the Water Resources department to monitor motor bearings etc.
Practice there was to use the iron/constantan wiring to the thermocouple AND the use of the same metals terminal blocks.
Any other metals will throw your results in the rubbush bin.

11

A Type T Thermocouple will get you down to -270C. A look at any Type T chart will tell you that. A type T is likely the least expensive choice.

T Copper (+) vs. Constantan (-)
MAXIMUM TEMPERATURE RANGE
Thermocouple Grade
– 328 to 662°F
– 200 to 350°C
Extension Grade
– 76 to 212°F
– 60 to 100°C
LIMITS OF ERROR
(Whichever is greater)
Standard: 1.0°C or 0.75% Above 0°C
1.0°C or 1.5% Below 0°C
Special: 0.5°C or 0.4%
COMMENTS, BARE WIRE ENVIRONMENT:
Mild Oxidizing, Reducing Vacuum or Inert; Good
Where Moisture Is Present; Low Temperature
and Cryogenic Applications
TEMPERATURE IN DEGREES °C
REFERENCE JUNCTION AT 0°C

I used Type T extensively for cryogenic work including plenty of LN (Liquid Nitrogen). The IndiaMart seems to have plenty of Type T Thermocouples available in India.

You need to decide exactly which thermocouple design you want? Grounded or ungrounded, sheath material if you want a sheath, sheath diameter, how fast response time and the list goes on.

Ron

12

This may be worth a try. The below pdf describes how to make accurate cryogenic measurements using a 1N914 diode and an LM317 regulator as a current source

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13

Not so, the output from the thermocouple increases as the temperature difference between the measurement and “cold junction” increases”

At -270 you get a whopping ~6mV

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