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Author Topic: How to use a multimeter for measuring really Low Temperatures  (Read 694 times)

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Online Kiriakos GR

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How to use a multimeter for measuring really Low Temperatures
« on: December 28, 2016, 11:31:50 AM »
Most or all multimeter they do come with temperature range this measuring even sub zero temperatures.

At the same time 99% of multimeter they are not designed for outdoor measurements’.
Technically any multimeter exterior case and internal electronics, both should never be exposed to harsh weather conditions.

Factory calibration this is made at about 23 Celsius, and by room temperature or atmospheric temperature this getting lower and lower, significant measuring error will eventually occur.
Practically any multimeter this exposed at below 12 Celsius this will starting to add partial inaccuracy in the measurement.

For example lets assume that outdoor temperature this is 7C and we try to measure that by a multimeter and it thermocouple.
If body temperature of multimeter this is around 14C, we will measure close to accurate this outdoor temperate, as long duration of measurement this is less than 2~3 minutes.

It is not recommended or accepted to let the multimeter outside in the cold for five or more minutes.
This action will cause an error of about four degree Celsius, when environment temperature this is at 7C.

Other outdoor temperature sensors as for example mini weather report stations (for home use), they fight this inaccuracy by having a much sorter measuring range, as for example minus 25C up to 50C.   
Digital HH Multimeter they do have a much larger measuring range, and therefore this makes them more prone to measurement errors.

In conclusion it is recommend you to expose at cold or hot temperatures only this thermocouple sensor and keep your handheld multimeter at room temperature.

This topic it is for experienced electricians, and therefore I will skip talking about of what moisture this can do to electronics by assuming that this is all ready known.
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Online Kiriakos GR

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Re: How to use a multimeter for measuring really Low Temperatures
« Reply #1 on: January 06, 2019, 10:03:14 PM »
Two Decembers later the same thought bothered me again, and this is what trickery to do for measuring temperature of a cold night when external temperature this is at 1.5 Celsius or about there?

Handheld multimeter lucking cold junction adjustment for thermocouple compensation and practically this is a dead end.
But the answer and solution came to me by thinking that Zero Celsius calibration this is equal to a K type thermocouple shoved in to the snow.  :)

Therefore workaround suggested this is leaving outside a glass of water for an hour and then measure water temperature indoor .... this workaround will increase measuring accuracy because of all reasons mentioned at my post above.

Second interesting testing by shoving a thermocouple in to the snow, this is inspection of multimeter calibration.
Today I do own three U1272A,  and Zero Celsius calibration after testing all three, it is measured at +/- 1 Celsius.       
First meter measurement:  minus 0,5
Second meter measurement: 0,0
Third meter measurement:  Plus 1,0 Celsius 

Naturally any measured difference when comparing identical multimeter, this having to do with precision of calibration adjustment when this was performed at factory or elsewhere.
From the other hand any calibration report this serves and the purpose of consultant for us when we seek ultimate measuring accuracy, in a way we should mathematically compensate any detected deviation marked at calibration report from our own measurement.       
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Online Kiriakos GR

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Re: How to use a multimeter for measuring really Low Temperatures
« Reply #2 on: January 07, 2019, 08:07:02 AM »
Glass of water as measuring object really works well,  but you must be fast at taking your measurement by a multimeter this be powered (warmup) for 15 minutes at least.

In this experiment as soon the class inserted in door and thermocouple inserted  to it,  multimeter measured right away  3.5C.
Unfortunately for such a measurement process just a minute later temperate started to gain influence from indoor temperature.

Even so I do classify this work around as highly successful method    8) about measuring Low Temperature by a multimeter and a thermocouple.
Alternative option this is buying a ten meters long thermocouple, but over all this is not practical idea because you will have to find or drill a hole, so the wire to pass from in-door to outdoor.

Therefore my very own suggestion using a glass of water this is much preferred one, but be quick  ;D ;D     
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