Temperature measurement with DMM

[Davee3]

Looking to inexpensively monitor temperature variations without much concern for actual temperature. Ranges around 150C. Would a Thermopile with 500mA output connect directly to a DMM ? Or is there another way. Cold junction would be possible --Ice water or? As you can see Electrical not my fortee

 

[btrueblood]

How inexpensively, how accurately?

If you have power available (2 or 3 volts), use a silicon temp. sensor chip (LM34, see National Semiconductor site,

http://www.national.com).

Accuracy can get as good as +/-.5 deg. F.

Cheaper, but less accurate are thermistors - read them directly with an ohm meter; these are good to +/- 1 or 2 deg. C when calibrated, or used as differential sensors.

Cheapest: you can read a thermocouple directly in mV with a DMM, effectively measuring the temp. difference from the meter to the probe end.

 

[Skogsgurra]

There are some real cheapo DMMs fom south-east that can indicate temperature. Sometimes a thermocouple is included in the bargain.

Fluke, of course, have temperature probes that can be connected to any DMM. Not only theirs. They also have a non-contact surface temperature transducer.

Google +DMM +temperature for a long list.

If you want to experiment, you can always use a thermistor and a couple of resistors to have a limited linear range.

http://www.aicl.com.tw/ntc04/application/application.htm

shows a few examples.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

Hi Davee3,

All the above suggestions are fine.. They just require a heck of a lot of mucking around and table look ups, with the exception of the National part. Which all increase the chance of a screw up. I have used all the above methods with various success.

Lay hands on a non-contact temperature measurer. One of those point-the-laser-spot-read-the-temp guns.

The temp gun sees the light of warm objects, so as you use it imagine everything giving off light that signifies it's temp, and use the gun appropriately.

I use mine to check the temperature of my aquarium, the chili I was cooking yesterday, room temperature, my oven temperature. You can use them to find which cylinder is missfiring. The one with the 20F colder header pipe....

I use mine just about every day! I use it on motors, vacuum pumps, refrigerators, IC's. Just a whole lot of things. You can measure spots that any other measurement method works poorly on. Surface temperature of a motor is a good example. If you want the temp of a motor that isn't instrumented internally the temp gun is great.

Here are a bunch under a hundred bucks.

http://www.techinstrument.com/acata...hemometers.html

http://www.toolsource.com/ost//prod...EGDTVL90HBJFFME

http://www.calright.com/_coreModule...uctMasterID=188

http://www.nottheusualstuff.com/cat...?products_id=50

 

[OperaHouse]

If you just want a number to match against, use a cheap meter and a silicon diode like 1N4001. Most low cost meters have a diode check position that puts enough voltage on the diode.

 

[johnwm]

Anyone who wants to follow those links above:

http://www.techinstrument.com/acatalog/Infrared_Themometers.html

http://www.toolsource.com/ost//prod...2165&mscssid=0LQ45AWH3ELU9HAPNEGDTVL90HBJFFME

http://www.calright.com/_coreModules/eShopping/productDetail.aspx?productMasterID=188

http://www.nottheusualstuff.com/catalog/product_info.php?products_id=50

itsmoked
When you copy someone's post from another board (

http://www.clubhotrod.com/t13354.html)

make sure you expand the links rather than copy&paste

Good Luck
johnwm
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[itsmoked]

Hi johnwm; Thanks, I never even noticed..How annoying!!

Thanks for hunting up the correct ones.

That took some sluicing to hunt that back to my original post.

 

[johnwm]

...not really - a Google on 'non-contact temperature measurer' from your post and it's the first result !

Good Luck
johnwm
________________________________________________________
To get the best from these forums read faq731-376 before posting

UK steam enthusiasts:

http://www.essexsteam.co.uk