Multimeter question

5 Jun 2008
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United Kingdom
Can anyone please tell me what a type K thermocouple wire with plug is for a multimeter? Is it a connection that tests the working of a thermocouple? Or can it be used to test the resistance of wet pocket thermistors/certain thermistors? Thanks for any help.
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type k is for checking temps.if your trying to check thermistors or look at getting to know how a multimeter works first e.g thermocouples work on millivolts.were as thermistors work on resistance.basically though, in all you need to know what the relationship is.for example a thermistors range is in accordance with a temp.depending on what thermistor is used.
the thermocouple wires are made of strange alloys. You might think there is a temperature sensor on the end, but it is just the two ends of the wires joined together. I imagine they are welded, but you can actually join them yourself by twisting the bare wires ends together and bashing the joint with a big hammer.

The junction of the two wires generates a tiny voltage dependent on temperature. The multimeter has a scale which interprets this voltage according to some performance curve, and you can read out the temp on the display. They are not always perfectly accurate, it is worth testing by immersing the sensor end in a pan of boiling water to see if it reads about 100C.

K type is the most common, AFAIK the plug and socket are always coloured yellow to identify them. There are others which are more accurate at different temperature ranges. "K" is Ok for fridges, heating radiators, domestic stuff.

Depending on what you are using them for, it can be cost-effective to clip and clamp them in position on whatever you are testing, with the plugs handily accessible, so that you can leave themn in place ready for when you have to come back and test again. They are cheaper bought in bulk.
Thanks for both of your replies.

Basically I know how to use a multimeter. I have used one in the past (my £10 one from B & Q) to test on fault motorised valve's, cylinder thermostats and a fault thermistor (no resistance, just infinity).

I just wondered what the type K thermocouple connection was for as I am going to buy a new multimeter.

Some thermkistors apparantly require a clip on / adaptor to the meter leads so I wasn't sure what this type K was about!
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If you think you are going to want to measure temperatures, buy a meter with a "K" socket

It would be very tiresome without.

If you are interested in boilers, radiators and thermostats, it will be very handy.

You can get cheap import thermocouples of Ebay, they may not be perfectly accurate but you can test them befere use and make allowance if not.
JohnD, thanks for helping me here I really appreciate it mate.

In the catalgoue, it says Type K is for measuring Theromocouples though. What do you mean abotu measuring temperatures? Do you mean pipe temp's??

I am interested in boilers/rads/thermostats. What can this Type K adaptor do exactly?

Thanks again for your help mate.
type K is a sort of thermocouple. You get a length of thin, stiff wire with a bare or insulated end (it may be inside, or at the end of, a probe). You press this sensitive end against something, or into it, or immerse it, and it tells you the temperature. It is very small and light so it heats up almost at once. The other end of the wire has a special standard plug on it to fit your meter.

I don't know the official temperature range of a K-type (you can look it up) but it is something like -50C to +250C, so is adequate for domestic heating and freezing.

Other types cover different temperature ranges but you would have to buy a meter calibrated to read them.

the length of the wire is variable, you can buy a convenient size. The plug and socket are standard. You can also buy the wire in reels if you want to make your own thermocouples, but it would be a bit fiddly.

you can see some on
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cant see how a type k can measure a standard thermocouple.a standard multimeter will measure i said millivolts on a multimeter.keep it simple.i only use type k temp probes for differential temps on reallity though why do you want to know how boilers work.are you a homeowner or registered for gas.
JohnD, thanks for your help again :D So basically a type K isn;t for measuring thermocuples but for measuring temps!! So I plug the lead into the meter, touch a rad or pipe and it tells me the temp? Is that how it works?

Holty - I am not gas safe registered, but just wanted to knw what the type K thermocouple on a multimeter was for!!! I am interested in boilers though generally.
agree. a type K is for measuring a temperature not for measuring a thermocouple (e.g. one attached to a gas valve). If you wanted to test a boiler thermocouple you could verify what (tiny) voltage it output when in a flame, but I wouldn't know about that.

You could also put one under your tongue or inside some other orifice to check your body temperature, or you could put it in your tea to see how hot it was.


A type K is a thermocouple

It is "a type K thermocouple"

It is a general purpose temperature measuring device, it is not a boiler part.
JohnD, could the Type K be put on a rad and test for cold spots or for testing the temp of a boiler flow pipe then?
it will measure the temperature of whatever you press it against or immerse it in. At the moment mine is telling me the temperature of the air in my house.

I am not a heating engineer, but I have sometimes used mine to measure pipe temperatures. I had to tape it on to keep it in place, and pushed insulation over it.
Thanks JohnD for all of your help, I really appreciate it mate.

I could do with one for measuring pipes/rads if in the future I get any probs. You just need to hold the probes down tightly I guess!!??

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