Connecting K type thermocouple to multimeter?

Platypus

Could I have some advice please on connecting a K type thermocouple to a temp reader. The reader came with the basic thin flexible temperature probe but can I use the old yellow connector for the new k type or would I be better buying a more suitable one, in which case, any suggestions please? Thanks

DavecUK

The colours are wrong for a K type thermocouple, usually they are Red and Yellow. The wore colours you have indicate a Type R thermocouple??

Also the Red wire is always the negative (which seems unusual, but that’s the convention.

This is a good site to cover the wire colours of the different type https://www.thermocoupleinfo.com/type-r-thermocouple.htm

If you do have have a K Type there, then you can remove the terminals and connect them as Red -ve and black +ve.

Platypus

@DavecUK Thanks for the link & advice.

Here is the receipt with it being sold as a K type?

Adrianmsmith

Platypus

If you have an accurate dc mV multimeter you can check if its J type with ref to the table in daves link

And k type, also starting from daves link

https://www.thermocoupleinfo.com/type-k-thermocouple.htm

Gagaryn

Different countries use different colour standards but it’s not unusual for some manufacturers to just use black and red, in which case black is normally negative.

In the UK K-type are normally blue and brown, brown being +ve. In the US, red and yellow as Dave mentioned.

DavecUK

Use a magnet and which ever wire (not connector) is attracted, that’s the -ve wire.

Platypus

DavecUK Use a magnet and which ever wire (not connector) is attracted, that’s the -ve wire.

Will do, that’s handy to know . Thanks for your help .

Adrianmsmith

DavecUK Use a magnet and which ever wire (not connector) is attracted, that’s the -ve wire.

J-type (Iron / Copper-Nickel): The positive iron wire is magnetic, making J-type thermocouples easily identifiable with a magnet.

K-type and N-type (Nickel-Chromium / Nickel-Silicon): These materials are generally non-magnetic, so K-type and N-type wires won’t attract a magnet.

T-type (Copper / Copper-Nickel): Copper is non-magnetic, and the copper-nickel alloy has weak magnetic properties, making magnetism an unreliable identifier for T-type wires.

Tal

All of our k types at work are green/white with green plugs, N types pink, J types brown. Just to throw some new colour combos into the ring :)

DavecUK

Adrianmsmith K-type and N-type (Nickel-Chromium / Nickel-Silicon): These materials are generally non-magnetic, so K-type and N-type wires won’t attract a magnet.

No that’s not actually correct…when you alloy Nickel and Chromium (Chromel), Nickel which is ferromagnetic loses this property as the molecular structure is randomised by the Chromium content.

When you alloy 95% Nickel with 2% Aluminium, Maganese and 1% silicon (Alumel), it remains magnetic.

Adrianmsmith

DavecUK

I guess my information just goes to show you cannot believe every fact you read on the internet this seemed to be In good detail but it just goes to show 🤔

My k type thermocouples are all sealed both ends and encapsulated. I can confirm the whole “wire” is magnetic but obviously I can’t check which core.

In my past life, one of my jobs was setting the offsets and calibrating various temperature displays using a certified millivolt source. …. In reverse…. It is worth checking any unknown thermocouples at room temperature with a multimeter assuming it’s accurate enough and referring to the tables for the various thermocouple types. It is also relatively easy to check at near 0 and 100C.

I must try and source Some of those very thick polystyrene cups we used to use in the science lab back in the school days 😎