# I want to learn thermocouple type k,j etc,

#### GTronics

Joined Jan 30, 2021
7
Hello evryone,
I start studying Eletrical and computer engineering and I want to learn thermocouple type k,j etc, however I've been searching and I can find to measure temperatures is using water bath 0° in cold junction so voltage will be the same as thermocouple tables on google, however that's not practicall so can someone help me to understand how that "cold junction" is made electronically? Or am I understanding the cold junction concept wrong?

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#### nsaspook

Joined Aug 27, 2009
8,390

#### atferrari

Joined Jan 6, 2004
4,329

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Joined Jan 15, 2015
5,934
You may want to give this a read. CJC (Cold Junction Compensation) is explained and the use of an ice bath slurry. Also a few images of transition reference junctions are shown.

Ron

#### Harvy Wallbanger

Joined Jan 13, 2021
7
The short answer is to measure the temperature at the "cold junction" separately and add it to the reading at the "hot junction"

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,768
You have the tables. Polynomials or a lookup table for t(v) is available at 0 deg C.

You have to independently measure the temperature of the terminals (isothermal) where the thermocouple connect with a )e.g. calibrated thermister, diode or silicon sensor), then reverse lookup the voltage at that temperature.

You then add or subtract, forget which, your measured value and then lookup the temperature for that voltage.
Cold junction compensation is generally valid over a smaller range.

#### GTronics

Joined Jan 30, 2021
7

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,768
To understand it, you can do the ice bath thing and a voltmeter.

Then, you want an isothermal connection. You can probaby make one. Get couple of to220 insulator kits and some copper or brass and make a fairly large thermal mas, but thermally conductive and read the temperature with some other sensor.

You can buy isothermal blocks for thermocouples.

One last thing: Th wire with the Red insulation is negative,