K Thermocouple to Digital Converter

Other Hardware Science and Measurement
1

Dear all,

I am quite intrigued to build myself a K-type thermocouple reader. This could be useful in my lab as well as
for some stuff at home.

I read that people recommend the MAX6675 or MAX31855 (Mixed-signal and digital signal processing ICs | Analog Devices) to amplify the thermocouple voltage...

What I am struggling with is to find a UK supplier. RS components sells the 6675 but I would rather have one that is already on a breakout board (as you can get them on ebay in the US).

Does anyone know another place to order those?

If I can't get it on a breakout board, what other options are there to mount it?

Is there a different part more readily available in the UK?

Regards,
Bob

2

I use Adafruit's breakout boards, they've worked well. She's in the US, but maybe someone in the UK carries her stuff? This chip is an SOIC package, not that hard to solder, so that's a definite option in my book. In fact I have a couple waiting for a future project that will be on a custom board instead of using the breakout boards.

3

Hopefully some of the Euro based participants will know of a local source for a breakout board. If not...

The MAX parts don't need any external parts, except maybe a cap across power. You can solder it to an SOIC proto-board or generic breakout board pretty simply. If all else fails, SOIC pin spacing is 0.1" the same as DIP. In a pinch, you can gently bend the leads straight down and (sometimes) get them in a breadboard; sometimes the leads are too short to reach the contacts reliably. They will fit in a DIP proto / breakout board. You can also 'dead bug' the part. Glue the part upside down and solder wires directly to the pins.

The AD597 amplifier is available in a proto-friendly leaded package, although it is not cheap. Perhaps others parts are also, it was just the first one I found.

You can buy thermocouple amplifiers that are pre-made, such as you would use on a standard DMM.
http://www.toolup.com/ideal_61-465_thermocouple-adapter.aspx?utm_source=scGPS&utm_medium=cse&utm_campaign=sc&scpid=2&scid=scsho1094016

http://www.toolfetch.com/accessories-07525g.shtml?gclid=CPvyr6utl7ICFelaMgodvUYApA

Steve

4

Some possibilities here: Distributors and Hackerspaces

5

Probably off topic, but having worked with thermocouples for many decades in a oil refinery, unless someone actually requires the very high temperatures that couples can work at, they are not a very accurate sensor unless very expensive ultra pure material types are purchased. We always found RTD temp sensors to be much more accurate and would work up to 500 to 1,000 degrees F depending on specific brand and model RTD sensor was selected. The electronics interfacing for TC sensors (cold junction reference, etc) was more difficult then that required for RTD interfacing. At lower temperature ranges even selected termistors or solid state temperature sensors can give better performance and be more cost effective.

Again unless one needs to measure temps above 500 degrees or so, thermocouples are rarely the best choice.

Care to discuss?