Thermocouples

[Andy]

This question is for those of you who are logging data and using either phidgets or bluetherm. Just curious: Which thermocouple(s) do you use and why? I have been using iCelcius, which works great and has its own dedicated non-TC probe; but I may eventually want to switch to a method that has wireless capability. There are several kinds of K type TC probes on the bluetherm site  -- and other places too, of course -- that look as if they would be suitable for roasting. So what do you use, or which do you think is best?

[Danny Hall]

I prefer insulated (ungrounded) K type probes. The insulation keeps them isolated from electrical noise. I've tested with both, and have never had any problems with either, but I like the idea of knowing I'm not picking up and motor interference from the metal housing of the roaster. The down side is they're more expensive, and have s lightly slower response time that their uninsulated counterparts, but the insulated types are supposed to last longer.

Omega.com is a great source for thermocouples. They have a broad range of length and diameter options.

Also, if you decide to build Phidgets and also want to go with a spiral cord thermocouple, Grainger.com is a good source for the probe mini connectors and mounts. See snapshot of my Phidgets board.

[Andy]

Good information. Thanks. I would guess insulated TCs are perhaps more durable as well. What about the shape of the probe; blunt, pointed, thick, thin,long, short, etc. Does that affect response time?

[Danny Hall]

Length - no. The magic happens where the two metals join, and that is right near the tip. Same for the tip shape - I can't see that affecting anything.

I'm not sure about the diameter, but I have a number of TCs for testing of varying diameters and types. The two I like to use when roasting, though, are blunt tip K types, and they're 3/16" - so thicker than the normal 1/8". And they're plenty quick for me.

[Andy]

Thanks. Just what I wanted to know.