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Thermocouple probe source needed
Hello from a new member. I have been home roasting for 6+ years, and looking to take my next step.

I'm looking for a good place to purchase a thermocouple bean immersion probe for use on a Fuji PID. I'm currenly using a 1mm (.040" ) diameter probe that works well, but I need to add a disconnect style one to my new project. The ones Mike shows on his "Modifying a Poppery 1 (third article)" look nice. A fast response <1 sec. is preferred. McMaster Carr has what I'm looking for, but a little pricey.

I really wanted to build an RK Drum roaster. They look great. I enjoy lighter roasts, and just can't get past not having a bean mass temperature probe, so I'm going another way.

I made the plunge and ordered a Fuji PXG controller and an analog SCR heater control good for 4000W. What it actually controls will likely be a journey. I'm starting simple with a HG/BM and will see where it takes me.


Here's a company (Omega) that I've used and they have a large selection of thermocouples. They can also custom build to your specific needs, but you have to call them for any custom builds that are not already in their system.

Direct link to Omega's thermocouple area:§ion=a


As mentioned omega is a great source of TCs. I'd be curious to know which you choose - right now i'm just using K-type wire twisted together (very high tech) - I'm leaning towards this probe from omega ( but would be interested if you know about something better. I'm using a tweaked FR8 and just insert the probe directly into the beans so maybe your app is a little different? They do have some neat surface mount probes etc...

Edited by Pete on 04/07/2007 11:24 AM
This is what I have been using. http://www.circui...icOid/3406

It works excellent!

s:2s:2 s:1

The first one lasted more than a year... until I left it out in the rain.
So next I bought two of them.
It is nice to have a spare, and the shipping is the same.. one or two.

Hope this helps,


This is what I found today:

Not a bad price, but I have found them for as little as $2.75.

Unfortunately all that info disappeared when my PC crashed :(s:7

PeterZ c:3
Peter, I've ordered those probes from that ebay store to fit the Circuit Specialists thermometer. I can't remember if you mentioned this, but it is PAIR of probes you're getting. The last I checked it was $7.99 including shipping but I think they may have raised it a bit.

They come from Hong Kong but the shipping took less than a week from the time of order. The temp range goes beyond what is posted. I've had mine up north of 650 and it does fine. The rope casing finally began to wear away on my first one after about 100 roasts so I got these as replacements. There is a bit of blue plastic on the end where the probe is and it will burn off on the first roast.
Edited by jonathan on 04/11/2007 11:28 AM
Are there any issues with the material that coats the wires in terms of toxins? Kind of remember reading someplace that teflon might be bad - can't remember where now, maybe from Felix D.
There can be issues if Teflon is overheated.
These probes are coated with fiberglass I believe. Not sure what the blue part on the end is but that is removed.
I run them through a very thin tube and just leave the tip exposed. No more than the ball end and a small section of bare wire ever sees the beans.
Edited by peterz on 04/12/2007 12:36 PM
Think I'll give these probes a try - the one's I'm looking at from OMEGA are likely overkill for a hacked up coffee roaster - thanks PeterZ!

here is what someday may be my pride and joy

I've just been feeding the TC down through the top. Be nice to cut a hole in the chamber but I'm a little bit afraid of cutting the glass - especially with the heating and cooling

Edited by Pete on 04/12/2007 7:45 PM
Wow, it is very difficult to cut tempered glass!
Good luck with your efforts. Please do lots of research on it first.
I tried sawing a section out of a turbo oven lid, being very careful with a Dremel, cutting disk, and going very slow so it would not heat and crack.
I took a break and walked away.
When I came back in half an hour the lid was shattered into millions of very small pieces.s:6 Shock
So I replaced the lid with metal.Grin

PeterZ c:3
uggg - maybe just sticking down the top is OK :)
Thanks for the tips!
I ended up ordering from They sell extension wire by the foot, which was cheaper than buying a spool from omega.

This is what I got, 39095K96
Mini-Plug Thermocouple with Bendable Probe Flat-Pin Connector, Type K, 3'Cable, 7" L, 1/16" Dia, In stock at $28.60 Each

I also got a female connector and extension wire.

The probe is grounded, which requires me to insulate it from the grounded BM roaster I'm using; at least for the Fuji controller I'm using.
Hey John,

How's your project coming along?

I'm curious, the thermoprobes that you purchased from McMaster - they are listed as "mini=plug."

I don't know anything about thermoprobes as I have up till now used a non-digital candy thermometer.

Will that mii plug fit into a standard connection like something on this http://www.licens...TMD90A.htm

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