A Thermocouple And A Temp Probe

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Boston Bay Brewery
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Well all the questions regarding using a keg for a mash tun has encouraged me to start the project.

Now as we all know, with most projects the initial plan involves the use of all the best gear available for any item on your brewery, but as we get into the project the old guilt of how much it will all cost seems to take over and you start to look for ways to do it a bit cheaper.

I have a meat thermometer type temp guage in my current rubbermaid mash tun and I am now thinking of using it in the converted keg and what I want to know is that how does a thermocouple work?

I assume it is a tube that is sealed with the temp probe inside and it measures the temp by heat transfer to the probe.

Am I correct so far?

If I am then, can I make a thermocouple out of say a piece of copper pipe fitted through the side of the new tun with the temp probe inside?

Would the pipe have to be filled with a medium like water or glycerine or something that would transfer heat or would the air in there be enough?

These brewing equipment questions seem to never end!!!!

Thermocouples work by having two different metals that produce a small amount of electricity depending on the temperature.
A bit more complex than my explanation, but that will do i guess.
There are basically three types, grounded, ungrounded and exposed. The grounded and ungrounded can be immersed directly into the liquid or gas, where as the exposed tends to be sensitive to anthing that could corrode it.

The exposed are the quickest sensing, followed by grounded, then ungrounded.
So basically you can drop them directly into the wort.
If you are going to sitck it in the tube, i'd definately solder it to the tube to get the best thermal contact.
a mate in canberra has done then - fed a wire down a small copper tub soldered the wire to the Temp IC and epoxied it on the end of the tube.

Then that goes to the thermo couple /computer for measuring the temp.
dicko said:
what I want to know is that how does a thermocouple work?

These brewing equipment questions seem to never end!!!!

Jgriff has explained it there, it is quite simply how they work dicko.

here's a couple pages' for your reading enjoyment.

here's what i have for the my controllers. I have three Cool room, MLT/HERMS and HLT. B)

Anyway happy reading
and the u-beaut thermocouples are expensive as well but look the goods as per jayses set up.
i will email you when your online with what i found out about availability.
That brings up the next questions on everybodies lips, where can i get all this stuff and at a good price? Just getting the stuff looks quite hard.
I have a couple electrical engineers in the family and all my stuff fell of the back of a truck and was custom built.
I don't have anyone with acsess to these at the moment.
Anyway i can agree that they can be up to a whole 1c out but i think my temp control stuff is my greatest bits of brewing gear along with the gas solienoid for the HLT.

E-Bay has controllers with probes for 75.00aus ea...
Thanks for all that info guys, now I know what they are all about.
I think I misunderstood the term "thermocouple" and now I know what they are and how they work I can see their usefulness.
So in essence the probe on my meat thermometer is a thermocouple and the guage is a mini computer so that you can read the temp.
Gives me some food for more thought.
Thanks fellas,
Just checking out ebay, There are a few controllers there like mine and i will be watching to see how much they sell for.
heres some links,
this ones a different brand then mine but looks pretty much the same. If these don't come with a manual most manuals can be downloaded of the net in .pdf if you do a search.


This is the exact same one as mine. you can't really see much in the pic.

these controllers can be used with any type of thermocouple or RTD.
I use all type K thermocouples.
So basically the only thing you need to do is get whatever then work out how to wire it proberly.

heres some thermocouples



anyway it looks like theres plenty of this stuff floating around on ebay.

Those ones i posted above are just the brain behind everything.
If you just get that part and a thermocouple you also need a relay also.
Mine is all built into a box see pic below.
Mine also as a manual over ride switch to turn whatever your controlling off.
I'll post a pic that shows you how you would wire it up on the next post.

As you can see these ones i posted from ebay are not plug and play. You'll need to do some wiring yourself and make a box for it all.
The front panels are water resistent i have my cool room one out in the rain.
anyway heres a side view of one which shows how you would wire it up.


I use a Ranco Digital Temp Controller from Morebeer.com ($64US) to controll the solenoid on my HLT burner...

Oh yeah you think DTC's are expensive.... Wait till you start looking at solenoid valves for gas....

Asher for now
What happens if the pilot light goes out?
Does the solenoid still allow gas out?
dicko said:
If I am then, can I make a thermocouple out of say a piece of copper pipe fitted through the side of the new tun with the temp probe inside?

Would the pipe have to be filled with a medium like water or glycerine or something that would transfer heat or would the air in there be enough?
Sounds more like you're talking about a thermowell?
A thermowell is basically a metal tube with one end sealed off and the other end welded to the vessel so that the tube is inside the vessel, with the thermometer inside the thermowell.
Darren the solenoid has no idea if the pilot is lit or not. I just keep a eye on it if it is very windy.
Heres a pic of a very similar solenoid to the ones i have.
Mine are made in japan by SMC the model of both the ones i have are VT307-7d-01
i can't find this perticular model on the SMC site or anywhere else on the net. It is a 240 volt model.
I have no idea how much they cost either but looking at some other prices it does look to be quite a bit for such a simple thing.

Cheers Jayse

Yes Hoops,
That was my original thoughts but it has been interesting to read all the info supplied on this post.
I didn't realise that so many were in to temp control bits and pieces.
I have worked out that I am going to fit a length of 3/8" copper pipe into the side of my mash tun and fit the probe into that with a small length of plastic tubing to seal it off.
Basically what it will do is protect the probe when I am stirring, cleaning etc.

Another question is:

At what position in the mash do you guys and girls recommend placing the temp probe?

That is;

1. Near top of grain bed.

2. Middle of grain bed.

3. Bottom of grain bed.

I have read many articles on the net and many opinions vary on this subject.


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