# Probe for hottop!



## benjbob (Apr 25, 2016)

Hey guys,

So iv just fitted a new bean temp probe in my hottop.....go to do a test roast with everything in place and starts off ok.....ish but its not recording the temperature data anywhere near fast enough

Not going to lie the probe wasn't the most expensive out there but it seemed to record data.

So it needs replacing for a faster and more reliable probe as the roasting curve was more like a flat line with a small gradient.

Has anyone got a link to a well suited probe that will fit in the hottop under the manufactures air temp probe??

Any help would be greatly received!


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## MrShades (Jul 29, 2009)

Difficult to say what will be better, unless you can provide more info concerning what you're using now???


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## benjbob (Apr 25, 2016)

Give me 2 seconds ill see if i can find a link to it


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## benjbob (Apr 25, 2016)

Reet so it number 28

http://m.ebay.co.uk/itm/K-TYPE-THERMOCOUPLE-PROBES-SENSORS-UK-SELLER-VAT-INVOICE-/121535678690?nav=SEARCH

It was only cheap so i wasn't expecting miracles but it was simply shocking!

The first probe i ordered was too big and the probe can only be short so it doesn't hit the drum support arms :/


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## MrShades (Jul 29, 2009)

Hmmm.... well - what you're using is a K type thermocouple, which is the same as the thermocouple that's being used to measure the environmental temp in a Hottop (if it's a B2K or whatever it's called - got a K in the model name anyway!). The overall mass of the sensor may be an issue - and causing the slow reaction. I guess you're just hooking it up to a multimeter that'll read temp from a K TC?

I assume this is what you're doing: http://www.home-barista.com/home-roasting/installing-et-and-bt-probes-in-hottop-t15145-10.html#p181549

Can you grab a similar photo of your installation?


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## benjbob (Apr 25, 2016)

Exactly like that







im at work at the mo so will post a pic tomorrow when im back


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## PottyMouthedBuddhist (Oct 18, 2016)

May be a stupid question but you're sure it's the thermocouple and not the meter you're reading it with? I bought cheap thermocouples from an Ebay seller (might even have been the same one as the ad looks very familiar) and they worked absolutely fine. I connected mine to an Arduino taking a reading every second - apart from the very occasional and insignificant wobble, they were very stable.


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## benjbob (Apr 25, 2016)

Not a stupid question at all







well i tested it originally by using my hand temp with a multimeter victor 86b which seemed ok so knew it was working at least but then once in the hottop itself just didnt preform at all.

Im wondering if maybe its the amount of probe in contact with the beans that may be the problem as im not sure if you can see by the pics but there seems to be a screw fitting for a nut covering the majority of it.....im rubbish with anything DIY lol


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## benjbob (Apr 25, 2016)

Just under the manufacture probe


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## PottyMouthedBuddhist (Oct 18, 2016)

Looks like you've got a very similar length probe to the ones I ended up with. I didn't bother with a nut on mine as I needed to be able to remove the drum of my bread maker roaster in order to remove and cool the beans quickly, but I had about the same amount exposed to the beans - fractionally more if anything. I know mine worked fine, not just because the ET and BT gave different readings, but also because the BT dropped significantly more at the point of charge, and the delta between ET and BT varied throughout the roast.

I put the occasional wobble on my readings down to not securing the probes with a nut - the BT probe would get the odd whack from the bread maker paddle, and occasionally move a little, but that probably occurred only once in every 5 roasts or so, so a ratio of thousands of good readings to one duff one.


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## benjbob (Apr 25, 2016)

Hmmmm very odd, the temperature does change just no where near fast enough. Iv gone back to my through the drop shoot lid probe which works very well but there is a lot of it located outside of the bean mass.

Unless unluckily iv ended up with a slightly faulty probe?? Will try again


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## dsc (Jun 7, 2013)

Keep in mind that if you are using a simple multimeter to read the temp rather than a dedicated thermocouple logger / meter you can get delays in the updates due to the meter not being up to the task. Generally a TC won't introduce delays as such unless it's a heavy coated one with a lot of termal mass which will improve stability buy decrease rate of change.

T.


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## benjbob (Apr 25, 2016)

The probe that i had originally which is about 6-7" long was rigged up to the lid is far thinner than the one that has been put in the back so probably a form of food probe maybe?? (I bought it of ronsil ages ago)

I have seen people with these long kind of probes epoxy'd into the back or use a compression nut instead to hold it in place with the remaining probes located in the back next the motor.

What would we think of that?


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## dsc (Jun 7, 2013)

What's the probe measuring? bean temp, or air temp? will it get knocked by anything, like moving beans or is it free from knocks, simply sitting suspended in mid air? I'm asking as this will all affect what probe you can use. If it's being constantly knocked around by beans etc. I'd suggest a stainless steel sheathed probe, but a rather thin one so you don't get the high thermal mass affect which can delay readings:

http://www.omega.co.uk/pptst/JTIN.html

Typically these are held in place using compession fittings like you mentioned, although anything from metal tie wraps to epoxy should work (assuming it doesn't damage the wires). If the probe is only suspended in air and doesn't come into contact with anything, I'd suggest an exposed tip stainless steel sheath or simply a wire probe with no sheathing what so ever, although you'd have to watch out for the max temp rating of the wire coating as this typically only goes to around 200degC (or something close to this).

http://www.omega.co.uk/pptst/5LSC_5SRTC.html

Here's a ceramic insulated one for super high temp environments:

http://www.omega.co.uk/pptst/XC.html

Mind you these are not cheap, but if you shop around on ebay a bit you might be able to find used TCs in good condition which can be reasued (make sure they are food safe though and not been used in some weird oil / corrosive environment if there's going to be food / bean contact).

T.


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## benjbob (Apr 25, 2016)

Its purley for bean temp i will add a slightly more accurate air temp probe later when i can move things on phidgets (need to wait for some spare cash first)

Thats perfect thank you very much i can get a different probe in there and jobs a good un!

Thanks muchly


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## dsc (Jun 7, 2013)

No worries, shop around though as Omega is rather expensive and I'm sure you can find cheaper alternatives (UK made, quality products). Have a look on ebay for sellers called:

tempsensor2014

tms-ltd

I've dealt with them before and got very good service (they can make custom probes if you need one)

T.


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## benjbob (Apr 25, 2016)

Awesome thank you very much







!!!


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