Sorry, I was supposed to look at my sensor and report back. The heatshrink covering the joint between the cable and the stainless cap can be slid up the cable a little. I did that and took a look, but the cable is glued into the cap and does not come out if I pull on it. There is evidence of some white glue (epoxy?) at the joint.
Incidentally, there are two types of heatshrink. Regular, and adhesive-lined. I guess the adhesive-lined type would make a good job here.
I have ordered 5 metres of 6mm ID silicone tube. When it gets here I will cut about 40 cm from it to make a silicone ‘thermowell’. I decided my first idea (cutting a hole in the side of the brewing vessel) was not as good as cutting a hole in the lid of the vessel.
Ah, good. The shrink wrap sensors are not really waterproof, they do tend to fail under the shrink wrap. Because of this I found a new supplier and are now selling much better sensors.
If I was to cover your temperature sensors with food grade heat shrink tubing (like shown in picture #3), covering all the cable and only leaving some of the probe exposed would it be ok to just have it “dipped” into the wort and bypass the need of a thermowell? Provided I got a tight fit from the heat shrink.
I think it would probably be okay. It’s the same idea I had of slipping silicone tubing over the sensor. Your problem might be at the other end, where the wire enters the vessel. You’d need a good seal between the outside of the heatshrink and the hole. I am hoping that the silicone is compressible enough to form a seal in a slightly undersized hole.
My silicone tube arrived from China today. It cost $7.66 for 5m, with free shipping. I only need about 30cm, but that’s ok. It is food-grade for coffee machines (it links the tank to the heater and the outlet). Inner diameter is 6mm, outer diameter is 8mm. I will drill a 7mm hole in the lid of the brewing vessel and push the tube through from the inside (I only need to push a couple of centimetres through).
I need a connector on the end of the flying lead that is less than 7mm diameter as that will be pushed through first. Maybe I’ll use a 3.5mm stereo plug and just remove the housing. I can protect the wires with some heatshrink instead.
I wouldn’t trust putting a probe with shrinkwrap in beer - you probably will never get it 100% sanitary. A thermowell avoids these issues since they are completely smooth and can be sanitized easily.
I think @MmmBrewPi was suggesting putting only the stainless probe part through the cable gland. At least I hope that was what he meant.
I agree that any temperature sensor with shrink wrap cannot be trusted.
Hey guys! @mdma & @Elco Thanks for the response. Well what if I said I’d intended to just heat shrink the temp sensor up and have it dangling in the beer?.. Is it really that bad an idea? Not really gone on the thermowells for 2 reasons, laziness and being awkward.
The thermowells sound great, but how sensitive/resposive are the temp sensors through a layer of steel, air medium, more steel, epoxy, temp sensor. Re-reading that is making me feel pedantic. But… food for thought?
In a dream world I’d prefer to have the bare sensor (no steel sleeve) in the thermowell with a pool of thermal paste/fluid in the base.
Is the reason for concern with the heat shrink in beer the opening seal? I was kind of going to check out how tight I could get the seal when the temp sensors arrive and make a decision based on that maybe add some aquarium silicone if needed.
Thermowells are metal in contact with the metal of your sensor (no need for expoxy) so the response is fast. Orders of magnitude faster than the response time of the beer to temperature changes.
Does anyone have any experience/opinions of immersing a DS18B20 directly in the beer? A DS18B20 is encased in epoxy which is quite inert. It could be pushed into the end of some 4mm I/D silicone tubing, with a couple of mm of teh package sticking out, then the tube and sensor can be dropped into the beer from above.
Beer is slow to change temperature, the slow response of the sensor doesn’t matter at all in this application.
Here are some photos of a prototype sensor we’re developing. This will be good for mounting directly in a kettle or fermenter wall.
The flange on this prototype is 24mm, we’ll increase it to 35mm so it is the same diameter as the sealing locknut. Then it will press the wall flat and there won’t be a gap between locknut and wall.
The latter implies a fitting to convert from BSP/NPT to Tri-Clamp, but in any case the intent is to get the probe close to the middle of a large volume.
This is the maximum length they can drill from a single piece of metal.
For a longer probe, they have to weld a tube into a threaded flange, something which my current supplier cannot do.
I think for those lengths, you can just as well buy a thermowell and insert a normal probe.
I will do a new prototype with the bigger flange first (2 weeks) and then a production run (3 weeks).
Maybe faster, but I expect it will take at least a month.
I am currently doing brew in a bag, mashing in my 32 litre kettle. I have it on a halogen hob which I can use manually to provide a bit of heat if required during mashing. How high up the kettle wall do people think would be a good place to mount the thermowell for this use?
Is it really that bad an idea? Not really gone on the thermowells for 2 reasons, laziness and being awkward.
