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Installing a DS18B20 inside a thermowell?

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cat007

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Hey all

To mount my DS18B20 temp sensors I was thinking of using some heat sink paste injected into the end of the thermowell and then shoving the DS18B20 temp sensor, and wiring, down into it. Then squirting some epoxy down the thermowell to seal and hold the sensor in place.

Would this work?

Does heat sink thermo paste work well in this sort of environment where there's a larger amount of it rather than a thin amount spread over a large surface area?

Any other suggestions?

Cheers :)

Hunt
 

QldKev

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I looked at it a while back for a project. I ended up buying some s/s probes for a few dollars each.
 

cat007

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Except I want some of my probes to extend ~10 inches (about the middle) of some of my vessels.

How are you mounting these probes? Do they just dangle into your vessels from above or?
 

roller997

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Thermal paste is not overly great at conducting heat, however it is much better than air. The reason you are supposed to put it on as thinly as possible on CPU heatsinks is for it to fill in the tiny manufacturing indentations on the CPU and heatsink. For CPU's and other electronic equipment, they don't recommend to put it on in a thick fashion.
Since it has better thermal conducting properties than air, I would think that your idea would result in less lag time for the sensor to pickup the temperature. You would want to make sure when injecting the thermal paste it doesn't have any conductivity since you might not see if you are bridging the pins on the DS18B20.
Another consideration is that once you have done this and epoxied the sensor in, it will be a bit more challenging to replace the sensor if it has any issues.

Personally, I would neither use thermal paste, nor use epoxy glue. Instead I would use some sort of silicone stopper to hold the cable & sensor in place in the thermowell.
I suspect the temperature measured would be identical, however your solution would have less lag time to get to the current temperature.
 

dmac80

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If the well is mounted upside down, the thermo paste will run down away from the tip if there is an air gap between the paste and the epoxy. I had this happen to me.

I ended up having a tube with the DS18B20 sealed in with epoxy, the end of the sensor being immersed in the process. It was meant to be a temporary solution, but it's still going.

Cheers
 

cat007

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I was planning on actually putting some thermopaste down the end of the well, shoving the sensor as far in as it will go and then applying a little more over the top. Then while having the well held vertically, pour some epoxy down it and tap the well for 30 seconds or so to make sure there's no air bubbles.

But I see your point about what happens if the sensor has issues and I need to replace it....

What else could I use to replace the epoxy that will be able to handle up to 100C and stop the sensor and paste from escaping?

Perhaps some high temp automotive silicone/gasket? Although that might be pretty tricky to remove ones it's set?
 

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