Temperature Probes

[erk]

My ENV-TMP probe seems to no longer be linear. Possibly damaged? I'm going to try it on a different input to my Arduino, but in the mean time, what replacement temperature probe should I be looking at? Seems the main probe to use now is the DS18B20, but they aren't saltwater resistant. Platinum RTD seems nice, but I don't want an extra board. What is everyone else using?

Also, I hate dealing with obsolescence.

 

[theatrus]

My ENV-TMP probe seems to no longer be linear. Possibly damaged? I'm going to try it on a different input to my Arduino, but in the mean time, what replacement temperature probe should I be looking at? Seems the main probe to use now is the DS18B20, but they aren't saltwater resistant. Platinum RTD seems nice, but I don't want an extra board. What is everyone else using?

Also, I hate dealing with obsolescence.

I always bias to PRTD myself (100 or 1000 4 wire). What are you interfacing with?

 

[erk]

I always bias to PRTD myself (100 or 1000 4 wire). What are you interfacing with?

I currently use an Arduino because the ENV-TMP is analog. But if I go with the DS18B20, then I'll just connect directly to the RPi.

 

[erk]

I'm now thinking of purchasing one of these thermowells:

https://www.directmaterial.com/thermowell-ss-316.html

And then slipping a DS18B20 into it. They are made of 316L SS and should last forever. I could add a T into my return line and thread the thermowell into it. Then just replace the probes as they go bad without touching water. Can use a 1/2" NPT cable compression fitting to hold the probe securely inside the thermowell.

 

[Chuk]

I'm now thinking of purchasing one of these thermowells:

https://www.directmaterial.com/thermowell-ss-316.html

And then slipping a DS18B20 into it. They are made of 316L SS and should last forever. I could add a T into my return line and thread the thermowell into it. Then just replace the probes as they go bad without touching water. Can use a 1/2" NPT cable compression fitting to hold the probe securely inside the thermowell.

You don’t want 316SS. It will not last long term in continuous immersion in saltwater. High chlorides will corrode it. You’re going to want to go titanium if you get a Thermowell. Most thermowells are internally threaded for insertion of a specific length thermocouple or RTD and the contact between the bottom of the well and the probe is important to accurate temperature readings. I would recommend you make sure you get the right thermowell and temp probe combination to make sure you don’t end up chasing bogus temp readings due to an air gap insulating your thermocouple.

 

[Chuk]

Oh I forgot if you do get a thermowell and the thermocouple doesn’t go all the way to the bottom you can get thermal grease to fill the gap between the bottom of the probe and well so you can get accurate readings.

 

[Mikeneedsahobby]

I potted my entire probe in epoxy. I used a piece of pvc as the mold. But there is also this one.

T-PRO DS18b20 Waterproof Temperature Sensors Temperature Transmitter Stainless Steel Probe Soft handle Silicon shield cable (1, Red) https://www.amazon.com/dp/B073XKK3YS/ref=cm_sw_r_cp_api_i_yybACbAQE3283

 

[erk]

You don’t want 316SS. It will not last long term in continuous immersion in saltwater. High chlorides will corrode it. You’re going to want to go titanium if you get a Thermowell. Most thermowells are internally threaded for insertion of a specific length thermocouple or RTD and the contact between the bottom of the well and the probe is important to accurate temperature readings. I would recommend you make sure you get the right thermowell and temp probe combination to make sure you don’t end up chasing bogus temp readings due to an air gap insulating your thermocouple.

316L SS is rated for use in saltwater and coastal regions due to its ability to fight corrosion. The temperature probe I currently have had a case made of 316SS and has never corroded. 300 series SS is not rated for prolonged usage in saltwater/corrosive environments.

The tip about the thermal grease is a good one. I'll probably use thermal grease just to help get the sensor into the well and ensure there are no sia gaps.

 

[erk]

I potted my entire probe in epoxy. I used a piece of pvc as the mold. But there is also this one.

T-PRO DS18b20 Waterproof Temperature Sensors Temperature Transmitter Stainless Steel Probe Soft handle Silicon shield cable (1, Red) https://www.amazon.com/dp/B073XKK3YS/ref=cm_sw_r_cp_api_i_yybACbAQE3283

I purchased this probe and it is very well built. I installed it in a thermowell with MX-4 thermal grease to add in conduction. The readings I'm getting are very stable. I'm happy with the hardware, but now I have to make significant software changes.