10K Precision Epoxy Thermistor -- Questions
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10K Precision Epoxy Thermistor -- Questions

by Rehan on Fri Dec 07, 2012 4:01 pm

Hello Adafruit Support,

I recently purchased some 10K Precision Epoxy Thermistors for a home project involving a roof solar evacuated tubes setup.

My intention is to have two sensors, one up on the roof near the solar heat collector and one sensor in the solar water storage tank in my basement. These sensors will interface with this simple differential temperature controller: http://www.mydtcstore.com/uploads/2/8/2 ... 40.jpg?336
Manual here: https://docs.google.com/document/d/1dPD ... gz9RY/edit

I have a few questions about whether these thermistors would be suitable for my application:

1. Are these thermistors suitable for full-time immersion in water? If not, what can I do to make the sensor and the wires waterproof?
2. I don't expect my temperatures to go beyond boiling once the sensors are in and the circulation pump is working to move hot water down from the roof. When I do not have a functioning pump in place, the temperature of the water on the roof does reach around 200F pretty quickly but hopefully with the replacement pump this shouldn't be an issue. That being said, is there an alternative that would be better suited for water temps that gets close to boiling?
3. If these sensors simply won't work in my application, is there any other sensor that I can purchase that will work with a differential temp controller like I have? I see this product here: http://www.adafruit.com/products/642 but am not sure if that would be able to interface with the type of controller that I have.

Thank you so much for taking the time to help me. :)
Rehan
 
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Re: 10K Precision Epoxy Thermistor -- Questions

by adafruit_support_bill on Sat Dec 08, 2012 6:23 am

The manual doesn't state what type of temperature sensors this controller was designed for. The sensors pictured on the web-site look more like thermocouples than thermistors.
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Re: 10K Precision Epoxy Thermistor -- Questions

by Rehan on Sat Dec 08, 2012 9:47 am

Thank you for your reply!

The controller is designed for 10K thermistors and the 10K precision epoxy thermistor I purchased from Adafruit does give readings on it.

But not sure how to proceed due to the questions I stated above. Could you please respond to those? Thank you!!
Rehan
 
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Re: 10K Precision Epoxy Thermistor -- Questions

by adafruit_support_bill on Sat Dec 08, 2012 10:44 am

1. They are designed for 'damp' applications. To make them completely waterproof, you could use epoxy or silicone with heat-shrink tubing.
2. These are rated to 105C. If you are measuring water temperature, the phase-change should keep you below that temperature unless you boil it dry.
3. From what you describe, #642 would not work since it is not a 10K thermistor. For a wider Thermistor selection, you can check the Omega catalog. http://www.omega.com/prodinfo/thermistor.html
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Re: 10K Precision Epoxy Thermistor -- Questions

by Rehan on Sat Dec 08, 2012 10:52 am

Thank you for your response!

Your answer gives me hope that I can just use Product 372 with my current controller.

As for the waterproofing -- do I need to only waterproof the wiring with epoxy/silicone and heat shrink tubing or does the actual sensor part also need to be modified in any way?

Thank you again. Your answers have been very helpful.
Rehan
 
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Re: 10K Precision Epoxy Thermistor -- Questions

by adafruit_support_bill on Sat Dec 08, 2012 11:02 am

To prevent water from wicking up inside the heat-shrink, you need to seal the end. What I usually do is to dip the end of the sensor in epoxy, then shrink the tube around it before the epoxy cures. Be sure to use an epoxy that is rated for underwater use.
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Re: 10K Precision Epoxy Thermistor -- Questions

by Rehan on Sat Dec 08, 2012 11:09 am

Thank you so much. :)
Rehan
 
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