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Make a Waterproof Temperature Probe
Find out how to make a waterproof temperature probe
We include a pair of LM335Z (1) temperature sensors with our solar water heating pump controllers (2). They are reliable, relatively inexpensive, and very easy to use, however they do have one disadvantage - they are not at all waterproof. One sensor has to be fitted to the side of the hot water tank under the insulation - typically a nice dry area - but it can sometimes be difficult to fit the second sensor to the outlet pipe from the solar water heating panel (3) as this is installed outside. In some situations (such as heating swimming pools (4)) the temperature sensor must be submerged. Therefore in this article we will look at how a standard temperature sensor can be turned into fully waterproof temperature probe.
Making a waterproof temperature probe is actually quite simple, requires few tools, and the component parts required are inexpensive. In short the temperature sensor must be soldered to insulated leads, and the soldered joints protected with heat shrink tubing (to prevent short circuits). The sensor is then inserted into a suitably sized stainless steel tube or around 50mm length (6mm inside diameter for LM335Z sensors), and filled up with epoxy potting compound. The potting compound is impervious to water, the stainless steel tube, will not corrode, and the steel-epoxy combination will transfer heat to the temperature quickly enough for pretty much all solar (5) applications. The leads sticking out of the epoxy at one end of the tube can then be connected up as required.
Buy Stainless Steel Tubing and Potting CompoundStainless steel tube is not a very easy thing to find, but fortunately there are many sellers on eBay UK (6) who have it on sale. Click here to search for the latest listings for Stainless Steel Tube (7). Similarly, click here for Potting Compound (8), and here for Heat Shrink Tubing (9).
Recommended ReadingDIY Submersible Temperature Probe (10) - from Home Brew Talk website.
Web Link References(1) http://www.reuk.co.uk/buy-LM335Z-TEMPERATURE-SENSOR.htm
Article from REUK.co.uk:
Published: 1st June 2009
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