Solar hot water temperature sensor and display

[David HK]

Can anyone offer some thoughts on the following.

I want to set up an external temperature display in a weatherproof housing outside my kitchen window and facing back into the kitchen. The aim is that when I am standing in the kitchen and washing the dishes I can see the temperature of the hot water in my solar water heater and the outdoor ambient temperature. It will aslo tell my wife and daughter when they can use the solar hot water for dish washing etc and not bother with the usual hot water heater.

I already have a digital ambient temperature display - such things are common and easy to purchase. For the solar hot water display my problem is that the distance between the kitchen window and the solar hot water sensing point is about 40 feet (around 13 metres).

Most digital display temperature readers with an umbilical wire sensor have an operating maximum distance of around 10 feet (3 metres) and it is not possible to extend this because the display will show and error reading - probably meaning no signal.

I am hoping to avoid making up a dedicated circuit board and would prefer the simplicity of modifying an existing off-the-shelf product.

Regards

David HK

[zap]

My first thought would be a wireless thermometer.  I picked up one at Radio Shack on clearance for $10, it even has the atomic clock feature and has been working for about 3 years with the sensor in the attic.  I believe the temp range is something like -60 to +160F.

Maybe even a wireless BBQ thermometer?

[electronbaby]

The only thing I can possibly think of that would cause erroneous readings with the umbilical cord type, would be wire loss (resistance). 40 feet is not very far and if you just sized the wire based on  a wire loss chart or decreased the resistance slightly, im sure it would work fine. like instead of the 24 awg used, you could use 18 or 20 AWG (alarm wire). Would not be very expensive. Find out the ohms/kilo foot and keep the ratio the same if you want to be real accurate.

[nick1234]

those digital temperature display units use a capacitor as temp sensing device so use same type wire and solder all connections i have gone 30 ft okay try it and test

enjoy

nick