Current Cost Support Forum

So....

I have a solar water-heating panel on , which obligingly provides three temperature readings via sensors to a wall unit (roof, top of tank, bottom of tank).

I'm hazarding what I think is a pretty reasonable guess that these are passive resistive two-wire temperature sensors, so, the question is... given an analogue dev board, can I read one into my Envi?

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Currently running:
Envi (E.On-branded)
3kW solar PV + clamp + OptiSmart + home brew Perl scripts + graphing
Solar water heating

The first step would be to confirm that they are passive, resistive sensors. IE Thermistors. (Digital multimeter may be able to help with this if they are)

If they are, then you would have to find their resistance values across the expected temperature range and do a bit of math to calculate a suitable resistance value that you could add with the thermistor to create a potential divider circuit.

You would use this potential divider setup, fed from the 3 volt supply of the Analogue Dev board to provide a varying voltage output to drive the input on the dev board.

Unfortunately the numbers that will be displayed will show as a wattage reading and not as a temperature reading as the Dev boards are on designed to broadcast wattage values, not temperatures.

The range of values you will get, will depend on what nominal resistance value the thermistor is and what value resistor you use with it to form the potential divider.

If you are unsure on what i mean by potential divider etc then a search on the internet should give you the answers. You are effectively turning a resistance into a voltage, based on a ratio between two series resistances.

Also if you do attempt this you will have to perminantly disconnect the temperature sensors from your existing monitor panel as there cold be any number of stray voltages or isolation issues which would interact with the dev board and destroy it or vice versa.

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