I started working on a Forest Mims related moisture meter using a NPN transistor and an ammeter (multimeter actually)
and then thought about an arduino version! a low and behold
Faludi has done it, changed it to a voltage, then sold it as
Botanicalls, a really cool product. So changed by circuit to Faludi's version, tested the analog signal with a voltmeter and all looks good. The new circuit look like this
and there is an interesting tutorial on
converting an ammeter circuit into one that can use a voltmeter. ALso talks about how to measure internal resistance of meter.... Still a little confused about the use of the trim pot though.
and then thought about an arduino version! a low and behold Faludi has done it, changed it to a voltage, then sold it as Botanicalls, a really cool product. So changed by circuit to Faludi's version, tested the analog signal with a voltmeter and all looks good. The new circuit look like this 
and there is an interesting tutorial on converting an ammeter circuit into one that can use a voltmeter. ALso talks about how to measure internal resistance of meter.... Still a little confused about the use of the trim pot though.
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