I am a digital person and know enough Analog to be dangerous. I have a requirement for a wood moisture sensor. The resistance values range from 100k to 100m. I've enclosed a sketch of a digital solution. It involves a mux with different R values being driven by a constant current source. I would keep switching in different R values until I got a reading on the ADC then multiply the reading by the selected R value to get the final resistance. It will work but it seems a little kludgy to me. Can any of you hot shot analog wizards out come up with an auto ranging solution using op-amps or ???
Any help will be greatly appreciated.