By the way, none of this is to discourage you. But you really need to test your ideas before you jump in.

For example, can you get any useful data from a simple DMM? If not, you will need to do more than measure resistance to get useful numbers.

Thanks - I'm not easily discouraged The second link in your previous post looks like a very good start. Using a couple of cheap DMMs they claim to detect buried walls which is perfect for now. If I can find some way to get the readings into the smartphone so I can plot them then I'm ready to roll.

 

Thanks - I'm not easily discouraged The second link in your previous post looks like a very good start. Using a couple of cheap DMMs they claim to detect buried walls which is perfect for now. If I can find some way to get the readings into the smartphone so I can plot them then I'm ready to roll.

There are Bluetooth DMMs

 

Quick update. Based on Yaakov's link (the second one), I bought a couple of cheap multi-meters, built a frame with some 6" nails as probes and did a survey of my back garden. The whole setup cost about £30. I manually recorded the values in a notebook and plotted them in Excel. The result below has a small amount of smoothing applied but looks pretty good I think. The values correspond to loam (about 100) to sandy loam (about 300) to sand (about 500) which matches what I can see when I dig. The green area does hold water better when it rains. Not sure what the two sandy areas are, I suspect that when the ground was leveled for the house, the builders removed a couple of trees and filled the holes with the same sand they used to level the site. I'll dig one to confirm. Next step though is to get the voltage and amp values into my phone. Unfortunately I don't think simple Bluetooth DMMs are an option as it requires two devices.

 

Quick update. Based on Yaakov's link (the second one), I bought a couple of cheap multi-meters, built a frame with some 6" nails as probes and did a survey of my back garden. The whole setup cost about £30. I manually recorded the values in a notebook and plotted them in Excel. The result below has a small amount of smoothing applied but looks pretty good I think. The values correspond to loam (about 100) to sandy loam (about 300) to sand (about 500) which matches what I can see when I dig. The green area does hold water better when it rains. Not sure what the two sandy areas are, I suspect that when the ground was leveled for the house, the builders removed a couple of trees and filled the holes with the same sand they used to level the site. I'll dig one to confirm. Next step though is to get the voltage and amp values into my phone. Unfortunately I don't think simple Bluetooth DMMs are an option as it requires two devices.

Possibly a cpiuple of these? They talk SPI, so you should be able to stack them.

https://store.digilentinc.com/dmm-shield-7-function-digital-multimeter-shield/