Some sort of ''soil testing'' instrument. I want to make another.
Decades ago I bought a box of junk that had a ''soil testing'' instrument. It had a copper colored electrode and a silver colored electrode and a little plastic box with a gauge. I've no clue as to what it supposed to do.
But it was good for testing the moisture level in the soil of potted plants. Stick the electrodes in the soil and the gauge moved to crudely indicate the amount of moisture in the soil.
I got shipped out. The junk was tossed and time passed.
Now I am wondering if I could make another with some copper and aluminum and a multimeter?