Shown in set up mode with test probes connected by bottom switch. Left 714 k ohm resistor is adjusted to give full scale 2 milliamp reading on meter. Transistor is 2n35. Test probes are two 10 inch lengths of 1/ 8 inch diameter brass welding rod mounted 1 inch apart on piece of Plexiglass. Solder terminal lugs to welding rods and bolt to Plexiglass and file brass probe bottoms to sharp points. Erase bottom switch to show two probes.
Place probes in soil to check moisture level. 1 milliamp reading should be adequate soil moisture but note plant response to different levels and meter reading that helps plants to thrive the best.
Use meter to take guess work out of when or how much to water.
