Multifunctional conductivity tester circuit

The circuit of the multifunctional conductivity tester is composed of a detection electrode, a resistor divider, a buffer circuit and a two-color diode, as shown in the figure. The detection electrode can sense the resistance of the object being measured, and control the two-color light-emitting diode to emit light according to the resistance of the object being measured. When the detection electrode senses that the resistance of the object being measured is greater than 300kΩ and less than 1000kΩ, the green indicator light turns on; when it senses that the resistance of the object being measured is less than 300kΩ, the red indicator light turns on, making the two colors synthesize into an orange-red light; when it senses that the resistance of the object being measured is greater than 1000kΩ , the two-color indicator lights VL3 and V⒕ do not light up. Adjusting the potentiometer RP can change the sensing range of the detection electrode.