Crystal oscillator

Photocoupler

The figure above shows a downhole oxygen concentration detection circuit that can be used in underground environments to detect oxygen concentrations in the air. The oxygen concentration detecting sensor in the circuit turns the detection result into a DC voltage. After the circuit amplifier ICl-1 and the voltage comparator ICl-2, the transistor is driven, rri, and then the relay is driven by rri. The buzzer sounds to remind the oxygen concentration is too low, causing people's attention.