How to tell whether an object is underwater or out of water?

1. Use the conductivity of water (pure water is not conductive, ordinary water is conductive)

Install positive and negative electrodes in an open space on an object. When an object falls into the water, the circuit is connected. The circuit ammeter is 0, and the circuit ammeter is 1.

2. Using the refraction of light

A laser transmitter is installed on the object, and glass with a certain thickness is installed in front of the receiver. The laser hits the glass surface obliquely and reaches the receiver through refraction. When an object falls into the water, the laser refraction path changes and it cannot receive light. The light receiving meter is 0, and the light receiving meter is 1.

Using photosensitive equipment

If the light intensity in space is relatively stable, photoresistors can be used. When an object falls into the water, the light intensity is obviously weakened and the resistance is increased. Using the principle of voltage division, the voltage of the resistor will rise. At this time, the unidirectional conductivity of the diode can be used to set the other end to a low potential, and when the voltage of the resistor rises, the diode can be turned on. The ammeter is 0 and the ammeter is 1.