Optical Liquid Level Sensor

Liquid Level Sensor

Optical liquid level sensors do not measure the liquid level, instead, they detect the presence or absence of liquid. Optical sensors consist of two main parts; An infra-red LED and a phototransistor that is accurately positioned at the base of the sensor tip.

When the tip is in the air, infra-red light reflects internally around the tip of the phototransistor providing strong optical coupling between the two. When the sensor tip is immersed in liquid, the infra-red light escapes from the tip causing a reduction in the amount of light at the phototransistor which makes the output change state.

Advantages  of Optical Liquid Level Sensors:

The main selling points for an optical liquid level sensor is their compact size, their solid-state design, their low cost, and their reliability. However, while extremely accurate for point-level sensing in high pressure, temperature, and at times corrosive environments; they are less useful for continuous-level measurement applications.