This is a photoelectric water liquid level sensor that is operates using optical principles. The advantages of this are good sensitivity and no need for mechanical parts - meaning less calibration! The corrosion resistant probe is easily mounted and can handle high temperature and high pressure. The sensor is equipped with an interface adapter for compatibility with the DFRobot "Gravity" interface.

To ease the difficulty of using this sensor,  a Gravity Interface is adapted to allow plug&play.  The Arduino IO expansion shield is the best match for this sensor connecting to  Arduino. As this sensor is able to work at 3.3V which makes it compatible with Raspberry Pi, intel edison, joule and curie.
 
Note: Avoid placing the sensor near bright lights or in direct sunlight as these can cause interference.
 
Specification:
Model: FS-IR02
Type: Photoelectric liquid level sensor
Operating voltage: 5 VDC
Output current: 12 mA
Working temperature: - 25 ~ 105 ℃
Low level output: < 0.1 V
High level output: > 4.6 V
Liquid level detection accuracy: ±0.5 mm
Material: PC
Measuring range: No limit
Life: 50,000 hours
Dimension: 28 x 28 mm/ 1.1 x 1.1 inches
Cable Length: 450mm
Weight: 26g
Packing List:
Liquid Level Sensor-FS-IR02 probe x1
Liquid Level Sensor convert board x1