Product description:
This water level sensor module has a series of parallel exposed traces to measure droplets/water volume in order to determine the water level. Very Easy to monitor water level as the output to analog signal is directly proportional to the water level. This output analog values can be directly read via ADC and can also be connected directly Arduino’s analog input pins.
 
Parameter:
1) Working voltage: DC voltage 5 volts.
2) Working current: less than 35MA
3) Type: analog sensor
4) Test area: 40 mm x 18 mm
5) Working temperature: 10 ° C - 30 ° C
6) Working humidity: 10% - 90% without condensation
7) Fixed hole size: 3mm in the middle
8) 60 mm × 22 mm

Applicable occasions:
Design features of water level alarm: simple, easy to use, small size, light, high cost performance
 
Resources:
1. How Water Level Sensor Works and Interface it with Arduino
2. How does a Water Level Sensor Work and How to Interface it with Arduino?