The Portable Liquid Level Indicator is designed to measure the presence or absence of liquid at a certain height position in a container. 
The indicator can also be used to detect the presence or absence of liquid in pipelines.
Measurement Accuracy
<2mm
Measurable range of wall thickness
3～30mm
Measurable tank material
Steel, stainless steel, glass, unformed plastics
Measurable medium
Pure liquid, milky liquid, suspension liquid
Ambient temperature
-20℃~60℃ (-4℉~+140℉)
Power supply
Two 18650 lithium batteries. One 2000mAh lithium polymer batter(4.2V --- 3.5V)
Current
150mA(on average)