In my project I intend to use an HC-SR04 to determine if a water barrel is sufficiently full of water or not.
I only intend to measure when I actually need to pump water from the barrel, so I would like to be certain of the result of the measurement.
As a test - and with two different HC-SR04, I am measuring every 5s over a fixed distance. Although I am overall satisfied with the measurements, every now and then, I have noticed that the reading is 0cm and not the expected 68cm(ish).
Since I have tried with two different sensors, my assumption is that it is not a hardware failure.
Have anyone else seen something similar?
I am using the NewPing library.