IoT water tank telemetry project – ultrasonic sensor – #1 described an inexpensive ultrasonic ranging sensor for trial.
Above is a bunch of HC-SR04 ultrasonic ranging sensor.
Above is a plot of the simulated dam level measured over a fixed range of about 2.4m. For hours, the data is pretty tightly clustered, and would be quite suitable for this application. This is after tweaking algorithms to take the median of 13 measurements to try to eliminate ridiculously wrong measurements.
we see occasional spikes that make the sensor quite unsuitable to the application.
The four units tested all show similar problems.
These are relegated to the Cheap Chinese Junk category.
A work in progress…