IoT water tank telemetry project – HC-SR04 – first trial mentioned an inexpensive ultrasonic ranging sensor for trial.
Above is the JSN-SR04T-3.0, a waterproof transducer on a cable and the electronics board. The protocol is HC-SR04 PWM. No specifications or datasheet were found (other than the seller's brief description).
Above is the plotted simulated dam volume, occasional spikes that are grossly in error.
0.00718 0.007198 0.008108 0.009086 0.01335 0.013393 0.013413 0.013421
Nevertheless, zooming in on the data we can see that the temperature compensation scheme is working.
The sensor did not respond proportionately to range for range less than about 0.25m.
This is one to dismiss as unsuitable.
A work in progress…