A week ago I wrote that HC-SR04 ultrasonic rangefinder is crap and it is still true. Only around 1m useful range and very jumpy behavior above are at least problematic...

There is a better solution. US-100 ultrasonic rangefinder. Comparing to HC-SR04, it has at least twice the useful range. My preliminary tests gave solid readout over concrete up to 2 meters and something. Let's call it 2 meters. But what more important, US-100 was reporting out-of-range state instead of some random values when being out of range! Huge step forward comparing to HC-SR04.

us-100 is much better than HC-sr04

Unfortunately, better does not mean good. US-100 also has some problems.

us-100 is much better than HC-sr04 ut still not good

Readouts becomes "jumpy" at the edge of useful range and they are far far away from declared. But OK, declared always means "perfect conditions". Still, trust me on this, comparing to this, HC-SR04 is crap...