I am using the HC-SR04 distance sensor with my Arduino Uno 3. This works fine until I stop moving my hand in front of the sensor or removing my hand completely. Then it stops working (in my case, goes back to 0.00 inches). I can remove the ground pin, then plug it back in and the sensor begins working again. I have tried this using several distance sensors and the same thing happens. Have you any ideas about what may be causing the sensor to just stop?