Yes, I set the maximum distance at 300 but then the sensors return 0's. All the sensors are pointing at a solid wall 250cm away, but the sensors are returning 0's rather than seeing the wall, thus I'm assuming out of their range. I thought it strange as the Hr04's measured/worked fine over this distance. I've tried different delay times to see if there is any interference, up to 100ms but it makes no difference to the readings