I have a ceiling mounted Sonar Phidget pointing straight down. Looking at the control panel while not standing under it, I see the sonar reflections array has two or three elements and the reported distance is 2230 mm,about the distance to the floor.
When I stand under the sensor the reflections array goes blank but the reported distance is still 2230. This happens consistently.If I reach my hand up closer to the sensor it gives what look like accurate readings.
We need to know when someone is standing under the sensor. I guess we can say when the reflections array has zero elements someone is standing under it, but that is not how I had thought it would work.
The array will only be empty when the sonar is failing to receive the signal back, meaning it is measuring too far away, or is hitting something that doesn't reflect the sound back. The chances of this happening increase greatly with "QuietMode" turned on, so as a starting point if you haven't tried this yet, turn off "QuietMode" and see if it helps.
It seems odd that the array is not empty until someone is standing under it. So you're saying the sound shooting down at a person will not bounce back?
I wouldn't intuitively think so, I would expect it to bounce back, especially when quiet mode is turned off. 2m is not very far, I don't expect there to be problems, but I've never tested that exact scenario myself. Do you have more than 1 DST1200 you could verify has the same behaviour?
A good way to verify if the sound is dispersing off the top of the human body in such a way is to hold a flat object over your head when you walk under it. Like a piece of cardboard or wood (like 1-2' by 1-2') and see if that changes it to show reading correctly. This will give the sonar a better/cleaner reflection, and will tell us if the sonar is in fact working correctly and not defective.
