Sonar Readings wrong

[GoogleCodeExporter]

What steps will reproduce the problem?
1.In Mission Planner enabled sonar, tried all models
2.In terminal Windows Tests Sonar
3.

What is the expected output? What do you see instead?

Accurate distance expected
Starts out with an accurate distance, as I move it around it displays 
an accurate distance, when it sits not moving for a while (like 10 seconds) the 
distance goes to 555cm and stays there until it moves. 
Once I start moving it again it goes back to accurate distances. 
What version of the MegaPirateNG are you using?
beta 2.9.1 R303

Please provide any additional information below.

Original issue reported on code.google.com by tjone...@gmail.com on 11 Jun 2013 at 2:05

[GoogleCodeExporter]

The 555 value means: "Sonar reading out of range". So it maybe some failure in 
sonar. If it possible, try another one.

Original comment by Alexey.K...@gmail.com on 14 Jun 2013 at 5:52

[GoogleCodeExporter]

I have ordered another but it really doesn't seem like a hardware issue to me. 
All I have to do is move the copter gently higher and it will go back to 
reading actual values. I will report back when I have a second to test. 

Original comment by tjone...@gmail.com on 15 Jun 2013 at 1:09

[GoogleCodeExporter]

I have the same Problem.
The distance goes to 555cm without a change in Position.

And I have a much bigger Problem. When I turn on the sonar, the copter flies a 
few seconds. The Copter turned abruptly on the head and rashes. 
After I turn off the sonar, he flies back stable.

It`s the Version 2.9.1 and the HC-SR04 Sonar.

Original comment by Alex.Kur...@googlemail.com on 19 Jul 2013 at 7:27