Re: [Flightgear-devel] OT: real world tilt sensor

[Christian M. <mail@ChristianMayer.de>]

There are very sensitive magnetic sensors. Having three of those
standing in 90 deg angles on each other you can get exactly any 3D
direction change.

I was once using those. They were providing me with a frequency
modulated rectangle wave. So it's easy to process the data digitally. 
I can't tell you where you can get those. My boss just gave them to
me...

CU,
Christian

Martin Spott wrote:
> 
> Hello toghether,
> maybe one of you has some experience on this topic.
> I need a tilt sensor for a real world experimental plane project. An easy
> way to build this is using two accelerometers to measure earth gravity.
> One of these points down 45 degrees to the nose of the plane and one points
> 45 degrees to the back.
> 
> If both show the same acceleration (1 g * (1/sqrt 2)) then my plane is
> parallel to the surface. If the one pointing towards the nose increases and
> the other decreases to the same amount, my plane has the nose down. That is
> proven to work. There's just one obstacle that prevents this configuration
> to work in a real environment: When the whole plane accelereates, then I
> also get an agle different to horizontal plane because the configuration is
> sensing the acceleration even when the pitch is still the same.
> 
> If I had the money to buy a ready-to-go "Intertial Measurement Unit", then I
> would not ask. But for a plane whose first prototype is in model plane size,
> this would exceed the existing budget.
> 
> Does anyone know how this is done in a real plane ? I don't believe the
> virtual horizon is showing strange pitch when the plane is acceleration on
> the runway  :-)
> 
> Thanks,
>         Martin.
> --
>  Unix _IS_ user friendly - it's just selective about who its friends are !
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