🚀 go-pugleaf

In article <1992Apr8.005925.455@ee.ubc.ca>, jthornto@ee.ubc.ca (Johan
Thornton) writes:
|> In article <1992Apr7.031033.19729@njitgw.njit.edu>
andrews@rehab.njit.edu (John Andrews) writes:
|> >     I am starting a project that requires me to locate and
|> >     track a device in 3-space.
|> 
|>  [stuff deleted]
|> 
|> The way I would do this is by using ultrasound.  Construct an
imaginary
|> cube around the space you need to track the object.  In the center of
each
|> of three non-parallel faces you put an ultrasound transducer (mike).
|> 
|> [stuff deleted]
|> 
|> Using v=330 m/s, even just 1 MHz timing resolution will give you the
location
|> accurate to 0.3 mm.  
|> 
   [stuff deleted]

The accuracy of such a measuring system will also be limited by the
wavelength of the ultrasound (US). Let us assume that the
we need one full wave for reliable detection and that we are operating
at 250 kHz. Tperiod=4 us, v=330 M/s, Lambda
(wavelenght)=Tperiod*v=0.00132 m (1 mm).
You might be able to detect within less than one wavelenght,
but usually in US there is plenty of noise around and the detection
circuitry introduces errors of this kind.

Additionally v is dependant on teperature, you probably want to measure
it (temperature) and compensate for it in you calculations.

250 kHz is, I believe, the highest frequency
you will find being used, higher than that the dissipation in air
starts becoming a problem

Sjur Vestli