Airflow measurement - again...

[RABBITT_Andrew at mv8.orbeng.com.au]

>Instead of using a MAF w/ its flow reversion problems, why not use a
>strain gauge?  Put a small object, like a sphere, in the airstream 
>connected to an aerodynamic shaft to a strain gauge oriented to 
>measure force in the direction of flow.  Should be able to read drag 
>on the object quite precisely and ...

  [snip]

>... low speed sensitivity, but I think that it would be MUCH less 
>restrictive than a flap type meter.

Stephen, I see a couple of problems here.

1 - it won't be a mass flow device, in the same way a AFM (flapper) is 
not a mass flow meter, therefore you will need barometric pressure and 
temperature compensation.

2 - it will be susceptable to shock and vibration due to the mass of 
the ball on the end of it's (I assume) cantilevered and strain-gauged 
support.

What I'd be interested in is a LDA (laser-doppler-anemometery) type 
air velocity sensor.  If we can make cheap CD players, we should be 
able to make cheap LDA units.

Andrew Rabbitt