Hi Wagner,

You are absolutely right, you would have to know the temperature to
determine the wind speed. However, I don't see why it would have to be
enclosed. As long as the second thermistor is not self-heating, then it
shouldn't matter if the wind is blowing around it. Although, the need for a
second sensor (and therefore,the need to determine the difference in temp
curves between them) makes my idea less attractive :-(

Sean

At 06:30 PM 1/15/00 -0500, you wrote:
>You should use two temp sensors, one enclosed, another exposed, if not,
>your will ending up measuring air temperature instead velocity.
>
>The linearity issue was created by my generation, at a time when
>microcontrollers and data processing was not possible, so transistors
>would indicate values in a simple milliamper meter (dumb indicators). 
>At this age with fast microcontrollers, e2proms (to hold calibration
>tables) and interpolation routines, it is a shame that people still
>wasting gray brain power to solve the problem at the front-end and using
>all the silicon potential as the old dumb meter.
>
>Sean suggestion is nice, but how it will discriminate between a wind of
>3mph (10¡F) and 40mph (80¡F)?  It needs an enclosed second sensor,
>creating a delayed Delta-T reference.  Even so, there are many induced
>errors in this kind of air speed measurement. I believe that today's
>cheap low pressure sensors can be more effective (temp compensation and
>else).
>
>Wagner Lipnharski - UST Research Inc.
>Orlando, Florida  - http://www.ustr.net
>---------------------------------------
>

|
| Sean Breheny                   
| Amateur Radio Callsign: KA3YXM 
| Electrical Engineering Student  
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