I haven't looked at the article, but why should non-linearity be an issue?
Why not just make a temp controller which uses a transistor in a constant
current configuration to heat a thermistor, and the whole thing is exposed
to the air? You use the controller to maintain a constant temp,and then
just measure how much voltage is being delivered to the transistor and that
is linearly proportional to the heat delivered, again linearly proportional
to the heat being lost. Then, the only non-linearity would be in the
interaction of the air with the sensor.

Sean

At 02:14 PM 1/14/00 -0700, you wrote:
>>Did anyone mention the hot wire anemometer?  I've also seen a "hot
>>transistor" anemometer as a Design Idea in Electronic Design, here->
>>http://devel.penton.com/ed/Pages/magpages/may2598/ifd/0525ifd.htm
>>Scroll down past the first article.
>>
>>-Jim
>
>Aaahh! Beauty!
>
>A PIC could do that much better!  With a little computation the nonlinearity
>could be completely accounted for.  Plus you could use simple thermistors
>instead with the PIC reading them and controlling the current through the
>hot one.  Since thermistors come in really tiny packages with low thermal
>mass (much smaller than the TO-92 that the LM334 comes in) you could get
>much faster response time.
>
>This sounds fun!  Now if I can just scrape together the time to play with
>this...
>
>Cheers,
>
>Ken
>
|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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