It might be realistic to look at Dwyer Instruments; there are many
offerings. In particular, the $50 unit
http://www.dwyer-inst.com/htdocs/air...riesMWSpec.CFM is 0-55
kt, resolution of 0.2 kt. Accuracy is about 5% of reading. There are
mini-pitot based models, rising vane (as used on some ultralight type
craft I've seen) and these rotating units.

On Tue, 22 Apr 2008 20:23:30 -0500, "Maxwell" luv2^fly99@cox.^net
wrote:


"Dick" wrote in message
news:fevPj.5393$Ux4.1316@trnddc07...
Thanks. Interesting and I've asked manufacturer if a higher mph range
might be made available.

I wonder what the downside of such an instrument is??

The up side (besides cost) is extremely good resolution at slow air speeds.
Especially 0 to 30, where conventional ASIs are usually less reliable, if
even calibrated in that range. I bought one from AS&S years ago calibrated
for a helo that wasn't bad, but not nearly as repeatable as a Hall in the
low speed range.

The only down side I recall is their reliance on gravity to oppose their
reading. They bump around a little bit on bumpy days, and of coarse are
useless when inverted. I don't recall much change on positive G's. They
seemed accurate in 2 or three G turns because the indicating disk is very
light weight. Just the zero and half G's loads were a problem.