AFMs

[Brian Neill Tiedemann]

Hi all,
Some quick questions on AFM types:
I know fairly well the old flappers, and Bosch type Hot Wires with analog
out, and I have seen some calibrated bypass type hot wire ones by Hitachi
with (I think) a frequency output..... now, I have read a little about
Karmann Vortex types and am immediately interested. What pros and cons are
associated with this method of air flow measurement? Is it a MASS FLOW
measurement? Does a problem occur at low (read idle) flow rates (of
resolution)? Are there many commercial ones around? (Reasons to use, not
to use?)
I have noted them in use in an Australian built Mitsubishi Magna 2.6 and
they have me thinking.... the meter assembly has an atmospheric pressure
sensor as well, and air temp, so a couple of these might make a nice
intake for a 5 litre engine, with little need for other sensors in the
intake tract (excluding TPS).
All this stems from me being a little nervous about using Bosch hotwires
in a high vibration offroad application.

All contributions/opinions gratefully accepted......

Thanks,
Brian.
NOW: bnt at minyos.its.rmit.edu.au