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[tom cloud]

>Is ther any reason why I cant build my own mass meter wth some nichrome
wire, and a foot of 6" drain pipe?
>
 [ snip ]

>Like, I think the Idea is: Keep the current constant, measure the voltage
across to get that current, have another bit of wire as a reference, and an
absolute air temp/ atmospheric pressure reading, and away you go?
>
Okay, can I speculate too??  I know that liquid and gas measurements
have been made by using a heated wire (or thermocouple).  The concept
was to use two of them.  One a reference and the other in the flow.
Measure the temp of each and the difference is proportional to the flow.
If the same current passes through both wires (or 'both' is actually
the same wire), any error from heating current variation ought to be
lessened.

Bye-the-bye; to get a constant current, one would not want to measure
the voltage across nichrome, as it changes resistance with temperature
(e.g. air flow).  The voltage you measure, with the current constant,
would therefore be related to air flow.  If you were to take two pieces
of NiCr, say 1" long each (and very thin, say 30 AWG).  Put one in
the air flow and the other where it is cooled by only convection
(where?).  Wire them in series and measure the difference in the
voltage dropped across each of them??

Tom