On 04/13/11 07:24 PM, Jim Barber wrote:
> I wonder if a hand-held anemometer would have significant back pressure?
I would not think it be very significant myself.
> It's fairly easy to convert flow rate to volume if the duct size is known.
> Inexpensive units go for 20-30 USD on eBay.
My ex-boss (Prof. D. T. Delpy) used a technique for measuring air *velocity*,
which I don't think is particularly relevant here, but I'll describe it since
it
is quite interesting. Although it used platinum wires, I suspect you could use
copper, though I do see platinum would have some advantages.
It was used for measuring the speed babies breathed out air, so had to have
negligible restriction on the airflow. Using a plastic bag would not have been
very good for this purpose!
Going left to right there is:
Source of air --- > heater ---- > thermometer
1) The source of air. This was the babies mouth.
2) Heater. This is a thin platinum wire through which a short pulse of high
current is passed. I've no idea of the temperature the wire reached, but it's
not important to know the temperature.
3) Thermometer. This is another thin platinum wire, forming part of a platinum
resistance thermometer. This responds very rapidly to temperature changes.
The time between heating the first platinum wire, and when the temperature
increase was observed on the second is measured. Knowing the distance between
the two wires and the time allows one to calculate the velocity.
> The "Bagometer" method is straightforward as well; just curious about
> alternatives.
Well, above is a curious alternative, though not very useful in this
application.
I'd be surprised if this technique was not described in some medical journal by
him, but a quick glance with Google Scholar was unable to unearth the paper.
--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
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Dave
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