You have just described the airflow meter in all the modern automobile fuel
management systems.
Bob
K8MLM
-----Original Message-----
From: Dr. David Kirkby <david.kirkby@onetel.net>
To: amps@contesting.com
Sent: Fri, Apr 15, 2011 4:23 am
Subject: Re: [Amps] Airflow meter
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.
y ex-boss (Prof. D. T. Delpy) used a technique for measuring air *velocity*,
hich 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
opper, though I do see platinum would have some advantages.
It was used for measuring the speed babies breathed out air, so had to have
egligible restriction on the airflow. Using a plastic bag would not have been
ery 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
urrent is passed. I've no idea of the temperature the wire reached, but it's
ot important to know the temperature.
3) Thermometer. This is another thin platinum wire, forming part of a platinum
esistance thermometer. This responds very rapidly to temperature changes.
The time between heating the first platinum wire, and when the temperature
ncrease was observed on the second is measured. Knowing the distance between
he 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
pplication.
I'd be surprised if this technique was not described in some medical journal by
im, but a quick glance with Google Scholar was unable to unearth the paper.
--
: Because it messes up the order in which people normally read text.
: Why is top-posting such a bad thing?
: Top-posting.
: What is the most annoying thing in e-mail?
Dave
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