The previous generation of airflow meters used a duct with a hinged flap
inside, which was turned by the airflow. The flap was connected to a
potentiometer. The potentiometer is designed to be connected to the ECU,
so obviously isn't calibrated in CFM!
The BOSCH L-Jetronic used this type of airflow meter. This was used in
cars up to the 1990s. Bosch then switched to the platinum-wire system.
The L-Jetronic is explained here:
http://www.hiperformancestore.com/Ljetronic.htm
Recently, I was able to find one such airflow meter for my vintage 1985
Fiat X19 for $20 on E***y.
73
Angel Vilaseca HB9SLV
k8mlm@aol.com a écrit :
> 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.
>
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