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# Peak flow meter

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#### letrik_shock

##### New Member

can any1 help me how to make a digital peak flow meter?
i dont know what sensor to use and the circuit...

any1 plzz help me because i want to make this product as my final year project..
i appreciate all ur ideas...

thnks

peak flow of what, water, air, maple syrup.....

Wouldn't it make more sense to build something you design yourself for a final year project?0

flow of air..mean air from our lungs actually...
because we need to blow and the sensor will detect the strength of air flow..

actually i want to use this as my basic project..
after that i want to upgrade another function to me a compact one..
i think want to upgrade such termometer and another ..

plzz help me..

What sensor are you going to use?

actually i dont know what kind of sensor to use..
that y i ask in forum..mybe smeone know what type of sensor the company use..

u think can i use strain gauge sensor?
but i know nothing about the sensor..hahha

Since it's a final year project aren't you supposed to demonstrate your knowledge on the subject?

Hi

Look here - this may give you some ideas.

yeah..
but i need an idea..haha

Looking at the reference provided by gaspode42 ....reply #8, above ....It seems like the fundamental quantity that is being sought after is the actual force of the subject's airflow, as it is exhaled.. In terms of basic physics, this is the product of mass flow, the mass here being air, and velocity.... This force quantity is sometimes referred to as the momentum flux of a fluid stream .... It derives from the Newtonian definition of force as the derivative of momentum .... F = d(p=mv)/dt = m dv/dt + v dm/dt .... where the former term is not relevant, but the second term is the fluid velocity times the mass flow rate of the fluid, as it crosses an arbitrary boundary .... If all you want is a relative figure of merit, then you can just employ the volumetric flow rate in the equation.... as mentioned above.

Consequently, it would appear that the force of the airstream produced by the subject would serve as a reasonable and practical measure of the quantity in question.

One possibility would be to have the test subject exhale through a tube, which allowed the airstream to impact a plate or surface area that would be attached to a cantilever beam, and a suitable strain gage. The objective would then be to record the maximum deflection of the strain gage during the test, as the airstream deflected the cantilever beam.

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Alternatively do a search for anemometer, you could build a suitably small device and do your calculations for airflow based on the RPM

If you're not looking for accuracy, but only peak flow indication, you could use a simple hot-wire anemometer concept. This is what I was playing around with at one time. I used four low-voltage lamps, with the glass envelopes removed, in a Wheatstone bridge. Two filaments are placed in the air stream, and two are placed in still, ambient air. The output was direct to the o-scope, with no amplification. The breath signal-decay slope is related to the temperature and thermal mass of my filaments. The small pulses on top of the flow was just some puffing.

This can be done with tiny thermistors and a differential amplifier.

ken

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thanks for all bcause help me..
i appreciate all ur idea..
i do a research and if i have a problem i will post here..

i have to submit my bio fluid mechanics project. Our teacher told us to convert a basic water bath reservoir or a spirometer or a pistons apparatus into digital. Can anyone please help me or give me some idea.

Can you post photos of the water bath, spirometer, and piston device that you need to modify for a project. I've worked with all of the mechanical versions of these in the past.

Ken

hi,

When breathing against a glass, a shape of the air that comes out of the nasal cavity is left on that glass.
Usually those 2 shapes look a little different.
Is there a sensor to test the area that (the exhalation in this case) is left on the glass?
Is it related to the temperature?
Could an utrasonic or pressure sensor be used for that test?

Regards,

hi,

When breathing against a glass, a shape of the air that comes out of the nasal cavity is left on that glass.
Usually those 2 shapes look a little different.
Is there a sensor to test the area that (the exhalation in this case) is left on the glass?
Is it related to the temperature?
Could an utrasonic or pressure sensor be used for that test?

Regards,

I would tape graph paper behind the glass, then quickly take a photo of the nasal condensate, count the pixels.

You are measuring the difference between the dew point of the exhaled air Nd thermal conductivity of the glass. Breathing warmer air, holding breath longer to raise humidity level, changing the temperature or materials of construction of the panel you are exhaling onto (e.g. plastic sheet that has poor heat transfer than glass will all change the amount of condensate).

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