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 Post subject: Questions from novicePosted: Tue, 20 Dec 2011 22:34:24 UTC
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Joined: Tue, 20 Dec 2011 22:16:31 UTC
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Being a physician I´m in the middle of a project. I want to measure air flow using a turbine. Outout will be more or less a square wave with frequency of up to 200 Hz for flow rates up to 10 L/s. My problem is that frequency will not be linear to flow and that the propeller in the turbine will have inertia that has to be taken into account. I haven´t got a decent clue about how to proceed. Is it possible to set up a schematic algorithm for this, including a factor for linearity, one for some unlinearity and one for inertia? I have the "correct" flow signal for various flow patterns so I can do the simulations by calculations only.

I´m not shure this is the right forum, and even less the right section. Please point me in some direction

The Swede

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 Post subject: Re: Questions from novicePosted: Wed, 21 Dec 2011 01:03:24 UTC
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Joined: Mon, 29 Dec 2008 17:49:32 UTC
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Being a physician I´m in the middle of a project. I want to measure air flow using a turbine. Outout will be more or less a square wave with frequency of up to 200 Hz for flow rates up to 10 L/s. My problem is that frequency will not be linear to flow and that the propeller in the turbine will have inertia that has to be taken into account. I haven´t got a decent clue about how to proceed. Is it possible to set up a schematic algorithm for this, including a factor for linearity, one for some unlinearity and one for inertia? I have the "correct" flow signal for various flow patterns so I can do the simulations by calculations only.

I´m not shure this is the right forum, and even less the right section. Please point me in some direction

The Swede

Somehow, I doubt the propeller can tell the difference between a square wave of frequency 200Hz from a uniform flow (unless you have a ridiculously big damping coefficient).

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 Post subject: Re: Questions from novicePosted: Wed, 21 Dec 2011 09:52:51 UTC
 S.O.S. Newbie

Joined: Tue, 20 Dec 2011 22:16:31 UTC
Posts: 2
Sorry - maybe its my english - the flow turning the propeller will be variating and up to 10 L/s. No square wave. The output from the sensor (fototransistor I believe) is a light/shadow signal for each turn of the propeller. This signal will be sort of a sqare wave with max freq of 200 Hz. It would be great if the frequency of this square wave signal would be directly proportional to flow rate, but of course it is not. It is "sort of proportinal", and that is my problem - how I should compensate for A) unlinearity and B) the inertia of the propeller since it wil have some lag. The task will be to adjust the signal so it is truly proportional to flow rate.

/M

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