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	Wed, 22 Jan 2014 12:13:35 -0800 (PST)
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Date:	Wed, 22 Jan 2014 15:13:35 -0500
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Subject:	Re: [geda-user] Best way to measure RPMs
From:	Nathan Stewart <therealnathanstewart AT gmail DOT com>
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That depends a lot on whats attached to the shaft, how fast it's turning,
and what's driving it.  Obvious solutions are encoder, interrupter (photo
or magnetic - ic engines typically use an inductive pickup on gear teeth),
or even counting pulses on the drive current. If you already have an
encoder for other purposes, that makes a lot of sense. If you don't already
have anything else that might work, interrupter and divide by is probably
the most direct method. Sensing the driving forces can be a lot of things,
from stepper motor pulses to spark plug firing.

What's the application?




On Wed, Jan 22, 2014 at 3:00 PM, Rob Butts <r DOT butts2 AT gmail DOT com> wrote:

> I have a shaft that I want to measure the rpm of.  I'm looking for
> opinions on the best and cheapest way.  The design is still in development
> phase so I have freedom.
>
> Thanks
>

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<div dir=3D"ltr"><div>That depends a lot on whats attached to the shaft, ho=
w fast it&#39;s turning, and what&#39;s driving it.=A0 Obvious solutions ar=
e encoder, interrupter (photo or magnetic - ic engines typically use an ind=
uctive pickup on gear teeth), or even counting pulses on the drive current.=
 If you already have an encoder for other purposes, that makes a lot of sen=
se. If you don&#39;t already have anything else that might work, interrupte=
r and divide by is probably the most direct method. Sensing the driving for=
ces can be a lot of things,=A0 from stepper motor pulses to spark plug firi=
ng. <br>
<br></div><div>What&#39;s the application?<br></div><div><br></div><br></di=
v><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Wed, Jan=
 22, 2014 at 3:00 PM, Rob Butts <span dir=3D"ltr">&lt;<a href=3D"mailto:r.b=
utts2 AT gmail DOT com" target=3D"_blank">r DOT butts2 AT gmail DOT com</a>&gt;</span> wrote:=
<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div>I have a shaft that I =
want to measure the rpm of.=A0 I&#39;m looking for opinions on the best and=
 cheapest way.=A0 The design is still in development phase so I have freedo=
m.</div>
<div>=A0</div><div>Thanks</div>
</div>
</blockquote></div><br></div>

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