Message from discussion HP quadrature decoder?

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Newsgroups: sci.electronics.components
Subject: Re: HP quadrature decoder?
From: Lostgallifreyan <no-...@nowhere.net>
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Date: Sat, 18 Nov 2006 04:39:52 GMT

"PolyVinalDistillate" <PolyVinalDistill...@yahoo.co.uk> wrote in 
news:1163822188.188994.188320@e3g2000cwe.googlegroups.com:

> I have to show my ignorance and admit I have no idea what a
> 'quadrature' direction decoder is :) But I assume it's effectively a
> device
> that provides ready-decoded left and right outputs.

You got it. It's not entirely ready as a simple one-bit flag might be for 
direction, but that's what it does. Not sure about this actual part, but it 
probably is one. Two sensors, placed so that slots making a 50% duty cycle 
will place a leading edge on one sensor when the second sensor is still 25%  
behind, hence quadrature, a phase shift of a quarter cycle. A circuit can 
test which sensor is trailing, regardless of speed, and get direction from 
that.