----- Original Message -----
From: Mark Robinson 
To: 
Sent: Thursday, May 31, 2001 8:38 PM
Subject: Re: Not so simple photoelectrics, or are they?


> This brings to mind the Centronics QD7-5 quadrant photodetector that
> http://www.rs-components.com sell as part number 652-027.
>
> This is a windowed hermetic TO5 package with foursensor elements
> arranged as quadrants. It seems rather well suited to measuring very
> small angular defelections in one or two dimensions when illuminated by
> a cheap diode laser. Sadly the detector itself is not cheap.
>
> have fun folks
>
> Mark

This can be replaced by two solar cells plus either a small incandescent or
laser diode
projected through a hole which covers half of each cell at a cost of about
$5.

George Harris
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