Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!mintaka!ogicse!zephyr.ens.tek.com!videovax!bill
From: bill@videovax.tv.tek.com (William K. McFadden)
Newsgroups: sci.electronics
Subject: Re: Electonic scales question...
Message-ID: <5907@videovax.tv.tek.com>
Date: 16 Jul 90 19:34:38 GMT
References: <25815@unix.cis.pitt.edu>
Reply-To: bill@videovax.tv.tek.com (William K. McFadden)
Organization: Tektronix TV Measurement Systems, Beaverton OR
Lines: 33

In article <25815@unix.cis.pitt.edu> fmgst@unix.cis.pitt.edu (Filip Gieszczykiewicz) writes:
>	2) I read in Consumer Digest of a advertising scheme that
>	some companies used in similar scales. Seems some
>	claimed that THEIR scales could be used on carpets. But
>	in the fine-print stated otherwise, WHY? Mine seems to
>	work on a carpet but the directions specify a hard, level
>	surface, why?

It seems that since the carpet has a springy pad underneath, the scale will
read too low.  This is because the scale will only measure the compression of
its internal spring, and some of that compression gets used up by the carpet.
Now, if the scale had pointy feet on the bottom, it would have less carpet to
compress, hence giving a more accurate reading.

>	3) There is an adjustment pot for the end-user (on the
>	fron panel) and another one on the pc board that's not 
>	accessible so easily, what is it for?

The user pot is most likely the zero offset adjustment.  This is how you set it
to read zero when no one is on the scale.  The internal pot probably adjusts
the gain (the number you multiply by to get the weight).  If it has enough
range, you can probably calibrate it for either pounds or kilograms.

My mom once had an electronic scale that was exactly the same as a mechanical
one, except the dial had been replaced by an optical interrupter wheel that fed
a digital counter.  Talk about cheap!  When it broke I told her to get a
mechanical scale.  It was equivalent to her electronic one and a whole lot
cheaper!
-- 
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-639  Beaverton, OR  97077
bill@videovax.tv.tek.com,     {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
Phone: (503) 627-6920       "The biggest difference between developing a missle
component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI