🚀 go-pugleaf

References: <5907@videovax.tv.tek.com> <4145@ash31.UUCP> <3861@kitty.UUCP>
Sender: Eric H. Gundersen (gunderse@cs.utah.edu)
Organization: University of Utah CS Dept
Keywords: Digital Scales

Subject: Re: Electonic scales question...

>stress will most likely cause an erroneous weight reading due to
>spurious stress and/or deformation imparted upon the spring mechanism
>and/or LVDT or load cell in the case of an electronic scale.

In regards to the hum mentioned in the first aricle, I took apart our GE dig.
scale at home and took a look. Its "load cell" (or whatever you want to call 
it) consisted of 2 parallel stretched wires with a thin metal strip placed
across these wires. At each end of this metal stip there was a coil that was
connected to the electronic circuitry. When the scale was turned on by 
standing on it, the metal strip vibrates (like a paddle laying across a 
rocking canoe. A lever system stretches the wires so that the tension of these
supporting wires is proportional (or at least related) to the pressure on the 
scale. Anyway the final effect is that the frequency of this vibrating strip
varies depending on the weight on the scale. Most probably one of the coils
forces this vibration and the other is a sense coil.
	It seems that the digital stuff (mostly built into the LED display
module) is just a frequency counter sort of circuit. Looks like someone did
some real engineering to make it work. Just thought it might be of interest.

	Eric Gundersen

PS my scale also says not to use it on the carpet. I wondered why it said
	that too.