Russell,

What do you mean by "By mechanically biasing one you get two axis"? How can
a single analog signal represent two axes? (I can think of lots of possible
trickery where you encode a digital signal, representing two degrees of
freedom, as an analog signal - but such is inherently non-analog and I
don't think it's what you meant)

Sean


On Sat, Aug 1, 2015 at 4:45 AM, RussellMc <apptechnz@gmail.com> wrote:

> You can get some extremely good strain gauges in digital kitchen scales -
> and some very poor ones. Odds are even the poor ones will be good enough.
> By mechanically biasing one you get two axis (and may be able to use it
> over a useful range without biasing.
>
> I have seen various kitchen scales with poor accuracy, poor linearity and
> quite often poor temperature sensitivity.
>
> Quite some years ago (10+?) a local supermarket chain endlined some scale=
s
> with 2kg max reading and 1 gram resolution.
> A test showed that a sample was able to resolve added or removed 2g test
> weights (coins) anywhere across the range and that accuracy and resolutio=
n
> allowed it to be used as a coin counter for as many hundreds of coins as =
I
> has to hand. ie extremely good for what they were. Temperature shift was
> essentially zero when heated to well over 50C - again, amazingly good.
> AFAIR they have an extra gauge apart from the main bridge quad for
> temperature compensation.
> They sold for under $10 each as I recall. I and a friend bought the dozen
> or so available and I've been 'using them up' ever since. I'll be sad whe=
n
> I destroy the last one.
>
> If a cheap looking low priced scale can achieve the above performance 10+
> years ago a few hours spent in a few Kitchenware departments may reveal a
> modern equivalent. (You'll need a source of warm air for likely
> candidates).
>
> You may be able to access the amplified analog signal in such devices, bu=
t
> even if not adding an instrumentation amplifier per channel is affordable=
..
>
>
>
>
>  Russell
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