Re: Zeroing load cell data


alex wrote:

Scott Seidman wrote:
Jerry Avins <jya@xxxxxxxx> wrote in news:1rSdnX9JHaesQ7fZRVn-ug@xxxxxxx:

Am I missing something?

Jerry


Perhaps my ability to read ascii art is waning, but to me it looks like a
time record-- zero load, followed by placing a known load on and leaving it
there awhile, followed by removing the load, at which point it returns to a
-different- zero. If this is the case, then I can understand what
nonlinearity everybody seems to be talking about.

You referred to a force/voltage curve. It doesn't look like any
force/voltage curve I've ever seen. Just seems to be a voltage vs time
curve. The two calibration points would be at one of the zeros, and the
value at the plateau.

FWIW, the only times I've seen a load cell do stuff like that was cases in
which something was mechanically loose, or maybe the system had some play
in it and started out somewhat bound. Personally, I'd put most of my
effort into finding out what's wrong instead of finding some way to
calibrate a system that can't be calibrated.

--
Scott
Reverse name to reply

Hi Scott,

The sensor though not easily calibrated with a polynomial fit is able
to be calibrated with another function; I have achieved this
succesfully.

This was purely a programming question and so should not have posted it
in this group; please accept my apologies to all.

Have a nice day!

Alex

Sorry, guys, the curve in Figure 1 above was purely used as an example
of a particular curve that I wanted to zero; what axis was what does
not really matter. But for the curious, Figure 1 was supposed to be y =
Force and x = time. The final curve that I use is the one which is a
voltage/force curve and because of the nature of the curve it does not
matter which way you write the equation because you will only get one
solution; where as above you would get two solutions.

In some cases of course, if you were wanting an input of force to get
an output of voltage then you would write V = ????F; otherwise you
would write F = ????V; but you can minimise the equation to find V if
you have the first equation but this is a little more tricky.

.

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