Re: [EE] Measuring increasing mass over a 1/2 day period

Joel -

Thanks for the email, interesting.

I should say that this is not for trade - I use the syrup on my
pancakes and waffles, so super accuracy isn't needed.

The ideal sugar percentage of maple syrup is more for trade (and storage).

However one thing really irritates me:  if there is an overboil the
bimetallic breaker in the still will flip off and I want to avoid
those if possible.  I was taught a long time ago that bimetallic
breakers have a limited life.

I used to avoid the breaker flip by underboiling - but then I have to
do a finish boil which is like making candy, which I hate because any
loss of concentration on my part can result in bad things happening -
I ran into this especially with birch syrup.

Now I'm hoping I can get better control over the process by measuring
mass instead of volume.

I suspect that Juran and Deming are in the great hearafter shaking
their heads at my process control efforts :)

Chuck

On Thu, Mar 12, 2026 at 7:15 PM <[email protected]> wrote:
>
> Many people confuse readability with accuracy.
>
> A 20,000 gram digital scale may give a readability to 1 gram but how
> accurate is that reading?
>
> Load cells that are used to weight have an accuracy of a percentage of
> the capacity of the load cell.
>
> A precision load cell may have an accuracy of +/- 0.25% of the full
> scale value.
>
> Most of the inaccuracy comes from the analog output of the load cell,
> not from the digital circuits.
>
> The output of a 20,000 gram load cell may have a window of uncertainty
> of +/- 50 grams (0.25% of 20,000) due to several factors:
>
>      linearity: the output of the load cell may be greater or less than a
> straight line between min and max.
>
>      Self-heating: A load cell uses the voltage drop across resistors to
> measure the load.  The resistance changes with the resistors heating up
> as time passes.
>
>      Repeatably: The load cell output may not give the exact same result
> with multiple readings.
>
>      Hysteresis: The output of the load cell may not follow the same
> curve when the        weight is decreasing as when the weight is
> increasing.
>
>      Return to zero: The output may not return to exactly zero when the
> weight is removed.
>
>      Long term shift: The output curve may shift as time passes.
>
> When choosing a balance or load cell, one should pick one with a maximum
> reading slightly higher that the anticipated load for the smallest
> window of uncertainty.
>
> Joel T. Curneal
> [email protected]
>
>
> On 2026-03-12 15:18, Chuck Olson wrote:
> > James -
> >
> > Thanks, I suspected that a re-zeroing might be needed over time.
> >
> > I will make up a pedestal for the still which will allow the extra
> > height needed to slip my kitchen scale under the water container.
> > I'll wait until last last few minutes before doing this - hopefully I
> > can try it tomorrow.
> >
> > Chuck
> >
> > On Thu, Mar 12, 2026 at 3:02 PM James Cameron <[email protected]> wrote:
> >>
> >> In my experience with scales, there's a good chance a zeroing will be
> >> needed over half a day, depending on how close to the mass you want
> >> the reading to be.
> >>
> >> There may be other methods other than force of gravity arising from
> >> mass pushing on a load cell.
> >> --
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