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Load cell zero offset - how much is too much?

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magic:
Is anyone familiar with typical specifications and behavior of load cells?

I'm measuring the load cell of a digital scale which struggles with repeatability; it's some no-name thing only marked with capacity and "class C3".
I found that excitation is a stable 5V, zero load output is -13mV (2.6mV/V) and full load sensitivity is 7mV (1.4mV/V).

I have no datasheet of course, but I tried looking up specs of similar load cells. As far as I see, my measured sensitivity figure is fairly average, but zero balance is usually quoted in units of "%FS" with a single-digit number, so I presume offset should be at least an order of magnitude lower than full scale output, right?

So this cell is dead for good, isn't it?

David Hess:
Good load cells are trimmed during manufacturing to have a small zero offset, so if you find one which is far off of zero, it implies that it was overloaded and damaged.

SiliconWizard:
Yep an excessive zero offset is a sign of damage.
I'm assuming you measured the differential output, ideally disconnected from the differential amplifier (there must be one), if possible, just to rule out a fault in the input stage of the amplifier itself rather than the load cell.

Kleinstein:
Normally the offset should be smaller. For a low cost product it is still possible to have a load cell with quite some offset. Modern electronics has less of a problem with compensating for offset and loosing 1-2 bit is not a big issue.

David Hess:

--- Quote from: Kleinstein on June 09, 2023, 06:42:40 am ---Normally the offset should be smaller. For a low cost product it is still possible to have a load cell with quite some offset. Modern electronics has less of a problem with compensating for offset and loosing 1-2 bit is not a big issue.
--- End quote ---

In the past offset was a problem because it is difficult to remove without introducing drift.

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