A new load cell rarely sits at exactly zero output. Datasheets allow a zero balance tolerance, commonly ±1% of rated output, and this is a manufacturing reality rather than a quality problem: the four bridge arms cannot be trimmed to perfect equality without adding cost that buys nothing.
What the indicator can absorb
Most industrial indicators accept a zero offset of several millivolts and provide a zero or tare function that removes it. The practical limit is the input range of the amplifier: if the offset uses half the range, the usable span is halved. With 2 mV/V sensitivity at 10 V excitation, 1% offset is 0.2 mV, which is trivial for any modern instrument.
When offset signals a fault
An offset that appears after installation is different from one present at delivery. Moisture ingress into the cable or the cell, a damaged gauge, or a lightning-induced bridge change all shift zero. If the offset exceeds the datasheet tolerance plus the thermal allowance, and the wiring has been checked, the cell is suspect.
Trimming in the field
Some junction boxes include a zero trim potentiometer. Use it only to bring a large offset back into the indicator range, and record the change; a trim that keeps needing adjustment is telling you the cell is drifting.
Kevin Huang