= Tare device
A \b[tare device] establishes a zero indication on a <weighing scale> while a load remains on its <load receptor>. An <additive tare device> preserves the weighing range for net loads; a <subtractive tare device> reduces that range.<Non-automatic weighing instruments, Part 1>[OIML R76-1:2006(E), T.2.7.4, printed p11]{ref}
For example, place an empty $0.40\,\mathrm{kg}$ container on the <load receptor> and operate the <tare device>. The display reads zero even though the scale still supports the container. Adding $1.10\,\mathrm{kg}$ of material gives <gross mass> $1.50\,\mathrm{kg}$ and, ideally, an indicated <net mass> of $1.10\,\mathrm{kg}$. Removing both material and container without clearing the tare would ideally give $-0.40\,\mathrm{kg}$. This negative indication is consistent with the changed reference.
The cancellation can be seen in a linear model. If the unrounded indication before tare is $r(m)=am+b$, and the supported container has <tare mass> $T$, the indicated result after adding <net mass> $N$ is
$$
r(T+N)-r(T)=aN.
$$
The additive offset $b$ and the container contribution cancel. A response scale factor $a\ne1$ remains, so taring alone does not establish <calibration> across the load range.
The container's physical load remains on the scale after taring. Consequently the available <maximum weighing capacity> depends on the kind of <tare device>, even when two instruments show the same zero. A <preset tare device> performs a related numerical subtraction using an entered or recalled value, rather than necessarily measuring this particular empty container.
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