= Additive tare device
An \b[additive tare device] is a <tare device> that can establish a zero indication with a load present without reducing the weighing range available for net loads.<Non-automatic weighing instruments, Part 1>[OIML R76-1:2006(E), T.2.7.4, printed p11]{ref} The supported container still contributes <tare mass>; the instrument provides a separate tare allowance rather than obtaining extra capacity simply by changing a displayed number.
Consider a deliberately specified model with <maximum weighing capacity> $\mathrm{Max}=5\,\mathrm{kg}$ for net loads and a maximum additive tare allowance $T_{\rm add}=2\,\mathrm{kg}$. Assume these ranges are available together for the stated configuration:
$$
0\leq N\leq5\,\mathrm{kg},
\qquad
0\leq T\leq2\,\mathrm{kg},
\qquad
G=N+T.
$$
A container with <tare mass> $T=1.2\,\mathrm{kg}$ can then accompany <net mass> $N=5\,\mathrm{kg}$, giving <gross mass> $G=6.2\,\mathrm{kg}$. The model's full combined boundary is $7\,\mathrm{kg}$ when both allowances are used. These numbers are chosen examples, not specifications for a particular scale.
By comparison, a <subtractive tare device> with a $5\,\mathrm{kg}$ gross-load budget would leave only $3.8\,\mathrm{kg}$ for <net mass> after the same $1.2\,\mathrm{kg}$ container is tared. Both displays can initially read zero; their available net-load capacities differ.
The OIML definition of <maximum weighing capacity> explicitly omits additive tare capacity, while its maximum-tare-effect terminology records the tare device's capacity separately.<Non-automatic weighing instruments, Part 1>[T.3.1.1 and T.3.1.6, printed p13]{ref} A complete load description therefore identifies the container's <tare mass>, the desired <net mass> and the instrument's declared tare allowance. The <load receptor> continues to carry their combined physical load.
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