Additive tare device

An 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.^[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 $T_{\mathrm{add}}=2\mathrm{kg}$. Assume these ranges are available together for the stated configuration: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.^[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.