Tare & Net Weight

• Tare weight — the weight registered before the material of interest is added; typically the empty container, but can include any prior material being subtracted.
• Net weight — the weight of the material of interest only; net = gross − tare.
• Gross weight — the total weight on the balance, including container and all contents.
• Pre-tare — a stored tare value used when the same container is reused (with discipline).
• Auto-tare — balance feature that sets the current reading to zero with one button.

1. Place the empty container on the balance.
2. Wait for the reading to stabilise.
3. Tare (auto-tare button or system-instructed).
4. Confirm the display reads 0.000 g.
5. Add the material until the in-tolerance band is reached.
6. Confirm the net reading; the system records gross, tare and net.

Skipping or mis-ordering any of these steps is the single most common dispensing mistake. The kiosk should enforce the sequence.

When multiple ingredients are weighed sequentially into the same vessel, there are two valid patterns:

Either pattern is acceptable if executed correctly. Re-tare is simpler for operators; cumulative is faster but requires the kiosk to track the running total. Mixing patterns within one recipe is the surest path to error.

• The tare value is subject to the same balance class limits as the net (OIML R76).
• A very heavy container relative to the net charge magnifies relative tare error — see minimum-weight rules (USP <41>, USP <1251>).
• Container drift (e.g. condensation, static) shifts the tare during the weighing event; long dwells trigger re-tare.
• Static-prone containers (plastic) introduce drift; ionisers or wet wipe-down mitigate.
• Vibration during tare invalidates the value; balance bench isolation matters.

• Operator presses tare with container off the balance — tare becomes zero; net = gross afterwards; double-dose.
• Container changed mid-weigh without re-tare — net wrong by the difference in container weights.
• Cumulative gross pattern with one ingredient skipped — running total no longer matches expected.
• Pre-tare used after container has been rinsed/cleaned and is now wet — net under-reported.
• Auto-tare suppressed during 'fast' dispensing — operator eyeballs net from gross, misreads.
• Display not stabilised before tare — tare captured during oscillation; net wrong by the oscillation amplitude.

• Pharma OSD — re-tare per ingredient standard for clarity; eBR shows tare, gross, net for each.
• Pharma sterile — re-tare into sealed beakers; tare captured before sealing.
• Biopharma compounding — pre-tare from validated bottle weights when using sterile single-use containers.
• Cosmetics — cumulative gross common in fragrance compounding where many tiny additions are made.
• Food bakery — cumulative gross for large bulk additions; re-tare for minor allergen-segregated ingredients.
• Cannabis — re-tare per ingredient in extraction lab; state regulators expect explicit tare/net in records.