Choosing a Counting Scale: Resolution and Sample Size

How does a counting scale actually count?

A counting scale weighs the total load and divides it by the average piece weight. It derives that piece weight from a reference sample you place on the pan once and enter. Counting accuracy therefore does not depend on the displayed weight, but on the internal resolution and on how cleanly the piece weight was determined.

What matters is the internal resolution (counting division), not the display division. Good counting scales resolve internally at 1/100,000 or finer, while the display only shows coarser steps. The finer the internal measurement, the lighter the parts may be relative to capacity.

What resolution does your parts range need?

The required resolution follows from the lightest part and the lot size. A scale with 6 kg capacity and 6,000,000 internal counts resolves about 1 mg internally - enough to count parts from around 3 mg reliably. For heavier screws or fittings a coarser resolution is fine, but capacity rises in return.

• Internal resolution beats display division - select on that basis.
• Choose capacity so a full container of parts still fits the weighing range.
• Check the tare range if heavy boxes or bins are weighed along.
• For mixed lots always use the lightest part as the benchmark.

How many parts should the reference sample have?

The reference sample size determines how well the average piece weight is captured. With parts that scatter in weight, a larger sample averages out the differences. Common values are 10, 25, 50 or 100 pieces - the larger the sample, the smaller the count error for uneven parts.

If parts scatter strongly (stamped or cast small parts with burr), choose 50 to 100 pieces as the sample. For very uniform turned parts, 10 to 25 pieces suffice. Verify the result by spot-checking a known quantity against the reading.

What matters at goods-in and in the warehouse?

In daily use, ease of operation and connectivity decide. A two-platform setup (bulk plus reference scale) speeds up counting large lots: the reference is set on the fine scale and the quantity is read on the large one. RS-232, USB or Ethernet transfer counts straight into the ERP or to a label printer.

• Set up on a stable, vibration-free surface - draughts and vibration distort light parts.
• Adjust regularly with a test weight, especially after moving the scale.
• Store the container weight via tare to count net quantities directly.
• Pick an interface that suits your inventory management system.

Frequently asked questions