The old national standard treated "weighing" sensors and "force-measuring" sensors-which differ significantly in their applications and operating environments-as a single category, failing to distinguish between their testing and evaluation methods. The old standard comprised 21 parameters, all tested at ambient temperature; the accuracy class of the load cell (designated as 0.02, 0.03, or 0.05) was determined by the maximum value among six specific parameters: nonlinearity, hysteresis error, repeatability error, creep, additional zero-point temperature error, and additional rated output temperature error.
A load cell is a type of force sensor used in weighing instruments. It converts the gravitational force acting on an object into a measurable output signal at a specific ratio.
Accounting for the effects of gravitational acceleration and air buoyancy at different locations, the key performance parameters of a load cell include nonlinearity, hysteresis error, repeatability error, creep, zero-point temperature characteristics, and sensitivity temperature characteristics. In various weighing instruments and mass measurement systems, a "combined error band" is typically used to comprehensively control sensor accuracy; this band is correlated with the weighing instrument's error band to facilitate the selection of a load cell appropriate for a specific accuracy class. The International Organization of Legal Metrology (OIML) stipulates that the sensor's error band (δ) constitutes 70% of the weighing instrument's error band (Δ), and that the sum of nonlinearity, hysteresis, and temperature-induced sensitivity errors (within the specified temperature range) must not exceed δ. This allows manufacturers to adjust the individual components contributing to the total metrological error, thereby achieving the desired level of accuracy.