Metrological Standard
International metrological standards specify testing procedures and performance limits for strain gauge force transducers used in commercial weighing systems. Achieving oiml r60 load cell compliance certifies that a transducer meets strict accuracy classes regarding linearity, hysteresis, and creep under controlled environment testing. The designation governs legal-for-trade sensing elements integrated into industrial electronic scales.
Error Envelope
Test protocols evaluate total combined error across specified load ranges, temperature intervals, and barometric pressure fluctuations. Accuracy classes categorize sensors by maximum allowed verification intervals, ranging from Class D up to high precision Class C devices. Creep testing monitors signal drift under constant rated load over four-hour evaluation windows, limiting maximum permissible error accumulation.
Span stability requirements mandate that output sensitivity remains stable across repeated loading cycles without re-calibration. Zero return testing measures bridge output recovery within thirty minutes following complete load release. Physical mounting strain and unlevel installation bases introduce mounting distortions that consume available error budgets before electrical calibration occurs.
Structural design of the spring element must balance stress distribution across strain gauge grids to minimize parasitic side-load sensitivity.
Temperature Drift
Temperature compensation networks built from matched thermistors adjust Wheatstone bridge excitation or balance to offset thermal effects. Span thermal coefficient testing exposes active load cells to temperature steps ranging from minus ten to plus forty degrees Celsius. Uncompensated thermal expansion of the strain gauge alloy causes zero balance shifts that breach metrological compliance limits.
