Load Cell

Load cells are the sensing elements in virtually all electronic weighing systems and force measurement applications. The most common type uses bonded strain gauges on a precision-machined metal element (beam, column, or shear web) that deforms slightly under load. The strain gauges change resistance proportionally to the applied force, and a Wheatstone bridge circuit converts this to a measurable voltage signal. Load cell capacities range from grams to millions of pounds.

Calibration of load cells involves applying known forces and measuring the electrical output. Reference standards include calibrated deadweights, force-generating machines with reference load cells, or buildup systems using multiple calibrated load cells. Calibration evaluates linearity, hysteresis, repeatability, creep, and temperature effects. The calibration is performed at multiple load points (typically 5-10 points) across the range, with ascending and descending loads to detect hysteresis.

For calibration management, load cells present challenges related to their installation and environmental exposure. In-situ calibration (calibrating the load cell in its installed position) is often necessary because removal can change the loading conditions. Environmental factors like temperature, humidity, vibration, and electromagnetic interference affect load cell performance. Calibration intervals are typically 12 months for laboratory use and 6-12 months for production and process applications. Overload events, side loading, and cable damage are common failure modes that should trigger immediate recalibration.