Load cell datasheets often quote a fatigue life, for example 10 million cycles at rated capacity. The number is not a warranty, and it is very sensitive to the load amplitude.
Why amplitude dominates
Metal fatigue follows an S-N curve: life falls sharply as stress amplitude rises. A cell cycled between 0 and 100% of capacity accumulates damage roughly an order of magnitude faster than one cycled between 0 and 70%, and running to 150% shortens life again. This is why dynamic applications such as checkweighers and filling machines need a cell with a capacity well above the working load.
Design margin
A common rule for dynamic weighing is to size the cell so the working load is 50-60% of capacity. That keeps stress amplitude low, preserves overload headroom, and leaves room for the peaks that occur during filling and discharging.
Failure signature
Fatigue cracks usually start at a stress concentration and produce a gradual loss of sensitivity followed by a sudden zero shift when the crack propagates. If a cell in a high-cycle machine starts reading low and the error grows over weeks, replace it rather than recalibrating.
Kevin Huang