Why Load Cell Accuracy Matters
In force measurement, the accuracy of your load cell directly determines the reliability of your test results, quality control decisions, and regulatory compliance.
An inaccurate load cell doesn't just give wrong numbers — it cascades into: • Failed quality audits when products pass testing but fail in the field • Material waste when manufacturing tolerances are set too wide to compensate for measurement uncertainty • Safety risks in structural testing, crane loading, and vehicle component verification
Understanding the individual accuracy parameters helps you specify the right load cell for your accuracy requirements — and avoid over-specifying (and overpaying) when high precision isn't necessary.
All accuracy specifications are expressed as a percentage of Full Scale Output (FSO), which is the total electrical signal range of the load cell from zero to rated capacity.
Non-Linearity
Non-linearity is the maximum deviation of the load cell's actual output from an ideal straight line drawn between zero load and full rated capacity.
In simple terms: If you apply 50% of rated load, you should get exactly 50% of rated output. Non-linearity measures how far off this ideal relationship gets.
Typical specification: ±0.02% to ±0.1% of FSO
Example: A 1000 kg load cell with ±0.05% FSO non-linearity can deviate by up to ±0.5 kg at any point across its range. At 500 kg applied load, you might read 499.5 kg or 500.5 kg.
Why it matters: Non-linearity is usually the largest single contributor to load cell error. It's determined by the mechanical design of the spring element and cannot be improved after manufacturing — only compensated by multi-point calibration.
At JRAGRAU, our load cells achieve non-linearity as low as ±0.02% FSO through precision CNC machining and optimized strain gauge placement.
Hysteresis
Hysteresis is the maximum difference in load cell output when the same load is applied from two different directions — increasing (loading) versus decreasing (unloading).
In simple terms: If you load a cell to 500 kg and then unload it back to 500 kg, the readings may differ slightly. This difference is hysteresis.
Typical specification: ±0.02% to ±0.05% of FSO
Example: A 1000 kg load cell with ±0.03% FSO hysteresis can show up to 0.3 kg difference between the loading and unloading reading at the same actual load.
Why it matters: Hysteresis is caused by mechanical friction in the spring element and molecular-level stress in the strain gauges. It is most significant in: • Cyclic loading applications (fatigue testing, spring testing) • Applications where loads are applied and removed frequently • Weighing systems where tare operations are common
Lower hysteresis is a sign of better metallurgy, heat treatment, and strain gauge bonding quality.
Creep
Creep is the change in load cell output over time when a constant load is applied continuously.
In simple terms: You place a known weight on the load cell, and over 30 minutes, the reading slowly drifts up or down even though the weight hasn't changed.
Typical specification: ±0.02% to ±0.05% of FSO over 30 minutes
Example: A 1000 kg load cell with ±0.03% FSO creep under a constant 800 kg load might show a drift of 0.3 kg over 30 minutes.
Why it matters: Creep is critical in: • Static weighing (silos, tanks, hoppers) where loads remain for hours or days • Calibration deadweight machines where reference weights sit on the cell during use • Force holding applications in material testing
Creep is caused by viscoelastic behavior in the adhesive bonding the strain gauge to the spring element. High-quality bonding with controlled cure cycles minimizes creep.
Creep recovery is the related specification — how quickly the output returns to zero after the load is removed.
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Repeatability
Repeatability is the maximum difference between load cell outputs for repeated identical loads applied under the same conditions and in the same direction.
In simple terms: If you apply exactly 500 kg five times in a row under the same conditions, how close are all five readings to each other?
Typical specification: ±0.01% to ±0.03% of FSO
Why it matters: Repeatability is often the tightest specification on a load cell and is the most important spec for: • Quality control applications where you're comparing parts to each other (pass/fail testing) • Batching systems where consistent dosing is more important than absolute accuracy • Calibration laboratories where measurement reproducibility determines accreditation scope
Good repeatability means the load cell is mechanically stable and the strain gauge pattern is consistent. A load cell with poor repeatability has internal mechanical friction or unstable bonding.
Combined Error & Total Accuracy
Combined Error brings together non-linearity, hysteresis, and repeatability into a single accuracy figure. This is the most practical specification for comparing load cells.
| Accuracy Class | Combined Error | Typical Application |
|---|---|---|
| Standard | ±0.1% FSO | General industrial weighing |
| High Accuracy | ±0.05% FSO | Testing machines, quality control |
| Precision | ±0.03% FSO | Calibration, laboratory reference |
| Ultra-Precision | ±0.01% FSO | National standards, deadweight machines |
Total system accuracy is always worse than the load cell alone. It includes: • Load cell combined error • Signal conditioning (amplifier) accuracy • A/D converter resolution • Temperature effects • Cable resistance changes • Mounting errors
Rule of thumb: Your measurement system accuracy is at best 2-3x the load cell's combined error specification after accounting for all system components.
JRAGRAU load cells are available from standard (±0.1% FSO) to precision (±0.02% FSO) grades, and we provide complete measurement systems with matched signal conditioning for optimal total system accuracy.
Temperature Effects on Accuracy
Temperature changes affect both the zero balance and span (sensitivity) of a load cell. These are specified separately:
• Temperature Effect on Zero (TKO): Typically ±0.002% to ±0.005% FSO per °C • Temperature Effect on Span (TKC): Typically ±0.001% to ±0.003% FSO per °C
Example: A load cell with ±0.003% FSO/°C TKO operating across a 20°C temperature swing will show an additional zero drift of ±0.06% FSO — which may exceed the base non-linearity specification.
Compensated temperature range is the range over which the manufacturer guarantees the temperature coefficients. Outside this range, errors increase rapidly.
Practical advice: • For outdoor or process environments, always check the compensated temperature range • Allow 30 minutes for thermal stabilization after power-on • Consider ratiometric excitation to cancel some supply-related drift
