Load Cells: Working Principle and Selection Guide
1. Working Principle
Resistance strain-gauge load cells work on the strain effect: external force produces a minute elastic deformation of the spring element; the bonded strain gauges deform with it and change resistance. A Wheatstone bridge converts the resistance change into a millivolt voltage signal proportional to weight (typically 1–3 mV/V), which the weighing indicator amplifies and displays.
2. Common Structural Types
- Bending beam: e.g. the TEDEA-HUNTLEIGH 3410 series, 5–500 kg capacity, high accuracy and easy mounting — widely used in platform, packaging and sorting scales
- Shear beam: 0.5–10 t capacity, strong resistance to eccentric loads, used for floor scales and silo weighing
- S-type tension/compression: measures both pull and push, 50 kg–5 t, used in hanging scales, hopper scales and belt-scale tension detection
- Wheel-spoke / column: large 10–100 t capacities for truck scales, rail scales and high-capacity silos
- Single-point: dedicated to small-platform electronic scales — one cell supports the whole platform
3. Key Selection Parameters
1. Capacity: choose 1.2–1.5 times the maximum weighing load; permanent full-load operation shortens life;
2. Accuracy class: C3 (combined error ≤0.02%) for trade weighing; C2 is sufficient for industrial process control;
3. Protection: choose IP67/IP68 welded-seal types in wet washdown environments;
4. Output and interface: analog mV/V pairs with a weighing transmitter; modern smart types output 4-20 mA, RS485 (Modbus) or PROFINET directly;
5. Material: nickel-plated alloy steel for dry environments; stainless steel for chemical, food and wet/corrosive environments.
4. Installation and Usage Notes
Avoid lateral and torsional forces; the mounting base must be level and rigid; multi-cell platforms need a junction box to adjust corner differences; surge protectors are recommended in lightning-prone areas; calibrate periodically with standard weights and replace promptly if zero drift exceeds tolerance.