Weight Sensor
Converts applied force into an electrical signal. A strain-gauge load cell senses deformation of a designed elastic element; its capacity, sensitivity, accuracy and allowed loading direction belong to the exact device.
Strain gauges bonded to a load-bearing element change resistance as the element deforms. In a common design, a Wheatstone bridge converts those changes into a small differential voltage under excitation. Signal conditioning and calibration are needed to turn that output into a useful force or weight reading.
In plain terms
Like a tiny diving board with a paint-strip on top — when someone steps on, the board flexes, the paint stretches, and you read the stretch as the person's weight.
Why designers use it
- Measuring force or weight with a suitable calibrated transducer.
- Choosing tension, compression or shear designs to match the load path.
- Integrating weighing information into industrial equipment and instrumentation.
Best for
- Scales
- Force testing
- Process weighing
Key specifications
- Capacity and direction: Rated load, overload and permitted load path
- Sensitivity: Use the specified output and excitation conditions
- Error budget: Linearity, hysteresis, repeatability, creep and temperature
- Environment: Check the exact enclosure and material ratings
When not to use it
- Where dynamic, high-frequency force is needed (impact, vibration) — pull a piezoelectric force sensor.
- In tight curve or rotating geometry — load cells need a defined force vector; multi-axis applications require purpose-built parts.
Common mistakes
- Exceeding rated load, safe overload or allowed side load.
- Ignoring mounting forces, temperature, creep or calibration.
- Assuming a bridge cancels every temperature and bending error.
- Treating ADC resolution as the load cell's measurement accuracy.
Where you will find it
- A Mettler-Toledo IND570 industrial scale at a Tyson Foods packing line uses a Mettler MTB-300 stainless shear-beam load cell at each corner of the platform: the four-cell sum gives 0.01 % accuracy across the 300 kg full-scale range, certified for legal-for-trade weighing of meat trays.
- A Wahoo Kickr Move smart trainer measures applied bicycle pedalling power through a single OEM load cell wired to a TI HX711 24-bit ADC: the strain-gauge bridge resolves the rider's instantaneous torque to ±2 % accuracy at 1 kHz, feeding Zwift's virtual-world watts.
- An Instron 5969 universal testing machine uses a 50 kN load cell with a Honeywell Model 41 sealed transducer at its crosshead: the load cell's 0.05 % accuracy is what lets a metallurgy lab certify ASTM E8 tensile-test data for aircraft titanium with traceable measurement uncertainty.
A short history
Load cells use several measurement principles, including strain-gauge, hydraulic and pneumatic approaches. In the strain-gauge type, an elastic element deforms under load and bonded gauges convert that deformation into an electrical signal. The mechanical design and calibration are as important as the readout electronics.
Good to know
- A high-resolution ADC cannot repair a poorly mounted load cell.
- Tension, compression and shear describe different ways force is applied.