A load cell is a transducer that converts force or weight into an electrical signal. In most industrial weighing systems, a strain-gauge load cell uses a metal sensing element, bonded strain gauges, and a bridge circuit to produce a small signal that a compatible indicator or amplifier converts into a weight reading.
How a strain-gauge load cell works
When force is applied in the cell’s specified direction, its elastic metal element deforms slightly. Strain gauges bonded to the element stretch or compress with it, changing electrical resistance. The gauges form a Wheatstone bridge, which converts those small resistance changes into a measurable voltage signal. Within the rated range, the signal changes with the applied load.
Most analog weighing load cells have a low-level output expressed in millivolts per volt (mV/V). For example, a cell rated at 2 mV/V produces about 10 mV at rated load with 5 V excitation. The value and allowable excitation depend on the model’s datasheet; the indicator or amplifier must be compatible and calibrated with the cell.
Other sensing principles also exist. Do not assume output, wiring, accuracy, or operating limits are the same across all load cells. Check the documentation for the specific model.
Common load cell types
- Single-point: commonly used beneath a small platform; the cell is designed for a specified platform size and mounting arrangement. Browse single-point load cells.
- Bending or shear beam: used in platform, floor-scale, and process-weighing assemblies. The number of cells and mounting arrangement depend on the system design. Browse beam load cells.
- S-type: a compact form used in tension or compression applications when the specific model is rated for that direction. Browse S-type load cells.
- Canister or compression: used in many higher-capacity vessel, tank, and platform applications with suitable mounting hardware. Browse canister load cells.
These are common form factors, not universal installation instructions. Use each model’s datasheet for rated capacity, load direction, mounting, and environmental limits.
What to check when choosing a replacement
- Capacity and loading: account for the live load, platform or vessel dead load, load distribution, and any dynamic forces. Stay within the rated capacity and specified load direction.
- Mechanical fit: compare dimensions, mounting-hole pattern, interfaces, clearances, and required mounting hardware. Similar appearance or capacity alone does not establish interchangeability.
- Electrical compatibility: match rated output (mV/V), excitation range, bridge resistance, cable configuration, and wiring to the indicator or amplifier. Follow the exact model wiring diagram.
- Environment and approvals: verify ingress protection, material, temperature limits, and any trade-use or application-specific certification required for the installation.
For a replacement check, gather the model and capacity from the label, the mounting dimensions, the cable or connector details, and the indicator model. Compare these with the manufacturer datasheet before ordering or wiring the cell.
Load cell signal example
A rated output of 2 mV/V means approximately 2 mV of output per volt of bridge excitation at rated load. With 5 V excitation, that is about 10 mV at rated load before accounting for zero balance and the exact calibration data. A weighing indicator amplifies and interprets this small signal; the load cell by itself does not display a weight.
For a more detailed explanation, see HBK’s guide to load-cell design and operation and Rice Lake’s overview of load-cell operation and common types.
Find load cells and weighing components
Explore single-point load cells, beam load cells, S-type load cells, canister load cells, scale indicators, and mounting parts. For help identifying a replacement, contact The Load Cell Depot with the information listed above.