45 Degrees Shear Strain Gauges for Half Bridge Load Cell

45 Degrees Shear Strain Gauges for Half Bridge Load Cell

Model: HA-D series
Carrier Material: Phenolic Aldehyde /Polyimide/Epoxy
Measuring Material: Foil(nickel copper alloy, Constantan or Karma)
Resistance: 120-1000 Ohm
Operational temperature: －20～＋80℃, Temperature compensation range ＋10～＋80℃
Four (4) solder points, long terms stable.

Note: Other models and sizes are available according to customer request

The Principle: When a load is applied to the beam, it deforms slightly. This deformation (strain) is concentrated in the thin "shear web" sections near the ends of the beam, specifically designed to flex under load.

Strain Gauge Placement: Strain gauges are bonded directly onto these shear webs. Crucially, they are mounted at 45-degree angles relative to the beam's long axis.

Why 45 Degrees? This orientation aligns the gauges with the direction of maximum shear strain induced in the beam material when the load is applied. Shear stress/strain is highest at 45 degrees to the applied force.

Gauge Configuration (The Wheatstone Bridge): Shear beam cells typically use four active strain gauges wired together in a full Wheatstone bridge circuit.

Two Gauges per Shear Web: Usually, two gauges are bonded on one side of a shear web, and two on the opposite side (or sometimes two on each of the two shear webs).

Opposing Orientation: Gauges are mounted in pairs with their sensitive axes perpendicular to each other (one at +45°, its partner at -45° relative to the beam axis). This maximizes the bridge output signal.

How it Measures Shear (Indirectly):

Under tensile load, the material stretches longitudinally and contracts laterally (Poisson's effect).

Under compressive load, the material shortens longitudinally and expands laterally.

At 45 degrees, the strain gauge experiences a combination of these longitudinal and lateral strains caused by the shear stress in the beam. The specific +45°/-45° pairing ensures that:

Gauges oriented to experience tension under shear load increase resistance.

Gauges oriented to experience compression under shear load decrease resistance.

This creates a significant imbalance in the Wheatstone bridge circuit proportional to the applied force.

Key Advantages of this Configuration:

High Sensitivity: Measures the sensitive shear strain region effectively.

Temperature Compensation: The full bridge configuration inherently compensates for temperature effects that would cause all gauges to change resistance equally (which the bridge cancels out).

Cancellation of Bending Moments: The placement on opposite sides of the web helps cancel out the effects of small bending moments that might occur due to slightly off-center loading.

Cancellation of Axial Load Effects: The opposing orientations (+45°/-45°) help cancel out pure axial tension/compression strains, making the bridge primarily sensitive to shear strain. (Pure axial load would cause similar resistance changes in all gauges, which the bridge would cancel out).

Linear Output: Provides a highly linear voltage output proportional to the applied force.

Dummy Gauges (Sometimes): While the four active gauges form the core bridge, some designs might include additional "dummy" gauges bonded to unstrained parts of the load cell solely for advanced temperature compensation within the instrumentation circuitry.

In Simple Terms:

The shear beam is designed to flex predictably under load.

Strain gauges glued at 45° angles on the thin flexing sections ("shear webs") change electrical resistance when the beam bends.

These gauges are wired in a special circuit (Wheatstone bridge) that turns tiny resistance changes into a measurable voltage signal.

This voltage signal is directly proportional to the applied force (weight).