Strain gauges: bridge circuits, transducers and rosettes
Gauge factor, Wheatstone quarter, half and full bridges, calibration, lead-wire and temperature effects, force, bending, torque and pressure transducers, and rosette evaluation after Keil.
Define the task and bridge circuit, link signal and strain, estimate error sources, then convert strains into stresses.
Calculators in this category
Strain-gauge basic equation: resistance change from strain and gauge factor
Calculate the relative and absolute resistance change of a strain gauge from nominal resistance, gauge factor and strain, including the corresponding quarter-bridge signal.
Open calculator →Transverse sensitivity: correction for two perpendicular gauges
Correct the indicated strains of two perpendicular strain gauges for transverse sensitivity q and report the error without correction.
Open calculator →Temperature response: apparent strain of a gauge under temperature change
Calculate the thermal resistance change and apparent strain from the grid's temperature coefficient, thermal expansion of part and grid, and the gauge factor.
Open calculator →Bridge excitation voltage and gauge self-heating
Calculate power loss, current and power density per gauge from excitation voltage, resistance and grid area, and find the maximum excitation voltage for a guideline power density.
Open calculator →Wheatstone bridge: output voltage of the unbalanced bridge
Calculate the bridge output voltage and ratio U_M/U_B exactly from the four arm resistances and the excitation.
Open calculator →Basic strain-gauge bridge equation: signal from four strains
Calculate the bridge output from the strains in the four arms and the gauge factor – linearised and with the exact equation 4.6.
Open calculator →Quarter, half and full bridge: bridge factor and signal
Determine the bridge factor B and output signal for Keil's nine elementary strain-gauge bridge circuits from strain, gauge factor and Poisson's ratio.
Open calculator →Strain and stress from the bridge signal (mV/V)
Convert a measured bridge signal into strain and uniaxial stress, with correction of the quarter-bridge non-linearity per eq. 4.7.
Open calculator →Shunt calibration: shunt resistor for a defined bridge signal
Calculate the shunt resistor R_N for a desired calibration signal (exact and per the approximation eq. 8.7) and the strain it simulates.
Open calculator →Lead-wire resistance: sensitivity loss and apparent strain in 2-, 3- and 4-wire connection
Determine the cable resistance from length and cross-section and its effect on sensitivity and zero for full bridge, half bridge and quarter bridge in two- and three-wire connection.
Open calculator →Parallel connection of load cells: matching sensitivities with trim resistors
For up to four parallel full-bridge transducers, calculate the trim resistors in the output leads that make all cells contribute equally to the summed signal.
Open calculator →Axial force transducer: strain, stress and bridge signal
For an axially loaded measuring body, calculate longitudinal strain, stress and the output of the chosen gauge circuit – including the sensitivity in mV/V per rated force.
Open calculator →Bending beam with strain gauges: outer-fibre strain, deflection and bridge signal
For a cantilevered rectangular beam, calculate bending stress, strain at the gauge location, deflection at the load point and the signal of the chosen bridge circuit.
Open calculator →Torque transducer: shear stress, 45° strain and full-bridge signal
For a solid or hollow shaft under torsion, calculate shear stress, principal strains at ±45° and the strain-gauge full-bridge signal from torque, diameters and material data.
Open calculator →Shear force measurement with 45° gauges in the web: shear stress and bridge signal
From shear force and web area, calculate the mean shear stress in the neutral fibre, the 45° strains and the signal of a half or full bridge.
Open calculator →Diaphragm pressure transducer: strains, deflection and diaphragm-rosette signal
For an edge-clamped circular diaphragm under pressure, calculate stresses and strains at centre and edge, centre deflection with the linearity limit and the ideal full-bridge signal of a diaphragm rosette.
Open calculator →0°/45°/90° rosette: principal strains and principal direction
From the three strains of a rectangular rosette, compute centre and radius of the strain circle, principal strains ε₁, ε₂, maximum shear strain and the unambiguous orientation angle α per Keil Tab. 9.1.
Open calculator →0°/60°/120° (delta) rosette: principal strains and principal direction
From the three strains of a delta rosette, compute centre and radius of the strain circle, the principal strains and the unambiguous orientation angle per Keil eq. 9.83 and Tab. 9.2.
Open calculator →Principal stresses from principal strains: Hooke's law for plane stress
From the two principal strains at a free surface, compute the principal normal stresses, the third principal strain, the maximum shear stress and the von Mises equivalent stress.
Open calculator →Separating axial force and bending: four gauges around a bar
From four longitudinal gauges at 0°, 90°, 180° and 270° of a mast or bar section, compute the axial strain, bending strains in two planes, the bending-plane orientation and the resulting stresses.
Open calculator →Thermal stress from restrained expansion: separating load and temperature components
From the strain measured with a compensation gauge, the temperature change and the expansion coefficient, compute the free thermal strain, the prevented strain, the degree of restraint and the thermal stress.
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