How to Measure Mechanical Strain with a DAQ

+ Data Acquisition System

Characterize Mechanical Strain Across Test Points

Mechanical strain measurement requires detecting very small changes in a strain gauge as a structure stretches, compresses, or bends under an applied mechanical load. A strain gauge measurement relies on the relationship between physical deformation and the resulting change in electrical resistance. The measured change can be small relative to the nominal gauge resistance, so the test must account for gauge factor, wiring resistance, initial offset, sensor placement, and the mechanical direction of the applied strain. When several gauges are attached to different locations on a structure, each measurement point may experience a different combination of tensile, compressive, axial, or bending strain. Multichannel strain acquisition must preserve these individual responses so engineers can compare deformation across the structure rather than treating the specimen as a single measurement point.

Bridge strain measurement introduces additional variables because the strain gauge forms part of a Wheatstone bridge whose output changes as one or more active gauge elements change resistance. Quarter-, half-, and full-bridge configurations produce different electrical responses depending on the number and orientation of active gauges. Excitation voltage, bridge balance, temperature effects, lead resistance, gauge factor, and the unstrained reference all influence the measured result. In a data acquisition (DAQ) strain measurement, small bridge-output changes must be captured repeatedly while mechanical loading changes over time. Engineers may also need to compare measurements from several gauges simultaneously or sequentially to determine how strain propagates through the test article. The resulting mechanical strain measurement therefore depends on consistent strain gauge measurement conditions, stable reference values, and repeatable acquisition across every monitored location.

Mechanical Strain Measurement DAQ Solution

Performing a strain test requires connecting strain gauges to the measurement channels, defining the gauge and bridge parameters, establishing an unstrained reference, and acquiring measurements as the mechanical load changes. A Keysight DAQ system with a compatible multiplexer provides the measurement framework for direct strain and bridge strain measurement across multiple test points. Engineers can configure strain gauge measurement channels for direct resistance-based measurements or quarter-, half-, and full-bridge configurations, depending on the sensor arrangement. For bridge measurements, the test setup uses an external excitation voltage and the appropriate gauge factor and bridge parameters to convert the measured bridge response into strain. The DAQ can establish a strain offset representing the unloaded condition and apply that reference during subsequent measurements. Multichannel strain acquisition then enables engineers to monitor tensile, compressive, axial, or bending responses across several locations while recording the resulting mechanical strain measurement data.

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Block Diagram of Mechanical Strain Measurement DAQ Solution

How to Measure Mechanical Strain with a DAQ - Block Diagram

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