- August 18, 2025
Choosing the Right Strain Gauge: A Practical Guide for Engineers
In mechanical testing, strain measurement plays a critical role in validating structural design, supporting finite element analysis (FEA), and improving the accuracy of modelling calculations. Beyond this, strain data is essential in quantifying measurement uncertainty, particularly when experimental results feed directly into safety-critical or high-precision applications.
While several technologies are available for strain measurement, including extensometers and electromechanical testing machines, in many cases due to their high accuracy, low cost, and adaptability across a broad range of applications.
However, the effectiveness of a strain gauge isn’t just about how well it’s installed. Selecting the right strain gauge for the application is just as important. A poor match between gauge and application can reduce accuracy, increase costs, and compromise the integrity of the test. In this guide, we outline the key selection factors that engineers and technicians should consider.
- Strain Gauge Design & Configuration
Strain gauges are available in a wide range of geometries tailored to different force directions and structural layouts. These include:
- Linear gauges: Best suited for measuring strain along a single direction, typically aligned with the primary load.
- Double linear: Dual gauges for use on bending beams where strain develops on opposite surfaces.
- T-rosette & stacked rosette: Multiple gauges at known angles (e.g. 0°, 45°, 90°) for capturing multi-axial or unknown strain directions.
- Shear gauges: Designed with 45° grids to measure torsional or shear strain, particularly on rotating shafts.
- Full bridge configurations: Used for complete compensation and high-sensitivity applications.
Application Tip: Choose the gauge geometry based on the strain direction, type of loading, and surface characteristics of the test specimen.
- Gauge Length
Gauge length refers to the effective length of the measuring grid. Its selection influences both spatial resolution and averaging:
- Short gauge lengths (≤ 1 mm): Ideal for stress concentration areas like fillets, notches, or narrow surfaces where fine spatial resolution is needed.
- Longer gauge lengths (≥ 5 mm): Better for inhomogeneous materials (e.g. concrete, composites), as they average out microstructural variability over the grid length.
Application Tip: If you need to detect local strain peaks or fit into small mounting areas, go short. For larger structures or average strain, use longer gauges.
- Electrical Resistance
Typical strain gauges come in standard resistance values of 60 Ω, 120 Ω, 350 Ω, and 1000 Ω. This affects performance, power consumption, and signal stability.
- High-resistance gauges (350 Ω and above):
- Reduce self-heating (ideal for battery-powered or long-duration tests)
- Less power demand
- Better for long cable runs due to lower current draw
- Low-resistance gauges (60 Ω or 120 Ω):
- Lower susceptibility to electrical noise
- Less affected by insulation resistance changes
Application Tip: For portable systems or where heat generation is a concern, opt for high-resistance gauges. For environments with high EMI or short measurement paths, consider low-resistance options.
- Temperature Compensation
Changes in ambient or test temperature can affect both the gauge and the test material. To ensure measurement integrity:
- Use self-temperature-compensated (STC) gauges, calibrated to match the coefficient of thermal expansion (CTE) of materials like aluminium, steel, titanium, or plastics.
- Pair the gauge with temperature-matched adhesives and check adhesive ratings for max/min temperature exposure.
Application Tip: If your structure operates under fluctuating temperatures, always choose an STC-matched gauge to reduce thermal strain errors.
- Mounting Method & Adhesive Selection
Bonding or welding methods are used depending on the material and application:
- Adhesive bonding: Most common; suitable for metals, composites, and plastics. However, performance can degrade at high temperatures due to adhesive creep.
- Welding: Suitable for high-temperature or long-term applications where adhesive failure is a risk.
Application Tip: Always consider environmental exposure (temperature, humidity, vibration) when choosing adhesives or opting for welded gauges.
Strain gauges are not one-size-fits-all. The success of your strain measurement program depends on a careful match between your testing objectives, operating conditions, and gauge specifications.
If you’re uncertain about the right configuration, resistance, or installation method for your application, our team of experts is ready to assist.
Need help choosing the right strain gauge?
Contact MeasureX Australia to discuss your application and we’ll help you to select or tailor the best fit equipment for your application.
If you’re working on building a complete strain measurement system, you might also find these helpful:
Step-by-Step Guide to Installing and Calibrating Your Strain Gauge Signal Conditioner – A practical walkthrough to help you set up your signal conditioner for accurate and stable readings.
How Signal Conditioning Improves the Reading of Your Strain Gauge Data – Learn how signal conditioning enhances data quality and helps you avoid common measurement pitfalls.
