Fiber optic strain gauges for precision measurement

Fiber optic strain gauges for demanding measurement environments

Fiber optic strain gauges measure mechanical deformation using light rather than changes in electrical resistance. They are particularly useful in environments where conventional electrical sensors may be affected by electromagnetic interference, high voltages or other challenging operating conditions.

Althen's OSP-A fiber optic strain gauge is a miniature optical strain sensor designed for deformation monitoring in demanding environments. With different measurement ranges, cable options and optical connections available, it can be integrated into test and measurement systems and customized OEM applications.

How do fiber optic strain gauges work?

Fiber optic strain sensors use changes in optical properties to detect mechanical deformation. The exact measuring principle depends on the sensor technology. The OSP-A is designed to work with compatible White Light Polarization Interferometry (WLPI) signal conditioners, which convert the optical measurement into usable strain data.

Unlike electrical resistance strain gauges, optical sensors do not require a conventional Wheatstone bridge circuit. However, they do require compatible optical interrogation and signal conditioning equipment.

What are the advantages of fiber optic strain measurement?

Depending on the sensor model and measurement system, benefits can include:

• Electromagnetic immunity: Suitable for measurements near electrical equipment and in environments with strong electromagnetic fields.
• Electrical isolation: No electrical measurement current is required at the optical sensing point.
• Compact sensor dimensions: Miniature sensors can be used where installation space is limited.
• Temperature performance: The OSP-A is designed to be insensitive to temperature changes, reducing the need for separate temperature compensation.
• Flexible integration: Different cable and protective sheath options support industrial, research and OEM applications.

Where are fiber optic strain gauges used?

Typical applications include:

• Strain monitoring in high-voltage and electromagnetic environments.
• Mechanical measurements in civil engineering and geotechnical projects.
• Marine and subsea monitoring applications.
• Strain measurements in confined spaces, bolts and load-sensing components.
• Test and measurement systems requiring electrically isolated sensing points.

Suitability for hazardous or explosive atmospheres must be verified for the complete measurement system and the applicable certification requirements.

What should you consider when selecting a fiber optic strain gauge?

• Measurement range: Select a sensor range that covers the expected tensile and compressive strain.
• Resolution and accuracy: Check the required measurement performance for the application.
• Operating temperature: Confirm the temperature limits of the sensor, cable and optical connections.
• Signal conditioner compatibility: Ensure that the optical sensor and interrogation equipment use compatible technology.
• Cable and connector selection: Consider routing distance, mechanical protection and connection requirements.
• Installation: Verify the mounting procedure and how strain is transferred from the specimen to the optical sensor.

Always consult the individual sensor datasheet and compatible signal conditioner specifications before selecting the complete measurement system.