Does the sensor’s length of 10 cm and 1 m affect the measurement results?
In Fiber Bragg Grating (FBG) sensing technology, the packaging length of a sensor (often referred to as Gauge Length in mechanical measurements) is a critical parameter that determines its physical measurement properties. Whether a sensor is made to be 10\text{ cm} or 1\text{ m} has a decisive physical impact on the measurement results, specifically manifesting in the following three dimensions:
1. Impact at the Physical Measurement Level: Local Strain vs. Regional Average Strain
Fiber Bragg grating strain sensors measure the average deformation within their effective packaged length (gauge length L). The fundamental physical relationship is:
\varepsilon = \frac{\Delta L}{L}
Where \varepsilon is the strain measured by the sensor, \Delta L is the total displacement deformation between the two fixed (anchored) points of the measurement segment, and L is the gauge length.
- 10\text{ cm} Sensor (Local Strain Measurement):
This reflects the strain level within a very small local area. If the measured structure has local stress concentrations, micro-crack propagation, or deformation at weld edges, a 10\text{ cm} sensor can provide very high spatial resolution, accurately capturing local strain peaks. - 1\text{ m} Sensor (Regional Average Strain Measurement):
This reflects the macroscopic deformation trend over a 1\text{ m} range. If there are local strain discontinuities within this one-meter interval, a long gauge length sensor will