Detailed Product Description

The Strain Gage SG-01 is the fibre optic equivalent of an electrical strain gage. It consists of a fibre containing a FBG that can be mounted directly on the surface of a structure by means of an adhesive. In this way, the fibre sensor makes direct contact with the surface and therefore measures directly the strain at the surface. Installation of the optical strain gage happens preferably by means of the FOS&S Strain Gage Installation Kit (SGK-01) .

The FBG is a Draw Tower Grating (DTG): the grating is written in the fibre while drawing it and before the fibre coating is being applied. This gives the sensor high strength (> 5 % strain at breakage) and therefore ensures an excellent fatigue behaviour at moderate strain levels. The coating is an Organic Modified Ceramic (ORMOCER), which has ideal bonding with the fibre glass and which is excellent for transferring strain because of its relatively high Young's Modulus. These properties make that the coating does not need to be removed prior to installation of the sensor. Like for electrical foil gages, the optical strain gage is also sensitive to temperature variations. However, these can be eliminated by means of standard compensating methods.

In its standard configuration, the sensor has a protective tubing before (2) and after (3) the sensor area (5) and it has a free fiber length of 28 mm centred around the FBG (5). A rubber sleeve (8) is placed over the free fiber part for protective purposes and needs to be removed before installation. The sensor has a connector at one end (1) and an anti-reflection termination (angled cleave) at the other end (6). The fiber is glued at both ends in the tubing so that it can be kept straight by slightly pulling at the tubing.

• Buffered fiber sensor with a free fiber length around the FBG for direct fixation of the sensor to various surfaces.
• High strength FBG, implying high strain levels and excellent fatigue resistance.
• Fiber coating does not have to be removed before fixation because of its relatively high Young's modulus and excellent bonding properties to the fibre glass.
• The gage factor is determined at batch level with high accuracy.