Device and method for measuring strain

1. A device for measuring strain on a surface of an object, comprising:

a carrier which is provided with a central section and two end sections which are arranged on either side of the central section,

a strain element which is connected to the carrier and is provided with a strain sensor,

in which two supporting feet are provided which are attached directly to the surface of the object to be measured at a distance apart, and the end sections of the carrier are detachably connected to, in each case, one supporting foot, and

in which the carrier has a longitudinal axis which is determined by a straight line between the supporting feet, and in which the strain element is attached to the carrier at two attachment locations in order to form a free section which extends substantially parallel to the longitudinal axis, and in which the free section is provided with the strain sensor.

2. The device of claim 1 , in which the ratio between, on the one hand, the distance between the supporting feet and, on the other hand, the distance between the attachment locations of the carrier is in the range from 1 to 2 or is smaller than 1.

3. The device of claim 1 , in which the distance between the supporting feet is greater than 5 cm.

4. The device of claim 1 , in which the distance between the attachment locations of the carrier is smaller than 7 cm.

5. The device of claim 1 , in which the strain element is provided with a temperature sensor.

6. The device of claim 1 , in which the carrier comprises at least one elastic section which is arranged between the central section and an end section of the carrier.

7. The device of claim 6 , in which the free section of the strain element is arranged between the attachment locations under prestress.

8. The device of claim 1 , in which the carrier is provided with a monitoring element for monitoring the correct operation of the strain element.

9. The device of claim 1 , in which the supporting feet each have an upright pin, and in which the end sections of the carrier each have a lateral receiving slot which runs substantially transversely with respect to the longitudinal axis, and in which the lateral receiving slots can receive the upright pins, and in which a cover element is arranged over each upright pin, and in which a spring means is prestressed between the inner side of the cover element and the carrier.

10. The device of claim 1 , in which the supporting feet each comprise two or more supporting foot parts which are each provided with a flat side, and the end sections of the carrier are provided with an opening having two bearing surfaces on either side of a longitudinal axis of the carrier, in which the flat sides and bearing surfaces bear against one another during use.

11. The device of claim 1 , in which the strain element comprises an optical fibre, and in which a temperature sensor is incorporated in the optical fibre.

12. The device of claim 1 , in which the strain element comprises an electric strain gauge.

13. A device for measuring strain on a surface of an object, comprising:

a carrier which is provided with a central section and two end sections which are arranged on either side of the central section,

a strain element which is connected to the carrier and is provided with a strain sensor,

in which two supporting feet are provided which can be attached directly to the surface of the object at a distance apart, and the end sections of the carrier are detachably connected to in each case one supporting foot, and

in which the supporting feet each comprise a gluing chamber which is formed in the bottom surface of each supporting foot, in which the bottom surface of each supporting foot is substantially annular and is filled with a first type of glue for attaching it to the surface of the object, and in which the gluing chamber has a supply opening for a second type of glue for attaching the supporting foot to the surface of the object.

14. A method for measuring strain on a surface of an object, comprising:

providing a device according to claim 1 ,

removably attaching the supporting feet to an accessory at a fixed distance apart,

fixing the supporting feet attached to the accessory to the surface,

removing the accessory,

removably attaching a carrier to the supporting feet fixed to the surface,

calibrating the strain element of the carrier.

15. The method of claim 14 , in which the carrier is removed from the supporting feet, and in which a further carrier is removably attached to the supporting feet, in which the further carrier substantially corresponds to the carrier, and in which the further carrier has been precalibrated and is not calibrated again after it has been removably attached to the supporting feet.

16. The method of claim 14 , in which the strain element comprises an optical fibre which is secured in the carrier using fastening material which largely surrounds the optical fibre, and in which the method furthermore comprises monitoring the connection between the optical fibre and the carrier by measuring the optical properties of the optical fibre during use.

17. The device of claim 1 , in which the ratio between, on the one hand, the distance between the supporting feet and, on the other hand, the distance between the attachment locations of the carrier is smaller than 1.

18. The device of claim 1 , in which the distance between the supporting feet is greater than 8 cm.

19. The device of claim 1 , in which the distance between the attachment locations of the carrier is smaller than 6 cm.