CS251320B1 - Strain gauge frame for foil mounting with resistance strain gauges - Google Patents

Abstract

The frame of the strain gauge sensor for mounting the foil /4/ with resistance strain gauges /7/ consists of a prism-shaped body /3/ and is provided with notches /8/ perpendicular to the longest wall of the body /3/. The foil /4/ is attached to the body /3/ in a state of tensile mechanical stress acting in the direction of the longest wall of the body /3/.

Description

BACKGROUND OF THE INVENTION The present invention relates to a strain gauge sensor frame for attaching a film with resistive strain gauges for measuring the relative deformations of masonry and concrete, and in particular for measuring small dynamic relative deformations.

At present, resistive bonded strain gauges, which are either wired, foil or semiconductor, are most commonly used for measuring relative deformations. The surface of concrete constructions is glued from torsion wire strain gauges with a measuring length up to 100 mm, which is given by the dimensions of the concrete aggregate. On brick or stone masonry, the use of glued strain gauges is problematic due to the considerable size and variety of the individual masonry components. Semiconductor strain gauges- cannot be used for direct bonding due to their small measuring length ·

Measurement of relative deformations of dynamic character is difficult on building constructions usually because the dynamic deformations tend to be small, sometimes of the order of 1 micrometer / meter. The measurement then encounters a number of difficulties in processing the electrical signal at a very low level, as the signal is usually devalued by various interfering effects.

The closest solution, similar to our solution, appears to be a strain gauge pressure sensor, which consists of a frame in which a diaphragm with strain gauges is fixed, but this is intended to measure the pressure perpendicular to the plane of the diaphragm.

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The above-mentioned drawbacks are eliminated by the strain-gauge sensor frame for fastening the foil with resistive strain gauges, consisting of a block-shaped body supported by its longest wall on the measured structure according to the invention. the foil is attached to the body in a state of tensile mechanical stress acting in the direction of the longest wall of the body ·

Frame up. it is fitted to the surface of the structure by means of holes and by means of pins mounted on the structure. An advantage of the inventive rhinitis is that the force caused by the prestressing of the foil is not transferred to these pins because it is absorbed by the rigidity of the frame. Another advantage is to increase the sensitivity of the measurement by the distance between the pins mounted on the structure being greater than the length of the film. High sensitivity can be achieved for longer by using high strain-rate semiconductor strain gauges, glued to the foil and connected to the entire bridge so that they are all active. Direct bonding of semiconductor strain gauges to masonry or concrete is not possible. The frame according to the invention can be reused.

BRIEF DESCRIPTION OF THE DRAWINGS The invention and its effects are explained in more detail in the description of an exemplary embodiment thereof according to the accompanying drawing, in which Fig. 1 shows the frame according to the invention in longitudinal section and Fig. 2 shows a plan view of the frame according to the invention.

The frame according to the invention is fixed to fixed studs 1 and 2 mounted on the structure, the studs 1 and 2 are fitted into a hole in the masonry or concrete and are cemented either with cement mortar or a grout of plastic. On the steel structure, the pins 1 and 6 can be welded or cemented. Fitting is performed using -Dblbl. the pins 1 and 2 are threaded and stepped in the projecting portion. A prism-shaped frame body 3 fitted with round holes and fastened by the KozLmoak nuts to the longest wall is mounted on the pins 1 and 6.

AND

In the central part of the body, χ is a rectangular opening in which a metal foil 6 is fastened to the frame by means of shims 5 and screws J5. The foil is biased by a force that ensures its sufficiently large first transverse natural frequency. Four active semiconductor strain gauges χ are attached to the foil connected to the Wheatstone bridge. The entire frame is protected against sudden temperature changes with a polystyrene foam cover.

The strain gauge sensor is attached with its two end holes to two pins χ and χ mounted on the surface of the measured structure. The surface deformation of the structure is transmitted to the body X of the frame at the base between Pins 1 and 2. When the body X is deformed, the film 6 is axially stressed. Deformation of foil χ is measured by strain gauges χ. The X strain gauges are connected to the entire Wheatstone bridge so that they are all active. Signal processing from the bridge diagonal is carried out by conventional methods.

The frame of the strain gauge sensor for holding the foil with resistance strain gauges according to the invention is particularly useful in the construction industry for dynamic measurement of small relative deformations.

Claims (1)

SUBJECT OF THE INVENTION Strain gauge sensor frame for holding a film with resistive strain gauges, consisting of a prism-shaped body supported by its longest wall on the structure to be measured, characterized in that it has slots (8) perpendicular to the longest wall of the body (3) and is attached to the body (3) in the state of tensile mechanical stress acting in the direction of the longest wall of the body (3).