Abstract: A device for measuring compressive forces, comprising an annular body (1) having a pair of opposite, force-receiving front surfaces (2, 3) which are perpendicular to the central principal axis (4) of the body, and an annular cavity (5) essentially concentric with the principal axis and receiving a sensor means (6) for delivery of an electrical signal representing the force influence. The sensor means (6) comprises a sensor element (9) placed on the radially inner surface (7) of the cavity (5), said surface being situated at a distance from the principal axis (4) essentially corresponding to the radius (r.sub.R) for moment equilibrium for that part of the ring body (1) which receives a load.

Abstract: The present invention relates to a surveillance system for measuring and surveying e.g. the preload in screws (23) or similar. It comprises a number of sensor systems (1) electrically connected to a common electronic and computing system, each said sensor system (1) comprising sensor means (2) being provided with a magnetoelastic material (6) sensitive to the preloads and a sensing device (3) comprising a coil system at least partly surrounding the sensitive material (6). The sensitive material (6) is excited via the coil system with a frequency of at least 300 kHz so as to make the system insensitive to external disturbing fields.

Abstract: The present invention relates to a sensor and to a method for measuring torque and/or axial stresses applied to an object as well as a method for manufacturing magnetoelastic material to be used therefore. The sensor (20) comprises a magnetoelastic material and a sensing device (210) for non-contactingly sensing changes in permeability of the magnetoelastic material due to torque and/or axial stresses, said sensing device (310) comprising a coil system carrying out both an excitation and a pick-up function. The excitation frequency is so chosen that the pre-dominating process of magnetization of the magnetoelastic material will be small angle magnetization rotation, the excitation frequency being at least 300 kHz.

Abstract: The invention relates to a sensor system for measuring e.g. the preloads in screws, bolts or similar. It comprises sensor means (2) comprising a magnetoelastic material (6) sensitive to the preloads to which the object is exposed and a sensing device (3) comprising a contact portion (4) and gripping portion (5). The contact portion is so arranged that it at least partly surrounds the sensor means (2) and the magnetoelastic material (6) is excited with an excitation frequency of at least 300 kHz.

Abstract: A method of measuring the volume (V) of a gas in a container (20) comprises varying the container volume according to a sine wave between a minimum and a maximum value, the variation being made at a constant frequency but at varying amplitude, to obtain a predetermined pressure difference (.DELTA.p), and the volume difference (.DELTA.V) corresponding to said predetermined pressure difference (.DELTA.p) being determined by detecting the points of time when at least two points on the sine wave are attained which correspond to two predetermined values of the container volume. By measuring the time between the two points on the sine wave, the sine wave peak values for the volume difference (.DELTA.V) corresponding to said predetermined pressure difference (.DELTA.p) may be calculated and, thus, the said volume difference (.DELTA.V). By means of the formula V=.DELTA.Vxp.sub.0 x.eta./.DELTA.p, wherein p.sub.0 =the static pressure and .eta.