Variable-reluctance accelerometer

• US 4,754,644 A
• Filed: 03/03/1987
• Issued: 07/05/1988
• Est. Priority Date: 03/04/1986
• Status: Expired due to Fees

• Current Assignee: ITW Fastex Italia S.p.A. (Illinois Tool Works Inc.)
• Original Assignee: Illinois Tool Works Inc.
• Inventors: Valentini, Mario
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US07/020,966
• Time in Patent Office: 490 Days
• Field of Search: 73/517 R, 73/499, 73/654, 340/669, 307/121
• US Class Current: 73/514.31
• CPC Class Codes: G01P 15/11 by inductive pick-up

Abstract

An accelerometer comprising a permanent magnet which, when idle, is maintained dynamically balanced by virtue of magnetic fields acting on opposite sides in relation to its poles, and which is designed to travel along a respective guide. The accelerometer has a coil arranged coaxially in relation to the traveling direction of the magnet, and is designed to generate an electric signal, the intensity of which depends on the relative acceleration of the coil in relation to the magnet and in the traveling direction of the same.

Claims

1. An accelerometer comprising a main permanent magnet, a guide housing said main magnet and enabling it to travel in a given prearranged direction, first and second magnetic field generating means wherein the respective north and south poles are arranged facing identical north and south poles on said main magnet, said first and second magnetic field generating means exerting respective repelling forces on the said main magnet which, when idle, maintain the said main magnet dynamically balanced inside said guide, a coil located between said first and second magnetic field generating means and coaxial in relation to said main magnet and in said traveling direction, an input signal means or providing a constant supply current to said coil including a common base connected transistor having a resistor-capacitor network connected in series across its emitter-base terminal and said coil connected in parallel with the resistor of said resistor-capacitor network, and signal comparator means for comparing the output signal generated by said coil.

2. An accelerometer as defined in claim 1, wherein said signal comparator means comprises several threshold comparators, each having a comparing input connected to a respective reference voltage.

3. An accelerometer as defined in claim 2 further comprising a number of optical signaling means, each connected to the output of one of said threshold comparators.

4. An accelerometer as defined in claim 3, wherein each of said optical signaling means comprises a light-emitting diode.