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Force Sensor

IP.com Disclosure Number: IPCOM000093271D
Original Publication Date: 1967-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Kloepper, RM: AUTHOR [+2]

Abstract

The force sensor is a two-axis accelerometer contained in hermetically sealed housing 1. Mass 2 is suspended from member 3 which passes through an opening, not shown in insulator block 4. Attached to the opposite end of member 3 is a pair of knife-edges 5 and 6. Four AT-cut similar crystals, such as the two crystals 7 and 8, are arranged in two pairs. The elements of a particular pair are disposed in opposing sides of block 4. Associated with each crystal are two terminal blocks 9 and 10. The latter are also imbedded in block 4 and to each is connected one of the crystals' twin electrodes e.g. electrode 11, disposed on opposite faces of the crystal. Mass 2 and member 3 are arranged in an inverted T-bar relationship.

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Force Sensor

The force sensor is a two-axis accelerometer contained in hermetically sealed housing 1. Mass 2 is suspended from member 3 which passes through an opening, not shown in insulator block 4. Attached to the opposite end of member 3 is a pair of knife-edges 5 and 6. Four AT-cut similar crystals, such as the two crystals 7 and 8, are arranged in two pairs. The elements of a particular pair are disposed in opposing sides of block 4. Associated with each crystal are two terminal blocks 9 and 10. The latter are also imbedded in block 4 and to each is connected one of the crystals' twin electrodes e.g. electrode 11, disposed on opposite faces of the crystal. Mass 2 and member 3 are arranged in an inverted T-bar relationship. Thus in the upright position of the sensor, mass 2 preloads the crystal pairs symmetrically under no-load conditions, i.e., zero applied external force due to the effects of gravity.

Each crystal of a crystal pair provides an output signal which is fed, along with the output signal of the other crystal of the associated pair, to an A to D frequency converter. Thus each crystal pair is associated with a converter. The two converters are mounted as modules, e.g., module 12, on printed circuit board
13. Each converter measures the frequency difference between the output signals of its associated crystal pair. Bracket 14 is attached to block 4 and the assembly is supported by board 13.

Under no-load conditions, each crystal pair provides equal, nominal high- frequency output signals. C...