Electronic levelling cell

US4521973A · kind A · utility

Assignee

• Getronics AB · SE

Inventors

• Klas R. Wiklund · Täby, SE
• Lars Ericsson · Cambridge, GB

Key dates

• Filing date: May 11, 1983
• Grant date: Jun 11, 1985
• Expiry date: May 11, 2003

Classification

• Technology area (CPC G): Physics
• CPC primary: G01C9/06
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An electronic level includes a conductive gravity-levelled reference element (33) and one or more pairs of sensing electrode members (A1-D1) supported in spaced confronting relation to the reference element on a flat rigid support (37) which is movable relative to the reference element. A dielectric fluid separates the reference element (2) from the sensing electrode members so that at least one pair of capacitors is formed the capacitances of which capacitors vary oppositely in response to deviation from level position of a line joining the pair of sensing electrode members and the consequent loss of parallelism of that line with the reference element. Alternating voltages are applied to the capacitors such that the product of the capacitance and the applied voltage is equal for both capacitors when parallelism exists. A detecting means senses variations of the capacitances and provides an indication of any deviation from level position of the flat support (37). The detecting means comprises an inverting amplifier including a feed-back capacitor formed by the reference element (33) and an additional electrode member (E1) disposed symmetrically with respect to the sensing electrode…