Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1991-04-03
1993-08-17
Strecker, Gerard R.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
324660, 324686, 34087037, 73780, G01R 2726, G08C 1910
Patent
active
052372847
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus for and a method of measuring the capacitance of capacitors, and parameters related thereto; and more particularly to such an apparatus and method for measuring the displacement of a movable object by measuring the electrical capacitance between two electrode systems one of which is movable by such an object relative to the other electrode system.
In a prior apparatus of that kind, a plate electrode of one electrode system has been disposed face-to-face with, but spaced from, plate electrodes of a second electrode system, and the electrodes of the two systems have been relatively movable in their own planes so as to alter the dispositions of the electrode systems relative to one another without altering the transverse separation of the two electrode systems, and means have been provided for sensing changes in the electrical capacitance between the electrode systems as the displacement of the two systems has been changed.
U.S. Pat. No. 4,437,055 (MEYER) discloses such a capacitive displacement measurement apparatus in which a displacement sensor comprises (a) a flat-plate primary electrode which opposes a plurality of uniformly-spaced, co-planar, smaller flat-plate secondary electrodes, at constant spatial separation, and (b) an electronic circuit means arranged to detect the displacement of the primary electrode from a central position relative to the secondary electrodes as a change in the distribution of capacitive currents flowing to and from the primary electrode when the secondary electrodes on either side of a central secondary electrode are oppositely energised in a predetermined cyclic manner. This is achieved by progressively and cyclically varying a balancing voltage applied to the central secondary electrode between the respective voltages currently applied to the adjoining secondary electrodes, and noting the magnitude of the balancing voltage, or its phase, when the net current flow to the primary electrode falls to zero value in each measurement cycle.
In order to accommodate a large range of displacement measurement, the secondary electrode system is repeated, and electronic switching means are provided for transfering the respective energising and balancing voltages progressively along the sequence of secondary electrodes as the primary electrode progresses along that secondary electrode sequence.
The present invention seeks to provide inter alia an advantageous alternative approach to the determination with high accuracy of the displacement of an object, using fewer secondary electrodes and less complex electrical circuitry.
According to a first aspect of the present invention, there is provided a capacitive displacement measurement apparatus which includes two mutually-opposed electrode systems spaced transversely apart, one such system being displacable relative to the other without changing the transverse spacing of the electrode systems, which apparatus is characterised by: comprising a single primary electrode plate, and the other electrode system (called hereafter the secondary electrode system) comprising two similar secondary electrode plates which are closely spaced apart, which together span fully or substantially so the whole of the primary electrode plate, and which on relative displacement of the two electrode systems suffers a progressive reduction in the overlap of the primary electrode first with one secondary electrode and then with the second secondary electrode; successive clock periods; to supply to the primary electrode via a first one of the secondary electrodes first predetermined packets of electrical charge during selected first clock periods so as to increase the electric charge on the primary electrode, and when operating in a second mode to withdraw from the primary electrode via the second of the secondary electrodes second predetermined packets of electrical charge during selected second clock periods so as to decrease the electric charge on the primary electrode; present on the primary electrode, and for causing the char
REFERENCES:
patent: 3071758 (1963-01-01), Wolfendale
patent: 3297941 (1967-01-01), Wolfendale
patent: 3566222 (1971-02-01), Wolfendale
patent: 3668672 (1972-06-01), Parnell
patent: 3683402 (1972-08-01), Parnell
patent: 3777257 (1973-12-01), Geisselmann
patent: 3857092 (1974-12-01), Meyer
patent: 3873916 (1975-03-01), Sterki
patent: 3938113 (1976-02-01), Dobson
patent: 4217543 (1980-08-01), Strong
patent: 4241995 (1980-12-01), Takahama
patent: 4347478 (1982-08-01), Heerens et al.
patent: 4350981 (1982-09-01), Tanaka et al.
patent: 4420754 (1983-12-01), Andermo
patent: 4437055 (1984-03-01), Meyer
patent: 4543562 (1985-09-01), Burckhart et al.
patent: 4743902 (1988-05-01), Andermo
Do Diep
Presidium Promotions Limited
Strecker Gerard R.
LandOfFree
Measurement of capacitance and parameters related thereto for de does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measurement of capacitance and parameters related thereto for de, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measurement of capacitance and parameters related thereto for de will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2246983