A capacitive motion encoder, for sensing the position of a moving object relative to a stationary object, includes at least one stationary element, coupled to the stationary object and a moving element, coupled to the moving object and in proximity to the stationary element. A field transmitter generates an electrostatic field, which is modulated by a change in capacitance between the stationary and moving elements responsive to relative motion of the elements. A conductive shield, is electrically decoupled from both the moving and the stationary objects, and encloses the moving and stationary elements so as to shield the elements from external electrical interference. Processing circuitry is coupled to sense the modulated electrostatic field and to determine responsive thereto a measure of the position of the moving object.

Capacitive displacement encoder

The present invention relates to an optical sensor apparatus (21) for remotely monitoring a utility meter or the like. The optical sensor apparatus (21) includes optically sensitive detector, in this case, a dynamic RAM device (40) which consists of an array (42, 44) of light sensitive elements. Light from a light source (56) is reflected off the faceplate (52) of the meter. Microprocessor control system (100) operatively interconnected to the optically sensitive dynamic RAM device (40) controls the exposure of the RAM device (40) to the light. The microprocessor control system (100) further determines the angular position of the individual pointer members (50) of the meter by correlating a binary image stored in memory to a predetermined geometic shape. The microprocessor control system (100) further includes logic for converting the angular positions of the pointer members (50) of the meter stages to a decimal value representative of the meter reading. A transmitter device is operatively interconnected to the microprocessor control system (100) for transmitting the decimal values to a remote site.

Optical sensor apparatus and method for remotely monitoring a utility meter or the like

Displacement of a movable transducer element is measured by exciting a capacitive gap (preferably differential capacitive gaps) with triangular waves of voltage to obtain a square current wave output into a zero input impedance amplifier. The square wave output is amplified and synchronously detected to produce a d.c. output signal proportional to displacement. The d.c. output signal is fed back to force rebalance electrodes to electrostatically rebalance the movable transducer element. The feedback signal is a measure of the force being transduced. Initial offsets in the position of the transducer element and capacitances of the capacitive gaps are compensated by signals derived from the capacitive gap excitation waveforms.

Capacitive detector for transducers

A device for measuring the relative position of two objects by variation of capacitance. The device comprises a capacitive detector of the differential type which has at least two first electrodes adapted to be mechanically connected to one of the objects and at least a second electrode adapted to be mechanically connected to the other object and forming with the first electrodes two capacitances which vary as a function of the relative position of the objects. These two capacitances are in a ratio which is only a function of this relative position. There is provided a circuit for determining the values of these capacitances. The measuring device further comprises switching means for selectively connecting said capacitances to the input of said value determining circuit so as to measure successively said capacitances and also the parasitic capacitance inherent in the measuring system.

Device for measuring the relative position of two objects

The present invention relates to a magnetic sensor apparatus (21) for use in a remote meter monitoring system (20) for remotely monitoring the dials (54a-e) of a utility meter (56) by use of Hall Effect devices (40-49). The Hall Effect devices (40-49) are concentrically positioned about the axis of rotation of a pointer member (64) having a permanent magnetic member (66) attached to a free end thereof. The Hall Effect devices (40-49) are axially displaced from the permanent magnetic member (66) and are in alignment with the circumferential path of travel of the permanent magnetic member (66). A microprocessor (68) electrically interconnected to the Hall Effect devices (40-49) selectively drives each of the Hall Effect devices (40-49). The microprocessor (68) further monitors the Hall Effect devices (40-49) and obtains output signals therefrom representative of the angular position of the pointer member (64).

Magnetic sensor apparatus for remotely monitoring a utility meter or the like

A contactless rotational angle transducer for developing an output signal indicative of the angular position of a rotatable object comprising a fixed stator plate having a plurality of electrically isolated sector members, a parallel spaced-apart confronting plate, and a sector rotor plate situated between the stator and confronting plates and rotatably coupled to the rotatable object. An AC excitation voltage is impressed at a fixed phase relationship on each sector member such that the voltage induced in the confronting plate is a function of the angular position of the rotor plate. A pulse generator circuit responsive to the relative phase difference between the voltage induced on the confronting plate and the applied excitation signal develops a pulse-width modulated or pulse-positionmodulated output signal indicative of the angular position of the rotatable object, wherein the number of complete or partial turns of the rotatable object can be measured.

A Shimotori

Papers

Rotational angle transducer