Abstract: The present invention relates to a device for demonstrating the antistatic properties of at least one first transparent glass substrate, at least part of one of the main surfaces of which is an antistatic surface, said device comprising a hollow box having an upper surface provided with at least one window to which said first transparent glass substrate is fitted, wherein said box contains elements capable of moving under the action of electrostatic attraction, said elements being chosen from cellular particles of synthetic or natural polymers, individualized fibres of synthetic or natural polymers and their blends. The present invention further relates to a method for demonstrating the antistatic properties of at least one first transparent glass substrate by means of the above device.

Abstract: A sensor comprising: at least one sensor probe comprising: a pair of electrodes; a vertically aligned nanotube disposed between the pair of electrodes; optionally a piezoelectric polymer on the nanotube; and optionally, a field source for generating a field, the field source operatively connected to the pair of electrodes; whereby when the sensor probe is contacted, a change in the field occurs or electricity is generated. Methods of using the sensors are also described.

Abstract: A sensor 10 comprises an array of electrostatic sensor elements 12, each centred at a respective sensing position 14. Each element produces a respective output signal at 16. The outputs 16 can be used to drive respective pixels of a display. This allows an image to be created to represent the electrostatic charge distribution across the region to which the sensor is directed.

Abstract: A miniaturized and highly integrated optical deflection apparatus is realized in which the number of electrodes for driving the optical deflection apparatus is reduced. The optical deflection apparatus implements a sheet member that is electrically floating and plural electrodes that are implemented on a substrate. The sheet member includes a member having a light reflection region and an electret member that is charged at a predetermined electric potential. The sheet member is tilted by applying an electric potential that is substantially equivalent to an electric potential of the electret member to one of the electrodes and applying a ground potential to another one of the electrodes.

Abstract: An RF power sensor for measuring power for an RF signal using capacitance includes a substrate preferably formed of a semiconductor, such as silicon or of a dielectric substance, a fixture part fixed to the substrate and forming a signal line and ground lines that transmit RF signals, and a bridge connected to the ground lines and floating over the signal line, wherein the bridge is driven by an external driving force, and the external driving force induces capacitance between the bridge and the signal line. Accordingly, power for an RF signal can be measured through the capacitance between the signal line and the bridge. The RF power sensor facilitates matchings, reduces insertion loss, and can be used in a wide bandwidth because it is based on transmission lines having characteristic impedance. Further, high power can be measured depending upon bridge designs.

Abstract: A testing device is operative to sense or monitor a radiated field emitted by an igniter for heating equipment such as an oil burner and to indicate the detection corresponding to a normal operating state of the igniter.

Abstract: A capacitive actuating element is driven using a control signal of duration T1. This duration T1 is related to prescribed or measured values for charging, discharging and open periods T2, T3 and T4: (T1+T3?T2?T4)?|X| and is compared with a magnitude (limit value |X|). If a magnitude greater than |X| is obtained, then a fault is inferred.

Abstract: An on-board micro-electromechanical (MEMS) isolator is provided on board a power semiconductor device for measuring voltage, current, or both. In particular, the power semiconductor may comprise a plurality of transistors connected in parallel, such that a MEMS isolator connected in parallel with one of the transistors measures voltage across the semiconductor. A MEMS isolator may further be connected in series with the transistors to measure current flow thereacross. A compensation circuitry may be provided to receive the current output from the isolator, and determine total current flow through the power semiconductor.

Abstract: An electric potential sensor comprises a tuning fork having two legs; a detecting electrode provided on one leg of the tuning fork so as to face a surface of which an electric potential is to be detected; a driving piezoelectric member provided on at least one leg of the tuning fork; and feedback piezoelectric members respectively provided on both legs of the tuning fork.

Abstract: A Hall effect sensor or device may be used in a variety of embodiments, such as measuring current within an associated conductor by helping to measure flux density within a gap of a ferromagnetic power meter core, such as in a power meter. A high linearity interface for a Hall effect device is provided for minimizing offset effects without using complicated electronic circuits. Hall effect device is characterized by first and second opposing surfaces, first and second device inputs, and first and second device outputs. A substrate is layered adjacent to one of the first and second opposing surfaces of the Hall effect device and is electrically connected to an output pin of the Hall effect device to eliminate any effects caused by asymmetry of the voltage appearing in the channel relative to the substrate.

Abstract: A method for measuring the level of stress in a polymeric or pre-polymeric composition within a given volume that includes combining the polymeric or pre-polymeric composition with a plurality of microparticles having a non-ferromagnetic or non-ferrimagnetic core provided with a coating that is ferromagnetic or ferrimagnetic to form an admixture in which the microparticles are substantially uniformly dispersed throughout the composition. The microparticles have a detectable magnetic characteristic which correlates with level of stress in the composition within a given volume. The change in the magnetic characteristic of the microparticles is then measured to determine the level of stress in the composition within a given volume.

Abstract: Disclosed is a method and device for compensating a bias voltage on a wafer disposed over an electrostatic chuck in a processing chamber of a plasma processing system. The plasma processing system includes an electrostatic and RF power supplies that are coupled to the electrostatic chuck. The bias compensation device includes a voltage converter, a storage unit, and a voltage adjusting circuitry. The voltage converter is coupled to the electrostatic chuck for detecting a voltage Vpp of the electrostatic chuck. The voltage converter converts the detected voltage to a lower voltage Vref. The storage unit stores a predetermined slope and a predetermined offset of a calibration curve, which is derived by fitting a plurality of wafer bias voltages as a function of electrostatic chuck voltages.

Abstract: An electric potential sensor includes a piezoelectric tuning fork provided with a vibrating body of tuning fork type, a driving piezoelectric element provided on a first arm of said vibrating body, and a feedback piezoelectric element provided on a second arm of the vibrating body. A detection electrode is provided on the piezoelectric tuning fork. A signal-processing circuit, which is connected to the detection electrode, detects changes in the electric signal generated in said detection electrode which are attributable to the quantity of charge on the surface of an object to be measured. A self-oscillation circuit has an input end of which is connected to the feedback piezoelectric element and an output end of which is connected to the driving piezoelectric element. A gain control circuit is provided on the self-oscillation circuit. A comparator includes an input end which is connected to the feedback piezoelectric element and an output end which is connected to said gain control circuit.

Abstract: A method and apparatus for measuring a charge on a surface, such as on a semiconductor wafer, arising during plasma processing is provided. Such a charge may be measured on an insulating film applied to such a wafer. By the present invention, the charge on such an insulator exposed to plasma is measured in-situ using micro-cantilevers. The micro-cantilevers include an insulating base positioned on the substrate and a cantilevered beam extending therefrom to over the substrate. The beam is formed of a conductive material. A charge on the beam causes an opposite charge to form on the substrate. The opposite charges attract to move or deflect the beam towards the substrate. The amount of movement or deflection corresponds to the magnitude of the charge. This movement or deflection of the beam can be measured to determine the charge by bouncing a light source, such as a laser, off of the beam. In another embodiment, the cantilever includes a flexible bridge interconnected between the base and a rigid beam.

Abstract: A method and apparatus for measuring a charge on surface, such as on a semiconductor wafer, arising during plasma processing is provided. Such a charge may be measured on an insulating film applied to such a wafer. By the present invention, the charge on such an insulator exposed to plasma is measured in-situ using micro-cantilevers. The micro-cantilevers include an insulating base positioned on the substrate and a cantilevered beam extending therefrom to over the substrate. The beam is formed of a conductive material. A charge on the beam causes an opposite charge to form on the substrate. The opposite charges attract to move or deflect the beam towards the substrate. The amount of movement or deflection corresponds to the magnitude of the charge. This movement or deflection of the beam can be measured to determine the charge by bouncing a light source, such as a laser, off of the beam. In another embodiment, the cantilever includes a flexible bridge interconnected between the base and a rigid beam.

Abstract: An apparatus (2) comprising one substantially transparent electrode (12), a second shielded electrode (10) where the document (26) is to be placed between the first and second electrodes (12, 10), an optical device (18) capable of generating a rapid optical pulse that would be incident upon the document and an electrical impulse detection device connected to the second electrode (10) for detecting charge given off by the piezoelectric material in response to the optical pulse.

Abstract: Transformers of electric voltage meters based on mechanical waves. The invention is based on the generation of elastic waves in transformers which are composed of a transmitter, a receiver, a dielectric body and a mechanical connection, whereby the transmitter converts the variations in tension in elastic waves, which propagate through the dielectric body to the receiver by means of a connection device, and the receiver converts the mechanical waves in electric signals which are then amplified by means of an electronic unit in order to generate elastic waves from the electric fields from which electric waves are produced; piezoelectric and electrostrictive materials are utilized to build four different types of transformers depending on the structure: monolithic (one-piece), self-connecting, directly-connecting and externally-connecting transformers.

Abstract: A convenient, non-optical method for scanning probe microscopy tip-to-sample distance control based on the impedance change in a shear-force dither piezo. This is accomplished by determining the tip-sample distance by measuring the impedance change in a shear-force piezo-member. A Wheatstone type bridge can be utilized to regulate the tip-sample separation. Alternatively, an electrical bridge, having an output, regulates the tip-sample separation relative to the bridge output by driving the piezo/tip with a sine wave and combining said sine wave with a phase-referenced wave of equal amplitude at a 180.degree. phase shift. The electronic bridge detects impedance changes of about -100 dB across loads with impedance phases between -90.degree. to +90. Power dissipation is determined by measuring changes in electric impedance that a dither piezo presents to an oscillator.

Abstract: A handheld fieldmeter is implemented with an automatic function to drive the voltage on an output node of signal processing circuitry to circuit ground while a sensing electrode is disposed in a static-free environment. In response to a binary signal indicating whether the output node voltage is above or below ground, a microprocessor repeatedly increments/decrements a stored auto-zero multibit number, and generates successive PWM pulse streams of differing duty cycles determined by the incremented/decremented auto-zero number. The successive PWM pulse streams are integrated to ultimately produce fine zero adjustment current used by the signal processing circuitry to drive the output node voltage essentially to circuit ground. The fieldmeter also includes a pair of LEDs relatively positioned with the sensing electrode to emit light beams that intersect at the surface of a charged object when the sensing electrode is positioned a prescribed distance from the charged object.

Abstract: A movement actuator includes an elongate filament made of a flexible material, and a strip of shape memory alloy disposed on the surface of one side of the filament. The shape memory alloy is responsive to actuation signals, heat or electrical signals, for changing its shape and when its shape changes, it causes the filament to move, i.e., bend, to accommodate the change in shape of the alloy. Also included is a signal supply device for selectively applying heat signals or electrical current to the strip of shape memory alloy to causes the alloy to change its shape and cause the filament to bend. Other patterns for the shape memory alloy could be disposed on the filament to cause other kinds of movements. For example, a helical pattern of the shape memory alloy about the filament would cause the filament to twist when the helical pattern were caused to shorten or lengthen.

Abstract: An electrometer having small width size and stable characteristics includes a chopper portion for chopping electric line of force emitted from an object to be measured. The chopper portion is constituted with a tuning fork type bending vibrator including a first metal plate as a detection electrode portion for receiving electric line of force, a second metal plate and an insulating plate for connecting the first and second metal plates in a plane. The bending vibrator is arranged such that its vibrating direction is coincident with direction of electric line of force, so that the width size of the electrometer can be reduced and the characteristics thereof can be stabilized.

Abstract: The invention is a method and apparatus for electrostatic potential sensing by using electromechanical microstructures. The mechanical microstructure may be fabricated by either surface micromachining or bulk-micromachining. The sensor comprises a movable plate which is movable in the lateral dimension and which is suspended from and above a substrate bearing an isolated electrically conductive layer. The layer acts as the sensor electrode and is brought in contact with or near the object the electrostatic potential of which is to be sensed. The movable plate is suspended between two fixed, suspended and cantilevered plates. The three suspended plates collectively form two capacitors with the two fixed plates comprising the first plate of first and second capacitors and the movable plate comprising the second plate of both capacitors.

Abstract: An electrostatic voltmeter suitable for use in a non-contacting, positive or negative potential sensing, type electrostatic voltmeter. The invention enables a flexible, low cost electrostatic voltmeter to be produced using high-voltage field-effect transistors in the circuit design. The invention further includes input conditioning components that enable high-voltage sensing and high-voltage feedback in such a manner that processing of the input signal from the sensor is accomplished without producing a variation in the current passing through the field-effect transistor in response to voltage variations. Elimination of this variation further reduces the susceptibility of the remaining signal processing circuitry to transient direct current signals. A differential cascode as the input stage is the preferred configuration for the input conditioning components.

Abstract: A probe assembly for measuring resistivity of a soil is connected to a measuring apparatus capable of generating a constant DC current signal into two electric leads. The probe assembly includes a short circuit connector; double-pole double-throw switch having two fixed contacts, and two switched contacts alternatively connectable to the electric leads or to the short circuit connector, respectively; and two electrodes connected to the fixed contacts respectively. Each of the electrodes has a portion of its surface forming a conductive surface. The conductive surfaces are substantially opposite to each other when the electrodes are put into the soil. In a stand-by position, the switched contacts are connected to the short circuit connector.

Abstract: A circuit tracer for determinating the location of a conductor, such as a wire, which is either an open or closed circuit, and which may lie underground. The tracer includes a transmitter which is connected to the conductor, a hand-held probe, and a receiver which is connected to the probe. The probe has three different sensors: an electric field sensor, primarily for locating the terminus of an open-ended conductor or for distinguishing such a wire in a bundled cable of wires; a differential electric field sensor, for determining the direction to and location of an open-ended conductor located above ground; and an inductive sensor for determining the direction to and location of a current-carrying conductor, including an open-ended conductor lying below ground. A switch selectively provides the output from one of the sensors to the receiver unit, which determines the magnitude of any signal based upon the direction the probe is pointing.

Abstract: A ground-free device for measurement of electrostatic potentials on objects. The device is based on the fundamental concept that the static charge on most objects can be estimated by means of a discharge terminal equipped with a capacitor.

Abstract: A sensor for electrical charge fabricated as an integrated circuit and including an electrode (1) for receiving charge, a potential-sensitive switching device (2) for generating a pulse whenever the charge received on the electrode (1) is sufficiently great, a counting device (4) for counting the number of times the switching device operates, and a member (3) for restoring the potential on the electrode (1) to its initial potential each time the switching device (3) operates and/or continuously towards its initial potential. An integrated circuit having an array of such sensors and digital logic for controlling their operation is included. The array may be used as a multiple-channel detector for charged particles, particularly as a detector for electrons emerging from a channel plate electron multiplier. Dispersive particle and photon spectrometers, especially mass spectrometers, using such a detector are also provided.

Abstract: An electrostatic voltmeter adjacent to the surface of a photoreceptor belt or drum between, for example, the electrostatographic imaging station and developing station. A surface of the photoreceptor is charged at a charging station and the charged area is rotated and stopped adjacent to the electrostatic voltmeter. After a predetermined period of time, the surface potential of the charged area is measured by the voltmeter. Additional measurements can be made at subsequent times to determine a dark decay rate of the charged photoreceptor. Surface potentials at other areas adjacent the photoreceptor surface, such as in the development zone, can be determined based on the initial voltage applied to the photoreceptor surface at the charging station and the rate of dark decay. The invention allows for close monitoring/control of the surface potential at one or a plurality of development zones without the need for locating voltmeters within each development zone.

Abstract: A system for transducing a signal voltage into an optical signal, transmitting the optical signal via an optical fiber to a remote location in the form of light attenuation frequency and interpreting the light frequency at the remote location to the amplitude and wave form of the signal voltage. The electro optic modulator includes an elongated piezoelectric member which changes length when an electric field is imposed across it. A mirror is attached to a free end of the piezoelectric member and strains or alternately moves toward and away from a partially reflecting surface at the end of an adjacent optical fiber. Light is introduced into the fiber with a portion reflected back by the movable mirror and part by the end of the fiber. A detector at the second end of the optical fiber receives the reflected light.

Abstract: The invention is an instrument for determining the work functions (unbiased) or absolute surface potentials (biased) of conducting sample surfaces. These values are inferred from measured surface potential differences between the sample and the instrument's non-contacting sensor. Charge incurred in the sensor by the proximity and surface potential of the sample surface alters the impedance of a semiconductor channel within the sensor. The deviation in the charge dependent impedance of the sensor from a calibrated zero-field reference is used by a feedback controller to alter the base potential of the sensor to eliminate the deviation signal. In this state, the surface potential of the sensor matches that of the sample thus forming a zero-field condition, as a result no charge is induced in the sensor. The surface potential difference between the sample and the sensor is then equal to the sensor base voltage, which is directly measured by a voltmeter.

Abstract: A sensor for measuring disturbances to an electrostatic field caused by the intrusion of a charged body or a charge producing body. The sensor employs at least two probes displaced from each other which have attached beads of radioactive material to provide free ions in the vicinity of the probe. The free ions enhance the signal created by each probe when it is affected by a disturbance in the electrostatic field in which it resides. The signals thus created are conditioned for transmission to a differential amplifier which combines them and produces an output signal which represents the detection of an intruding charged body, its distance, and its characteristics. The sensor can be configured with more than two probes seeded or placed in an array and a computer for real-time selection of the two yielding optimum signals for charged body location, velocity, direction of travel, and electrostatic signature.

Abstract: A non-contacting electrostatic voltage follower comprising a detector electrode sensitive to electrostatic quantities such as electrostatic fields, voltages, charges and the like, a modular coupled to the electrode for modulating the capacitance coupling between the electrode and a surface bearing an electrostatic quantity to which the electrode is exposed, a detector amplifier of the current summing type having the summing input thereof connected to the detector electrode, and a high bandwidth amplifier having an input connected to the output of the detector amplifier. A probe comprises a transparent carrier element coupled to the modulator, a first conductive and transparent film on a surface of the carrier and defining the detector electrode, and a second film of conductive and transparent material on the remainder of the surface of the carrier and spaced from the first film.

Abstract: A non-contacting electrostatic voltage follower employs a vibrating capacitance detector coupled to a measured surface containing both wideband electrostatic A.C. data and D.C. potentials. A detector amplifier having an inverting input is connected to the detector, while its output is connected to the input of a high bandwidth amplifier. A first feedback path is provided from the output of the high bandwidth amplifier to the non-inverting input of the detector amplifier which provides both a signal which is equal to and follows the wideband electrostatic A.C. potentials on the measured surface, and a signal, at the vibrating capacitance modulation frequency, representative of the D.C. potential of the measured surface. A second feedback path is provided including a demodulator and integrator to monitor the first feedback path to provide a D.C.

Abstract: Direct voltage measurements of electrical signals are extracted from transmission lines for display in a manner to permit such measurements with picosecond temporal and submicron spatial resolution utilizing a noncontacting electro-optic probe. The probe may have multiple quantum well (MQW) structure. The NQW structure defines an active region sufficiently small (less than a micron if desired) in width so that it can be placed between neighboring lines on an integrated circuit. A short pulse laser beam is used to sense the absorption change at the time window of interest. The electroabsorption effect in the MQW structure is a nonlinear function of the strength of the electric field. Detection can be carried out by sampling techniques to provide the measurement of the voltage or the display of the signal.

Abstract: An electrostatic voltmeter with probe for measuring the charge on a surface, the probe comprising a microdeflector unit having a base; a flexible finger supported on the base in cantilever fashion, the finger deflecting in response to a potential difference thereacross; means to bias the base to a predetermined potential; a sensing electrode on the finger having a side positionable in spaced relation to the surface, the capacitive relation established creating a charge representative of the charge on the surface on the sensing electrode causing deflection of the finger; means to impinge a beam of light on the finger; and a detector disposed to detect reflection of the beam by the finger on predetermined deflection of the finger corresponding to a preset charge measured on the surface.

Abstract: A non contact voltmeter includes a multilayered structure adapted to configure a plurality of coupled capacitors in a manner to permit high speed operation. A high frequency input signal is applied to a plate capacitivity coupled to both the test object and a sensor. The structure is also configured to capacitivity couple the sensor directly to the test object. The structure allows for circuit configurations with low time constants permitting outputs at the input frequency as well as a small and inexpensive solid state configuration.

Abstract: This invention relates to a voltage sensor for sensing a voltage on an electrically charged object such as a distribution line or the like, the sensor being disposed with an insulation space to the object. The voltage sensor includes an amplifier circuit for outputting a signal having a waveform similar to that of a displacement current inflowing from the electrically charged object via the insulation space, and a filter circuit for extracting a signal having predetermined frequencies from the output of the amplifier circuit and outputting an alternating current waveform similar to the potential of the electrically charged object.

Abstract: A surface potential detector of a non-contact type which comprises first and second detecting electrodes arranged in a separated manner from a measured surface so that charge variations are induced on the first and second detecting electrodes on the basis of the potential of the measured surface. The surface potential detector further comprises apparatus for making the amounts of charge variations induced on the first and second detecting electrodes different from each other, first and second detecting devices respectively detecting the amounts of charge variations induced on the first and second detecting electrodes and correction apparatus for performing arithmetic on the ratio between the outputs from the first and second detecting devices to correct the output of the first or second detecting devices on the basis of the ratio.

Abstract: For the measurement of the voltage parameters, such as instantaneous value, phase position, absolute value or sign of the high voltage of a high voltage conductor (1), a sensor (15) is conductively connected with a reference electrode and a non-earthed electrode (10) arranged along an equipotential surface in the proximity of the high voltage conductor (1), which electrodes both lie at a defined potential. The reference electrode can be the high voltage conductor (1), a second electrode (50) arranged on an equipotential surface or an auxiliary conductor (57) conductively connected with the high voltage conductor (1). The sensor, which can be a one-sidedly clamped mechanical piezo-oscillator, modulates the brightness of a radiated-in light bundle (32), which is reflected to the measuring device, converted by a receiver (40) into an electrical signal and evaluated.

Abstract: Apparatus and method for mapping an existing electric field involve exposing a field responsive element to the electric field to produce movement of the element in the path of a light beam, and detecting modulation of the light beam by the element. In a preferred embodiment the light beam is passed to and from the field responsive element by optical waveguides.

Abstract: The invention is directed to an optical fiber device for measuring of current and/or voltage, including at least one light conductor for transmitting optical signals between an optical transducer and light generating and light processing circuitry, respectively. A sensed electrical measuring signal is transmitted to a transducer for conversion to a mechanical movement which modulates the light flux received by the transducer.

Abstract: A panoramic electrostatic field sensor includes a central monitoring electrode for detecting an electrostatic field oriented about a 360.degree. arc peripheral thereto. An apertured housing is concentrically arranged about the monitoring electrode, the housing having circumferentially spaced windows through which the central electrode can "see" any electrostatic field radially disposed with respect to the sensor. A cylindrical shielding cap is rotated in the annular space between the monitoring electrode and the housing, the cap incorporating at least one slot to expose the monitoring electrode periodically to any fields viewed through the housing windows. Electronic means for measuring the voltage in response to the field detected is adapted to activate a static neutralizer for emission of positive and negative ions into the field or to actuate a variety of peripheral indicating or triggering devices which provide signals, alarms or readout functions.

Abstract: A current sensor, integratable with power switching and control circuitry on a common substrate and insulatable from current-carrying conductors, utilizes a piezoelectric element located between a pair of current-carrying conductors. The conductors carry a current flowing in the same direction, causing an attractive force therebetween to act upon the piezoelectric element and generate a voltage therein proportional to the square of the conductor currents. Use of a pair of sensors, each in a different portion of a half-bridge circuit, and associated electronics for providing a sensor output proportional to the instantaneous value of the sensed current, is also described.

Abstract: A current sensor, responsive to the first power of a current to be measured, utilizes a piezoelectric element located between a current-carrying conductor and a permanent magnet having its north-south poles aligned normal to the direction of current flow through the conductor. The substantially constant magnetic field provides a sensor output, taken from electrodes upon opposite surfaces of the piezoelectric member, which is proportional to the first power of current flowing in the single conductor.

Abstract: A voltage and electric field measuring device using light as an operating parameter. An electro-optic crystal, a quarter-wave plate, and a polarization analyzer are arranged in that order in the direction of advancement of applied light. A voltage may be applied to the electro-optic crystal through electrodes arranged thereon. The electro-optic crystal belongs to a cubic system, such as bismuth silicon oxide or bismuth germanium oxide.

Abstract: In a generator of strobe signals an electret is interposed between a fixed and a movable armature moving with a translatory or rotary movement. The strobe signals are generated by the electrostatic induction of the electric charges trapped in the electret according to a selective flux pattern.

Abstract: An electrometer having reduced spacing sensitivity, with the electrometer including a probe with a charge receiving sensor element and a surrounding shield. A voltage equivalent to that sensed by the probe element is fed back to the shield to render the electrometer substantially spacing insensitive. A duty cycle control regulates the width of electrical pulses to a power transformer whose output is fed back to the probe shield to maintain the spacing insensitivity. Means are also provided to automatically test and calibrate the electrometer prior to use.

Abstract: An apparatus is disclosed for measuring the electron escape potential (or: Volta potential) of a metal surface. This apparatus comprises a conductive plate to be placed into the vicinity of and parallel to a metal surface under examination in order to form a capacitor; switch means for electrically connecting the conductive plate to a reference potential point; means for subjecting the conductive plate to vibration in a direction vertical to the metal surface; and an external circuit for measuring a measuring potential which is proportional to a current emitted by the capacitor. The conductive plate together with the switch means and part of the vibration-generating means are located in a probe and this probe is connected with the remainder of the apparatus by means of a flexible line which includes the required electric connections.

Abstract: Feedback circuit for the probe of an d.c. type electrostatic voltmeter to reduce spacing sensitivity thereof. A variable gain amplifier is employed to control the amplitude of the a.c. signal output of a square wave oscillator in response to the potential sensed by the probe. The a.c. signal output drives a high voltage transformer, the output of which is rectified to provide a d.c. signal output matching the potential sensed by the probe. The d.c. output is returned to the probe housing to bias the housing to a potential equal to the potential read by the probe. A sample and hold circuit enables readout of the d.c. signal output.

Abstract: A rapid-response generating voltmeter for measuring a high d-c voltage between a high voltage electrode and ground comprises two sets of stator segments, the segments of each set being electrically interconnected and each set being connected through its own capacitor to ground. Each set of stator segments has a time-varying capacitance with respect to the high voltage electrode, but the sum of these time-varying capacitances is maintained substantially constant with time.First and second circuit means respectively sense the voltages e.sub.1 and e.sub.2 present across said two capacitors and develop first and second intermediate signals e.sub.5 and e.sub.6 substantially proportional to e.sub.1 and e.sub.2, respectively, minus, in each case, an error voltage attributable to discharge of the associated one of said capacitors. Summing means develops an output signal substantially proportional to the instantaneous sum of e.sub.5 and e.sub.