Abstract: A position encoder is described that generates a signal whose phase varies with a position to be determined. A phase detector determines a first phase measurement of the sensor signal during a first mode and a second phase measurement of said sensor signal during a second mode. The phase detector then differences the first and second phase measurements to obtain a phase difference measurement, which it uses to determine an indication of the position to be sensed. A controller controls a signal generator in order to set a start phase of signals generated in at least one of the first and second modes so that the timings at which said sensor signal crosses a reference level are substantially the same.

Abstract: An obstacle detection system includes a static capacitance detection module including a sensor strip for detecting a static capacitance, an RF oscillator connected to the sensor strip, a phase lock loop section for maintaining the oscillation frequency of the RF oscillator to a selected value and a first MCU for controlling the operation of the phase lock loop section, a control module including a second MCU for remotely controlling the first MCU of the static capacitance detection module and a transmission line for connecting the static capacitance detection module and the control module and transmitting the information acquired by the first MCU so as to be transmitted to the control module, a control signal to be transmitted from the second MCU to the first MCU and drive power of the static capacitance detection module.

Abstract: Provided is a multi-channel capacitive sensing circuit, in which at least one capacitive sensor has the capacitance changed corresponding to the change of external environment, and generates change signals corresponding to the capacitance change, respectively. An oscillator outputs a carrier wave modulating the capacitance change signal. At least one capacitance-to-voltage converter receives the capacitance change signals modulated by means of the carrier wave and outputs voltage signals corresponding to the modulated capacitance change signals, respectively. A multiplexer receives the voltage signals, selects any one of the voltage signals and sequentially outputs them. An analog-to-digital converter (ADC) receives the voltage signals outputted from the multiplexer, converts them into digital voltage signals and outputs them. Accordingly, it is possible to output the capacitance change signals each generated in the at least one capacitance sensor to one ADC using the multiplexer.

Abstract: A capacitance-type encoder capable of obtaining position data of a movable element with low power-consumption. The capacitance-type encoder comprises a stator, a movable element arranged to confront the stator, an excitation device and a signal processing device. The stator has at least three excitation-electrode sets electrically independent from each other, each set constituted of excitation electrodes arranged cyclically and electrically connected with each other so that a predetermined number of excitation-electrode groups are formed. The movable element has connection electrodes having the same number as the excitation-electrode groups. The excitation device applies excitation signals to the excitation-electrode sets periodically in a predetermined sequence.

Abstract: A system for measuring clearance between a first object and a second object is provided. The system includes a sensor configuration to generate a first signal representative of a first sensed parameter and a second signal representative of a second sensed parameter. The system also includes a clearance measurement unit configured to process the first and second signals based upon a ratiometric technique to calculate clearance between the first and second objects.

Abstract: The present invention is a detection device, system and method for detecting an external electromagnetic event such as lightning or a high intensity radiated field. In an exemplary embodiment, the detection device includes a free space capacitive sensor and a protected amplifier circuit coupled with the free space capacitive sensor. The free space capacitive sensor and the protected amplifier circuit are configured to respond to a voltage waveform produced by an external electromagnetic event. The free space capacitive sensor serves as a single input capable of detecting the external electromagnetic event and the coupling of the free space capacitive sensor to the protected amplifier circuit allows subsystems in communication with the sensor and amplifier circuit to generate a coordinated response to the detected external electromagnetic event.

Abstract: A circuit for detecting the presence, position or the approach of an object in an observation area, the circuit has a sensor electrode assembly with an electrode that forms part of a capacitor system whose capacitance relative to a reference potential (e.g. ground) is dependent on the presence, position or approach of objects in the observation area. An evaluation circuit coupled to the sensor electrode detects a phase shift of the capacitance of the condenser system. An LC network is coupled to the capacitor system, and an oscillator connected to the electrode applies a frequency to the system formed by including the electrode and the LC network at a frequency within the range of a parallel resonance frequency of the LC network.

Abstract: A capacitance detection circuit containing an input protection circuit and having high sensitivity is provided. A capacitance detection circuit for detecting the capacitance of a capacitive sensor, comprising a buffer amplifier connected to the capacitive sensor via a signal wire and having a voltage gain of 1; diodes connected in series between the signal wire and a positive power supply; diodes connected in series between the signal wire and a negative power supply, wherein an output terminal of the buffer amplifier is connected to a junction point of the diodes and to a junction point of the diodes.

Abstract: Methods, systems and devices are described for determining a measurable capacitance for proximity detection in a sensor having a plurality of sensing electrodes and at least one guarding electrode. A charge transfer process is executed for at least two executions. The charge transfer process includes applying a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, applying a first guard voltage to the at least one guarding electrode using a second switch, sharing charge between the at least one of the plurality of sensing electrodes and a filter capacitance, and applying a second guard voltage different from the first guard voltage to the at least one guarding electrode. A voltage is measured on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.

Abstract: Disclosed is a measurement system for measuring subsurface resistivity. The surfaces of interest are, for example, engineered surfaces such as roads and dams, and non-engineered surfaces such as greenfield sites. The measurement system may also be used on biological materials. The system includes signal input electrodes for inputting an input signal into subsurface material by capacitive coupling. Pairs of signal detection electrodes allow capacitive coupling detection of a detectable signal caused by the input signal in at least some of the subsurface material. A phase-sensitive meter such as a lock-in amplifier is provided to measure the amplitude and phase of the detectable signal.

Abstract: The present invention relates to a on-chip circuit for on silicon interconnect capacitance (Cx) extraction that is self compensated for process variations in the integrated transistors. The circuit (10) comprises signal generation means (20) for generating a periodical pulse signal connected to first and to second signal delaying means (31, 32) for respective delaying said pulse signal, wherein said second signal delaying means (32) are configured to have a delay affected by said interconnect capacitance (Cx); a logical XOR gate (35) for connecting respective first and said second delay signals of said respective first and second delay means (31, 32), said logical XOR gate (35) being connected to signal integrating means (40); and said signal integrating means (40) being connected to analog to digital converting means (50).

Abstract: According to the present invention an S-parameter file input section inputs S-parameters for each device constituting a system subject to a transmission analysis, a port position correspondence conversion section converts the input S-parameters so as to correspond to preset port positions to be connected, an S-parameter/T-parameter conversion section converts S-parameters to T-parameters, a connection calculation section carries out a connection calculation of T-parameters to obtain T-parameters of the entire system, a T-parameter/S-parameter conversion section converts T-parameters of the entire system to S-parameters of the entire system and an S-parameter file output section outputs S-parameters of the entire system.

Abstract: This invention is a method to determine the condition of rotating equipment, namely drive spindles, to enable the timely maintenance or replacement of same. The method uses an electrical signal from a vibration sensor mounted on part of the drive train to measure the level of vibration energy when the equipment is rotating under loaded and unloaded conditions. The relative vibration under the loaded and unloaded conditions is used as an indicator of equipment condition. Typically there is more vibration under load when the equipment is in good condition. When the level of vibration under the no-load condition matches or exceeds that seen under load, the equipment needs to be serviced or replaced.

Abstract: The present invention provides a capacitive sensing apparatus having utility in object detection security applications whereby the object detection field generated by the apparatus is made steerable. The apparatus includes a power source having a ground connection in communication with at least one sensing circuit operative to detect an object moving within the sensing field. At least one conductive element is provided in communication with electrical ground. To steer the direction of the sensing field, the relative position and distance between the conductive element and the sensing circuit is adjusted such that a desired sensing field pattern is obtained.

Abstract: A magnitude of radio frequency voltage and current, input into a load from a radio frequency power source, are measured at a single point along a transmission line. Phase difference between voltage and current is also measured. These measurements are used to compute VSWR and forward input power. The computed measurements may be compared against predetermined VSWR limits, and operation of the radio frequency power source can be adjusted to prevent damage to the detection apparatus or load.

Abstract: A circuit for detecting a difference in capacitance between a first capacitor and a second capacitor provided in a sensor includes an oscillator configured to generate an oscillating signal, a phase comparator coupled to the oscillator to output a signal responsive to a phase difference between the oscillating signal delayed by the first capacitor and the oscillating signal delayed by the second capacitor, an integration circuit coupled to the phase comparator to output an integrated signal made by integrating the signal responsive to the phase difference over a time period equal to a predetermined number of cycles of the oscillating signal, and a sample-and-hold circuit coupled to the integration circuit to output a signal made by sampling and holding the integrated signal at substantially an end of the time period.

Abstract: A Moisture and Density Detector (MDD) provides a method and apparatus to determine the moisture content and/or density, as well as presence and location of anomalies, and/or wood type of any dielectric material for various purposes. This device is very useful in detecting the moisture content of wood and wood-based materials, such as that of lumber in a dry kiln prior to, during and/or following drying. The MDD passes a radio frequency signal and/or any other signal between opposed or adjacent capacitance electrodes and measures the signal strength and phase shift of the signal. The addition of phase shift and multiple frequencies improves the accuracy of the results.

Abstract: The present invention provides a capacitive sensing technique that is advantageously useful for security applications wherein digital technology is used to measure frequency shifts caused by a conductive or grounded object moving within a capacitive sensing field. The system includes a floating reference to compensate for drifting or offsets caused by electrical noise or other environmental conditions. The system also includes a CPLD integrated circuit or microprocessor and operative to monitor changes in a sensing field signal and digitally compare a reference signal to the sensing field signal such that when a difference between the two signals exceeds a predetermined threshold, an object detection signal is generated by the monitor circuit which causes the activation of an alarm signal.

Abstract: An impedance spectroscopy technique and system for detecting in real time engine coolant contamination in lubricant. A probe is disposed in the lubricant and the probe excited with an a.c. voltage frequency sweep over a selected frequency range. The current and current phase angle are measured at selected frequency intervals and the reactance and resistance computed and plotted at each frequency internal as Nyquist plots. The Nyquist minimum is determined at various lubricant temperatures and a database compiled. The probe is then excited in-situ and current measurements taken for a selected frequency lower than the Nyquist minimum to insure measurement of electrode surfaces characteristics. The reactance and resistance are then computed and the angle ? of change (slope) of reactance with respect to resistance computed. The value of ? is then compared with values of contamination concentration ? versus ? in a database, and the value of ? determined by interpolation.

Abstract: A wood drying installation for a wood drying kiln including a pair of electrodes adapted to be inserted into a wood stack contained in the kiln, a resistance connected in a series circuit with the electrodes, an AC voltage source connected to apply an AC voltage across the series circuit, a phase detecting circuit connected to the series circuit operable to generate a signal representing the phase angle between AC voltages applied to different parts of the series circuit, and a processor to receive the signal. The system is operable to determine a moisture value corresponding to a capacitive component of the reactive impedance between the electrodes in accordance with a predetermined arithmetic algorithm relating the value to the phase angle.

Abstract: A method, apparatus and article of manufacture to aid in the characterization of a device establishes a device S-parameter matrix (SD) to represent electrical behavior of the device, an adapter T-parameter matrix (Ta) to represent all possible electrical paths through circuits to all device ports of the device, and a cascaded S-parameter matrix (Sc) to represent the circuits cascaded with the device. Values for the adapter T-parameter matrix are obtained either through measurement or modeling. The device cascaded with the circuits is measured to obtain values for the cascaded S-parameter matrix, permitting use of a general solution for the device S-parameter matrix as a function of the adapter T-parameter matrix and the cascaded S-parameter matrix.

Abstract: Method and apparatus for accurately determining the presence of voltage at capacitive test points and for determining the phase angle relationship between two capacitive points. The detection of the presence of the voltage at the capacitive test points is independent of the voltage range in the systems, independent of the contamination or defects that may occur in the capacitive test point systems. The phase angle relationship is determined based on the actual phase angle difference between the voltage waveforms at the capacitive test points independent of the capacitive divider ratio difference and the capacitive test point voltage accuracy.

Abstract: A method and apparatus for detecting moisture. An oscillatory electrical signal S1 generated by an oscillator is propagated into a body that includes an electrically insulative material. A signal due to S1 emerges from the body as an oscillatory electrical signal S2. The signals S1 and S2 differ in phase by ??, wherein ?? is indicative of moisture along a path traversed by S1 within the insulative material, and wherein the conductance ? of the insulative material is also indicative of the moisture along the path traversed by S1 within the insulative material. S2 is received at a sensing surface of a sensing part (e.g., probe, sensing antenna, etc.) and then transmitted to a moisture detecting device. The moisture detecting device determines from S1 and S2 a measure M of the moisture as a function of ?? or as a function of ?.

Abstract: A circuit configuration for assessing capacitances in a matrix, which has a number of rows with at least one capacitance in at least one dimension, includes a test arm connected to first electrodes of each of the capacitances to be assessed and by which two different potentials can be applied to the first electrodes, a measurement arm connected to second electrodes of each of the capacitances to be assessed and that has a first measurement path and a second measurement path connected to a common potential. The first measurement path has an instrument for assessing the capacitances and the first and second measurement paths can be connected to the second electrodes. The circuit configuration has a drive device that connects each of the capacitances to be assessed individually to the two different potentials.

Abstract: a measurement apparatus which measures a distance between a sensor probe and a target to be measured by using an electrostatic capacitance sensor, comprises first and second sensor probes (101, 102) which are arranged at respective predetermined gaps to the target (4), and first and second sensor amplifiers (111, 112) which are connected respectively to the first and second sensor probes, wherein when the distance between the target and the first or second sensor probe is measured, said first amplifier supplies a first current with the first sensor probe and said second amplifier supplies a second current which is different phase and/or amplitude from the first current.

Abstract: A wood drying installation for a wood drying kiln including a pair of electrodes adapted to be inserted into a wood stack contained in the kiln, a resistance connected in a series circuit with the electrodes, an AC voltage source connected to apply an AC voltage across the series circuit, a phase detecting circuit connected to the series circuit operable to generate a signal representing the phase angle between AC voltages applied to different parts of the series circuit, and a processor to receive the signal. The system is operable to determine a moisture value corresponding to a capacitive component of the reactive impedance between the electrodes in accordance with a predetermined arithmetic algorithm relating the value to the phase angle.

Abstract: A system and method for measuring capacitance between a probe and a semiconductor sample, which may be useful in the field of scanning capacitance microscopy (SCM). The present invention also includes a method for analyzing measured capacitance data by subtracting any changes in capacitance that are due to changes in long-range stray capacitance that occur when the probe assembly is scanned.

Abstract: An apparatus for monitoring deposition of a liquid-to-pasty medium on a substrate has a sensor fitted with two electrodes and an electronic circuit connected to the sensor for generating a signal which is characteristic of the substrate and the medium. The electronic circuit measures the imaginary component of the electrical permittivity of the substrate moving, together with the medium, between the two electrodes, and uses the measured value to determine the characteristic signal.

Abstract: Disclosed is a single-stage, switched capacitor circuit for measuring changes in a variable by measuring changes in a capacitor gap. The change in the capacitor gap corresponds directly to a change in a measurable variable, such as pressure and acceleration, and thus a change in voltage. The circuit includes at least one reference capacitor, a sensor capacitor, a plurality of switches responsive to a timing device, and a device for generating substantially constant reference voltages. The sensor circuit does not result in a DC offset value, but results in the AC component of the voltage being directly proportional to the change in the variable through a substantially constant voltage is supplied to a node near the sensor capacitance. The circuit may be trimmed using a digital to analog converter and/or capacitors coupled in parallel.

Abstract: A method and device for detecting condensation on surfaces of structural components. A evaluation signal is generated before dewing while the structural component is cooling. A detectable film is produced on a measuring arrangement a few degrees Kelvin before the dew point is reached. The temperature is measured directly on the layer where the dew is developing.

Abstract: Non-destructive method allowing in-situ evaluation, in a sensitive and reproducible way, for a given thermosetting composition, of the time left before gelation of said composition as a function of a quantity measuring its dielectric behaviour.

Abstract: Disclosed is a single-stage, switched capacitor circuit for measuring changes in a variable by measuring changes in a capacitor gap. The change in the capacitor gap corresponds directly to a change in a measurable variable, such as pressure and acceleration, and thus a change in voltage. The circuit includes at least one reference capacitor, a sensor capacitor, a plurality of switches responsive to a timing device, and a device for generating substantially constant reference voltages. The sensor circuit does not result in a DC offset value, but results in the AC component of the voltage being directly proportional to the change in the variable through a substantially constant voltage is supplied to a node near the sensor capacitance. The circuit may be trimmed using a digital to analog converter and/or capacitors coupled in parallel.

Abstract: A position-to-electrical transducer circuit primarily intended for use in meteorological instruments for measuring a characteristic of a surface of a workpiece. An excitation signal generator provides to a transducer an excitation signal whose voltage varies in a known manner with time and a processor analyzes an electrical signal from the transducer to generate a measurement signal. The processor corrects for any phase shift between excitation signal and the electrical signal to provide an accurate measurement. A meteorological instrument for measuring a characteristic of a surface of a workpiece in which a pivotably-mounted arm holding a stylus is traversed relative to the surface of the workpiece and a variable transducer converts the position of the stylus into a corresponding electrical signal.

Abstract: A sensor for sensing a direction of rotation of a body. The sensor comprises a first accelerometer arranged, in use, on the body, and having a first sensing direction; and a second accelerometer arranged, in use, on the body and having a second sensing direction. The two accelerometers are arranged such that the first and second sensing directions are not parallel to one another and are not parallel to the axis of rotation of the body, such that there is a phase difference due to gravitational effects between the outputs of the accelerometers when the body rotates in use. Means receives the acceleration indicative output signals from the first and second accelerometers and determines the phase relationship between the two signals to thereby determine the direction of rotation of the body.

Abstract: In one embodiment, a high-resolution measurement apparatus and method determine the position and motion of an object such as a human hand relative to a sensor array. Capacitance transferred to the array by the object within a sensor field produces minute phase changes in a fixed-frequency reference signal applied to the several elements of the array. The phase changes are measured by first heterodyning the phase-shifted reference signal with a second reference signal to obtain a low frequency intermediate signal, and then employing a phaselocked loop to multiply the phase information in the intermediate signal by orders of magnitude, thereby permitting the use of conventional methods to measure the resulting greatly magnified phase changes. Other embodiments provide direct digital measurement of unknown electrical properties, such as capacitance, inductance, and resistance.

Abstract: A static capacitance-to-voltage converter is capable of converting a static capacitance into a voltage without suffering from a stray capacitance formed between a signal and a shielding line or a stray capacitance formed between an exposed portion of the signal line and its surroundings. The static capacitance-to-voltage converter is formed of an operational amplifier placed in an imaginary short-circuit state between an inverting input and a non-inverting input thereof; a signal line having one end connected to the inverting input and the other end capable of being connected to a static capacitance; a shielding line surrounding the signal line and connected to the non-inverting input; an alternating current signal generator for applying the non-inverting input with an alternating current signal; and zero adjusters for adjusting the output of the static capacitance-to-voltage converter to minimum when no static capacitance is connected to the signal line.

Abstract: A testing apparatus and method for testing conductivity of electric pathways formed on a substrate, each pathway including a first wiring and a second wiring partially overlapping each other. The apparatus includes a first electric signal applier for applying a first electric signal having an electric parameter changing with time to an input portion of the first wiring, a first electrode facing a first portion of the second wiring, a second electrode facing a second portion of the second wiring, a second electric signal applier for applying to the second a electrode a second electric signal changing its electric parameter in the phase reverse to that of the first electric signal, and a monitor for monitoring the signal transmitted to the first electrode through its capacitive coupling.

Abstract: A low-cost, high-resolution capacitive position sensor is provided using a variable capacitor. A vane moves parallel to a stator, where a dielectric is interposed between vane and stator, such that the vane overlaps at least a portion of the stator, creating a capacitance that varies as the vane moves relative to the fixed stator. The capacitor circuit outputs a signal having a phase shift relative to an input driver signal based on the relative positions of the vane and stator. The phase-shifted signal is used to derive the absolute position of the vane with respect to the stator. Two or more stator can be provided to provide two phase-shifted signals and a difference signal free of common mode effects. Enhanced embodiments include interdigitated stator portions for greater sensing resolution, and/or a two or three-pole filter to double or triple the dynamic range of the sensor.

Abstract: A displacement sensor comprises a first scale (11) and a second scale (12) that are arranged opposing to each other and relatively movable in the measurement axis direction. The first scale (11) includes a transmitting electrode array (13) and a receiving electrode (14). The transmitting electrode array (13) consists of a plurality of transmitting electrode units arranged in a basic period (W1) in the measurement axis direction. Each transmitting electrode unit consists of n transmitting electrodes that are arranged in the measurement axis direction and receive respective phase signals of n-phase transmission signals. The receiving electrode (14) adjoins the transmitting electrode array (13) in the direction perpendicular to the displacement direction. The receiving electrode (14) has a width equal to the basic period (W1) and smaller than a width of the transmitting electrode array (13).

Abstract: A method for determining quality of lubricating oil using electrodes in contact with the oil includes applying a potential having a first amplitude to the electrodes, wherein the first amplitude is sufficiently low such that substantially no solution current will flow; determining a first voltage phase lag with respect to the potential when the potential has the first amplitude; increasing amplitude of the potential to a second amplitude at which solution current flows; determining a second voltage phase lag with respect to the potential when the potential has the second amplitude; and determining the quality of the oil based on the voltage phase lags. A system for practicing the method is also provided.

Abstract: For determining the respective geometrical position, the displacement or angle of a body by capacitive sensing, a supply voltage applied to a voltage-distribution element is switched, and/or phase-shifted voltages are applied, in such a way that at least two different distribution patterns of the supply voltage, that follow each other in time, are obtained across the voltage divider.

Abstract: Material resistivity measuring apparatus includes a transmitter for transmitting a measurement frequency current through the material to a receiver spaced from the transmitter. The transmitter includes a power amplifier wherein the measurement frequency current is amplified in discrete steps depending upon resistivity of the material. The current level of the transmitter is transmitted to the receiver by modulating the measurement frequency current by a modulation signal whose phase is indicative of power level. The measurement frequency current can be modulated by a second modulating signal which provides a reference phase for the first modulating signal.

Abstract: For determining the respective geometrical position, the displacement or angle of a body by capacitive sensing, a supply voltage applied to a voltage-distribution element is switched, and/or phase-shifted voltages are applied, in such a way that at least two different distribution patterns of the supply voltage, that follow each other in time, are obtained across the voltage divider.

Abstract: A circuit board has an arcuate array of conductor segments each subject to a digital waveform differing in phase for the various segments, and a concentric pickup conductor. A rotary encoder disk has a conductive pattern which sums and couples the waveforms from selected segments, depending on rotary position, to the pickup conductor. A synchronous phase detector generates a phase signal from the summed waveforms and the zero crossing of the phase signal is detected. A counter develops count signals used to generate the digital waveforms. The count signals are input to a latch which is clocked at the zero crossing point to latch the count value which is a digital measure of the encoder angle.

Abstract: A capacitive gaging system comprising a capacitive displacement sensor and an interface circuit is used to replace a Linear Variable Differential Transducer (LVDT). An output of the capacitive displacement sensor is modified by the interface circuit which provides an output signal or signals representative of different types of LVDT outputs. The capacitive displacement sensor and the interface circuit can then be used to replace the LVDT in an LVDT measurement system. Accordingly, the capacitive displacement sensor and the interface circuit replace the LVDT without replacing the rest of the measurement system.

Abstract: A capacitive throttle position sensor includes an electrode board having at least three electrodes, a driver for selectively driving the electrodes, and a rotary member including a dielectric that provides capacitive path to an output electrode. Preferably, a logical driver provides incrementally sequenced charges to the driver electrodes. The output electrode is coupled to a signal processor that prepares the signal for comparison in a logical decoder with respect to an initiating driver electrode signal. Preferably, the phase difference between the output and input of the capacitive sensor provides an output signal which is not dependent upon the absolute capacitance of the element, and thus provides an output signal which can be adapted to a number of formats for motor vehicle control. Both two piece and three piece versions of the stationary and rotary parts are disclosed, and the capacitive gap may be axially or radially aligned between the stationary and rotary components.

Abstract: A transducer (23) for producing a digital output signal proportional to a change in a sensed physical parameter includes first and second pairs of series-connected resistors (24, 25 or 26, 28). The electrical resistance of at least one of these resistors is variable in response to a change in the sensed parameter. The transducer also includes sine wave generators (31, 32) for applying first and second sine waves across the first and second pairs, respectively. However, these first and second exciting voltages are phase-shifted relative to one another by a constant phase angle. The voltages between the resistors of each pair are vector-summed. The phase angle of this vector-sEed signal is compared with the phase of the reference sine wave, and a pulse-width-modulated waveform is produced.

Abstract: A PLL (phase-locked loop) circuit is used in apparatus for testing individual circuits in circuit devices. The PLL circuit operates at an input frequency provided by the output of an input oscillator when this oscillator is connected to one of the inputs of a phase comparator within the PLL circuit. When this connection is not made, the PLL circuit operates at a freerunning frequency, which is varied by connecting a circuit under test with a frequency controlling node present within a voltage-controlled oscillator in the PLL circuit. In a first mode of operation, the circuit under test is initially connected to the frequency controlling node, but the input oscillator is not connected to the phase comparator. When the input oscillator is so connected, the frequency of oscillations moves from a freerunning frequency associated with the circuit under test to the input frequency.

Abstract: A device for detecting attempts at fraud by connection of an electric feed line (13) to an apparatus for reading and writing on a chip card (3) essentially comprises a resonance unit (6) coupled to a contacting element (2) of the apparatus, and a measuring device (7). In the resonance unit (6) a generator (4) which is coupled to a resonator (1) by way of an impedance converter (5) generates a standing wave. The feed line (13) disturbs the properties of the resonator (1), that being detected by the measuring device (7) and evaluated.

Abstract: A contactless sheet resistance measurement apparatus and a method for measuring the sheet resistance of a desired layer of a first conductivity type, formed upon a substrate of an opposite conductivity type, is disclosed. The apparatus comprises a junction capacitance establishing means, a point location alternating current AC photovoltage generating means for generating a laterally propagated AC photovoltage, an attenuation and phase shift monitoring means for monitoring the .laterally propagated AC photovoltage, and a sheet resistance signal generating means responsive to the-junction capacitance establishing means, the AC photovoltage generating means, and the attenuation and phase shift monitoring means for generating an output signal indicative of a sheet resistance R.sub.S of the desired layer according to a prescribed sheet resistance model.