Abstract: A shield for an inductive position sensor is configured in shape to avoid compromising the inductive field variations related to the sensor's moving target. Said shield is shaped as at least one conductive strip and is laid along the direction of motion of the moving target. Said shield is arranged to prevent induced current in the shield that could affect the part of the inductive field used by the sensor. Improvements are also conferred by a demodulator circuit implementing a zero phase oscillator which simultaneously measures the inductance and the temperature of the sensor windings to reduce and compensate for the effects of the shield. Said conductive shield may also provide for the electrical connection to the far end of the winding. For multi-layer windings, connection of the winding closest to the shield to the lower impedance side of the demodulator also reduces the effect of the shield.

Abstract: An improved sensor apparatus for developing a signal related to an inductive sensor in a resonant circuit are disclosed. This improvement is realized by adding a known capacitance to the resonant circuit and comparing the resulting natural resonance frequency to the frequency without the known capacitance. In this way a measure of the resonant capacitance is developed to correct the sensor signal for the effect of any changes in that capacitance. One disclosed embodiment adds an electronically variable capacitance which is adjusted to yield a constant capacitance that produces a sensor signal insensitive to variations in the resonant circuit capacitance. The resonant capacitance measurement may also provide an indication of another sensor state, such as temperature or pressure, which may be used to further correct for temperature or pressure sensitivities in the sensor signal. The invention is extended by juxtaposing the inductance for capacitance in the sensor resonant circuit.

Abstract: An auxiliary interface device, comprising an electronic circuit to interface to the signal output of a signal source, said signal source developing or receiving more than one signal, and providing for the user selection of at least one of the signals in deference to the others so that said apparatus provides for the selection of at least one special signal having predetermined characteristics, a detector which recognizes the presence of the at least one said special signal when present or part of a signal developed by the apparatus to which said auxiliary interface device is connected, said detector being able to distinguish between said at least one special signal and other signals ordinarily present or developed by the apparatus to which said auxiliary interface device is interfaced, a signal switch to substitute at least one auxiliary signal in place of a signal output by the apparatus to which said auxiliary interface is interfaced, said signal switch being configured to substitute said at least one auxil

Abstract: A circuit for modifying the impedance of a subject circuit includes a driving impedance element having an impedance characteristic which is substantially proportional to the impedance characteristics of the subject circuit. The circuit of the present circuit further includes a voltage controlled voltage source circuit which is coupled to the driving impedance element to proportionally add or subtract current from the applied subject circuit. The voltage controlled voltage source circuit provides a given voltage to the combined subject circuit and driver impedance element that is effectively proportional to the voltage potential difference across the subject circuit, thereby providing an enhanced effective impedance for the subject circuit.

Abstract: A circuit for modifying the impedance of a subject circuit includes a driving impedance element having an impedance characteristic which is substantially proportional to the impedance characteristics of the subject circuit. The circuit of the present circuit further includes a voltage controlled voltage source circuit which is coupled to the driving impedance element to proportionally add or subtract current from the applied subject circuit. The voltage controlled voltage source circuit provides a given voltage to the combined subject circuit and driver impedance element that is effectively proportional to the voltage potential difference across the subject circuit, thereby providing an enhanced effective impedance for the subject circuit.

Abstract: A signal conditioning system that receives inputs from at least one pair of conductors connected to its input. Each such input is processed by an input filter and presented to a buffer amplifier. Each such input filter and buffer amplifier refers to and is powered by independent power sources whose power return reference potentials are independently determined by the potential of the corresponding input signal potential reference conductor for the signal frequencies of interest. The outputs of all such buffer amplifiers, the power return reference potentials, and the power return reference potential of the conditioning circuit output are all appropriately added or subtracted in the next circuit stage. This circuit stage consists of an amplifier buffer having low output impedance which is powered by another independent power source whose power return reference potential is independently determined by the potential of the output signal reference conductor.

Abstract: Noise gate control circuitry eliminates in audio systems the effects of spurious signals on a transducer of a speaker. The noise gate control circuitry coordinates the electronic switching of the transducer to power sources in accordance with a remote turn on control signal, and coordinates this action with the application of power to power sources and signal processing circuitry via remote turn on provisions. The noise gate control circuitry senses and responds to the signals and rapidly connects and disconnects the transducer when the signal level drops to a level too low to be of any good effect. The effect of signal level on delays is removed to provide for suppressing undesirable changes in response.

Abstract: A signal conditioning circuit that receives inputs from at least one pair of conductors connected to its input. Each such input is processed by an input filter and presented to a buffer amplifier. Each such input filter and buffer amplifier refers to and is powered by independent power sources whose power return reference potentials are independently determined by the potential of the corresponding input signal potential reference conductor for the signal frequencies of interest. The outputs of all such buffer amplifiers, the power return reference potentials, and the power return reference potential of the conditioning circuit output are all appropriately added or subtracted in the next circuit stage. This circuit stage consists of an amplifier buffer having low output impedance which is powered by another independent power source whose power return reference potential is independently determined by the potential of the output signal reference conductor.

Abstract: A signal conditioning circuit having an input stage that receives inputs from at least one pair of conductors and processes the input signal through an input filter and a buffer amplifier. Each input filter and buffer amplifier are powered by independent power sources whose power return reference potentials are independently determined by the potential of the corresponding input signal potential reference conductor. The outputs of the buffer amplifiers, the power return reference potentials, and the power return reference potential of the conditioning circuit output are all appropriately added or subtracted in an output stage. The output stage consists of an amplifier buffer having low output impedance which is powered by a separate independent power source whose power return reference potential is independently determined by the potential of the output signal reference conductor. The output of this circuit stage is connected to an output inductor circuit which in turn drives the output signal conductor.

Abstract: A digital voltmeter which converts an input signal having an amplitude to be measured into a digital signal from which a series of pulses is developed having a duty cycle which is proportional to the amplitude of the input signal. These pulses are supplied are supplied to a digital-to-analog converter which develops an analog signal having an amplitude proportional to the duty cycle of the pulses and is compared with the input signal to stabilize the digital signal at a value corresponding to the amplitude of the input signal.

Abstract: Non-contacting sensor apparatus having two tank circuits from which an indication of the position of the moving part of the sensor is developed by measuring the relative resonance frequencies of the two tank circuits. As the moving part of the sensor changes position and moves toward and away from the inductance coil of one of the tank circuits, the relative resonance frequencies of the two tank circuits change. The outputs of the two tank circuits are multiplexed and drive a pulse generator which develops a first series of pulses having a repetition rate which corresponds to the resonance fequency of one of the tank circuits and a second series of pulses having a repetition rate which corresponds to the resonance frequency of the other tank circuit. The relative times required to count the same number of pulses of each series of pulses provides an indication of the position of the moving part of the sensor.

Abstract: Non-contacting sensor apparatus having two tank circuits from which an indication of the position of the moving part of the sensor is developed by measuring the relative resonance frequencies of the two tank circuits. As the moving part of the sensor changes position, the relative resonance frequencies of the two tank circuits change. The outputs of the two tank circuits are multiplexed and drive a pulse generator which develops a first series of pulses having a repetition rate which corresponds to the resonance frequency of one of the tank circuits and a second series of pulses having a repetition rate which corresponds to the resonance frequency of the other tank circuit. The relative times required to count the same number of pulses of each series of pulses provides an indication of the position of the moving part of the sensor.

Abstract: A musical keyboard having keys which carry metal spoilers that alter the resonance characteristics of tank circuits associated with the keys as the keys move toward and away from the inductance coils of the tank circuits. The tank circuits are connected sequentially to a frequency sensing circuit which develops indications of key positions by sensing the resonance frequency of each tank circuit.

Abstract: A frequency-to-voltage converter which responds either to frequency variations or to time period variations of a varying frequency input signal. When arranged to respond to frequency variations, the input signal is mixed with two fixed frequency framing signals having known frequency relationships to the frequency of a fixed frequency reference signal. One framing signal has a frequency greater than the maximum frequency of the input signal and the other framing signal has a frequency less than the minimum frequency of the input signal. By mixing the input signal with the framing signals and then measuring the relative times required to count a prescribed number of cycles of each of the difference signals produced by the mixing, an indication of changes in the input signal frequency relative to the reference signal frequency is developed.

Abstract: An inductance coil sensor in which a rotating spoiler (46) alters the inductance of a stationary coil (1230/1432) having two parts (12a, 12b; 30a, 30b/14a, 14b; 32a, 32b) disposed on opposite sides of the spoiler. Changes in inductance of the stationary coil are sensed to develop an indication of the rotary movement of the spoiler which, in turn, represents changes in the parameter being monitored. By locating one part of the stationary coil above the spoiler and one part below the spoiler, compensation is provided for undesired movements of the spoiler along its rotation axis.

Abstract: A digital-to-analog converter which develops an analog output representative of the difference between two digital inputs represented by the rates of two series of pulses. A prescribed number of pulses of each series is counted to develop two oppositely directed counter pulses, each having a duration dependent upon the time required to count the prescribed number of pulses. The counter pulses are integrated and the integration signal is sampled at the mid-point of each rise and decay. The average of the samples of each rise and decay represents the difference between the rates of the two series of input pulses.

Abstract: Non-contacting sensor apparatus having two tank circuits from which an indication of the position of the moving part of the sensor is developed by measuring the relative resonance frequencies of the two tank circuits. As the moving part of the sensor changes position, the relative resonance frequencies of the two tank circuits change. The outputs of the two tank circuits are multiplexed and drive a pulse generator which develops a first series of pulses having a repetition rate which corresponds to the resonance frequency of one of the tank circuits and a second series of pulses having a repetition rate which corresponds to the resonance frequency of the other tank circuit. The relative times required to count the same number of pulses of each series of pulses provides an indication of the position of the moving part of the sensor.

Abstract: The position sensor constitutes a fixed planar board having disposed on the surface serpentine coil structures of relatively low resistance and inductance. The coils are driven in a resonance mode which provides a frequency output according to the position of a moving planar member. The second movable planar board has disposed on the surface thereof planar loop coil structures. The second board is moved in proximity to the first board to vary the resonance characteristics of the first coil according to the position of the second board with respect to the fixed board. In this manner the frequency output of the system is a function of the position of the boards with respect to one another. Other embodiments depict means for compensating the thermal drifts of the frequency with respect to temperature.

Abstract: Sensor apparatus which uses non-contacting, inductance coil sensors to transfer information about a parameter being monitored from a moving member to an indicator mechanically isolated from the moving member. The inductance coil sensors each have a stationary tank circuit and a movable tank circuit which are inductively coupled to produce a double resonance curve for the stationary tank circuit. The parameter is sensed by a unit having inductively coupled components. This unit is connected to the moving tank circuit to change the inductance of the moving tank circuit in accordance with changes in the inductive coupling of the sensing unit which, in turn, are dependent upon the parameter being monitored. As the inductance of the moving tank circuit changes, the relative frequency, amplitude and phase characteristics of the resonance peaks of the stationary tank circuit change. The degree of change of these characteristics is a measure of parameter.

Abstract: A signal conditioning system that receives inputs from at least one pair of conductors connected to its input. Each such input is processed by an input filter and presented to a buffer amplifier. Each such input filter and buffer amplifier refers to and is powered by independent power sources whose power return reference potentials are independently determined by the potential of the corresponding input signal potential reference conductor for the signal frequencies of interest. The outputs of all such buffer amplifiers, the power return reference potentials, and the power return reference potential of the conditioning circuit output are all appropriately added or subtracted in the next circuit stage. This circuit stage consists of an amplifier buffer having low output impedance which is powered by another independent power source whose power return reference potential is independently determined by the potential of the output signal reference conductor.