Showing papers on "Negative impedance converter published in 1974"

Computation of the impedance characteristic of metal electrodes for biological investigations.

Abstract: In a previous study, basic electrochemistry was used to derive analytical expressions for the equivalent network components of the ac impedance of biological needle electrodes In the present paper, numerical parameter values are determined and inserted into these expressions Matching of computer-calculated characteristics with experimental results has been used to determine certain constants, which are difficult to determine in a more direct way The electrode impedance at very low frequencies turns out to be almost purely resistive in character and mainly determined by the exchange current density of the metal-electrolyte system In the intermediate-frequency range the diffusion impedance together with the double-layer capacitance are the decisive factors The magnitude of the impedance diminishes here with fn, where −1

Auto-ranging system for an electronic energy meter

Abstract: An auto-ranging system for an electronic watt-hour meter includes a current transformer for measuring the electrical current in at least one line of an electrical power consuming system. The measured current is converted to a voltage which is proportional to the measured current by means of a current/voltage converter. A means responsive to the output of the current transformer incrementally varies the gain of the current/voltage converter inversely as the level of the measured current reaches each of a plurality of successively increasing discrete current levels. The output of the current/voltage converter is multiplied by the line voltage which is detected by a potential transformer with the output of the multiplier being coupled to an analog-to-pulse rate converter. The analog-to-pulse rate converter generates a pulse train having a pulse rate which is proportional to the product signal at the output of the multiplier. A means responsive to the output of the current transformer incrementally varies the pulse rate of the pulse train as the measured current reaches each of the successive plurality of discrete current levels so that the pulse rate varying means compensates the variance of the gain of the current-to-voltage converter. Thus, a watt-hour meter is provided which has a substantially constant gain and an exceedingly large dynamic range.

Electronic variac surge current limiting circuit

Abstract: A circuit having a gated, symmetrical switch is provided for insertion between an AC source of power and a load, and prevents a surge current from entering the load when the AC input is initially applied. A symmetrical negative resistance device that begins conducting at a prescribed voltage and remains on as a constant voltage regulator until the AC input voltage drops below a sustaining value is connected to provide the prescribed voltage to the gate control of the gated symmetrical switch. An RC circuit controls the length of time required for the AC input voltage to reach the prescribed voltage at the input to the symmetrical negative resistance device. At least part of the resistance in the RC circuit is of the negative temperature coefficient type, resulting in the resistance value decreasing as the temperature of the negative temperature coefficient device increases, thereby shortening the time after which the prescribed voltage to the symmetrical negative resistance device is applied.

Direct current protection circuit

Abstract: When the oscillator which supplies the alternating drive voltage for a liquid crystal display fails, the circuit of the present application removes the direct current operating voltage from the liquid crystal driver transistors. The oscillator drives a voltage converter which produces the operating voltage. A transistor in series with the line carrying the operating voltage is controlled by the operating voltage developed by the converter so that when the oscillator fails and the converter goes off, the transistor cuts off.

Electronic power metering device

Abstract: The invention is an electronic power-to-frequency converter for measuring the amount of electricity used by an electrical system. The power-to-frequency converter includes a current transformer for continuously sampling the instantaneous current through the electrical system, a voltage transformer for continuously sampling the instantaneous voltage at which the current is drawn, and an analog multiplier for electronically multiplying the samples of voltage and current.

Apparatus for detecting the physical properties of magnetic or electric conductive heat-responsive or deformable material using negative input impedance network

Abstract: A measuring apparatus uses an impedance element whose impedance varies with the physical properties of an object consisting of magnetic or electric conductive, heat-responsive or deformable substance, under the condition where the impedance element is energized by a D.C. or A.C. voltage source of a predetermined level. Connected in parallel or series with the impedance element is a negative impedance network, with its input impedance set at a negative value, which comprises an amplifier and positive and negative feedback impedance networks each connected between the input and output terminals of the amplifier. At least either of the positive and negative feedback impedance networks is constituted by a low, high or band pass filter for eliminating an external noise component, whereby the measuring apparatus enables to detect the physical properties of the object with as high a sensitivity and accuracy as possible.

Active impedance multiplier

Abstract: An active impedance multiplier circuit that can, as one of its uses, be used in a mine ground fault detection system. The purpose of the multiplier is to create a very high impedance for an AC signal that normally flows through a low impedance legitimate load. To accomplish this, the output of the multiplier is put in parallel with the low impedance load and impresses upon the load an appropriate voltage and current. When used in a fault detecting system, the impedance multiplier will act to normally prevent current from flowing in the low impedance load. AC current will flow to the legitimate load from the multiplier in response to signals obtained from an alternating current detector located within each multiplier. In its most basic form, the active impedance multiplier can be said to consist of a current detector and a current amplifier to amplify the detected current by a constant factor. The amplified output from the multiplier is in turn connected in parallel across the legitimate load.

Method for exciting inductive-resistive loads with high and controllable direct current

Abstract: Apparatus and method for transmitting dc power to a load circuit by applying a dc voltage from a standard waveform synthesizer to duration modulate a bipolar rectangular wave generator. As the amplitude of the dc voltage increases, the widths of the rectangular wave generator output pulses increase, and as the amplitude of the dc voltage decreases, the widths of the rectangular wave generator output pulses decrease. Thus, the waveform synthesizer selectively changes the durations of the rectangular wave generator bipolar output pulses so as to produce a rectangular wave ac carrier that is duration modulated in accordance with and in direct proportion to the voltage amplitude from the synthesizer. Thereupon, by transferring the carrier to the load circuit through an amplifier and a rectifier, the load current also corresponds directly to the voltage amplitude from the synthesizer. To this end, the rectified wave at less than 100% duty factor, amounts to a doubled frequency direct voltage pulse train for applying a direct current to the load, while the current ripple is minimized by a high L/R in the load circuit. In one embodiment, a power transmitting power amplifier means having a dc power supply is matched to the load circuit through a transformer for current magnification without sacrificing load current duration capability, while negative voltage and current feedback are provided in order to insure good output fidelity.

Circuit for monitoring the inductance of an inductive load to indicate occurrence of a fault

Abstract: A circuit for monitoring the inductance of an inductive load controlled by phase-operated thyristor devices or similar devices. One embodiment of the invention comprises a first current sensitive device to produce a signal proportional to the current flowing through the load, a voltage sensitive device to produce a signal proportional to the voltage across the load, an inductor driven by the voltage signal and a second current sensitive device for producing a signal proportional to the current flowing through the inductor. The first current signal is then rectified and fed to a voltage divider consisting of five series connected resistors. The second current signal is also rectified and fed to the same voltage divider. A comparator is connected to the aforementioned voltage divider and senses any voltage change on the voltage divider due to a change in the ratio of the second current signal to the first current signal (or the inverse ratio) and thus in effect, senses any change in the impedance of the load.

Automatic turn-on circuit for a DC to DC down converter

Abstract: A DC to DC down converter having a semiconductor switch connected between the input and output terminals thereof, which switch is controlled by a variable pulse generator and an automatic turn-on circuit including a voltage divider connected between the input and output terminals of said converter, switching means operable in response to a voltage across said voltage divider and controlling the application of power to the variable pulse generator, and a diode connected between the semiconductor switch and the junction of the voltage divider and output terminal to allow the converter to shutdown when the load is removed from the output terminal.

A feedback pulse‐lengthener circuit for the peak voltage measurement of a single shot pulse as narrow as 2.5 nsec

Abstract: A circuit capable of measuring the peak voltage of a single shot pulse as narrow as 2.5 nsec is described. The circuit uses a pulse‐lengthener circuit that has an amplifier in its negative feedback path. The amplifier reduces the charging time constant of the pulse‐lengthener circuit to improve its speed capability. The measurable peak voltage of a single shot pulse ranges from about +0.3 to +3.3 V. The meter deflection is held constant for easy readout by A/D and D/A converters until the A/D converter is reset.

Dynamic range modifying circuits utilizing variable negative resistance

Abstract: Dynamic range modifying circuits, namely compressors and expanders, are disclosed in which series connected circuits respond to current or voltage drive to provide voltage or current output. One circuit has characteristics which do not vary with dynamic range and contributes a component to the output having dynamic range linearity relative to the input. A second circuit has variable impedance characteristics and contributes a component which does not have dynamic range linearity relative to the input and which effects the dynamic range modification. Devices are described in which the variable impedance characteristics include effective negative resistance which is itself varied and is shunted by a variable reactance. Devices are also described in which the second circuit is a two terminal network which responds to the current between the two terminals to determine the voltage therebetween and wherein the voltage is derived either by way of a variable filter which acts to restrict the voltage or by way of multiple paths including filters and limiters.

Single-ended dc-to-dc converter for the pulse control of the voltage at an inductive load as well as method for its operation

Abstract: A single-ended dc-to-dc converter which comprises a transformer having a primary winding which is connected to a d-c voltage source via a switch, a secondary winding which is connected to a load via a series valve and a choke, and a remagnetizing winding. In order to obtain an output voltage from the converter which is higher or lower, as desired, than the d-c supply voltage, provision is made for a first controlled by-pass valve to be shunted across the series connection of the secondary winding and the series valve and for a second controlled by-pass valve, poled in the direction of the load current, to be connected in parallel with the series connection of the choke and the load.

A DC-DC Converter for Radiation Monitors

Abstract: To provide supply voltages for a detector and electronic circuits is a problem which frequently arises in designing a radiation monitor. With portable assemblies, which use primary or secondary batteries, this problem must bo solved by using DC-DC converters. In general, for each supply voltage a separate DC-DC converter may be used, but in some cases a single converter can produce two or more output voltages. The DC-DC converter should have high efficiency and stable output voltage. The two principal reasons for which the output voltage might change its value are the changes of the batteries voltage and of the converter load. The converter which will be described here can stand very large variation of the batteries voltage and produces two output voltages, one for electronic circuits of the monitor, and the other for its GM counter.

Method and apparatus for the testing of single current-double current converter circuits and associated trunk lines in centrally controlled data switching installations

Abstract: A method and circuit arrangement are described by means of which a testing exchange station can determine whether a predetermined converter circuit and out-going trunk line are in an operative condition or a busy signal will be received therefrom. The method contemplates transmitting a test signal from a testing exchange station to the converter circuit in question and determining the conditions of the tested converter circuit by determining the condition of a reflected signal from said tested converter circuit to said testing exchange station. An apparatus is described whereby this reflecting procedure is facilitated by replacing the reflection-preventing contacts in the holding circuit for a transmission relay in the converter circuit with a continuous connection. Further, in those converter circuits which are permanently connected to a subscriber line contacts are added to the holding circuits for a transmission relay, and these contacts will connect a resistor in the holding circuit to a stop polarity. The aforementioned contacts are open when the converter circuit is in a dial condition.

A simple way to determine the driving-point impedance function of an n port

Abstract: It is well known that the driving-point impedance at any port of an n port can be written as a function of the load impedances across the other (n - 1) ports and that this function is a quotient of two polynomials in the load impedances. A method is given to determine the coefficients of these polynomials with one impedance-measurement on the n port plus one multiplication per constant.

Electrical communication switching network providing far-end crosstalk reduction

Abstract: A high impedance to low impedance transmission network in which an effective negative impedance is introduced at the demodulator end to achieve a further significant reduction in far-end crosstalk. The effective negative impedance is implemented by a feedback circuit for shifting the signal voltage at the far end of the network in a direction opposing the phase of the voltage at the high impedance end of the network. The net impedance seen from the latter end remains positive with the result that normally encountered instability problems attendant the use of negative impedance circuits are avoided.

Miller long-duration sweep generator

Abstract: A Miller-integrator circuit using a simple amplifier with positive feedback has been analysed. The circuit has the high input impedance inherent with insulated-gate field-effect transistors and the low output impedance characteristic of emitter followers. Owing to these properties and the high voltage gain, it is possible to obtain long-duration sweeps of good linearity. A sweep of about 2 h duration and of a linearity error of 0.05% has been obtained. The ratio of the dynamic range of the output voltage to the supply voltage is greater than 60%, and the output impedance is less than 10?.