Showing papers on "Current sensor published in 1970"

Apparatus having automatic re-set means for detecting a fault current

Abstract: A device for detecting fault current. The device senses the current in a line and converts it to a proportional voltage signal. The voltage signal is used to switch a solenoid to first and second positions depending upon the value of the signal. The device will re-set itself after sensing a fault current when normal line current is restored.

Line security system

Abstract: A system for insuring the security of electrical transmission lines extending between a monitor station and a remote station utilizes a voltage source at the monitor station which impresses an AC voltage signal on the transmission lines At the remote station, the AC voltage signal is rectified and the rectified signal is applied to a current regulator which provides a quiescent pulsed direct current of constant level to the transmission lines The current regulator is arranged to provide a higher alarm current when an intruder is detected at the remote station At the monitoring station, a shorted line fault detector provides a signal when a reversal in the direction of normal current flow occurs in the transmission lines, an open line fault detector provides a signal when a drop in current below the quiescent current level is detected, and an alarm current fault detector provides a signal when a rise in current above the quiescent current level is detected The impressed voltage is periodically reduced in amplitude to a level which barely sustains the minimum quiescent current level to test line impedance

Adaptive limit current

Abstract: A limit circuit responsive to varying input line voltages to an inverter in order to establish a variable current limit value or maximum current at which the inverter circuit is allowed to operate. If the load current attempts to exceed a variable value established by the input line voltage, the current is limited, and in the preferred embodiment the current is electronically interrupted.

Sensitive peak current detector for ground fault protection circuits

Abstract: A full- or half-wave peak current detector of a few milliamperes of power circuit fault current includes, for each polarity, a normally conducting first transistor continuously supplied with base current. In response to sensing an instantaneous abovethreshold fault current, the base current is diverted through a mirror-image connected second transistor, turning off the first transistor for so long as the above-threshold current exists. For full-wave detection the role of the transistors is reversed on the other polarity. This actuates one or more series RC filter networks to delay the output indication and reduce the detector sensitivity to high-frequency transients or noise. The valid power frequency output signal opens a circuit interrupter.

Load current sensor for a series pulse-width modulated power supply

Abstract: A load current sensor for use with a pulse width modulated power source and has an output filter inductor connected in series between a load and a pulse width modulated regulator. This inductor stores a portion of each pulse supplied to the load by the regulator. At the end of each pulse the stored energy in the inductor causes the current to continue flowing through the load via a freewheeling diode. This current is sampled by a sensor which is connected across the freewheeling diode and the series circuit made up of the output filter inductor and the load. The sensor comprises a gated transistor switch connected in series with a pulse transformer. The freewheeling diode has a forward conductance threshold (forward resistance) which is greater in magnitude than the series impedance of the transistor switch and the pulse transformer.

Rms voltage or current sensor

Abstract: A voltage or current sensor containing a heater resistor, a first heat responsive resistor in intimate thermal contact with the heater resistor, a second heat responsive resistor in intimate thermal contact with the ambient temperature, and insulator means separating the heater resistor and first heat responsive resistor from the second heat responsive resistor. A voltage or current to be measured is applied to the heater resistor, which produces a heat output that is proportional to the true RMS value of current flow through the heater resistor. This heat output is transmitted to the first heat responsive resistor, whose resistance value varies as a substantially linear function of temperature within a temperature range corresponding to the range of voltages or currents to be measured. The thermal resistance between the heat resistor and the first heat responsive resistor is much less than the thermal assistance between the heater resistor and a temperature reference comprising the case and a heat sink. A second heat responsive resistor has the same or opposite temperature coefficient of resistance of the first heat responsive resistor, and its resistance also varies as a substantially linear function of temperature, but since it is insulated from the heator resistor and is in intimate thermal contact with the temperature reference, its resistance will be determined by the ambient temperature rather than by the temperature of the heater resistor. Therefore, the resistance ratio of the first and second heat responsive resistors is proportional to the heat output of the heater resistor, which in turn is proportional to the true RMS value of voltage or current applied thereto and compensated for ambient temperature variations.

Method and circuit for driving inductive loads

Abstract: The relative current in a pair of inductive loads is rapidly varied by maintaining a current in each load, so that when current is removed from one the rapid decay of current in that coil permits a substantial relative current differential since the other load need not rise from zero current due to the current pre-established therein. To further enhance the rapid current differential a choke in series with a low voltage supply provides a constant current source so that a large voltage spike is generated when the current goes to zero in one load thus enhancing the current buildup in the other load.

Segment analog-to-digital or digital-to-analog converter

Abstract: A segment-type decoder in which binary signals representing the mantissa of a digital signal to be decoded are applied to a linear coder component to produce an output current from which there is added to or subtracted a first predetermined current in accordance with a sign bit. The resulting current is applied to a switched amplifier whose gain is determined by the characteristic portion of the digital signal and from whose output is added or subtracted a second predetermined current in accordance with the sign bit to yield an analog representation of the input signal.

Current control circuit for operating a deflection yoke

Abstract: A current control circuit having a pair of current generators connected in circuit with one another at a common circuit point for controlling a direct current voltage source in such a manner as to produce an alternating current through current utilization means coupled to the common circuit point. Where a substantially linear increasing sawtooth-shaped control signal is applied to the current generators, the current output at the common circuit point is also a linear increasing sawtooth, initially of one polarity, passing through zero and then of another polarity to produce a current sweep signal suitable for use with a printed circuit deflection yoke where such is used as the current utilization means.

Alternating current to direct current signal converter

Abstract: A converter for converting an alternating current signal to a corresponding direct current signal and which has a differential input stage connected to the input of class A amplifier. The amplifier has a shorting circuit connected between its input and a converter circuit therein which converts a voltage signal swing at the amplifier output into a current signal swing and which provides a ''''zero summing point'''' or circuit whereby the direct current output signal may be referenced directly to the converter ground, and also wherein the said output is directly related to the input signal current.

Two-wire millivolt to milliampere signal converter

Abstract: A circuit system for converting small DC signals into milliampere signals in which the signals from a voltametric sensing device are converted into standard level current signals for transmission over the same two-wire power lines that supply voltage to the circuit. A current sensor imposed across the output load of an operational amplifier provides fractional feedback to the input thereof and produces a voltage swing of approximately 30 volts, over the power lines. The power supply to the amplifier is regulated and temperature compensated and is fully compensated for zero shift.

Current drive deflection apparatus utilizing constant current generator

Abstract: Current drive deflection apparatus for providing a current to a beam deflection winding of a cathode ray tube is shown. The current drive deflection apparatus employs a constant current generator and a current control means which provide a sawtooth current to the winding. Current drive deflection apparatus which employs a complementary current amplifier is also shown.

Improvements relating to Regulating Circuits

Abstract: 1,179,761. Control of D.C. motors. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. 18 Dec., 1967 [20 Jan., 1967], No. 3210/67. Heading H2J. [Also in Division G3] In a regulating circuit of the type which switches between two states to maintain a first quantity, e.g. voltage, at a value set by a first reference signal, this first reference signal is arranged to be modified when a second quantity, e.g. current, reaches a predetermined relationship with a second reference signal, whereby control in dependence upon the second quantity supersedes control in dependence upon the first quantity. As shown, a load 10, e.g. the traction motor of an electrically-driven vehicle, is supplied from a D.C. source 10 by way of a chopper regulator 8 and a current sensor 2. A sawtooth waveform from a source 1 is compared in a comparator 3 with an adjustable D.C. reference voltage from a source 4 which may be associated with the foot-pedal of the vehicle and the output from the comparator, applied to the regulator 8 over a pulse generator 7, determines the voltage applied to the load; if the load current exceeds a predetermined value, a second comparator 5 associated with a second reference source 6 produces an output which is applied to the source 4 to modify the reference voltage supplied thereby. Thus current control overrides voltage control when an excess current flows in the load.

Current monitor for threshold detection

Abstract: A device for monitoring the current supplied to a missile and its firing mechanism which gives a GO-NO-GO indication during flight line checkout and thereby an alert to any existing malfunctions. A Schmitt trigger fires a monostable multivibrator which activates a current amplifier to trigger a power transistor with 5.9 ohms of load resistance connected to the emitter thereof. This load resistance simulates the actual missile firing mechanism. The current developed through the load resistance is applied to a current sensor that triggers a driver and relay. If the current is of sufficient magnitude, the relay is energized and a green lamp will illuminate indicating a ''''GO'''' condition. If insufficient current is applied to the device, the relay will not energize and a red lamp will illuminate indicating a ''''NOGO'''' condition.