Showing papers on "Current sensor published in 1988"

Battery state of charge indicator

Abstract: A device for indicating changes in the state of charge of a rechargeable battery including a current sensor to sense current flow into and out of the battery and to provide an output indicative of both the magnitude and direction of the current flow, a timer to provide a timing signal, and a computer programmed to compute from the output of the current sensor and the timer, a signal representative of the charge dissipated from or accumulated in the battery over a period of time. Preferably the device includes data storage to store an indicatioin of the state of charge of the battery and the computer is programmed to use the signal to update the stored data to provide an indication of the current state of charge of the battery.

Method for detecting a current flowing over the human body between a forward and a return conductor and a circuit configuration for carrying out the method

Abstract: The method and circuit detects a current flow over the human body between a forward conductor and a return conductor, and disconnects the network conductors. The output signal emitted by a current sensor connected to a network conductor is detected and a switch for disconnecting the network conductor is then actuated only at a value of the signal of the current sensor between an upper and a lower threshold value.

Stabilised current sensor using Sagnac interferometer

Abstract: A current sensor based on a stabilised fibre-optic Sagnac interferometer has been constructed and preliminary tests have been carried out Measurements made with this system are independent of variations in the following parameters: laser intensity, light intensity injected into the optical fibre and birefringence within the fibre The stabilised output is obtained by electronically combining the output signal from the interferometer with samples of the signal which have traversed the optical fibre in opposite directions The mathematical basis for the stabilisation technique and construction details for the instrument are given

Novel current sensor for PWM AC drives

Abstract: A novel current sensor which determines the currents flowing in an inverter driven induction motor from observations of the pulse currents existing in the DC busbar of the PWM inverter is described. The sensor can determine the real part of the current, and, if the motor is supplying mechanical power, the current magnitude. It is low cost and easy to implement, and experimental results show good accuracy over a range of operating conditions.

Magneto-optic current sensor

Abstract: A sensor (10) for sensing the magnitude of current flowing in a conductor (12) based upon the Faraday effect is disclosed. The invention utilizes a magneto-optic material having one or more layers (32) in which alignment with an optical fiber is not critical in achieving accurate current measurements. A magneto-optic material (28) in accordance with the invention includes one or more layers (32) each having a substrate having opposed surfaces coated with a material exhibiting the Faraday effect in which light from a light source is transmitted through the magneto-optic element without substantial internal reflection and is incident upon a surface area of the coating which is greater than the surface area of the beam of light. Furthermore, the invention measures the magnitude of current flowing in the conductor accurately by utilizing null detection for a first range of current values from zero to a first magnitude having either of two possible polarities and measures a second range of current values extending from the first magnitude to a second magnitude having either of the two possible polarities in which null detection is not utilized. By not utilizing null detection for the second range of current values, circuit response time is enhanced by allowing the inductance of the nulling coil to be reduced. Transient response is thus improved.

Integrated current sensor configurations for AC motor drives

Abstract: An AC polyphase motor drive includes a current-controlled inverter comprising a plurality of semiconductor devices made up of power switches, such as IGBTs, and diodes. Current sensors integral with respective ones of a first group of the semiconductor devices sense the current delivered to each of the motor phase windings and a controller compares the sensed currents to a set of command signals to control operation of a second group of the semiconductor devices.

Peripheral device power activation circuit and method therefor

Abstract: A first embodiment of the present invention has toroidal current transformer 11 having its outputs connected across full-wave bridge rectifier 12. The induced, rectified current produced by full-wave rectifier 12 is converted to a voltage by a load resistor. This voltage is compared to a reference signal, the magnitude of which corresponds to a quiescent current level, by comparator 13. When the load resistor voltage exceeds that of the reference voltage, a current surge is detected. The output of comparator 13 is directed to a retriggerable monostable multivibrator 14 which produces an activation pulse of a selectable and known duration. The activation pulse is directed to an electromagnetic or solid-state relay 16 which activates peripheral device 2 by connecting it to its power supply. The second embodiment of the present invention has line sensor 18 electromagnetically coupled to power supply line 3 the output of current sensor 18 is integrated by integrator 19. The integrated signal is then digitized by digitizer 20 and input into selector 21. A crossover detector 28 and line voltage sensor 25 are operably connected to power supply line 3 to monitor the crossover points and voltage level of the supply. The monitored voltage is digitized by digitizer 27 and input into selector 21. Selector 21 alternatively supplies microcontroller 22 with the digitized line current and voltage level values. Microcontroller 22 compares the relative values of the line current and voltage level to detect current surges in power supply line 3 due to increased activity of parent device 1. Microcontroller 22 then activates solid-state relay 24, thereby activating peripheral device 2.

Switch-mode power supply with dynamic adjustment of current sense magnitude

Abstract: In a dc-to-dc converter, alternating current or pulsating direct current produced by a cyclically switched power supply passes through semiconductor rectifiers or diodes. The rectifiers may be subject to unwanted conduction characteristics attributable to charge storage, which may result in cyclical current spikes during normal operation. A current sensor is coupled to sense a current which includes the cyclical spikes. A controllable attenuator or gain element couples the sensed current in a feedback loop to shut down the converter in the event of an overcurrent. To reduce the possibility of shut-down due to the normal cyclical current spikes, the attenuator or gain element is cyclically switched so as to reduce the sensitivity to the current spikes when they occur.

Integrated current sensor torque control for ac motor drives

Abstract: A method and apparatus for operating a current-controlled pulse width modulated inverter for driving a polyphase AC load includes using partial current feedback information, obtained from the inverter lower phase-leg switches and flyback diodes only, to regulate current flow in each phase of the load by synthesizing an analog feedback signal from the partial current feedback information.

Current regulator and method

Abstract: An integrated circuit for providing a regulated output current comprises an output transistor for producing the output current, a feedback circuit including a current mirror for sensing the magnitude of the output current and providing a feedback current proportional thereto and a driver circuit for comparing the feedback current to an externally generated current and biasing the output transistor accordingly to regulate the magnitude of the output current to a predetermined value. Preferably, the external current is generated through an external resistor coupled to an input of the driver curcuit and the current mirror wherein the magnitude of the external current is directly proportional to a reference voltage provided on chip and applied to an additional input of the driver circuit the latter of which functions as an operational amplifier.

Wide band large dynamic range current sensor and method of current detection using same

Abstract: A wide band large dynamic range current sensor operable to measure current leakage in an external conductor utilizing a magnetostatic spin wave delay line (MSW) device is described. The measurable changes in well known electromagnetic properties of ferrite films, as utilized in MSW devices when these films are exposed to external current induced magnetic fields, results in a current sensitive detection device. A method of current detection using this device is also described. Specific, low power microelectronic applications as well as, high power, local and remote current detecting embodiments are included.

Wide dynamic range current measuring apparatus

Abstract: WE 54,364 ABSTRACT OF THE DISCLOSURE Apparatus for measuring current over a wide range generates an eight bit accurate, 16-bit dynamic range digital signal from a current transformer secondary. Two signals proportional to the rectified secondary current, one generated by a large burden resistor and the other by an amplifier with programmable gain and an overrange indication, are applied through a multiplexer to an eight bit analog to digital converter which has three selectable reference voltages. A microprocessor selects the input signal, converter reference voltage, and one of four levels of amplifier gain which provide the greatest resolution for the magnitude of the current being measured, and provides an appropriate scale factor, from 20 to 28, for the eight bit accurate digital signal generated by the analog to digital converter.

Halogen monitoring apparatus

Abstract: There is disclosed apparatus for monitoring the concentration levels of halogen gas in a gaseous atmosphere as confined in an enclosure over a relatively extended period of time. Such monitoring apparatus includes a sensor including first and second electrodes disposed to define a space therebetween through which the gaseous atmosphere flows and a voltage source for applying a voltage between the first and second electrodes whereby an ionization current flows to the first electrode. A control mechanism illustratively in the form of a programmed microcontroller monitors the ionization current collected by the first electrode as the output signal of the sensor, to determine an increase therein as would be indicative of a halogen leak. Upon determining an increase of the sensor output signal above a predetermined difference, the control mechanism removes the energization from the halogen sensor whereby the ionization current is terminated and the life of the sensor extended. The control mechanism further causes an initial reading of the sensor signal to be taken and to be stored, whereby subsequent sensor readings may be compensated by subtracting the stored value therefrom to provide a compensated output indicative of the increased halogen level with respect to the initial background reading thereof. The relatively small halogen sensor output is amplified by a variable gain amplifier, whose gain setting is automatically set over a large range of sensitivities.

Current ratio device

Abstract: A current ratio device for use in constructing a current transformer comprises a first magnetic core, a second magnetic core, a measuring winding electromagnetically coupled with the first core but not with the second core, and a compensating winding electromagnetically coupled with both cores. An externally powered amplifier has its input connected to receive the voltage waveform across the measuring winding. Its output provides a compensating current through the compensating winding equal to a magnetizing current required to magnetize the second core. The amplifier output also provides a measuring current through the measuring winding in the direction opposite that of the compensating current and equal to the compensating current multiplied by the ratio of turns in the compensating and measuring windings. This device is a self-contained article of commerce that, when electromagnetically coupled (without electrical connection) to conventional primary and secondary windings and a burden, provides a current transformer with improved qualities. In particular, the magnetizing current needed by the transformer is provided by the separate current ratio device, thus avoiding the error inherent in current transformers that arises from the need to supply the magnetizing current from the primary circuit. Another disclosed feature is the ability to examine the waveform of the magnetizing current and in particular to detect the presence of even harmonics and hence a probability of direct current in the primary circuit.

Constant propagation delay current reference

Abstract: A constant propagation delay current reference is provided having an external source providing a reference frequency signal. A phase lock loop is provided which is responsive to the reference frequency signal and to an operating frequency signal to provide a current reference signal at the output of the loop. The current reference signal is provided to a current to frequency converter which generates the operating frequency signal. A current mirror, also coupled to the phase lock loop output provides an output current proportional to the current reference signal which is suitable for providing the injector current for I 2 L devices. The output current tracks the process, voltage and temperature variations of the integrated circuit, allowing the injector currents to be optimized for maintaining constant propagation delay in the circuits being powered.

Operation control system for internal combustion engines

Abstract: An operation control system for an internal combustion engine includes a first current detector for detecting a value of electric current flowing in a field winding of an AC generator of the engine, and an ECU responsive to the detected value of electric current for determining a control amount by which the operation of the engine is to be controlled, and for changing output torque of the engine in response to the determined control amount. A second current detector, preferably, a Hall element, detects a value of electric current flowing from the AC generator to electrical loads on the engine. The ECU detects a transient state of the electrical loads, based upon the detected value of electric current from the second current detector. The ECU is operable when the transient state is detected, for determining a transient correction amount of the determined control amount, in response to the detected value of electric current from the first current detector.

Device limiting the power supply current for a direct current motor equipped with such a device

Abstract: A device limits the power supply current for a direct current electric motor with electronic switching. The stator of the motor comprises several windings angularly displaced and successively energized by an electronic switching device to create an electric field. The device is arranged so as to establish a limitation of the current in accordance with an operating parameter of the motor according to a relation which takes the variation of the load into account according to the parameter and which only authorizes a slightly higher current than that necessary for normal operation.

Compensation principle current sensor

Abstract: In this sensor, the magnetic field generated in a magnetic core by the current to be measured is compensated by a compensation current, at least one strip-shaped element of amorphous soft-magnetic material being arranged for controlling the compensation current in the magnetic circuit of the magnetic core, which element is magnetised in a bipolar pulse-shaped manner with the aid of an indicator winding so that the imbalance of the current or, respectively, voltage amplitudes can be used for determining and evaluating the misalignment

Temperature compensated voltage generator

Abstract: A temperature compensation circuit for a device with a voltage output affected by temperature in a predetermined manner and a null output for which the voltage is zero regardless of temperature comprises a voltage to current converter responsive to the generated voltage to produce a proportional current, a current generator comprising elements responsive to the temperature of the device to generate a pair of compensation currents varying therewith in a predetermined manner so that the ratio of the compensation currents embodies a desired temperature compensation, and a transconductance multiplier effective to multiply the proportional current by the ratio of the compensation currents to generate a compensated output current. It may further comprise a current to voltage converter responsive to the compensated output current to produce a compensated output voltage.

Magnetically-coupled apparatus for measuring electrical current

Abstract: The present invention provides current measuring apparatus of the type using magnetic coupling, the apparatus comprising a transformer (Tr) having a gap (E) in which a device (G) is disposed suitable for providing a signal which is a function of the magnetic flux existing in the gap with the primary winding (P) of the transformer conveying the current (I) to be measured. The apparatus includes the improvement of employing a device for separating the high frequency A.C. components from the low frequency A.C. components and the D.C. component of the current to be measured. In addition, a device for providing a second signal proportional to the high frequency A.C. component is used, along with a summing device (e) for summing a first signal and the second signal as provided by the device located in the gap. The invention is applicable in the electrical industry to measure current.

Semiconductor-assisted ultra-fast contact breaker

Abstract: An ultra-fast contact breaker is described which includes an ultra-fast cut-off mechanism provided with a repulsion disk fitted with moving contacts (7, 7'), the said mechanism also including fixed contacts (9, 9'), to the input and output terminals (1, 3) of which there is connected an assistance circuit (10) including a capacitor (21) and a coil (23) as well as a group of semiconductors (13, 15, 17, 19), the coil (23) wholly or partly constituting the repulsion coil of the said ultra-fast mechanism, which includes at least two parallel branches (CD, EF), a first branch (CD) including two opposed diodes (13, 15) or similar in series, each directed in the non-conducting direction for the current entering the circuit, a second branch (EF) including two opposed thyristors or similar (17, 19), each directed in the conducting direction for the current entering the circuit, and the LC oscillating circuit (21, 23) which connects the common point of the two diodes (13, 15) or similar and the common point of the two thyristors (17, 19 ) or similar, the two thyristors (17, 19) or similar being remote controlled or controlled by a current sensor (20) which is built in and which detects the exceeding of a previously fixed triggering threshold which can be adjusted in the control electronics.

Optical system for a Faraday effect current sensor

Abstract: A system for monitoring an alternating current including: a current transducer (10) having first and second optical ports (12,14) and a component for causing optical radiation to travel between the optical ports (12,14) while interacting with the alternating current in a manner to cause the intensity of the optical radiation to vary as a function of variations in the amplitude of the current, with the polarity of the variation being dependent on the direction of travel of optical radiaiton in the transducer (10) between the optical ports (12,14); two optical cables (16,18) each optically coupled to a respective optical port; couplers (20,22) connected to the optical cables (16,18) for causing optical radiation to travel in both directions in the transducer (10) between the optical ports (12,14); and a circuit arrangement (24,26,28,30,38,40,52) for deriving a respective representation of the change in intensity experienced by the optical radiation traveling in each direction through the cables (16,18) and the transducer (10), and for combining the representations relating to both directions in order to derive an indication of the change in intensity experienced by the optical radiation when traveling through the transducer (10).

Current limited dc power controller

Abstract: A current limited DC power controller is provided with an output stage having a controllable solid state switching device for conducting current between a pair of output terminals and a drive circuit for controlling the operation of this switching device in response to a control signal. A programmable current source is used to produce a reference current signal in response to a command signal and this reference current signal passes through a resistor to produce a reference voltage signal having a magnitude proportional to the command signal. When the power controller is off, the reference voltage signal is clamped to a preselected value. A second voltage signal proportional to the load current is combined with the referenced voltage signal and used to produce the control signal to which the drive circuit responds.

Direct AC-DC converter fault protection system

Abstract: In a direct AC/AC converter, fault protection is performed with a minimal number of fault detecting devices and the rating of such fault detecting devices is reduced while still being able to respond quickly to a fault current. This is achieved by using a current sensor in common to at least all the current lines of one group of switches and by combining the operation of such common current sensor with the operation of one current sensor associated with the related output phase line. In another embodiment, all the current lines connected to a switch, for all the groups of switches, are passed through a common and single current sensor.

Frequency control apparatus of a multi-refrigeration cycle system

Abstract: A frequency control apparatus of a multi-refrigeration cycle is provided with a current sensor to detect a primary current for a motor or a pressure sensor to detect a pressure at the discharge side of a compressor to detect a load in the refrigeration cycle. When a value detected by the sensor is estimated as being lower than a predetermined value range, the frequency of a current to be supplied to the motor is increased, and when the value detect by the sensor is estimated as being higher than the predetermined value range, the frequency is decreased, whereby the rising time of the refrigeration cycle can be shortened. Further, the frequency is determined by a weighted error average value of the difference between target room temperature in the rooms and detected temperature in the rooms to thereby control the multi-refrigeration cycle to provide an appropriate performance.

System for evaluating the condition and performance of a valve and valve operator combination and sensor for measuring forces on a valve stem

Abstract: A device for measuring and indicating the forces on a valve stem (24) over at least a portion of the valve strokes is comprised of a strain sensor (38) secured to the valve yoke (16) for sensing strains experienced by the valve yoke (16). The sensed strains are proportional to the forces on the valve yoke (16) and are equal but opposite to the forces on the valve stem (24). The strain sensor (38) generates electrical signals proportional to the forces on the valve stem (24). A display (74), electrically connected to the strain sensor (38), is provided for receiving the generated electrical signals and for indicating the forces on the valve stem (24). A system for evaluating the performance of a valve (12) and valve operator (14), also utilizes the yoke strain sensor (38) in combination with other sensors, including a second strain sensor (220) for sensing strains experienced by the valve operator housing (14), a valve stem motion sensor (90), a spring pack motion sensor (102), a motor current sensor (104), a vibration sensor (105) and, possibly, a stem strain sensor (86), as well as an indicator (106) of the condition of torque and limit switches.

Precision tracking current generator

Abstract: A precision current generator provides an output current responsive to a reference supply voltage. The current generator comprises a voltage generator which drives the input to a buffer amplifier. The buffer amplifier output drives the bases of multiple output transistors, the collectors of which form the current outputs. The output current is not dependent upon transistor beta, junction voltage, temperature or supply voltage. The all NPN design enables the current generator to track the reference voltage at high frequencies without peaking or ringing of the output current and without voltage coupling between output devices.

Zero and span adjustment circuit for current/pressure transducer

Abstract: A zero and span adjustment circuit for current to pressure transducers. Current sources in parallel with the transducer bypass current around the transducer. One current source includes a variable resistor for adjusting the zero set point independently of the input current signal. The other current source includes a variable resistor for adjusting the span of the output pressure proportional to the input current signal. A feedback resistor couples a feedback signal from the transducer current to the other current source to vary the bypass current.

Dual limit programmable linear signal limiter

Abstract: A current signal limiter provides precise minimum and maximum current limiting. Both maximum and minimum current limits are easily programmable. The signal limiter operates at maximum frequency response without inversion of the input signal. Current signal limiting is achieved by an NPN transistor biased in a common base configuration with the base coupled to a reference voltage source and the collector providing the output current, a series diode coupled to the emitter of the transistor for receiving a trickle current which prevents the transistor from turning off as well as setting a minimum current limit, and a diode matrix for receiving two reference currents and an input current. The diode matrix steers the input and reference currents to the transistor or to the reference voltage source, depending on the magnitude of the input and reference currents. The minimum and maximum current limits are programmable by adjusting the values of the reference currents and the trickle current.

Capacitance measuring apparatus with means for nulling the resistive component

Abstract: A circuit and method for measuring the capacitance of a medium independent of the resistivity of the medium. A triangular voltage is applied to plates immersed in the medium to generate both a resistive current component in phase with the triangular voltage and a capacitive current component in phase with a differential of the triangular voltage. The resistive and capacitive current components are summed with a selectable current which is provided having a phase π radians out of phase with the triangular voltage and having an amplitude related to a control signal. The summed current is sampled over a time period phase shifted from the capacitive current component and then integrated so that the capacitive current component integrates to zero and the integral of the resistive current component minus the selectable current provides the control signal. In response to the control signal, the selectable current is varied until the sum of the selectable current and resistive current component are nulled. This summed current is then sampled in phase with the capacitive current component thereby obtaining a measurment of capacitance independent of resistance.