Showing papers on "Current sensor published in 1983"

An external cavity diode laser sensor

Abstract: A simple compact optical sensor system consisting of a near-field external cavity coupled to a semiconductor laser is reported. In this device, a change of phase in the light fed back into the laser cavity by the perturbed external mirror modulates the output of the laser by effectively changing the laser facet reflectivity. Phase shifts of 9\cdot10^{-8} rad and 10-6rad were measured at 10 kHz and 100 Hz, respectively, using a 1-Hz bandwidth and a 98-percent reflector placed less than 10 μm from the laser facet. The sensitivity of these devices is shown to be limited by the intrinsic amplitude noise of the laser. The implementation of this sensor configuration is reported as an acoustic sensor, hydrophone, magnetic field, and current sensor as well as an accelerometer.

Fiber-optic current and voltage sensors using a Bi 12 GeO 20 single crystal

Abstract: By using Faraday and Pockels' effects of a Bi 12 GeO 20 (BGO) single crystal, two kinds of fiber-optic sensors for electric current and voltage were tentatively fabricated. The optimum design of these sensors and their performances were investigated. It was verified that the BGO crystal is very available for either of the current and voltage sensors with regard to their sensitivity and stability. As for the experimental results, the minimum detectable magnetic field of 10-2Oe and the temperature dependence within ±2 percent in the temperature range of -25 to 85°C was obtained for the current sensor, while for the voltage sensor the sensitivity of 10-3V and the temperature dependence within ± 0.5 percent was in the same temperature range.

Method and apparatus for controlling an electric motor the rotational speed of which is automatically reduced in no-load idling operation

Abstract: A method and apparatus for controlling an electric motor, in particular a motor for driving hand tools, saws, and the like, the rotational speed of which is automatically reduced in no-load idling operation and increased when working under load to pre-determined speed values corresponding to desired working speeds. A current sensor picks up the current absorbed by the electric motor and causes the speed of the electric motor to be abruptly changed when a load condition has been detected. A timing relay maintains the electric motor at the higher working speed for a pre-determined period of time after termination of the operation under load. The threshold value of the sensitivity of the current sensor is raised simultaneously with the change-over to the higher working speed.

Pressure transducer with temperature compensation circuit

Abstract: A pressure transducer is disclosed comprising a pressure sensor portion having gage resistors in bridge formed on a thin diaphragm of a semiconductor substrate, and a power supply connected to the pressure sensor portion for driving the pressure sensor. The power supply includes a first current source for supplying a temperature-dependent current equivalent to the sum of a current almost proportional to the absolute temperature and a current independent of temperature, and a second current source for sinking the current almost proportional to the temperature characteristic of the gage resistors from the current of the first current source. A temperature compensation circuit is additionally provided to drive the bridge circuit by the difference between the temperature-dependent current and the current proportional to the temperature characteristic in a constant-current driving mode, and by a voltage proportional to the current difference when the output of the bridge circuit is connected to an amplifier whose gain is dependent on temperature.

Digital-to-analog converting apparatus equipped with calibrating function

Abstract: In a D/A converting apparatus which provides a converted analog signal at its output terminal by selectively yielding one or more currents from one or more current sources in accordance with an input digital signal, the current sources are selectively actuated to output the currents and an error in the current of each selected current source is obtained from the output derived at the output terminal in response to the outputting of the current From the current error of each current source is computed a final error corresponding to each input digital signal and corrected data corresponding to the final error is stored in a corrected data memory, which is read out by the input digital signal The output thus read out is converted into an analog signal, whereby a correct converted output is obtained

Single-coil current measuring circuit

Abstract: A single-coil wound on a ferrite core surrounding a current path is driven from a voltage controlled constant current source. The coil drive current is modulated with a fixed frequency squarewave. The average voltage present across the coil is sensed and integrated to provide an output signal which is proportional to the current flow and also provides a negative feedback to the voltage controlled current source to bias the modulated drive current in a direction which compensates for the biasing effects of the current flowing in the conductive path.

D-C Bus current monitoring system

Abstract: The d-c bus current, fed to an inverter through a low pass filter, having a shunt-connected capacitor, from the output of an a-c energized a-c to d-c converter (such as a phase-controlled SCR rectifier bridge), is monitored by using a-c current transformers to sense the filter capacitor current and the a-c current supplied to the converter. The transformer output signals are employed to produce a d-c signal which is a reduced amplitude replica of, and has the identical waveshape as, the d-c bus current. The monitoring system is electrically isolated from the power circuitry by means of the a-c current transformers.

Drive system for a DC motor with reduced power loss

Abstract: A high power efficiency drive system for a DC motor which controls the supply of power to polyphase coils has a DC-DC switching converter for changing an output voltage according to an ON-time ratio of the switching transistor, and a switching controller for controlling the ON-time ratio of the switching transistor. The DC-DC switching converter includes a switching transistor for chopping the voltage of a DC voltage source, a filter for smoothing the output voltage of the switching transistor, and a current amplifier for supplying the switching transistor with a base current pulse having a magnitude proportional to an input current. The switching controller controls the operation of the current amplifier for producing the base current pulse of the switching transistor. The system further includes a current detector for detecting the current to the polyphase coils, a current supplier for supplying the current amplifier with the input current corresponding to the detected signal from the current detector, so that the base current of the switching transistor at the ON-time changes corresponding to the current to the polyphase coils.

Remote current detector

Abstract: A remote current sensor for use in a fault detector for an electrical transmission system. The remote current sensor includes a Hall effect transducer for measuring the magnetic field surrounding a conductor of the transmission system to thereby monitor the currents flowing through the conductor. The transducer is positioned between a pair of tapered pole pieces for concentrating low density magnetic flux in the air into a high density magnetic flux focused onto the transducer. The pole pieces enable the sensors to be positioned a distance from the conductor which is greater than the electrical arcing distance so as to allow use of the air gap between the conductor and sensor as insulation.

Current supply for use in low voltage IC devices

Abstract: A current mirror provides an output current, for use in an IC, that is a multiple of a reference current input. A high gain negative feedback loop is coupled between the current mirror reference input and the output device. This forces the reference input to operate as a diode and stabilizes the circuit operation so that the output current accurately reflects the reference current independently of the β of the devices.

Electric discharge system including means to normalize the interpole gap to minimize abnormal discharge conditions

Abstract: A voltage sensor senses the gap voltage between an electrode and a conductive workpiece and compares it to a reference voltage using a comparator amplifier. The output from the comparator amplifier is used by an oil hydraulic servomechanism to raise and lower the electrode. An ultrasonic sensor detects impulse waves from discharges and a current sensor detects the working current for determining the working conditions of the gap. After a predetermined number of irregular discharges occurs the gap width may be widened by the servomechanism, the flow of dielectric fluid may be increased to remove sludge and debris, or the time between machining pulses may be increased.

Pressure transducer using integrated circuit elements

Abstract: A pressure transducer comprises a pressure sensor including a bridge connection of gauging resistors formed on a semiconductor substrate, and a power supply connected to the pressure sensor for driving it and basically acting as a constant current source. The power supply includes at least two transistors formed on the semiconductor substrate. One of the transistors provides a collector current which is less in temperature-dependency relative to that of the other transistor, and the other transistor has a collector circuit connected to the pressure sensor and provides a collector current corresponding to a sum of a substantially temperature-dependent current and a substantially temperature-independent current. A ratio of the temperature-dependent current to the temperature-independent current is adjusted by selecting operation characteristics of the two transistors such that a temperature characteristic of the collector current of the other transistor is substantially inversely proportional to a temperature characteristic of the output of the pressure sensor when it is driven with a constant voltage.

Method and apparatus for controlling an ac motor

Abstract: Disclosed is a control apparatus and a control method for an AC motor (3, 6) which is driven by a power converter (2) constituted by switching elements. A current control circuit (17) turns on/off the switching elements in accordance with a current pattern signal in the form of an AC signal to thereby control the motor current. The current pattern signal is obtained by a current pattern calculating circuit (14, 21, 24) based on a current command signal and a sinusoidal signal which determines the current phase. A current correction signal proportional to the deviation of the motor current from the current command signal is obtained by a current correction control circuit (32, 12, 13, 121, 122, 131, 132) and added to the current command signal to be applied to the current pattern calculating circuit.

Pump-drive device of power-assisted steering system

Abstract: A pump-drive device of a power-assisted vehicle steering system, comprising a motor (8) operative to drive a steering pressure pump (6), a first sensor (14) for detecting vehicle speed and producing an output signal (Sv) representative of the detected vehicle speed, a second sensor (15) for detecting the motor output speed and producing an output signal (Sn) representative of the detected motor output speed, a current control circuit (12) responsive to the output signals (Sv,Sn) from the first and second sensors (14,15), a main current supply line (27) connected between a power source (9) and the motor (8) through the current control circuit (12), a bypass current supply line (28) bypassing the current control circuit (12) between the power source (9) and the motor (8), the current control circuit (12) being operative to produce an output signal (Sd) to vary the current to be passed through the main current supply line (27) on the basis of the output signals (Sv,Sn) from the first and second sensors (14,15), a detecting unit (30) responsive to a predetermined operative condition of the steering system and operative to produce an output signal when the steering system is in the predetermined operative condition, and a line shifting switch unit (24) to provide electrical connection selectively between the power source (9) and the motor (8) selectively through the main and bypass current supply lines (27,28) in the absence and presence, respectively, of the output signal from the detecting unit (30).

Current-squared-time (i2 t) protection system

Abstract: A system for protecting an electrical component, drawing current from a power source, utilizes a sensor providing an output signal proportional to the square of the load component current. The squared-current signal, when greater than a squared-normal-current signal, is integrated and compared to a current squared-time value. A system output is enabled if the load component instantaneous i 2 t value is greater than the current squared-time value set at the comparator, to remove the current flow to the protected component.

Measurement of near-surface current from a moored wave-slope follower

Abstract: A simple theory is developed for the output from a current sensor mounted on a streamline follower in monochromatic waves generating Stokes drift. By treating the special case in which the streamline is the wave surface, it is shown that a sensor rigidly mounted beneath a waveslope follower will record a current equal to the surface drift provided the depth of measurement and the buoy diameter are small compared with the wavelength. The vertical shear of the Stokes drift cannot therefore be obtained by using this technique and making observations at several levels. The buoy hull dimension is also an important parameter in that it progressively attenuates contributions to the drift as the wavelength decreases. Experiments in regular waves in a wave tank using miniature sensors mounted on model buoys are described; they also use a floating composite electromagnetic sensor that permits simultaneous observations at four depths. The observations support the basic conclusions of the theory.

System for measuring load current in an electronically controlled switch

Abstract: A new sensor means for accurately measuring the current flowing in an electronically controlled switch is presented. An ac coupled current sensor is arranged in circuit with the electronically controlled power switch. The output of the sensor channel is zeroed (or restored to another fixed independent level) whenever the power switch is in the OFF condition. Using the natural modulation of the power switch itself to coordinate the reconciling of the sensor output level with the OFF state of the power switch helps restore to the dc level lost through ac coupling. This coordination of the sensor with the switch itself reduces dc offset and drift and allows ac coupling, which removes dc common mode and increases primary current sensor flexibility, all without adding complexity. A plurality of such sensors can be combined to measure indirectly the load current from a plurality of switches according to Kirchoff's Current Law.

Temperature compensated current sensing circuit

Abstract: A metal resistor having a positive temperature coefficient of resistance is connected to a current source to develop a voltage drop that acts as an offset for a ΔV BE differential amplifier. Since this offset voltage has a positive temperature coefficient it will compensate the resistor coefficient to develop a constant current. The constant current can be employed in a current sink sense-shutoff combination or it can be used to develop a plural output current source/sink combination.

Control circuit of pulse width modulation inverter

Abstract: The invention relates to a control circuit of a pulse width modulation inverter, wherein a current control circuit to output a current control signal corresponding to a current command signal is provided, main transistors of a main circuit of the pulse width modulation inverter are switchingly controlled in response to a current control signal, whereby a driving current supplied to a motor from the pulse width modulation inverter is controlled to a value corresponding to the current command signal. The current control circuit is of such an arrangement that the current control circuit corrects the current command signal in response to the speed detection signal to compensate an error in current control due to a counter electromotive force of a DC motor, while exercising a proportional control over the driving current in accordance with a current command deviation value of a driving current detection signal from the current command signal, so that the motor can be controlled at high speed and with high accuracy.

Apparatus for controlling a plurality of current sources

Abstract: A microprocessor controller converts one or more sensor signals to a time multiplexed digital signal which is converted to an analog voltage signal by a digital-to-analog converter. A switching circuit, under the control of the microprocessor, selectively applies the analog signal to a plurality of current sources thereby setting the output current from each current source.

Current limiting circuit for high current peripheral drivers

Abstract: In a peripheral driver circuit a switching output transistor is operated from digital logic control and is provided with a shut off circuit which turns the output transistor off when its collector supply current exceeds its saturation current. A controlled base drive current is generated in a circuit that includes a scaled reference transistor that is operated at the same current density and the same collector voltage as the output transistor at its rated current. The reference transistor base current is amplified in a circuit having a current gain equal to the scaling between the reference and output transistors. Thus the base current applied to the output transistor is related to the driver rated current which ensures that saturation will occur up to at least the rated current and above which the shut off will be effective.

Ignition current sensor for an electronic speed control system

Abstract: An electronic circuit for disengaging an electronic speed control system when the rate of change of the automobile engine speed exceeds a predetermined amount is disclosed. A ferrite or powdered iron ring current transformer generates an input signal to the electronic circuit from one of the spark plug wires in the engine. The pulses from the ring current transformer are passed through a monostable multivibrator circuit and a filter network to a differentiator. The output of the differentiator is connected to a high limit detector and a low limit detector. When the rate of change of engine speed exceeds a predetermined amount, a signal is generated to disengage the speed control circuit.

Circuit and method for reducing non-linearity in analog output current due to waste current switching

Abstract: An integrated circuit digital to analog converter includes circuitry having first and second resistors in a R/2R resistor ladder which scales bit current contributions to an analog output current. Each of the first and second resistors have a respective terminal connected to the collector of a bit current transistor, the emitter of which is connected to the emitter of a waste current transistor. The digital to analog converter includes a metal ground voltage conductor having a "shared node" and a distributed resistance between one side of the shared node and a main ground voltage connection. The collector of the waste current transistor and a second terminal of the first resistor are both connected directly to the shared node. In operation, the waste current transistor switches waste current into the shared node, rather than into a separate waste current ground conductor. This results in substantially less voltage variation across the distributed resistance of the metal ground voltage conductor, and consequently lower non-linearity, than is the case if waste current is switched into the separate ground conductor.

Device for monitoring the charge state of a starter battery

Abstract: The invention relates to a device for monitoring the charge state of a starter battery of a motor vehicle. The discharging or charging current of the battery - without the current of the starter however - is measured by means of a measuring resistor designed as a current transformer. The current signal derived from the measured current is fed to an integrator of a processor, which uses an approximated integration of the current signal within a certain finite operating time to form a charge signal in which the starting charging or the battery current during the starting operation is taken into account. The charge signal is fed to an indicating stage, in which it activates an indicating element. The charge signal represents the current balance in the overall system within a determined operating time in the immediate past and is consequently a measure of the proper operation of the electrical energy supply of the vehicle.

Electronic subscriber junctor

Abstract: An electronic subscriber junctor for connecting a subscriber line to a telephone exchange, comprising an output amplifier circuit connected to the line, first means for generating a compensation voltage proportional to a common mode voltage occurring on the line and for providing a direct current proportional to a DC component of the line current, second means for obtaining a constant current, for algebraically summing said constant current and said direct current, and for supplying to the output amplifier circuit a first control current equal to said algebraic sum of the constant current and the direct current, third means for providing from said compensation voltage, via two connecting wires and on each wire, a second control current to the output amplifier circuit so as to compensate for longitudinal currents on the line, each connecting wire carrying the first control current and the output amplifier circuit delivering on each line wire a current proportional to the algebraic sum, on each connecting wire, of the first and second control currents, and an interface circuit connected to the first means and to the telephone exchange.

Bzz and Byz sense loop geometries for cylindrical tensor gradiometer loop structures

Abstract: Each of two sensor loop patterns on a cylindrical substrate produces one of, specifically B zz and B yz , of the five independent magnetic tensor gradiometer outputs as pure terms, meaning respectively dependent only upon g zz and g yz , with no admixture of other gradient terms, specifically without admixture of g xx . Such magnetic tensor gradiometer outputs are received at a current sensor device, nominally a superconducting quantum interference device (SQUID). Each of the two sensor loop patterns is of ten segments, and is a continuous closed-loop superconducting path save only for the single break point at which the current sensor device is coupled.

System for the control of electric energy consumption, preferably domestic

Abstract: 1. System for controlling the electrical energy consumption, preferably in households, with an electricity meter (Z) which, on the output side, delivers to a load calculator (C) a pulse train, having a frequency which is proportional to the power, with a measurement period generator and with switching elements (s0-s3), which are assigned to the individual energy-consuming apparatus or apparatus groups (10-13), whereby these switching elements are able to be influenced by the load calculator as a result of a comparison between one limiting value dependent on the network load and the determined actual power value for a measurement period under consideration of a priority sequence of the operation, dependent on time, and distributed in a non-volatile memory of the load calculator (C), of the values of the electrical power of the apparatus or appartus groups (10-13) as well as of the time constants of the apparatus or apparatus groups (10-13) determined by the thermal inertia or inertia dependent on the memory quantity, characterized in that to each apparatus or each apparatus groups (10-13) there is assigned a current sensor (20-23) for the current flowing to the apparatus, the output signal of which is led to the load calculator (C) an in that the disconnection and connection of apparatus or apparatus groups (10-13) when reaching the limiting value depending on the piority sequence, as well as on the individual time constant and current flow times thereof, occur in such a way that if the result, because of the time constants and the current flow duration spreading to the disconnection, is that a high-priority apparatus has almost reached its operational end state, whilst a low-priority apparatus is first located in the commencing state, the high-priority apparatus disconnects prematurely and the low-priority apparatus switches and vice versa.

Low power signal detector

Abstract: A low power signal detector circuit in which a first current limiting device supplies current or draws currents to maintain the voltage across an integrating capacitance to a selected value. A second and variable current limiting means responsive to the RF input signal amplitude is coupled to a common junction of the integrating capacitance and the first current limiting device so as to oppositely affect the charge on the capacitance as provided by the first current limiting device dependent upon the input signal value with respect to a preselected input signal voltage threshold amplitude. The first current limiting device and the variable current limiting device are conveniently implemented using metal-oxide-semiconductor-field-effect transistors operated in the weak-inversion mode so as to maintain power consumption at a minimum.

Lamp failure alarm

Abstract: To detect faults in lamps (10), especially lamps of a traffic light set, supplied with current through lamp supply cables (11), a current sensor (14) detects if the current in the line is below a given threshold in the presence of the applied supply voltage, whereupon a fault decision circuit (15) enables an amplifier driver (16) driven by an oscillator (17), thereby to produce a high frequency fault signal coupled through a coupling circuit (18) back to the supply cables (11), whereby the fault signal is fed to a remote controller, such as a roadside traffic light controller, which is responsive to the fault signal to produce a warning signal for transmission to a maintenance station. If the lamp (10) is energised from a reduced voltage at night-time, the current threshold is automatically reduced accordingly.

Foldback current limiting driver

Abstract: A voltage driving circuit for a load requiring foldback current limiting characteristics, current limiting means and current latching means. The current latching means monitors the load current until a predetermined limit is reached, then latches the load current at a predetermined level lower than the predetermined limit until a logic signal is applied to the voltage driving circuit to turn off the load current. Such reduction in the current magnitude of the output current provides lower power dissipation in the load, a faster load turnoff time as a result of less energy stored in the load, and a more precise control of a variable duty cycle output.