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WO1998009176A1 - Circuit de mesure d'intensite et utilisations associees - Google Patents

Circuit de mesure d'intensite et utilisations associees Download PDF

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Publication number
WO1998009176A1
WO1998009176A1 PCT/DK1997/000355 DK9700355W WO9809176A1 WO 1998009176 A1 WO1998009176 A1 WO 1998009176A1 DK 9700355 W DK9700355 W DK 9700355W WO 9809176 A1 WO9809176 A1 WO 9809176A1
Authority
WO
WIPO (PCT)
Prior art keywords
conductor
circuit according
current
differential amplifier
fed
Prior art date
Application number
PCT/DK1997/000355
Other languages
English (en)
Inventor
Erling Nielsen
Original Assignee
Lk A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lk A/S filed Critical Lk A/S
Priority to AU41121/97A priority Critical patent/AU4112197A/en
Publication of WO1998009176A1 publication Critical patent/WO1998009176A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only

Definitions

  • a circuit for current measurement and uses thereof is a circuit for current measurement and uses thereof
  • the invention relates to a circuit for measuring current in a conductor, wherein a measurement signal proportional to the current in the conductor is sensed on an output of a differential amplifier.
  • EP 0 594 500 Al discloses a method of measuring phase currents which is of the resistive type. This method comprises connecting two points of a conductor with two in- puts of a differential amplifier. A shunt resistor is placed in parallel with the two inputs, and measurement of the voltage across the shunt resistor provides a value proportional to the current on the output of the differ- ential amplifier.
  • the measuring set-up includes a shunt resistor, a dissipating element is introduced, reducing the flexibility of the measuring circuit, as the shunt resistor will clearly have to adapted in size to the nature and size of the currents which are measured.
  • an object of the present invention is to provide a method of the type stated in the opening para- graph which gives greater flexibility, and wherein dissipating elements are eliminated.
  • the object of the invention is achieved in that the two inputs of the differential amplifier are connected to the conductor at two points which have a suitable spacing.
  • the measuring set-up includes no shunt resistor, which, of course, means avoidance of dissipating elements in the measuring set-up.
  • the supply voltage for the differential amplifier is tapped symmetrically from the potential of the conductor, it is ensured that the measurement and the measuring set-up itself are not destroyed or disturbed by destructive common mode voltages, if any.
  • the supply voltage for the differential amplifier may be provided by two batteries which are connected in series with opposite polarity, and so that the common point of the batteries is connected to the potential of the conductor.
  • This way of providing the supply voltage may be an advantage, if e.g. it is desired to use the measuring set-up in a situation where there is no access to a zero conductor.
  • a temperature correction signal is tapped from a junction between a resistor and an NTC resistor (a temperature-sensitive resistor) , said resistor being connected to the supply voltage, said NTC resistor being connected to earth and positioned physically in the vicinity of the conductor.
  • the measured current and the temperature correction signal are fed to a multiplexer which is connected in series with an A/D converter.
  • the signals from the A/D converters are fed to a calculation unit which is adapted to calculate the instantaneous power of the conductor, its instantaneous energy, the square on the cur- rent of the conductor, cos ( ⁇ ) , the curve shape of the current, the curve shape of the voltage and frequency contents .
  • circuit of the invention s used for monitoring individual parameters, such as for controlling a relay, as stated in claim 10, for simulating a safety fuse, or for simulating an arbitrary fuse characteristic, as stated in claim 11, and as an ex ⁇ cess current sensor, as stated m claim 12.
  • circuit of the invention may be used as a consumption meter for use m the monitoring of motor con- trol characteristics, as stated m claim 14, and finally for use m various amplifier characteristic monitoring processes .
  • fig. 1 shows the current sensor according to the invention
  • fig. 2 shows the supply voltage for the current sensor according to fig. 1, and
  • fig. 3 schematically shows the calculation unit for use in connection with the current sensor of fig. 1.
  • a differential amplifier 1 two inputs of a differential amplifier 1 are connected to a conductor 6, whose current I is to be measured.
  • the one input of the differential amplifier and the other input of the differential ampli- bomb are connected at two points 7 and 8, respectively.
  • the current in the conductor 6 causes a voltage loss between the two points 7, 8 which may be detected by the differential amplifier 1, which on its output 9 emits a signal which is proportional to the current in the con- ductor.
  • resistors R2 and R3 are connected to the negative input of the differential amplifier 1, and two resistors R4, R5 are connected to its positive input. These resistors are selected such that the impedance, as seen from the negative and positive inputs of the differential amplifier, will be of the same size.
  • the output signal 9 is fed to a multiplexer 3.
  • an NTC resistor R ⁇ in series with a resistor Rl is provided near the conductor.
  • the junction between Rl and T r is connected to the multiplexer 3.
  • the signal in the junction is representative of temperature changes that may occur in the conductor 6.
  • Both the measurement signal on the output 9 and the temperature correction signal are fed via the multiplexer 3 to an A/D converter 4, in which the signals are digitized and are fed from there to the calculation unit shown m fig. 3 at the point I, from which the signal processing of the measured values may proceed.
  • the differential amplifier 1 of fig. 1 is powered at the points D and F by means of the circuit set-up shown in fig. 2.
  • the supply voltage is provided on the basis of two oppositely polarized zener diodes Dl , D2.
  • the phase voltage of the conductor 6 is applied to the diodes at the point A.
  • a resistor R and a capacitor Cl, which is connected to earth, are inserted in series with the diodes.
  • the resistor R and the capacitor Cl are intended to provide protection against excess voltages, and these components are dimensioned such that all occur- ring voltage transients do not result m greater energy dissipations than is defensible.
  • Two series connections are connected in parallel with the zener diodes, said series connections consisting of a capacitor C2 and a diode D3, respectively, whose common point supplies the positive signal to the differential amplifier, while the other parallel connection consists of the capacitor C3 and the diode D4, supplying the negative potential to the differential amplifier 1.
  • circuit set-up in fig. 2 provides a stable fixed voltage. No matter how the signal at the point A changes, a smoothed DC voltage, e.g. of +7 volts and -7 volts, will be provided on the output of the supply at the points D and E. This stable supply ensures that no common mode voltages occur in the differential amplifier.
  • fig. 3 schematically shows a calculation unit 5 for receiving the signals from the current sensor of fig. 1.
  • Point E receives partly the sensed current signal m the conductor 6 and partly the temperature-corrected sig- nal from RT . Further, in an embodiment, the voltage across the conductor 6 at the point F is fed to the calculation unit.
  • calcu- lation unit 5 Numerous parameters may be derived by means of the calcu- lation unit 5, such as the instantaneous power of the conductor, its instantaneous energy, the square on the current of the conductor, cos( ⁇ ), the curve shape of the current and frequency contents.
  • control circuit (not shown) , which is capable of performing various functions m dependence on specific applications.
  • the circuit of the invention together with a breaking element, such as a relay or a controlled switch. It may be ensured by means of the control circuit that relays may be used for interrupting excess currents in connections which were not possible before.
  • the principle is that it is possible, via the current measurement and a periodically controlled cut-in to distinguish between the currents which are caused by a short-circuit proper, and the currents which occur in connection with capacitive cut-in which may not result in interruption. It is hereby possible to discon- nect a relay at an earlier time m the current.
  • the circuit of the invention can also replace fuses with the possibility of cutting-m the current after drop-out on the basis of the measured values, if special conditions so permit.
  • circuit of the invention lends itself for use in fixed installations, where the dimensions of the conductor being measured are known.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

Lorsque l'on mesure l'intensité dans un conducteur (6), on connecte les deux entrées d'un amplificateur différentiel (1) à ce conducteur, au niveau de deux points (7, 8) présentant un espace approprié entre eux. Grâce à cet agencement, on n'a pas à utiliser d'éléments dissipatifs d'énergie au cours de la mesure, ni d'éléments de bobinage. On a doté l'alimentation de l'amplificateur différentiel de prises symétriques par rapport au potentiel du conducteur. Outre la mesure de l'intensité dans le conducteur, on mesure la tension dans celui-ci, et on dirige vers des convertisseurs A/N à la fois les signaux de mesure d'intensité et de tension. Les signaux numérisés sont envoyés à une unité de calcul (5) conçue pour calculer la puissance et l'énergie instantanées du conducteur, le carré de l'intensité du conducteur, la forme de la courbe de l'intensité et les composantes fréquencielles. Le circuit susmentionné permet de commander un relais, de servir de fusible de sûreté, de détecter des intensités excessives, de même qu'il peut servir en tant que compteur de consommation, pour surveiller des caractéristiques de commande de moteur, et pour surveiller des caractéristiques d'amplificateur.
PCT/DK1997/000355 1996-08-30 1997-08-29 Circuit de mesure d'intensite et utilisations associees WO1998009176A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU41121/97A AU4112197A (en) 1996-08-30 1997-08-29 A circuit for current measurement and uses thereof

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO963624A NO963624L (no) 1996-08-30 1996-08-30 Kretslöp til strömmåling samt anvendelse derav
NO963624 1996-08-30

Publications (1)

Publication Number Publication Date
WO1998009176A1 true WO1998009176A1 (fr) 1998-03-05

Family

ID=19899772

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1997/000355 WO1998009176A1 (fr) 1996-08-30 1997-08-29 Circuit de mesure d'intensite et utilisations associees

Country Status (3)

Country Link
AU (1) AU4112197A (fr)
NO (1) NO963624L (fr)
WO (1) WO1998009176A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7629787B2 (en) 2007-01-03 2009-12-08 Qixiang Lu Current sensor having shunt resistor and clamper diode for motor control
WO2013041603A1 (fr) * 2011-09-23 2013-03-28 Continental Automotive Gmbh Dispositif de mesure de courant de batterie

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4186339A (en) * 1978-01-20 1980-01-29 Curtis Instruments, Inc. Method and apparatus for measuring current, especially useful in multi-ampere systems
US4584525A (en) * 1983-04-18 1986-04-22 General Electric Company Current-shunt system for known conductors
EP0594500A1 (fr) * 1992-10-21 1994-04-27 Sagem Sa Dispositif de mesure de courant par shunt

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4186339A (en) * 1978-01-20 1980-01-29 Curtis Instruments, Inc. Method and apparatus for measuring current, especially useful in multi-ampere systems
US4584525A (en) * 1983-04-18 1986-04-22 General Electric Company Current-shunt system for known conductors
EP0594500A1 (fr) * 1992-10-21 1994-04-27 Sagem Sa Dispositif de mesure de courant par shunt

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7629787B2 (en) 2007-01-03 2009-12-08 Qixiang Lu Current sensor having shunt resistor and clamper diode for motor control
WO2013041603A1 (fr) * 2011-09-23 2013-03-28 Continental Automotive Gmbh Dispositif de mesure de courant de batterie
US9360500B2 (en) 2011-09-23 2016-06-07 Continental Automotive Gmbh Device for measuring a battery current

Also Published As

Publication number Publication date
AU4112197A (en) 1998-03-19
NO963624D0 (no) 1996-08-30
NO963624L (no) 1998-03-02

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