WO1998009176A1 - A circuit for current measurement and uses thereof - Google Patents

A circuit for current measurement and uses thereof Download PDF

Info

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
French (fr)
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/en

Links

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.

Abstract

When measuring current in a conductor (6), the two inputs of a differential amplifier (1) are connected to the conductor at two points (7, 8) which have a suitable spacing. This obviates dissipating elements in the measurement as well as use of current encircling elements. The power supply for the differential amplifier is tapped symmetrically with respect to the potential of the conductor. The voltage of the conductor is measured in addition to the current, and both current and voltage are fed to A/D converters. The digitized signals are fed to a calculation unit (5) which is adapted to calculate the instantaneous power of the conductor, its instantaneous energy, the square on the current of the conductor, the curve shape of the current and the frequency contents. The above-mentioned measurement set-up lends itself for the control of relays, fuse cut-outs, excess current specifications, as a consumption meter, for motor controls, and for amplifier characteristic monitoring.

Description

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.
Several basic methods of measuring current in conductors are known. The most generally known ones include
resistive methods
pick-up coils
Hall elements
magneto diodes
- flux gates
various optical methods.
Of these methods the last 5 ones are galvanically insu- lated from the conductor during measurements, while a resistive measurement requires a direct connection to the conductor which is being measured. The absence of galvanic separation from the conductor does not necessarily mean that this is a drawback, since the measuring elec- tronics may subsequently be separated so that the user will not get in contact with the conductor which is being measured.
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.
Since 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.
Accordingly, 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.
Thus, the measuring set-up includes no shunt resistor, which, of course, means avoidance of dissipating elements in the measuring set-up.
When, as stated in claim 2, 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.
To stabilize the power supply to the differential amplifier additionally it is an advantage, as stated m claim 3, that the potential of the conductor is fed to two op- positely polarized zener diodes connected in series with an RC link, and that the two oppositely polarized zener diodes are connected in parallel with a capacitor connected in series with a diode and connected in parallel with an additional capacitor, which is connected in series with an additional diode, said two diodes having op- posite conducting directions.
Further, 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.
To stabilize the current measurement additionally with a view to correcting errors caused by temperature varia- tions which occur in the conductor when it carries current, it is an advantage, as stated in claim 5, that 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.
With a view to signal processing of the temperature cor- rection signal as well as the measured signal, the measured current and the temperature correction signal are fed to a multiplexer which is connected in series with an A/D converter.
To benefit additionally from the measuring circuit of the invention it is an advantage, as stated in claim 7, that the voltage of the conductor is measured, and that this voltage is fed to an A/D converter.
In order to make optimum calculations by means of the measuring set-up according to the invention, it is expedient, as stated in claim 8, that 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 (φ) , the curve shape of the current, the curve shape of the voltage and frequency contents .
This allows determination of any parameter which is to be derived from the measurements, cf. also the following.
Furthermore, it is an advantage, as stated m claim 9, if a control circuit is connected to the output of the cal¬ culation unit.
This allows equipment connected to the control circuit to be cut m and cut out in various ways, e.g. in connection with the uses defined in claims 10-15, on the basis of the measured parameters.
As appears from claims 10-15, the 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.
Moreover, the 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 .
The invention will now be explained more fully with ref- erence to an embodiment shown in the drawing, in which
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.
As will be seen m fig. 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- fier 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.
As will be seen, two 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.
It should moreover be noted that these resistors have so great values that they do not constitute dissipating elements with respect to the conductor 6. The output signal 9 is fed to a multiplexer 3.
To correct temperature variations which occur when a cur- rent flows in the conductor 6, an NTC resistor Rτ in series with a resistor Rl is provided near the conductor. The junction between Rl and Tr 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.
As will be additionally seen from fig. 1, it is possible to tap the voltage on the conductor 6 by means of a voltmeter 2. This voltage is fed to the calculation unit 5 at the point F, in which it, together with the other parameters, may be included in desired calculations.
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.
As will be seen 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.
The use of the 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.
Finally, 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.
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(φ), the curve shape of the current and frequency contents.
These parameters may be tapped from the point H in the calculation unit 5 and be fed to a control circuit (not shown) , which is capable of performing various functions m dependence on specific applications.
For example, it will be possible to use 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. It is also possible to measure excess current that may be DC or AC of an arbitrary curve shape, as the circuit of the invention can generate a measured curve shape and, on the basis of this, a control signal which results in cutting- off of the measured current, thereby preventing undesired current levels.
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.
Finally, it is noted that the circuit of the invention lends itself for use in fixed installations, where the dimensions of the conductor being measured are known.
However, nothing prevents the circuit from being used universally, as calibration of measuring set-ups may take place by allowing a known current to run m the conductor which is to be measured, and then adjusting the circuit for display of the known value, e.g. on an LCD display.
Although the invention has been explained in connection with various uses, it is possible to devise other uses within the scope of the claims, using the parameters which may be derived by the circuit of the invention.

Claims

P a t e n t C l a i m s
1. A circuit for measuring current in a conductor (6), wherein a measurement signal proportional to the current in the conductor is sensed on an output (9) of the differential amplifier (1), c h a r a c t e r i z e d in that the two inputs of the differential amplifier are connected to the conductor (6) at two points (7, 8) which have a suitable spacing.
2. A circuit according to claim 1, c h a r a c t e r i z e d in that the supply voltage for the differential amplifier is tapped symmetrically from the potential of the conductor.
3. A circuit according to claim 2, c h a r a c t e r i z e d m that the potential of the conductor is fed to two oppositely polarized zener diodes (Dl, D2 ) connected in series with an RC link (R, Cl), and that the two oppositely polarized zener diodes are connected m parallel with a capacitor (C2) connected in series with a diode (D3) and connected in parallel with an additional capacitor (C3), which is connected in series with an additional diode (D4), said two diodes (D3, D ) having opposite conducting directions.
4. A circuit according to claim 1, c h a r a c t e r i z e d m that the supply voltage for the differential amplifier is provided by two batteries which are connected in series with opposite polarity, and that the common point of the batteries is connected to the potential of the conductor.
5. A circuit according to claims 1-4, c h a r a c - t e r i z e d in that a temperature correction signal is tapped from a junction between a resistor (Rl) and an NTC resistor (RT) , said resistor (Rl) being connected to the supply voltage, said NTC resistor (Rτ) being connected to earth and positioned physically in the vicinity of the conductor (6) .
6. A circuit according to claim 5, c h a r a c t e r i z e d in that the measured current and the temperature correction signal are fed to a multiplexer (3) which is connected in series with an A/D converter (4) .
7. A circuit according to any one of the preceding claims, c h a r a c t e r i z e d in that the voltage of the conductor is measured, and that this voltage is fed to an A/D converter.
8. A circuit according to claim 5, c h a r a c t e r i z e d in that the signals from the A/D converters are fed to a calculation unit (5) which is adapted to calculate the instantaneous power of the conductor, its instantaneous energy, the square on the current of the conductor, cos (φ) , the curve shape of the current and frequency contents.
9. A circuit according to claim 8, c h a r a c t e r i z e d in that a control circuit is connected to the output of the calculation unit.
10. Use of a circuit according to claim 8 or 9 for controlling a relay.
11. Use of a circuit according to claim 8 or 9 for simulating a safety fuse, or for simulating an arbitrary fuse characteristic.
12. Use of a circuit according to claim 8 or 9 as an excess current sensor.
13. Use of a circuit according to claim 8 or 9 as a con- sumption meter.
14. Use of a circuit according to claim 8 or 9 for use in the monitoring of motor control characteristics.
15. Use of a circuit according to claim 8 or 9 for use in amplifier characteristic monitoring.
PCT/DK1997/000355 1996-08-30 1997-08-29 A circuit for current measurement and uses thereof WO1998009176A1 (en)

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
NO963624 1996-08-30
NO963624A NO963624L (en) 1996-08-30 1996-08-30 Circuits for current measurement and their use

Publications (1)

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

Family

ID=19899772

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1997/000355 WO1998009176A1 (en) 1996-08-30 1997-08-29 A circuit for current measurement and uses thereof

Country Status (3)

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

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 (en) * 2011-09-23 2013-03-28 Continental Automotive Gmbh Device for measuring a battery current

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 (en) * 1992-10-21 1994-04-27 Sagem Sa Current measuring device with a 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 (en) * 1992-10-21 1994-04-27 Sagem Sa Current measuring device with a 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 (en) * 2011-09-23 2013-03-28 Continental Automotive Gmbh Device for measuring a battery current
US9360500B2 (en) 2011-09-23 2016-06-07 Continental Automotive Gmbh Device for measuring a battery current

Also Published As

Publication number Publication date
NO963624L (en) 1998-03-02
AU4112197A (en) 1998-03-19
NO963624D0 (en) 1996-08-30

Similar Documents

Publication Publication Date Title
EP1397693B1 (en) Measuring devices
US7193827B2 (en) Single-sensor microcontroller-based approach for ground fault circuit interrupters
EP1970716B1 (en) Wide range current sensing method and system
EP2713175A2 (en) Battery tester
EP2293401B1 (en) Protective system for voltage transformers
AU2005288465A1 (en) Leak current breaker and method
WO2003036312A2 (en) Determining electrical faults on undergrounded power systems using directional element
AU2002310615A1 (en) Measuring devices
CN86107915A (en) Adopt the overcurrent circuit interruption device of RMS sampling
EP0746890B1 (en) Method and apparatus for rms current approximation
US5940257A (en) Method and apparatus for alternating current monitoring with phase and magnitude measurement
JP2005065382A (en) Dc current detector and dc earth fault current detector
CA3036562A1 (en) Method and system for hot socket detection in a utility meter
KR100342096B1 (en) Solid state overload relay
US6541954B1 (en) Circuit apparatus for sensing line conditions in a three phase power line
US10684315B2 (en) System for indicating the presence of voltage in a high-voltage network
WO1998009176A1 (en) A circuit for current measurement and uses thereof
WO2004093284A1 (en) Solar power system
JP2000035452A (en) Insulation resistance measuring device
KR100765344B1 (en) Apparatus for detecting power and current used electricity and electronic type
CN112180265A (en) Battery tester
EP4133289B1 (en) Energy metering and surge current detection
JPS6314566B2 (en)
US11740265B1 (en) Signal conditioning circuit
JP3424374B2 (en) Lightning arrester leakage current sensor

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AT AU AZ BA BB BG BR BY CA CH CN CU CZ CZ DE DE DK DK EE EE ES FI FI GB GE GH HU IL IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SK SL TJ TM TR TT UA UG US UZ VN YU ZW AM AZ BY KG KZ MD RU TJ TM

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH KE LS MW SD SZ UG ZW AT BE CH DE DK ES FI FR

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase

Ref country code: JP

Ref document number: 1998511190

Format of ref document f/p: F

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA