Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Reexamination Certificate
1999-12-27
2001-07-10
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
C324S244000, C324S096000, C324S207130, C250S227180
Reexamination Certificate
active
06259245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for sensing an electric current by measuring an intensity in magnetic field around an ultrasonic fiber constructed in the device.
2.Description of the Prior Art
Conventional devices for measuring magnetic field intensity include a semiconductor-type device, which makes use of the Hall effect or magnet resistance effect in a semiconductor. The semiconductor-type device is of practical use, however, has a problem that a dynamic range for measurement is limited. Recently, a device using an optical-fiber cable is proposed for measuring magnetic field intensity caused by an electric current flowing in an electric wire. The optical-fiber type of device makes use of a delay-time change accompanying with an intensity change in magnetic field, and has a problem of the difficulty in substantially shortening the optical-fiber cable.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electric-current sensing device capable of measuring magnetic field intensity and sensing an electric current flowing in, for example, an electric wire, without disturbing a flow of the electric current and nondestructively.
Another object of the present invention is to provide an electric-current sensing device capable of making a dynamic range for measurement widely.
Another object of the present invention is to provide an electric-current sensing device capable of a quick response with a high sensitivity.
Another object of the present invention is to provide an electric-current sensing device capable of decreasing an electric power consumption.
A still other object of the present invention is to provide an electric-current sensing device easy in use and having a small size which is very light in weight and has a simple structure.
According to one aspect of the present invention there is provided an electric-current sensing device comprising an input ultrasonic transducer assembly, an output ultrasonic transducer assembly and an ultrasonic fiber made of a magneto-strictive delay line. The input ultrasonic transducer assembly consists of an input piezoelectric vibrator having two end surfaces perpendicular to the thickness direction thereof, a driving electrode formed on one end surface of the input piezoelectric vibrator, an input ground electrode formed on the other end surface of the input piezoelectric vibrator, and an input vibrating plate cemented to the input piezoelectric vibrator through the input ground electrode. The output ultrasonic transducer assembly consists of an output piezoelectric vibrator having two end surfaces perpendicular to the thickness direction thereof, a detecting electrode formed on one end surface of the output piezoelectric vibrator, an output ground electrode formed on the other end surface of the output piezoelectric vibrator, and an output vibrating plate cemented to the output piezoelectric vibrator through the output ground electrode. The ultrasonic fiber is connected between the input vibrating plate and the output vibrating plate.
When an input electric signal is applied to the input piezoelectric vibrator through the driving electrode and the input ground electrode, the input piezoelectric vibrator is acoustically vibrated. An acoustic vibration in the input piezoelectric vibrator is transmitted to the input vibrating plate, and then, to the output vibrating plate through the ultrasonic fiber. The acoustic vibration in the output vibrating plate is transmitted to the output piezoelectric vibrator, and detected between the detecting electrode and the output ground electrode, as a delayed electric signal. If the ultrasonic fiber is left in a magnetic field, the delayed electric signal is changed in accordance with an intensity in magnetic field. Therefore, an electric current around the ultrasonic fiber can be sensed from the delayed electric signal.
According to another aspect of the present invention there is provided an ultrasonic fiber having a coil-shaped structure.
According to another aspect of the present invention there is provided an input- and output piezoelectric vibrators made of a piezoelectric ceramic, respectively, of which the polarization axis is parallel to the thickness direction thereof.
According to another aspect of the present invention there is provided an input- and output piezoelectric vibrators having a square pillar- or a cylindrical-shaped body with the same shaped pierced hall parallel to the thickness direction thereof. In addition it is better that the shortest distance between an outer- and an inner edges on an end surface of the body is approximately equal to the thickness thereof. When the input- and output piezoelectric vibrators have such a construction, the input vibrating plate is cemented to the input piezoelectric vibrator such that the input vibrating plate covers an opening of the pierced hall of the input piezoelectric vibrator, and the output vibrating plate is cemented to the output piezoelectric vibrator such that the output vibrating plate covers an opening of the pierced hall of the output piezoelectric vibrator.
According to another aspect of the present invention there is provided an input- and output piezoelectric vibrators having an approximately square plate- or an approximately square pillar-shaped body. In this time, the input vibrating plate is cemented to the input piezoelectric vibrator such that the input vibrating plate projects like a springboard, and the output vibrating plate is cemented to the output piezoelectric vibrator such that the output vibrating plate projects like a springboard.
According to another aspect of the present invention there is provided a signal analyzing unit consisting of an amplifier and a frequency counter. The amplifier amplifies the delayed electric signal and supplies the driving electrode and the input ground electrode with a part of an amplified electric signal. Thus, the input piezoelectric vibrator, the input vibrating plate, the ultrasonic fiber, the output vibrating plate, the output piezoelectric vibrator and the amplifier form a delay-line oscillator. The frequency counter receives a remaining part of the amplified electric signal and senses the electric current around the ultrasonic fiber in terms of a frequency of the amplified electric signal.
According to another aspect of the present invention there is provided a signal analyzing unit consisting of an amplifier and a frequency to voltage converter. The amplifier amplifies the delayed electric signal and supplies the driving electrode and the input ground electrode with a part of an amplified electric signal. Thus, the input piezoelectric vibrator, the input vibrating plate, the ultrasonic fiber, the output vibrating plate, the output piezoelectric vibrator and the amplifier form a delay-line oscillator. The frequency to voltage converter receives a remaining part of the amplified electric signal and senses the electric current around the ultrasonic fiber in terms of a voltage of a converted electric signal.
According to another aspect of the present invention there is provided a signal analyzing unit consisting of a signal generator and a phase comparator. The signal generator generates the input electric signal. The phase comparator senses the electric current around the ultrasonic fiber in terms of a phase difference between a phase of the input electric signal and that of the delayed electric signal.
According to other aspect of the present invention there is provided a feedback electrode formed on the one end surface of the input piezoelectric vibrator such that the driving electrode and the feedback electrode are electrically separated, and that an area of the feedback electrode on the one end surface is less than that of the driving electrode thereon. The feedback electrode and the input ground electrode transduce the acoustic vibration between the feedback electrode and the input ground electrode to an electric signal, and supplies the driving electrode and the input ground electrode wit
Metjahic Safet
Nguyen Jimmy
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