JPH0674977A - Non-contact type ammeter - Google Patents

Abstract

PURPOSE:To provide an ammeter with higher accuracy by shaping a detecting section like the form of a superconducting trochoidal coil, and using a ferromagnetic material for a winding core. CONSTITUTION:When current flows across a sample, current also flows in a Rogowskii coil and magnetic field is generated with a sensor coil connected to the Rogowskii coil in superconducting state. Thus, when a Hall element is laid across the sensor coil, Hall voltage is generated. In this case, accuracy is determined only on the basis of the performance of the Hall element and no accuracy improvement results. For this reason, a coil to offset a magnetic flux generated with the current flowing across the sample is provided, and the Hall element is used as a zero-point sensor entirely free from an error, even when subjected to an influence by external magnetic field. According to this constitution, a clear linear relationship is established between the sample current and cancel current, and highly accurate measurements can be undertaken. Furthermore, a ferromagnetic material is used for the winding core of the sensor coil, and the coil is shaped like a trochoidal form free from flux leak, thereby enabling measurement accuracy to be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an ammeter for measuring a sample current in a non-contact manner at a very low temperature.

[0002]

2. Description of the Related Art As a conventional technique, there is a method of measuring a magnetic flux generated by a sample current using only a Hall element. This method is difficult to calibrate and has a large error because the linearity of the Hall element collapses when the sample current increases. Moreover, when an external magnetic field is applied, the change in the magnetic flux created by the sample current is buried by the external magnetic field, and the error is ± 30.
It becomes very large with%.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to improve the accuracy of the conventional technique of ± 30% to an error of ± 0.1%.

[0004]

In order to achieve the above-mentioned object, the present invention uses a Hall element as a zero point sensor without any deviation so that an ammeter is configured to detect a magnetic flux generated by a change in a sample conductor current. It shall consist of a superconducting Rogowski coil, a detection unit covered with a magnetic shield, and a superconducting Rogowski coil for canceling the magnetic flux generated by the sample current. A ferromagnetic material is used for the core.

[0005]

According to this structure, even when an external magnetic field is applied, the accuracy can be increased to ± 0.1%.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a non-contact type ammeter according to an embodiment of the present invention.

The present invention will be described with reference to FIG. In FIG. 1, when a current flows through the sample, a current flows through the Rogowski coil, and a magnetic field is generated by the sensor coil superconductingly connected to the Rogowski coil. Therefore, the Hall voltage is generated by disposing the Hall element between the sensor coils. With only the above configuration, it is difficult to improve the accuracy because the accuracy is determined only by the performance of the Hall element. Therefore, by providing a coil that cancels the magnetic flux generated by the sample current, the Hall element is used as a zero point sensor that is absolutely stable even when affected by an external magnetic field or the like. With this configuration, a clean linearity is established between the sample current and the cancel current, which enables highly accurate measurement. Furthermore, FIG.
As described above, by using a ferromagnetic material such as pure iron for the core of the sensor coil and making the coil shape a toroidal shape with no leakage of magnetic flux, high accuracy can be achieved. The use of a ferromagnetic material such as pure iron as the coil winding frame is not normally used because of the effect of saturation when the magnetic field becomes strong,
Since this configuration is for measuring the zero magnetic field, if it is near zero, a magnetic flux of about 100 times that in the case of the air core is generated, which can contribute to higher accuracy. Figure 3 shows a comparison of the accuracy between the air core and the iron core. Further, since the toroidal coil has less leakage of magnetic flux than the solenoid coil, it can contribute to about twice the accuracy. A comparison of the accuracy of the air-core toroidal coil and the air-core solenoid coil is shown in FIG.
Due to the above effects, the measurement error can be reduced to ± 0.1% or less.

[0009]

According to the present invention, highly accurate measurement of ± 0.1% or less can be performed in a non-contact manner even in the measurement of a superconducting conductor under a large magnetic field and a high magnetic field. In addition, since it is a non-contact method, it is possible to measure the current of devices used in the permanent current mode with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of a non-contact ammeter according to the present invention.

FIG. 2 is a perspective view of a toroidal coil-shaped iron core sensor coil according to the present invention.

FIG. 3 is a characteristic diagram showing an error when the sensor coil has an iron core toroidal shape and an air core toroidal shape.

FIG. 4 is a characteristic diagram showing an error when the sensor coil has an air-core toroidal shape and when the sensor coil has an air-core solenoid shape.

Claims (5)

[Claims] 1. A non-contact type current composed of a superconducting Rogowski coil for detecting a magnetic flux generated by a change in a sample conductor current and its detecting portion, and a superconducting Rogowski coil for canceling a magnetic flux generated by the sample conductor current. The non-contact ammeter, wherein the detector has a superconducting toroidal coil shape and a ferromagnetic material is used for the winding core. 2. The non-contact ammeter according to claim 1, wherein the ferromagnetic material used for the winding core is pure iron. 3. A non-contact type ammeter according to claim 1, wherein the detecting portion has a superconducting solenoid coil shape and a ferromagnetic material is used for the winding core. 4. The non-contact ammeter according to claim 1, wherein a Hall element is used as a zero point detection sensor in the detection section. 5. The non-contact ammeter according to claim 1, wherein the detection unit is covered with a magnetic shield.