JP2005055298A - Clamp sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove common mode noise on laid wires from shield cases down to a ground changeover switch as to a sliding clamp sensor equipped with the changeover switch selectively giving ground potential to the shield cases in keeping with the opening/closing of magnetic cores. <P>SOLUTION: This clamp sensor includes a body case 11 and a slide case 21, and is provided with: a pair of magnetic cores 12 and 22 severally opened/closed in keeping with the movement of the slide case 21; a switch means 13 on the body case 11 side, with one contact 13a thereof connected to ground and the other contact 13b connected to the shield cases 12a and 22a of the magnetic cores via the laid wires 14; and a switch drive means on the slide case 21 side for providing continuity between the contacts 13a and 13b when the magnetic cores are closed, and providing non-continuity between the contacts 13a and 13b when the magnetic cores are opened. The laid wires 14 are grounded via a capacitor element C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a clamp sensor capable of measuring a current flowing through a conductor to be measured while keeping it in a live state, and more particularly to a technique for eliminating common mode noise.

  The clamp sensor is known as a current sensor that has a pair of openable and closable magnetic cores that can directly enclose the conductor to be measured in a live state, and can measure the current by sandwiching the conductor to be measured in the magnetic core. However, in recent years, as the electrical equipment is downsized, the wiring has become denser, and a clamp sensor that measures by sandwiching the wiring material is desired to be smaller and have better operability. Yes.

  In order to meet such demands, a method of sliding a pair of magnetic cores that can be opened and closed by sliding the divided magnetic cores in a direction parallel to the abutting end face is not a method of rotating a pair of magnetic cores around a rotation support shaft. A clamp sensor has been developed, and the present applicant has proposed the invention according to Patent Document 1 described below for this slide type clamp sensor.

  This will be described with reference to FIGS. 3 and 4. This slide-type clamp sensor includes a main body case 11 used as an elongated grip portion, and a slide case 21 slidable with respect to the main body case 11. Yes. A first magnetic core 12 is attached to the tip of the main body case 11, and a second magnetic core 22 is attached to the tip of the slide case 21.

  In this example, both the first magnetic core 12 and the second magnetic core 22 are formed in a U-shape, and are opened and closed along the abutting end face as the slide case 21 is operated. That is, when the knob 23 is put on a finger and the slide case 21 is slid forward (left side in the drawing), it is closed as shown in FIG. 3, and the slide case 21 is slid rearward to be opened as shown in FIG.

  The first magnetic core 12 is housed in a shield case 12a, and an electrically insulating cover 12b is provided along the inner surface of a substantially U-shaped groove for receiving the conductor W to be measured. Similarly, the second magnetic core 22 is also housed in the shield case 22a, and an electrically insulating cover 22b disposed between the openings of the cover 12b when part of its inner surface is closed. Is provided. That is, only the butted end surfaces of the first magnetic core 12 and the second magnetic core 22 are exposed.

  A magnetic material such as permalloy is used for the shield cases 12a and 22a. However, in order to detect a low level current with high sensitivity, the shield cases 12a and 22a are connected to the ground terminal of the measurement circuit so as to have the same potential as the ground. It is preferable to do.

  However, when the shield case 12a, 22a is connected to the ground terminal of the measurement circuit, for example, when a bare bare wire without insulation coating is sandwiched, the bare wire is brought into contact with the end face of the shield case or the magnetic core. If they come into contact with each other, in the worst case, a short-circuit accident may occur, or the chassis of the clamp sensor may have a potential and may not be measured.

  Therefore, in Patent Document 1, for example, a micro switch 13 is provided as a ground switch on the main body case 11 side, one contact 13a thereof is connected to the ground terminal of the measurement circuit, and the other contact 13b is routed through the wiring 14. In addition to being connected to the shield cases 12a and 22a, switch drive means for turning on and off between the contacts 13a and 13b of the microswitch 13 in accordance with the sliding is provided on the slide case 21 side. Although the switch driving means is not shown in the figure, a projection-like one acting on the arm of the microswitch 13 is employed.

  According to this, when the slide case 21 is slid forward and the magnetic cores 12 and 13 are closed, the contacts 13a and 13b of the microswitch 13 are turned on (conductive), and the shield cases 12a and 22a are connected to the ground terminal of the measurement circuit. When the magnetic cores 12 and 13 are opened by sliding the slide case 21 rearward, the contacts 13a and 13b of the microswitch 13 are turned off (non-conducting), and the shield cases 12a and 22a are ground terminals of the measurement circuit. Detached from.

However, when this clamp sensor is used in a high frequency region, a problem due to common mode noise occurs. The common mode noise is noise generated between the signal line or the power supply line and the ground (GND). However, in the case of the sliding structure as described in Patent Document 1, the mounting position of the microswitch 13 is limited by design. In addition, since the wiring length of the routing wiring 14 has to be increased, the routing wiring 14 has an impedance particularly by a common mode at a high frequency, which may adversely affect the measurement.
Japanese Patent No. 3417661

  Accordingly, an object of the present invention is to provide a clamp sensor having a ground changeover switch that selectively sets the shield case to the ground potential as the magnetic core is opened and closed, on the routing wiring from the shield case of the magnetic core to the ground changeover switch. Is to remove common mode noise.

  In order to solve the above problems, the invention according to claim 1 of the present application includes a main body case and a slide case slidable with respect to the main body case, each of which is opened and closed as the slide case moves, A pair of magnetic cores forming a magnetic circuit that encloses the conductor to be measured in a closed state are provided, and one of the two contacts is connected to the ground and the other contact is routed around the main body case side. Switch means connected to the shield case of the magnetic core through wiring is provided, and the slide case side is brought into conduction between the two contacts when the magnetic core is closed, and the magnetic In a clamp sensor provided with a switch driving means for bringing the two contacts into a non-conductive state when the core is opened, the routing wiring is connected to the capacitor element. It is characterized in that it is grounded Te.

  The present invention is not limited to a slide type clamp sensor, and the present invention includes a clamp sensor that opens and closes around a rotation support shaft. That is, the invention according to claim 2 of the present application is a pair of magnets forming a main body case having a rotating spindle and a magnetic circuit that is opened and closed around the rotating spindle and encloses the conductor to be measured in a closed state. A switch means including one of two contacts connected to the ground and the other contact connected to the shield case of each of the magnetic cores through a lead wiring on the main body case side. The rotary operation knob on one of the magnetic cores is provided with a conductive state between the two contacts when the magnetic core is closed, and between the two contacts when the magnetic core is opened. In the clamp sensor provided with the switch driving means for making the non-conductive state, the routing wiring is grounded via the capacitor element.

  In either case of the slide type or the rotary type, it is preferable that the grounding location of the routing wiring via the capacitor element is a position closer to the shield case side of the magnetic core within a design allowable range.

  According to the present invention, since the routing wiring from the shield case to the ground changeover switch is grounded via the capacitor, common mode noise on the routing wiring can be removed, and the measurement reliability is improved.

  FIG. 1 shows a first embodiment of the present invention. The clamp sensor 10A according to the first embodiment is a slide type, and most of the configuration may be the same as that of Patent Document 1 described above. A main body case 11 used and a slide case 21 slidable with respect to the main body case 11 are provided. A first magnetic core 12 is attached to the tip of the main body case 11, and a second magnetic core 22 is attached to the tip of the slide case 21.

  In order to selectively connect the shield cases 12a and 22a of the magnetic cores 12 and 22 to the ground terminal of the measurement circuit in accordance with the slide operation of the slide case 21, for example, a micro switch 13 as a ground changeover switch is provided in the main body case 11. Is provided.

  One contact 13a of the micro switch 13 is connected to the ground terminal (GND) of the measurement circuit, and the other contact 13b is connected to the shield cases 12a and 22a via the lead wiring 14. On the slide case 21 side, there is provided a switch driving means (not shown) for turning on and off between the contacts 13a and 13b of the micro switch 13 in accordance with the sliding.

  That is, as described above, when the slide case 21 is slid to the left front in FIG. 1 and the magnetic cores 12 and 22 are closed, the contact between the contacts 13a and 13b of the microswitch 13 is turned on and shielded. The cases 12a and 22a are connected to the ground terminal of the measurement circuit. When the magnetic cores 12 and 22 are opened by sliding the slide case 21 rearward, the contacts 13a and 13b of the microswitch 13 are turned off and shielded. Cases 12a and 22a are disconnected from the ground terminal of the measurement circuit.

  In the present invention, the lead wiring 14 connecting the shield cases 12a, 22a and the microswitch 13 is connected to the ground terminal (GND) of the measurement circuit via the capacitor C. As a result, common mode noise on the routing wiring 14 is dropped to the ground, and highly reliable measurement can be performed even when used in a high frequency region. In order to increase the removal rate of common mode noise, the grounding portion by the capacitor C of the routing wiring 14 is preferably located closer to the shield case as far as the design allows.

  Next, a second embodiment of the present invention will be described with reference to the schematic diagram shown in FIG. The clamp sensor 10B according to the second embodiment is a rotary type, and as a basic configuration thereof, a pair of body sensors 100 and a pair of rotatably supported shafts 101 provided on the body case 100 are rotatably supported. Magnetic cores 110 and 120 are provided.

  Although not shown in detail in the drawing, the main body case 100 is made of a synthetic resin casing used as a grip, for example, and a circuit board of a measurement circuit is accommodated therein. The magnetic cores 110 and 120 are closed in a state where the base ends of the respective one end sides are pivotally supported by the rotation support shaft 101 and the butted end faces of the other ends thereof open and close around the rotation support shaft 101. A closed magnetic circuit is formed around the conductor W to be measured.

  In FIG. 2, the magnetic cores 110 and 120 are formed in a symmetrical U-shape, but may be semicircular or semielliptical, and around the conductor W to be measured in a closed state. If a closed magnetic circuit is formed, it is not always necessary to be symmetrical.

  The magnetic cores 110 and 120 are covered with shield cases 111 and 121, respectively, except for the abutting end face on the other end side and the base end part on the rotary support shaft 101 side. The magnetic cores 110 and 120 are housed in a synthetic resin core holder (not shown) including the shield cases 111 and 121, respectively.

  Although not shown, the magnetic cores 110 and 120 are provided with Hall elements or detection coils as magnetoelectric conversion means, and the magnetic cores 110 and 120 are urged by a spring means (not shown) so as to be normally closed. Yes. In this example, one magnetic core 110 is fixed to the main body case 100, and the other magnetic core 120 is movable and includes a rotary operation knob 122 formed integrally with the core holder.

  As in the first embodiment, the shield cases 111 and 121 of the magnetic cores 110 and 120 are selectively connected to the ground terminal of the measurement circuit as the magnetic cores 110 and 120 are opened and closed. For example, a micro switch 102 is provided as a ground changeover switch.

  That is, one contact 102 a of the microswitch 102 is connected to the ground terminal (GND) of the measurement circuit, and the other contact 102 b is connected to the shield cases 111 and 121 via the lead wiring 103, respectively.

  The rotary operation knob 122 includes a convex portion 122a as a switch driving means for turning on and off between the contacts 102a and 102b of the micro switch 102 in accordance with the opening / closing operation. The switch driving means is not limited to the convex portion 122a. In short, the switch is turned on when the magnetic cores 110 and 120 are in the closed position, and the magnetic cores 110 and 120 are in the open position. Sometimes it is sufficient to switch off.

  Also in the second embodiment, in order to eliminate the adverse effects due to the common mode noise, the lead wiring 103 connecting the shield cases 111 and 121 and the microswitch 102 is connected to the ground terminal of the measurement circuit via the capacitor C. Yes.

  As a result, common mode noise on the routing wiring 103 is dropped to the ground, and highly reliable measurement can be performed even when used in a high frequency region. In order to increase the removal rate of common mode noise, as in the first embodiment, the grounding portion of the lead wiring 103 by the capacitor C is preferably located closer to the shield cases 111 and 121 as far as the design allows.

  In each of the above embodiments, a micro switch is used as the ground switch, but the present invention is not limited to the type of the switch. Further, the present invention can be applied to all clamp sensors that take a form in which the shield case of the magnetic core and the ground changeover switch are connected via a wiring without being limited to the slide type and the rotary type.

The typical front view showing a 1st embodiment of the clamp sensor by the present invention. The schematic diagram which shows 2nd Embodiment of the clamp sensor by this invention. The typical front view which shows the state which closed the magnetic core with the conventional clamp sensor. The typical front view which shows the state which opened the magnetic core with the conventional clamp sensor.

Explanation of symbols

10A, 10B Clamp sensor 11, 100 Main body case 12, 110 First magnetic core 12a, 111 Shield case 13, 102 Micro switch 13a, 13b, 102a, 102b Contact 14, 103 Lead wiring 21 Slide case 22, 120 Second magnetic core 22a, 121 Shield case 23, 122 Knob C Grounding capacitor

Claims (3)

A pair of a main body case and a slide case slidable with respect to the main body case, each of which is opened and closed as the slide case moves, and forms a magnetic circuit that encloses the conductor to be measured in a closed state. A switch in which one of the two contacts is connected to the ground and the other contact is connected to the shield case of each of the magnetic cores through a routing wire is provided on the main body case side. Means are provided, and on the slide case side, when the magnetic core is closed, the two contacts are in a conductive state, and when the magnetic core is opened, the two contacts are in a non-conductive state. In the clamp sensor provided with the switch driving means,
A clamp sensor, wherein the routing wiring is grounded through a capacitor element. A main body case having a rotation support shaft, and a pair of magnetic cores that are opened and closed around the rotation support shaft to form a magnetic circuit that encloses the conductor to be measured in a closed state. Switch means is provided in which one of the two contacts is connected to the ground, and the other contact is connected to the shield case of each of the magnetic cores through the routing wiring, and either one of the magnetic The rotary operation knob on the core side is provided with a switch driving means for bringing the two contacts into a conducting state when the magnetic core is closed, and bringing the two contacts into a non-conducting state when the magnetic core is opened. In the clamp sensor that
A clamp sensor, wherein the routing wiring is grounded through a capacitor element.   3. The clamp sensor according to claim 1, wherein a grounding point of the routing wiring through the capacitor element is a position closer to a shield case side of the magnetic core within a design allowable range.

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