JP2008215900A - Noncontact current meter and measurement auxiliary tool of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a universal noncontact current meter for noncontactly, accurately and sensitively measuring a wiring current without removing wiring in a power supply such as a battery. <P>SOLUTION: A gripper 2a of the clamping current meter 2 with a wide current range clamps an inner periphery of a measurement auxiliary tool 1 and a battery wire 4. An inner periphery of a coil built in the measurement auxiliary tool 1 is clamped. A battery voltage is applied to a coil not shown in the figure. A predetermined current flows in the coil. When a minute dark current flows in the battery wire 4, a first magnetic flux due to the dark current and a second magnetic flux due to the measurement auxiliary tool 1 are superposed in the gripper 2a. The clamping current meter 2 adds the dark current and an offset current in proportion to the total magnetic flux due to the measurement auxiliary tool 1, and indicates a measured current. The dark current can be read from a difference between the measured current and the offset current in the wide range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-contact ammeter and a measurement auxiliary tool that clamp a current-carrying wiring and measure the current of the wiring, and in particular, a non-contact that can measure a minute current flowing from a battery when an automobile engine is stopped. The present invention relates to an ammeter and a measuring aid for the ammeter.

  Conventionally, a clamp-type ammeter is known as a non-contact ammeter in which a part of a ring-shaped core is cut out and a hall element is interposed in the gap portion. This type of non-contact ammeter detects a voltage across the Hall element because a voltage proportional to the magnetic flux generated in the core is generated at both ends of the Hall element when a direct current is passed through the wiring passing through the core. Thus, the through current can be measured. There is also known a non-contact ammeter that can be expanded and read up to a minute current of 1 / N of the range scale by setting the wiring penetrating the non-contact ammeter to N turns (see, for example, Patent Document 1). ).

On the other hand, since many electric devices are mounted on the vehicle or the like, a minute current flows from the battery even when the engine is stopped. Such a minute current is called a dark current, and a dark current of about 50 mA flows in a general vehicle. In the vehicle industry, there is an increasing demand for measuring such dark current as a guide for battery inspection. Further, not only for vehicles and the like, there is an increasing demand for measuring minute currents such as leakage currents flowing in indoor wiring and dark currents of household electric appliances.
Japanese Patent Laid-Open No. 63-210784 (second page, FIGS. 1 and 4)

  However, the general-purpose non-contact ammeter is in a range that can measure the alternator current when the vehicle's electrical equipment is operating and the cranking current when the engine is started. The scale is in the range of tens of amperes (for example, 20A or 100A).

  On the other hand, the accuracy and sensitivity of an ammeter is determined as a percentage of the instrument's full scale. For example, in the case of an ammeter with a full scale of 20 A and a first grade (± 1%), the accuracy and sensitivity are 0.2 A (200 mA), so a dark current of 50 mA cannot be measured. In particular, the sensitivity of ± 1% means that the indicator of the meter cannot be shaken at a current of 200 mA or less, so that a dark current of 50 mA cannot be measured as a matter of course. In the case of an expensive non-contact ammeter, a dark current of about 50 mA can be measured, but the price is several times (about five times) that of a general-purpose non-contact ammeter, so that it is suitable for general-purpose applications. It cannot be served.

  In the case of the non-contact ammeter disclosed in Patent Document 1, a minute current can be measured, but once the battery wiring is removed and the wiring is turned to N-turn and then connected to the battery again, the through current is measured. Since it has to be measured, there is a problem that preset values of various on-vehicle electric devices return to default values at the time of factory setting. Therefore, every time the current value is measured with a non-contact ammeter, the preset value must be reset for each electric device.

  The present invention has been made in view of the above problems, and is a general-purpose non-contact type capable of measuring a minute current in a non-contact manner with high accuracy and high sensitivity without removing a power source wiring such as a battery. An object is to provide a contact ammeter and a measuring aid for the ammeter.

  In order to achieve the above object, a non-contact ammeter of the present invention is a non-contact ammeter that measures the current flowing through a wire by passing the wire through a ring-shaped core that can be opened. When the wiring current flowing through the circuit is measured, the wiring current is measured by superimposing the wiring current and an offset current generated by a circuit provided separately.

  As a specific configuration of the non-contact ammeter according to the present invention, a clamp-type ammeter that allows a wire to pass through an openable ring-shaped core and measures a wire current flowing through the wire is provided separately from the wire. And a measurement auxiliary tool having an inner periphery of the coil penetrated by a core. As a result, the offset current generated by the coil of the measurement auxiliary tool is level-shifted with respect to the wiring current flowing in the wiring, so that the wiring current can be read with high accuracy and high sensitivity in the high range region of the non-contact ammeter. it can.

  According to the non-contact ammeter of the present invention, the wiring through which the current flows and the coil of the measurement auxiliary tool are clamped in parallel, and the wiring current (for example, dark current) flowing through the wiring is measured. Therefore, the wiring current can be measured in a non-contact manner without disconnecting the wiring, and the wiring current can be read with high accuracy and high sensitivity as the measuring range of the instrument is brought close to the full scale.

<< Summary of Invention >>
Hereinafter, a non-contact ammeter according to the best mode for carrying out the present invention (hereinafter referred to as an “embodiment”) will be described with reference to the drawings with a suitable example. Therefore, the outline of the non-contact ammeter according to the present invention will be described.

  The non-contact ammeter of the present invention is a general purpose clamp-type ammeter for measuring a large current, and when measuring the wiring current of a wiring in a non-contact manner, a measurement auxiliary tool in which a coil to which a voltage is applied is wound is measured. Clamp in parallel with the wiring. As a result, the second magnetic flux from the coil of the measurement aid is added to the core (gripping part) of the clamp-type ammeter with respect to the first magnetic flux proportional to the wiring current flowing through the penetrated wiring. Flowing. As a result, a current (offset current) corresponding to the second magnetic flux of the coil of the measurement auxiliary tool is added to the true wiring current (micro current). As a result, the non-contact ammeter has a wiring current (micro current). ), The offset current corresponding to the second magnetic flux of the coil is raised (that is, level-shifted) and indicated as the measurement current. As a result, the dead zone due to the instrument sensitivity near zero amperes of the non-contact ammeter is avoided, and the wiring current and the offset current of the measurement aid are added to indicate the measurement current. A flowing minute current (dark current) can be read.

  Next, some embodiments of the non-contact ammeter according to the present invention will be described in detail with reference to the drawings. In the following embodiments, a case where a non-contact ammeter measures the dark current flowing in the battery wiring when the automobile engine is stopped will be described as an example.

<< First Embodiment >>
FIG. 1 is a perspective view showing a usage state when the measurement auxiliary tool of the present embodiment is attached to a general-purpose clamp-type ammeter, FIG. 2 is an external perspective view showing the measurement auxiliary tool of the present embodiment, and FIG. FIG. 4 is a time chart showing the circuit operation of the measurement auxiliary tool of the present embodiment.

  As shown in FIG. 1, the non-contact ammeter 3 of the present embodiment includes a measurement auxiliary tool 1 and a general-purpose clamp-type ammeter 2. First, the clamp-type ammeter 2 will be briefly described with reference to FIG. The clamp-type ammeter 2 is a standard existing commercial product having a measurement range of 10.0 to 100.0 A or 20.0 to 200.0 A, for example, and includes a grip part (core) 2 a and a main body part 2 b. And is configured. The main body 2b is provided with a display unit 2c for displaying a current value, a pressing unit 2d provided so as to be able to perform a pressing operation, a changeover switch 2e for switching a measurement range, and the like. The grip portion 2a is U-shaped (or circular), and its distal end portion is formed in a divided manner, and is supported by the main body portion 2b so as to operate in a releasable manner. By pressing the pressing portion 2d provided on the main body portion 2b, the tips of the gripping portions 2a are separated from each other and opened. In addition, this clamp type ammeter 2 is used so that the battery wire 4 (refer FIG. 1) connected to the battery (not shown) of a motor vehicle may be penetrated to the holding part 2a.

  As shown in FIG. 2, the measurement auxiliary tool 1 attached to the clamp-type ammeter 2 has a rectangular and flat case 1a, and a rectangular through hole 1b penetrating vertically is formed in the center of the case 1a. Has been. Inside the case 1a, a coil L1 wound around the through hole 1b and a battery E1 and the like are provided. In addition, the through hole 1b is formed in a size that allows the gripping portion 2a of the general-purpose clamp-type ammeter 2 to be inserted. In addition, the measurement auxiliary tool 1 is provided with an operation switch SW1 that can be pressed and an indicator LED 1. In addition, the measurement auxiliary tool 1 of the present embodiment is used in a state where the grip portion 2a is passed through the through hole 1b of the case 1a (see FIG. 1).

  As shown in FIG. 3, the circuit of the measurement auxiliary tool 1 determines, for example, a coil L1 of 100T (turn) and a start timing of energization to the coil L1, and becomes a closed circuit (momentary) switch SW1 only when pressed. A charge / discharge time constant circuit comprising resistors R1, R2 and a capacitor C1, a transistor FET1 for controlling energization of the coil L1, a resistor R3 for limiting the energization current of the coil L1, and a coil when the transistor FET1 is turned off. A flywheel diode D1 for circulating the energy of L1, a display lamp LED1 that is turned on when the transistor FET1 is turned on and a current is flowing through the coil L1, a current limiting resistor R4, and a circuit of the measurement auxiliary tool 1 The battery E1 is a power source, and these are built in the case 1a. Note that the circuit shown in FIG. 3 corresponds to the circuit according to the embodiment of the present invention. In order to make the measurement auxiliary tool 1 shown in FIGS. 1 and 2 compact, it is preferable to use a button battery rather than an alkaline battery or the like as the battery E1 shown in FIG.

  Next, the operation of the circuit of FIG. 3 will be described with reference to the time chart of FIG. 4A shows the operation waveform of the switch SW1, FIG. 4B shows the gate G voltage of the transistor FET1 (that is, the voltage Va at the point a), and FIG. 4C shows the drain D voltage of the transistor FET1 (that is, the point b). Voltage Vb).

  For example, when a voltage of 3V is applied to the circuit by the battery E1 and the operator (measurer) turns on the momentary automatic return type switch SW1 at time t1, the charging time constant of the resistor R1 and the capacitor C1 sets the capacitor C1. The voltage Va at the point a (that is, the gate G voltage of the transistor FET1) rises, and the transistor FET1 is turned on at the time t2 (that is, the drain voltage Vb of the transistor FET1 becomes close to zero). The resistor R3 is set so that a current of 10 mA flows. At this time, the resistor R4 is set so that a current (for example, several mA) for turning on the indicator LED 1 flows.

  When the operator (measurer) releases the switch SW1 and turns off the switch SW1 at time t3 after a time extremely short (eg, several hundred mSec to 1Sec) after the time t1, the capacitor C1 and the resistor R2 The voltage Va at the point a of the capacitor C1 (the gate G voltage of the FET1) gradually decreases due to the discharge time constant, but the transistor FET1 continues to be turned on during this time (that is, the drain voltage Vb of the transistor FET1 is maintained at zero potential). In addition, the current is continuously supplied to the coil L1, and the indicator LED 1 is continuously turned on.

  Eventually, for example, at time t4 after about one minute, when the voltage Va at the point a of the capacitor C1 (the gate G voltage of the transistor FET1) drops below the operating voltage of the transistor FET1, the transistor FET1 is turned off (that is, the transistor FET1 The drain voltage Vb becomes the battery voltage 3V), the current of the coil L1 is cut off and the indicator lamp LED1 is turned off. That is, when the switch SW1 is turned on for a short period of time, during the time from the time t2 to the time t4 (for example, 1 minute), the current is continuously supplied to the coil L1 and the indicator LED 1 is kept on.

  When the transistor FET1 is turned off at time t4, if the current flowing through the coil L1 is cut off and the energy source is lost, high voltage noise is generated at both ends of the coil L1, and the transistor FET1 or the like may be damaged. There is. Therefore, when the transistor FET1 is turned off, the current generated in the coil L1 is circulated through the flywheel diode D1, thereby suppressing noise generated in the coil L1.

  The gripping portion 2a is inserted into the through hole 1b of the measurement auxiliary tool 1 configured as described above to clamp the inner periphery, and further, a wiring (battery wire 4) from a battery (not shown) is inserted into the gripping portion 2a. And clamp (see FIG. 1). At this time, the current direction of the measurement auxiliary tool 1 and the battery line 4 may be any direction, but in the following description, the current direction of the measurement auxiliary tool 1 and the battery line 4 is assumed to be the same. The full scale of the clamp-type ammeter 2 is assumed to be 20A.

For example, if a 20 mA dark current (wiring current, minute current) Ia flows through the battery wire 4 penetrating the gripping portion 2a of the clamp-type ammeter 2 at 1T (turn), the grip-type ammeter 2 A first magnetic flux corresponding to 20 mA × 1T = 20 mAT is generated in the portion 2a. Further, since a current of 10 mA flows through the coil L1 of 100T (turn) of the measurement aid 1 as shown in FIG. 3, it corresponds to 10 mA × 100T = 1000 mAT in the gripping portion 2a of the clamp type ammeter 2. A second magnetic flux is generated. That is, since a total magnetic flux corresponding to 1020 mAT is generated in the grip portion 2a of the clamp-type ammeter 2, the current (measurement current) I ₀ (current displayed on the display portion 2c) indicated by the clamp-type ammeter 2 is generated. Value) represents 1020 mA.

At this time, since the measured offset current I _L to advance the level shifted by aid 1 can be set for each measuring aid as a known value to say such as 1000 mA, the operator (measuring person) the clamp type current If the measurement current I ₀ indicated by the total 2 is 1020 mA, the dark current Ia can be intuitively read as Ia = I ₀ −I _L = 1020−1000 = 20 mA.

That is, if only the 20 mA dark current is read by the clamp-type ammeter 2, the dead zone due to the sensitivity of the instrument (for example, first-class sensitivity ± 1%) is 200 mA, and therefore the dark current of 20 mA cannot be read. However, by using the non-contact ammeter 3 in which the measurement aid 1 is added to the clamp-type ammeter 2, the dark current can be read in a relatively high region excluding the vicinity of zero ampere. Reading errors can be removed. Therefore, if read dark current Ia by level-shifting the offset current I _L to near full scale of the instrument by measuring aid 1, it is possible to read the dark current Ia with higher sensitivity.

Moreover, full-scale also the accuracy of the instrument (e.g., 20A) because it is determined as a percentage of, if read dark current Ia by a high level-shift the offset current I _L to range by measuring aid 1, more accurate The dark current Ia can be read.

Note that the relative relationship between the current direction of the battery wire 4 clamped by the gripping portion 2a of the clamp-type ammeter 2 and the current direction of the gripping portion 2a clamped by the measurement auxiliary tool 1 may be arbitrary. That is, since the measuring aid 1 according to the offset current I _L and the clamp-type ammeter 2 may be read as a dark current Ia the absolute value of the difference between the measured current I ₀ which instructs, clamp type current meter 2 of the grip portion 2a is clamped Since the battery wire 4 and the measurement auxiliary tool 1 may be oriented in any direction, the usability of the non-contact ammeter 3 is not likely to deteriorate.

For example, when the direction and orientation of the dark current Ia flowing through the battery lines 4 offset current _{I L} by the measuring aid 1 are different, the measurement current _{I 0} which clamping ammeter 2 is _instructed, I 0 = 1000-20 = It becomes 980 mA. The dark current Ia at this time is Ia = I ₀ −I _L = 980−1000 = −20 mA, but the absolute value of the differential current can be taken and 20 mA can be intuitively read as the dark current Ia.

As a general usage of the non-contact ammeter 3 shown in FIG. 1, the operator (measurer) turns on the clamp-type ammeter, performs zero adjustment, and then holds the measurement auxiliary tool 1 with the grip 2a. (Or with the measurement auxiliary tool 1 clamped to the gripping part 2a, the power is turned on and zero adjustment is performed), and the switch SW1 is turned on for a moment (for example, 1 second). Then, since the current (offset current) flowing through the coil L1 of the measurement auxiliary tool 1 is displayed on the display unit 2c, the battery wire 4 is subsequently clamped to the grip unit 2a. Thus, since the measurement current I ₀ of the offset current is added (superimposed) flowing through the measuring aid 1 and the wiring currents flowing in the battery line 4 is displayed on the display unit 2c, the measured currents I currently displayed ₀ The wiring current (dark current) is obtained by subtracting the previously displayed offset current from. When the switch SW1 is turned on, the indicator lamp LED1 is lit for about 1 minute. During this time, the battery wire 4 is clamped to the grip portion 2a and the dark current is measured.

Even if the time constant circuit and the transistor FET as shown in FIG. 1 are not provided, the switch is turned on only by the series circuit of the 100T (turn) coil, the switch and the limiting resistor shown in FIG. and it may be read dark current Ia flowing the offset current I _L by the measuring aid when being. By adopting such a circuit configuration, a semiconductor element such as a time constant circuit or a transistor FET becomes unnecessary, so that the measurement auxiliary tool 1 can be further reduced in size and cost can be reduced.

<< Second Embodiment >>
In said 1st Embodiment, it was set as the structure which incorporates an alkaline dry battery, a button battery, etc. in the measurement auxiliary tool 1 as a power supply of the measurement auxiliary tool 1, However, In 2nd Embodiment, it was built in the clamp type ammeter 2. It can also comprise so that the power supply of the measurement auxiliary tool 1 may be supplied from a battery (not shown). By doing in this way, the measurement auxiliary tool 1 can be made more compact.

<< Third Embodiment >>
Furthermore, in 3rd Embodiment, it can also comprise so that the power supply of the measurement auxiliary tool 1 may be supplied from the battery (not shown) mounted in the vehicle. By doing so, it is possible to apply a relatively high voltage to the coil L1 of the measuring aid 1, as a result, that a relatively high current value of the offset current I _L to level-shift the dark current Ia Therefore, the dark current Ia can be read in a high range region. Therefore, the dark current Ia can be read with higher accuracy and sensitivity.

<< 4th Embodiment >>
In the first to third embodiments, the offset current _IL is generated by using the measurement auxiliary tool 1 around which the coil L1 is wound, and the dark current Ia is level-shifted. However, in the fourth embodiment, the battery when measuring the dark current Ia connects the dummy load such as a lamp between positive and negative terminals of the battery may be a dummy current Id flowing through the dummy load configured as an offset current I _L.

FIG. 5 is a conceptual diagram of dark current measurement by a non-contact ammeter applied to the fourth embodiment of the present invention. As shown in FIG. 5, for example, when measuring the dark current Ia of a 12 V battery 5, for example, a 12 w (watt) lamp 6 is connected between the positive and negative terminals of the battery 5. Then, the battery wire (first wiring) 4 through which the dark current Ia flows and the lamp wiring (second wiring) 8 to which the lamp 6 is connected are paired and clamped by the grip portion 2a of the clamp-type ammeter 2. . Thus, the current of 1A flows in the lamp wiring 8 is offset current I _L, the measurement current I ₀ which clamping ammeter 2 instructs can be read as the sum of the offset current I _L and the dark current Ia. Therefore, it is possible to read the dark current Ia in a range region with high sensitivity and accuracy of the instrument.

<< 5th Embodiment >>
In the fifth embodiment, as a configuration combining the third embodiment and the fourth embodiment, the power of the measurement auxiliary tool 1 is supplied from the battery 5 mounted on the vehicle, and the lamp is connected between the positive and negative terminals of the battery 5. 6 is connected. Thus, the offset current I _L, since the sum of current corresponding to a second magnetic flux generated dummy current flowing through the lamp 6 by the measuring aid 1, relatively with less number of turns of the coils of the measuring aid 1 The measurement aid 1 can be configured in a compact manner.

It is a perspective view which shows the use condition when the measurement auxiliary tool of this embodiment is attached to a general purpose clamp type ammeter. It is an external appearance perspective view which shows the measurement auxiliary tool of this embodiment. It is a circuit diagram which shows the measurement auxiliary tool of this embodiment. It is a time chart which shows the circuit operation | movement of the measurement auxiliary tool of this embodiment. It is a conceptual diagram of the dark current measurement by the non-contact ammeter applied to 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measurement aid 1b Through hole 2 Clamp-type ammeter 2a Gripping part (core)
3 Non-contact Ammeter 4 Battery Wire 5 Battery 6 Lamp 8 Lamp Wiring Ia Wiring Current I _L Offset Current I ₀ Measurement Current L1 Coil

Claims (14)

A non-contact ammeter that measures the current that flows through the wiring through a ring-shaped core that can be opened,
A non-contact ammeter for measuring a wiring current flowing in the wiring by superimposing the wiring current and an offset current generated by a separately provided circuit. A clamp-type ammeter that passes through a ring-shaped core that can be opened and measures the wiring current flowing through the core, and
A measurement auxiliary tool having a coil through which an offset current is provided separately from the wiring, and the inner periphery of the coil is penetrated by the core;
A non-contact ammeter characterized by comprising:   The clamp type ammeter indicates, as a measurement current, a total current of a wiring current flowing through a wiring penetrating the core and an offset current corresponding to a magnetic flux generated by the measurement auxiliary tool penetrating the core. The non-contact ammeter according to claim 2.   4. The non-contact current according to claim 3, wherein when the clamp-type ammeter measures the measurement current, the offset current is cut off after a predetermined time from the start of energization of the coil. Total.   The non-contact ammeter according to claim 3 or 4, wherein a power source supplied to the coil is a battery built in the measurement auxiliary tool.   The non-contact ammeter according to claim 3 or 4, wherein a power source supplied to the coil is a battery built in the clamp-type ammeter.   The non-contact ammeter according to claim 3 or 4, wherein a power source supplied to the coil is a battery to which the wiring is connected. A non-contact ammeter that passes through a first wiring through an openable ring-shaped core and measures a wiring current flowing through the first wiring,
When measuring the wiring current flowing through the first wiring, the first wiring and a second wiring through which an offset current provided separately from the first wiring is passed in parallel through the core, A non-contact ammeter for measuring a wiring current flowing in the first wiring.   The non-contact ammeter according to claim 8, wherein the magnitude of the current flowing through the second wiring is determined by a dummy load connected to the second wiring. A measuring instrument for a clamp-type ammeter that penetrates a wire through an openable ring-shaped core and measures the wiring current flowing through the wire,
It has a coil through which an offset current flows separately from the wiring, and includes a through hole that penetrates the inner periphery of the coil through the core.
A measurement auxiliary tool, wherein a second magnetic flux generated by the coil is superimposed on a first magnetic flux flowing in the core by the wiring current.   The measurement auxiliary tool according to claim 10, further comprising a shut-off function that shuts off the energization of the coil after a predetermined time when the coil is energized.   The measurement auxiliary tool according to claim 10, wherein a power source supplied to the coil is a battery built in the coil.   The measurement auxiliary tool according to claim 10, wherein a power source supplied to the coil is a battery built in the clamp-type ammeter.   The measurement auxiliary tool according to claim 10, wherein a power source supplied to the coil is a battery to which the wiring is connected.

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