JPH04331374A - Current measurement device - Google Patents

Abstract

PURPOSE:To easily perform current measurement only by abutting on a measurement terminal even with the use of fixed wiring such as a wiring pattern of a printed board. CONSTITUTION:The device is composed of a pair of current terminals 1, 2, an ammeter 6, a power source 7 for supplying current to the current terminals 1, 2, a current control element 8 for controlling supply current, a pair of potential difference detection terminals 3, 4, and an operation amplifier 5 for amplifying a potential difference, respective terminals abut on two points of wiring for measuring current and a current control element 8 is controlled by the operation amplifier 5 so that the potential difference between the two points may be 0muV. The potential difference between the two points of the wiring is 0muV, the current is 0mA so that the current allowed to flow in the wiring before it abuts on the terminals may be wholly allowed to flow in current terminals 1, 2.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a current measuring device.
More specifically, the present invention relates to a current measuring device that does not require opening the circuit by cutting or disconnecting the wiring to be measured, and can measure the current by simply bringing a measuring terminal into contact with the wiring.

0002

[Prior Art] Conventionally, as a method for measuring current without opening a circuit, a method has been known in which only the wiring to be measured for current passes through a ring-shaped magnetic field sensor to detect and measure the magnetic field generated around the wiring by the current. It is being

0003

However, in the conventional method, it is necessary to separate the wiring to be measured from other wiring and pass it through the annular magnetic field sensor. In the wiring pattern of a printed circuit board, it is impossible to separate the wiring to be measured from other wiring, and therefore there is a drawback that the current in such wiring cannot be measured.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the prior art, and to make it possible to measure current simply by touching the measurement terminal to the wiring to be measured.Therefore, even fixed wiring such as the wiring pattern of a printed circuit board can be easily measured. The purpose of this invention is to provide a current measuring device that can measure current.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a current measuring device that includes a pair of current terminals, an ammeter that measures the current flowing through the current terminals, and an ammeter that measures the current flowing through the current terminals. A power source to be supplied, a current control element that controls the current, a pair of potential difference detection terminals, an operational amplifier that amplifies this potential difference, and an output of the operational amplifier that controls the current control element, and each The current is measured by touching the terminal to the wire whose current is to be measured.

[0006]

[Operation] A pair of current terminals and a pair of potential difference detection terminals of the current measuring device configured as described above are respectively brought into contact with two points on the wiring where the current is to be measured, and the potential difference between the two points on the wiring is 0 μV. A current is supplied to the current terminal by controlling the current control element using an operational amplifier so that the current is obtained, and the current is measured by an ammeter. The current between the two points on the wiring is 0 mA because the potential difference is 0 μV, and all the current on the wiring that was flowing before the current terminal and the potential difference detection terminal were brought into contact flows to the current terminal, so the current cannot be measured. This allows current to be measured without opening the circuit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an example of a current measuring device according to the present invention. In FIG. 1, 1 and 2 are current terminals, and 3 and 4 are potential difference detection terminals. The current terminal 1 is connected to one side of an ammeter 6, the other side of the ammeter 6 is connected to the cathode of a battery 7, and the anode is connected to the collector of a transistor 8. Connect current terminal 2 to the emitter of transistor 8,
Voltage terminals 3 and 4 are connected to the non-inverting input terminal and the inverting input terminal of operational amplifier 5, respectively, and the output terminal of operational amplifier 5 is connected to the base of transistor 8. In such a configuration, the operational amplifier 5 connects the potential difference detection terminal 3
and 4, and when the potential at the potential difference detection terminal 3 is higher than the potential at the potential difference detection terminal 4, the voltage at the output terminal of the operational amplifier 5 increases, the base current of the transistor 8 increases, and the collector current also increases. However, the current flowing through the ammeter 6 increases. When the potential difference between the potential difference detection terminals 3 and 4 is 0 μV, the current flowing through the ammeter 6 has a constant value.

FIG. 2 is a diagram showing an example of measurement according to the present invention. In FIG. 2, the anode of the power supply 10 is connected to one of the resistors 11, the other of the resistor 11 is connected to one measurement point 13 of the wiring 12, and the other measurement point 14 of the wiring 12 is connected to the power supply 10.
connected to the cathode of The current terminal 1 and the potential difference detection terminal 3 are in contact with a measurement point 13 on the wiring 12, and the current terminal 2 and the potential difference detection terminal 4 are in contact with a measurement point 14 on the wiring 12. The current measuring device 15 is a current measuring device according to the invention. In such a configuration, the potential difference between the measurement points 13 and 14 on the wiring 12 is 0 μV, so the current in the wiring 12 is 0.
It is mA. Since all the current flowing through the resistor 11 flows to the current measuring device 15, the current in the wiring 12 before the current terminals 1 and 2 and the potential difference detection terminals 3 and 4 come into contact is measured by the current measuring device 1.
5 can be measured.

Considering the measurement error of this device, for example, the resistance value between measurement points 13 and 14 on the wiring 12 is 5 mΩ.
When the offset voltage error of operational amplifier 5 is 1 μV, the potential difference between points 13 and 14 on wire 12 is 1 μV, so the current in wire 12 is 0.2 mA, and this current does not flow to the current measuring device. This will result in measurement error.

0010

[Effects of the Invention] As explained above, according to the present invention, current can be measured simply by touching the measurement terminal to the wiring to be measured, so that the wiring to be measured can be cut or removed. There is no need to open the circuit by opening the circuit, and current can be easily measured in a short time even with fixed wiring such as the wiring pattern of a printed circuit board.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a current measuring device of the present invention.

FIG. 2 is an explanatory diagram showing a measurement example according to the present invention.

[Explanation of symbols] 1, 2 Current terminal 3, 4 Potential difference detection terminal 5 Operational amplifier 6 Ammeter 7 Power supply 8 Current amplification element 10 Power supply 11 Resistor 12 Wiring 13 Measurement points 14 Measurement points 15 Current measuring device

Claims (1)

[Claims] 1. A pair of current terminals, a pair of potential difference detection terminals, an operational amplifier that amplifies the potential difference between the potential difference detection terminals, a current control element controlled by the output voltage of the operational amplifier, and the current control element. A current measuring device comprising: a power source that supplies current to the element; and an ammeter that displays the current flowing through the current control element.