JPH0587857A - Two-terminal circuit element measuring device equipped with contact check function - Google Patents

Abstract

PURPOSE:To detect the connection disorder at the measurement terminal of a DUT with high precision and measure the DUT impedance with high precision. CONSTITUTION:A dc current flows into a DUT 6 from a dc voltage source 3, and the dc current is detected by an ammeter 12. Further, an ac current flows into the DUT 6 from an ac voltage source 23, and the ac current is measured by an ammeter 22, and the response voltage of the DUT 6 is measured by a voltmeter 24. An ideal opened state can be obtained, and the measurement value of the ac ammeter 22 can be reduced to zero. When each measurement value of the dc ammeter 12 and the ac ammeter 22 is substantially zero, the connection trouble of the DUT 6 is detected surely, and when the measurement value of the dc ammeter 12 is substantially zero, and the measurement value of the ac ammeter 22 is not substantially zero, it is judged that the connection of the DUT 6 is normal, and the impedance of the DUT 6 is measured from the measurement value of the ac ammeter 22 and the measurement value of the ac voltmeter 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-terminal circuit element measuring device with a contact check function, which simultaneously inspects the insulation resistance of a sample (object to be measured) at the same time as the contact check and determines the electrostatic capacitance of the sample of the cable. The present invention relates to the above-mentioned measuring device capable of measuring without changing the connection.

[0002]

BACKGROUND OF THE INVENTION A typical application of an insulation resistance tester is to inspect the insulation resistance of a capacitor. In this inspection, the higher the insulation resistance of the sample, the better. Therefore, when the sample has a contact failure at the connection portion with the instrument, it is judged as a non-defective product even if the sample is a defective insulation product. That is, conventionally, there is a disadvantage that it is not possible to recognize (contact check) from the measured value whether or not the sample is normally connected to the instrument, which is a problem particularly in the automatic inspection process. By the way, when the sample is a capacitor, it exhibits a low impedance in terms of alternating current,
If the insulation resistance of the capacitor is measured using direct current and the high frequency impedance of the capacitor is measured using alternating current, it is possible to determine whether the contact state is good or bad, that is, whether the measurement of the insulation resistance is effective.

An insulation resistance meter generally has a structure as shown in FIG.
It is composed of an instrument body 1 and an extension cable 5. The instrument main body 1 is composed of a DC ammeter 12 in which one input terminal is connected to a shielded jacket 11, and a DC voltage source 13 for applying a DC high voltage between the shield jacket 11 and the ground. The extension cable 5 is composed of a first conductor that constitutes the central conductor, a second conductor that covers the first conductor, and a third conductor that further covers the second conductor. On one end side of the cable 5, the first conductor is connected to the other input terminal of the DC ammeter 12, the second conductor is connected to the jacket 11, the third conductor is grounded, and the other end side of the cable 5 is connected. The sample connection terminals a and b of the first and third conductors of
Sample 6 (parallel circuit of capacitance C and resistance R _DC ) is connected.

By the way, in the automatic inspection process, impedance measurement is usually performed together with the above-described inspection in order to inspect whether or not the sample has a predetermined characteristic.
In impedance measurement, the sample (that is, the measured object,
When the distance between the sample and the object to be measured is called DUT) and the measuring device is long, the cable of the measuring terminal needs to be extended (1 to 2 [m]), and the DUT is grounded by one wire. There are also cases where the measurement must be performed in the above condition.
Therefore, it is necessary to meet the following requirements for the measurement. (1) The increase in capacitance caused by the connection of the DUT can be stably determined regardless of the extension of the cable. (2) Being able to measure a one-wire grounded DUT AC. (3) The current path for measuring the DC resistance is not affected by an external electromagnetic field or the like, and conversely, the current path does not have an external electromagnetic effect. (4) There is no need to add a new cable for impedance measurement. However, the conventional impedance measuring device (one example of which is shown in FIG. 5) satisfies the condition (1) but has the following problems. That is, in the measurement circuit for the high impedance DUT, it is impossible to connect the one-wire grounded DUT in terms of the circuit, and the condition (2) is not satisfied. Also,
When the ground side terminal of the DUT, which should be grounded with one wire, is floated from the ground and measured, the influence from the external electromagnetic field becomes remarkable and the accuracy is greatly deteriorated, and the condition (3) is not satisfied. Further, since the one-terminal trio measuring device using two coaxial cables is used, it is necessary to add another cable, and the condition (4) above is not satisfied.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve the above problems, and in the case of inspecting using an automatic component feeder, the DUT can be used by one device.
It is an object of the present invention to provide a two-terminal circuit element measuring device with a contact check function, which can detect a connection failure at the measuring terminal with high accuracy and can also perform impedance measurement of the DUT with high accuracy.

[0006]

SUMMARY OF THE INVENTION The inventors have found that the configuration of the one-terminal trio measuring device in the separately proposed “one-terminal trio, two-terminal trio measuring device” is very similar to that of the insulation resistance meter shown in FIG. This measuring device is based on the above (1)-
We paid attention to the fact that all the conditions of (4) are satisfied. Then, it was concluded that the above-mentioned contact check function can be reasonably added by configuring as follows. That is, the device of the present invention includes an AC voltage signal source for applying an AC signal between the first and second conductors and the grounded third conductor in the measuring device body, and also the first and second conductors. And a DC voltage signal source for applying a DC signal between the third conductor and the third conductor,
An AC voltage measuring device for measuring an AC voltage value applied to the DUT by the AC voltage signal source, and the DC voltage signal source being a DUT.
And a direct current measuring device for measuring a direct current value injected into the DUT, and an alternating current measuring device for measuring an alternating current injected into the DUT by the alternating voltage signal source. The AC voltage signal source is composed of an AC voltage source and a ferrite core transformer inserted in the first and second conductors of a three-wire coaxial cable, and one end of the AC voltage source is 3
The DC voltage measuring device is connected to the third conductor of the wire coaxial cable, one end of the drive winding of the ferrite core transformer is connected to the other end of the AC voltage source, and the other end is connected to the third conductor. It is also characterized in that the inductor and the DC ammeter are connected in series, and the AC voltage measuring device is configured by connecting the capacitor and the AC ammeter in series, respectively, and these are connected in parallel between the first and second conductors. And

Hereinafter, the insulation resistance meter of FIG. 3 and FIG.
While referring to the separately proposed one-terminal trio measurement device shown in
The theory and operation of the present invention will be described. The separately proposed one-terminal trio measuring device is for measuring a high impedance DUT, and is composed of a measuring device main body 2 and a three-wire coaxial cable 5 as shown in FIG. The measuring device main body 2 is similar to the case of the insulation resistance meter, and the AC ammeter 22 corresponding to the DC ammeter 12 in FIG. 3, the AC voltage source 23 corresponding to the DC voltage source 13 in FIG. The circuit is composed of a total of 24 parallel connections. In the figure, an impedance Zx is connected instead of the sample of FIG. Therefore, the above object can be achieved by combining the insulation resistance meter of FIG. 3 and the one-terminal trio measuring device of FIG. 4 without causing interference.

FIG. 1 shows an example of the above combination (that is, one aspect of the device of the present invention). As in the case of FIGS. 3 and 4, one end of a three-wire coaxial cable 5 is connected to the measuring device main body 3. The capacitance C and the resistance R _DC are provided between the first and third conductors at the other end.
The DUT 6 shown in parallel connection with is connected. In addition, these series connections are connected to the connection parts of the ammeters 12 and 22 of FIGS. 3 and 4 similarly to the connection part of the DC voltage source 13 and the connection part of the parallel circuit of the AC voltage source 23 and the AC voltmeter 24. The DC voltage source 13 and the parallel circuit are connected in series. In FIG. 1, a DC / AC ammeter 1
2, 22, AC voltmeter 24 and DC, AC voltage source 13,
Reference numeral 23 corresponds to the DC / AC current measuring device, AC voltage measuring hand device and DC / AC voltage signal source of the present invention. In addition,
The present invention is not limited to the circuit connection shown in FIG. 1. For example, a series connection circuit of a direct current ammeter and an inductor is used as a direct current measuring instrument, and a series connection of a capacitor and an alternating current ammeter is used as an alternating current measuring instrument. You may make it measure a direct current and an alternating current by connecting these circuits in parallel and connecting between the 1st, 2nd conductors, respectively using a connection circuit. Further, a ferrite core transformer inserted through the first and second conductors is used as an AC voltage signal source, and an AC voltage is applied between the first, second conductor and third conductor via the ferrite core transformer. You can In the circuit of FIG. 1, a DC current is injected from the DC voltage source 13 into the DUT 6, and this DC current is detected by the ammeter 12. An alternating current is injected from the alternating voltage source 23 into the DUT 6, and the alternating current is measured by the ammeter 22 so that the response voltage of the DUT 6 is measured by the voltmeter 2.
4 is measured.

Further, in the device of the present invention, the ideal open state can be obtained, and the ungrounded first conductor is leak-guarded by the second conductor having the same potential.
Can be set to 0. When the measured values of the DC ammeter 12 and the AC ammeter 22 are both substantially 0, it is surely detected that the connection of the DUT 6 is defective, and the measured value of the DC ammeter 12 is substantially 0. When the measured value of the AC ammeter 22 is not substantially 0, the connection of the DUT 6 is normal. Therefore, from the measured value of the AC ammeter 22 and the measured value of the AC voltmeter 23, the impedance of the DUT 6 (substantially , The capacitance of the capacitor C) is measured. It should be noted that in the conventional measuring device that cannot obtain the ideal open state, a connection failure of the DUT 6 occurs and the DUT 6 is not connected.
When no current flows, the DC ampere meter 12 has a measured value of 0, but the AC ammeter 22 does not necessarily have a measured value of 0. Therefore, it is not possible to determine whether the connection is truly bad or whether the DUT 6 has a high impedance.

[0010]

EXAMPLE An example of the measuring apparatus of the present invention is shown in FIG.
This will be described with reference to (A) and (B). In FIG.
One end of a three-wire coaxial cable 5 is connected to the measuring device main body 4, and the first end of the other end of the cable 5 and the grounded third
The conductor has DUT measurement terminals a and b, and a DUT (shown by a parallel circuit of a capacitor C and an insulation resistance R _DC ) 6 is connected between these terminals a and b. A ferrite core transformer 41 is attached to the first and second conductors of the three-wire coaxial cable. One end of the drive winding wound around the transformer 41 is the AC voltage source 23 and the other end is the cable. The third conductor 5 is connected to the third conductor via the ground. In this embodiment, the transformer 41 and the AC voltage source 23 form the AC voltage signal source of the present invention. The AC voltage source 23 includes an AC voltage measuring device (see FIG. 2).
In (A), an AC voltmeter 24) is connected in parallel, which measures the AC voltage applied to the DUT 6 by the AC voltage source 23 via the transformer 41. FIG. 2B shows an equivalent circuit of the transformer 41, which includes a first conductor, a second conductor,
It shows that the drive winding forms a three-winding transformer. In this embodiment, the first and second conductors are simultaneously driven by the transformer 41, so that it is not necessary to separately provide a circuit for floating the ground.

Further, the frequency of the AC voltage source 23 is set to several hundreds kH.
With z or more, a small transformer having an exciting impedance of several tens of Ω can be easily constructed by winding a coaxial wire of 1 to 3 turns around a ferrite core. A DC voltage signal source (DC voltage source 13 in the figure) is connected between the first and second conductors of the cable 5 and the third conductor, and between the first and second conductors, A parallel circuit of a direct current measuring device formed by connecting the inductor 7 and the direct current ammeter 12 for small current in series and an alternating current measuring device formed by connecting a capacitor 8 and an alternating current ammeter 22 in series is connected. ing. Here, the inductance of the inductor 7 is set to be sufficiently larger than the impedance of the measuring circuit at the measuring frequency, and the capacitance of the capacitor 8 is set to be sufficiently smaller than the impedance of the measuring circuit. There is.

The operation of the measuring apparatus of FIG. 2A will be described below. A DC voltage is applied to the measurement terminals a and b by the DC voltage source 13, and an AC voltage of a predetermined frequency is applied by the AC voltage source 23 via the ferrite core transformer 41.
A superimposed voltage of a DC voltage and an AC voltage is applied between the terminals a and b. When a measured value other than substantially 0 appears on the AC ammeter 22, it is determined that the connection between the terminals a and b and the DUT 6 is normal. Then, the quality of the DUT 6 is judged according to the measured value of the DC ammeter 12 (that is, the smaller the measured value, the better the product), and the AC voltmeter 2
The impedance of the DUT 6 is measured from the measured values of 4 and the AC ammeter 22. On the other hand, when the measured values of the DC ammeter 12 and the AC ammeter 22 are both substantially 0, the terminal a,
It is determined that the contact of b is abnormal, and the DUT 6 is again inspected and measured.

[0013]

As described above, according to the present invention, the following effects can be obtained. (1) In particular, in the automatic inspection process, the contact check can be reliably performed, and the insulation resistance test and impedance measurement of the DUT can be performed without separately adding a cable. (2) Since the third conductor of the three-wire coaxial cable is grounded, it is not affected by the external electromagnetic field during insulation inspection and impedance measurement. Therefore, the accuracy of impedance measurement does not deteriorate due to the extension of the cable. Also, DU
Even when T is in the one-wire grounded state, the insulation resistance test and the impedance measurement can be performed with high accuracy. (3) Further, since the ideal open state is possible, it is possible to stably determine the increase in electrostatic capacitance caused by the connection of the DUT regardless of the cable extension. (4) In the device in which the ferrite core transformer is inserted through the first and second conductors, low frequency noise is not injected into the DC ammeter (that is, the current path for measuring the DC current is not affected), so the insulation resistance Inspection accuracy and contact check accuracy are improved. Further, there is no inconvenience of separately providing a circuit for levitating the common ground point of the DC current measuring system. On the contrary, in this device, the impedance measurement system is not affected by the current path for measuring the direct current, so that the accuracy of impedance measurement does not deteriorate.

[Brief description of drawings]

FIG. 1 is a circuit diagram illustrating the measurement principle of the device of the present invention.

2A is a circuit diagram showing an embodiment based on the circuit of FIG. 1, and FIG. 2B is an equivalent circuit diagram of the ferrite core transformer in FIG.

FIG. 3 is a circuit diagram showing a conventional insulation resistance meter.

FIG. 4 is a circuit diagram showing a high-impedance one-terminal trio measurement device according to another application.

[Explanation of symbols]

 3, 4 Measuring device body 5 3-wire coaxial cable 6 DUT 7 Inductor 8 Capacitor 12 DC ammeter 13 DC voltage source 22 AC ammeter 23 AC voltage source 24 AC voltmeter 41 Ferrite core transformer

Front page continuation (72) Inventor Shuji Tanaka 9-1 Takakura-cho, Hachioji-shi, Tokyo Yokogawa / Hi-Yuret / Patsu Card Co., Ltd.

Claims (2)

[Claims] 1. A three-wire coaxial cable comprising a first conductor, which is a central conductor, a second conductor that covers the first conductor, and a third conductor that further covers the second conductor, in a measuring device body. A measuring device having one end connected and first and third conductors at the other end of the cable having connection terminals to be measured, wherein a first and a second conductor and a third grounded state are provided in the measuring device body. The AC voltage signal source for applying an AC signal to the conductor, the DC voltage signal source for applying a DC signal between the first and second conductors and the third conductor, and the AC voltage signal source are An AC voltage measuring device that measures the AC voltage value applied to the measurement target, a DC current measuring device that measures the DC current value that the DC voltage signal source injects into the measurement target, and the AC voltage signal source is the measurement target AC current measuring device for measuring the AC current injected into the Contact check function with two-terminal circuit element measuring apparatus according to claim. 2. The AC voltage signal source comprises an AC voltage source and an AC voltage source.
And a ferrite core transformer inserted in the first and second conductors of the wire coaxial cable, one end of the AC voltage source is connected to the third conductor of the three wire coaxial cable, and the ferrite core transformer is driven. One end of the winding is connected to the other end of the AC voltage source, and the other end is connected to the third conductor, and the DC voltage measuring device is a series connection of an inductor and a DC ammeter. 2. The two-terminal circuit element measuring device with a contact check function according to claim 1, wherein the capacitor and the AC ammeter are respectively connected in series, and these are connected in parallel between the first and second conductors.