JP2001074792A - Two-terminal trio measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-terminal trio measuring instrument which can mea sure impedances with high accuracy by reducing a harmful voltage at a high frequency. SOLUTION: In a two-terminal trio measuring instrument, paired three-wire coaxial cables 1a and 1b are connected in parallel with each other by connecting first, second, and third conductors to each other at their one ends. A pair of DUT connecting terminals 10a and 10b which connect a device DUT 10 to be measured is connected to the first and third conductors on one end sides of the cables 1a and 1b. A voltage signal source 31 and a resistor 41 are connected between the first, and second conductors on the other end side of the cable 1b and a voltmeter 32 is connected to the first and second conductors on the other end side of the cable 1a. In addition, a voltage amplifier 35 is connected between the second and third conductors on the other end side of the cable 1a, and a variable current source 33 and an ammeter 34 are connected on the other end side of a third coaxial cable 2 connected in parallel with the cables 1a and 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-terminal trio measuring device for an impedance meter constructed using a three-wire coaxial cable (triaxial cable), and more specifically, to a device under test (hereinafter, referred to as a "device to be measured"). DUT) is a single-terminal grounded state, or a two-terminal trio measuring apparatus suitable for remotely measuring a DUT mounted on a circuit such as a printed circuit board in a single-line grounded state. In this specification, in order to measure the impedance,
Measuring circuits 31 to 35 that handle AC signals are used.

[0002]

2. Description of the Related Art A four-terminal pair method is known as a means for accurately measuring a wide range of impedance values over a wide frequency band with high accuracy. However, a four-terminal pair is most suitable for applications in which two-terminal components are floated from the ground, but the outer jacket of the four coaxial cables, which are "guard electrodes" in principle of operation, is the same as the ground. Since the sample is used as a potential, that is, a ground potential, a sample in a state where one terminal is grounded cannot be measured.

In order to solve this problem, the present inventor has proposed a method of changing the measuring terminal to a single-wire grounding system while maintaining the impedance dynamic range and the width of the frequency band of the four-terminal pair. In a patent application of 087845, a "two-terminal trio measuring device" using a three-wire coaxial cable was proposed. Here, in the three-wire coaxial cable, after forming the outermost grounding conductor via a dielectric coating on the outer side of the grounding conductor of the inner coaxial cable having the center conductor and the grounding conductor covering the center conductor, the outer circumference is insulated. The center conductor, the inner ground conductor and the outer ground conductor are formed coaxially. In this specification, a normal two-wire coaxial cable is simply referred to as a coaxial cable. In this publication, four types of embodiments are disclosed as proposed configurations of a two-terminal trio measuring apparatus as shown in FIGS. 5 to 8, and hereinafter referred to as first to fourth conventional examples, respectively. Here, the first and second
Is an ammeter floating type two-terminal trio measuring device in which an ammeter 34 is floated from the ground (ground potential), while the third and fourth prior arts are such that the voltmeter 32 is connected to the ground (ground potential). This is a voltmeter floating type two-terminal trio measuring device floated from.

In any of the first to fourth conventional examples, there is no difference in performance in principle with any of the configurations, but there is a difference in the difficulty of designing each part in practical use, and the obtained performance also has a characteristic. Will have. The significant difference between the first and second prior art ammeter floating type two-terminal trio measuring devices and the third and fourth prior art voltmeter floating type two-terminal trio measuring devices is as follows. This is a voltage generated between the outer conductor of the inner coaxial cable of the linear coaxial cable 1b and the outermost ground conductor.

Here, for the sake of convenience in the following description, each 3
The center conductor of each of the linear coaxial cables 1a and 1b is a first conductor, the outer conductor of the inner coaxial cable is a second conductor, and the outermost ground conductor that covers the second conductor and is located outside the third conductor is a third conductor. Called conductor.

First, consider the operation at a low frequency where the cable lengths of the three-wire coaxial cables 1a and 1b are sufficiently short with respect to the wavelength. The potential of the second conductor of FIGS. 5 and 6 is substantially equal to the voltage applied to the DUT 10, while the potential of the second conductor of FIGS.
As a result of the negative feedback control, the potential becomes almost the ground potential. When any of the configurations in FIGS. 5 and 6 is adopted, circuit blocks (circuits 33, 34, and 35 in FIG. 5, circuits 31 and 34 in FIG. 6) connected between the first conductor and the second conductor
In the case of 32), floating of the insulation from the ground is required, and the magnitude of the AC potential at the floating portion greatly affects the circuit feasibility.
Given that the AC potential divided by the ground-to-ground levitation impedance is a disturbance to occur in the system, the levitation requests of FIGS. 7 and 8 with lower potentials are more forgiving than those of FIGS. It is presumed to be convenient in terms of configuration.

[0007]

On the premise of a realistic assumption that a circuit configuration having a high floating potential portion is difficult,
Attention is now directed to the behavior at high frequencies of FIGS. 7 and 8 of the third and fourth conventional examples. There is no change in the operation that the voltage between the second conductor and the third conductor of the three-wire coaxial cable 1a becomes zero at both the left and right ends due to the negative feedback circuit formed by the amplifier 35 and the current source 33. As shown in FIG. 9, between the second conductor and the third conductor at the left end of the cable 1b, as the frequency increases, the harmful voltage Ve represented by the following equation is obtained.
Will occur.

[0008]

[Number 1] _{Ve = I DUT Z 0 sin (} 2πl e / λ)

[0009] Here, I _DUT: current flowing through the DUT 10, Z _0: 3-wire coaxial cable 1a, the second conductor and the third 1b
, The characteristic impedance of the transmission line formed between the conductors, l _e : the electrical length of the three-wire coaxial cables 1a, 1b, and λ: the wavelength in the free space of the operating frequency.

As is apparent from the above equation (1), when the frequency increases and the wavelength λ decreases, the harmful voltage Ve increases. That is, the third and fourth conventional examples have an advantage that the potential of a portion where insulation floating is required is lower in terms of basic properties compared with the first and second conventional examples. As they move toward higher frequencies, their dominance gradually diminishes, and circuit design inconvenience reoccurs.

An object of the present invention is to solve the above-mentioned problems, to reduce a harmful voltage Ve at high frequency, and to provide a two-terminal trio measuring device capable of measuring impedance with higher accuracy than the conventional example. To provide.

[0012]

According to the present invention, there is provided a two-terminal trio measuring apparatus, comprising:
, A second conductor covering the first conductor, and a third conductor further covering the second conductor, and the first, second, and third conductors are mutually formed. A pair of first and second three-wire coaxial cables connected in parallel to be connected at each end, and a pair of the first and second
A pair of connection terminals respectively connected to the first conductor and the third conductor on one end side of the three-wire coaxial cable for connecting a device under test; A voltage signal source connected to the end first and second conductors;
Between the voltmeter connected to the first and second conductors at the other end of the first three-wire coaxial cable and the second and third conductors at the other end of the first three-wire coaxial cable And a voltage amplifier for amplifying the voltage and outputting the amplified signal, and the second and third conductors at one end of each of the pair of first and second three-wire coaxial cables. A third coaxial cable having a center conductor and a ground conductor, wherein an output current is supplied between the center conductor and the ground conductor at the other end of the third coaxial cable in accordance with a signal output from the voltage amplifier. A variable current source to be controlled and an ammeter are connected.

[0013] The two-terminal trio measuring apparatus according to claim 2 of the present invention comprises: a first conductor constituting a center conductor;
A second conductor covering the first conductor and a third conductor further covering the second conductor are respectively formed, and the first, second, and third conductors are connected to each other at one end. And a pair of first and second three-wire coaxial cables connected in parallel to each other, and a first conductor and a third conductor at one end of each of the pair of first and second three-wire coaxial cables. A pair of connection terminals respectively connected to the device under test, and a voltage signal source connected to the first and second conductors at the other end of the first three-wire coaxial cable. A voltmeter connected to the first and second conductors at the other end of the second three-wire coaxial cable; and a second and third conductor at the other end of the first three-wire coaxial cable And a voltage amplifier that amplifies the voltage between the two and outputs the amplified signal, and one of the pair of first and second three-wire coaxial cables. A third coaxial cable having a center conductor and a ground conductor respectively connected to the second and third conductors on the other side, and a center conductor and a ground conductor on the other end of the third coaxial cable. A variable current source that controls an output current in accordance with a signal output from the voltage amplifier and an ammeter.

Further, in the two-terminal trio measuring apparatus according to claim 3 of the present invention, the first conductor constituting the center conductor, the second conductor covering the first conductor, and the second conductor
And a pair of first and second conductors respectively formed in parallel so that the first, second and third conductors are connected to each other at respective one ends. For connecting the device under test, which is connected to the first conductor and the third conductor at one end of each of the pair of first and second three-wire coaxial cables.
A pair of connection terminals, a voltage signal source connected to the first and second conductors on the other end of the second three-wire coaxial cable, and a first signal on the other end of the first three-wire coaxial cable. And a voltmeter connected to the second conductor, a center conductor connected to the second and third conductors at one end of the pair of first and second three-wire coaxial cables, and a ground. A third having conductors respectively
And a fourth coaxial cable; and a voltage amplifier that amplifies a voltage between the center conductor and the ground conductor on the other end of the third coaxial cable and outputs an amplified signal. A variable current source for controlling an output current according to a signal output from the voltage amplifier and an ammeter are connected between a center conductor on the other end side of the coaxial cable and a ground conductor.

Further, the two-terminal trio measuring device according to claim 4 is the two-terminal trio measuring device according to claim 3, wherein the first and second terminals at the other end of the first three-wire coaxial cable are arranged.
, Between the second and third conductors on the other end of the first three-wire coaxial cable, the first conductor on the other end of the second three-wire coaxial cable, and the voltage signal source. , Between the second and third conductors at the other end of the second three-wire coaxial cable, between the center conductor and the ground conductor at the other end of the third coaxial cable, and at the fourth A resistor for terminating in a state of impedance matching is inserted and connected between the center conductor and the ground conductor on the other end of the coaxial cable.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the above-mentioned problems are solved by modifying the third and fourth conventional examples shown in FIGS. 7 and 8. That is, a circuit configuration that eliminates a potential rise in a circuit block that requires insulation levitation is proposed.

<First Embodiment> FIG. 1 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring apparatus according to a first embodiment of the present invention. Have the same reference numerals. The two-terminal trio measuring apparatus according to the first embodiment is different from the third conventional example shown in FIG.
In addition to the first and second three-wire coaxial cables 1a and 1b, a third
And a variable current source 33 and an ammeter 34 are inserted and connected between the center conductor and the ground conductor on the other left side of the third coaxial cable 2 in the drawing. I have.

In FIG. 1, a pair of first and second three-wire coaxial cables 1a and 1b are composed of a first conductor constituting a center conductor, a second conductor covering the first conductor, and a second conductor. And a third conductor further covering the two conductors, and the first, second and third conductors are connected in parallel such that they are connected to each other at one end. The device under test DU is respectively connected to the first conductor and the third conductor on one end side of the pair of first and second three-wire coaxial cables 1a and 1b.
A pair of DUT connection terminals 10a for connecting T10,
10b is connected, and the DUT 10 is connected between the DUT connection terminals 10a and 10b. A voltage signal source 31 for generating and outputting an AC voltage having a predetermined frequency between the first and second conductors at the other end of the second three-wire coaxial cable 1b;
A series circuit with a resistor 41 having a resistance value Rp is connected;
A voltmeter 32 is connected to the first and second conductors at the other end of the first three-wire coaxial cable 1a.
a between the second and third conductors at the other end of the voltage amplifier 3 to amplify the voltage between these conductors and output an amplified signal
5 is connected. Here, the resistor 41 is a resistor corresponding to the internal resistance of the voltage signal source 31. Further, a third coaxial cable 2 having a center conductor and a ground conductor covering the center conductor is a pair of first and second three-wire coaxial cables 1.
The first and second conductors a and 1b are connected in parallel to the second and third conductors, respectively. A voltage amplifier 35 is provided between the center conductor on the other end of the third coaxial cable 2 and the ground conductor.
A variable current source 33 that controls to output an output current proportional to a signal input according to a signal output from
An ammeter 34 is inserted and connected.

In the two-terminal trio measuring apparatus of the first embodiment configured as described above, when the voltage signal source 31 applies a voltage to the first and second conductors of the second three-wire coaxial cable 1b, The current source 33 is the first three-wire coaxial cable 1
a, controlling the output current to the third coaxial cable 2 according to the voltage between the second and third conductors,
The voltage is controlled so that the voltage between the second and third conductors at each end of the linear coaxial cables 1a and 1b becomes zero, that is, the potential of the second conductor becomes the ground potential. Then, based on the voltage value measured by the voltmeter 32 and the current value measured by the ammeter 34, the impedance is measured in a known manner.

Here, the variable current source 33 and the ammeter 34 in the third conventional example shown in FIG.
b, is connected to the other end of the third coaxial cable 2 and the current by the variable current source 33 does not flow through the second conductor of the three-wire coaxial cable 1b. Does not occur between the second and third conductors of the second three-wire coaxial cable 1b. In other words, the floating potential of the voltage signal source 31 and the voltmeter 32 can be made equal to the ground potential, so that no harmful voltage Ve is generated even at a high frequency, and the impedance is more accurately compared to the conventional example. Can be measured.

<Second Embodiment> FIG. 2 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring apparatus according to a second embodiment of the present invention. Have the same reference numerals. The two-terminal trio measuring apparatus according to the second embodiment is different from the fourth conventional example shown in FIG.
In addition to the first and second three-wire coaxial cables 1a and 1b, a third
And a variable current source 33 and an ammeter 34 are inserted and connected between the center conductor and the ground conductor on the other left side of the third coaxial cable 2 in the drawing. I have.

In FIG. 2, as compared with the circuit configuration of the first embodiment of FIG. 1, the position of the ammeter 32 and the position of the series circuit of the voltage signal source 31 and the resistor 41 are switched. The other circuit configuration is the same.

In the two-terminal trio measuring apparatus of the second embodiment configured as described above, when voltage is applied to the first and second conductors of the first three-wire coaxial cable 1 a by the voltage signal source 31, The current source 33 is the first three-wire coaxial cable 1
a, controlling the output current to the third coaxial cable 2 according to the voltage between the second and third conductors,
The voltage is controlled so that the voltage between the second and third conductors at each end of the linear coaxial cables 1a and 1b becomes zero, that is, the potential of the second conductor becomes the ground potential. Then, based on the voltage value measured by the voltmeter 32 and the current value measured by the ammeter 34, the impedance is measured in a known manner.

Here, the variable current source 33 and the ammeter 34 in the third conventional example shown in FIG. 8 are detached from the other end of the second three-wire coaxial cable 1b, and the other end of the third coaxial cable 2 is removed. Since the current flowing from the variable current source 33 does not flow through the second conductor of the three-wire coaxial cable 1b, the harmful voltage Ve is applied to the second and third conductors of the second three-wire coaxial cable 1b. Does not occur during That is, since the floating potential of the voltage signal source 31 and the voltmeter 32 can be made equal to the ground potential, the harmful voltage Ve can be obtained even at a high frequency.
Does not occur, and the impedance can be measured with higher accuracy than in the conventional example.

<Third Embodiment> FIG. 3 is a circuit diagram showing the configuration of a voltmeter floating type two-terminal trio measuring apparatus according to a third embodiment of the present invention, which is the same as FIGS. 1 and 7. Are given the same reference numerals. The two-terminal trio measuring apparatus according to the third embodiment differs from the first embodiment in FIG. 1 in that, in addition to the first and second three-wire coaxial cables 1a and 1b, a center conductor and a ground conductor are provided at one end. Are connected in parallel with each other, and have a center conductor and a ground conductor respectively connected to the second and third conductors at one end of the first and second three-wire coaxial cables 1a and 1b, respectively. 3rd and 4th
Between the center conductor and the ground conductor on the other end of the third coaxial cable 2a on the left side in the drawing.
While inserting and connecting the input terminal of the voltage amplifier 35,
A variable current source 33 and an ammeter 34 are inserted and connected between the center conductor and the ground conductor at the other end on the left side of the fourth coaxial cable 2b in the drawing.

In FIG. 3, when compared with the circuit configuration of the first embodiment of FIG. 1, the coaxial cable 2 of FIG. 1 is a coaxial cable 2b, which is connected to the other end of the first three-wire coaxial cable 1a. The voltage amplifier 35 is connected to the other end of the coaxial cable 2a, and the other circuit configuration is the same.

When a voltage is applied to the first and second conductors of the second three-wire coaxial cable 1b by the voltage signal source 31 in the two-terminal trio measuring apparatus of the third embodiment configured as described above. , The variable current source 33 controls the output current to the fourth coaxial cable 2b according to the voltage between the second and third conductors of the third coaxial cable 2a, and a pair of first and second
Of the one end of each of the three-wire coaxial cables 1a and 1b.
Is controlled so that the voltage between the two conductors becomes zero, that is, the potential of the second conductor becomes the ground potential. Then, based on the voltage value measured by the voltmeter 32 and the current value measured by the ammeter 34, the impedance is measured in a known manner.

<Fourth Embodiment> FIG. 4 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring apparatus according to a fourth embodiment of the present invention, which is the same as FIG. 1 and FIG. Are given the same reference numerals. The two-terminal trio measuring apparatus of the fourth embodiment differs from the third embodiment of FIG. 3 in that the impedance matching terminating resistors 51 to 55 are inserted and connected as follows. (A) A resistor 52 having a resistance value Z ₀₂ ′ for terminating in an impedance matching state is inserted and connected between the first and second conductors at the other end of the first three-wire coaxial cable 1a. . (B) A resistor 51 having a resistance value Z ₀₁ ′ for terminating in an impedance matching state is inserted and connected between the second and third conductors at the other end of the first three-wire coaxial cable 1a. . (C) Between the first conductor at the other end of the second three-wire coaxial cable 1b and the voltage signal source 32, a resistance value R for terminating in an impedance matching state as in the third embodiment.
A resistor 41 having p is inserted and connected. Here, the resistor 41 is a resistor corresponding to the internal resistance of the voltage signal source 32. (D) A resistor 53 having a resistance value Z ₀₃ ′ for terminating in an impedance matching state is inserted and connected between the second and third conductors at the other end of the second three-wire coaxial cable 1b. . (E) A resistor 54 having a resistance value Z ₀₅ ′ for terminating in an impedance matching state is inserted and connected between the center conductor on the other end side of the third coaxial cable 2a and the ground conductor. (F) A resistor 55 having a resistance value Z ₀₆ ′ for terminating in an impedance matching state is inserted and connected between the center conductor on the other end side of the fourth coaxial cable 2b and the ground conductor.

Here, in a specific embodiment,

[Equation 2] Z ₀₁ '= Z ₀₃ ' = 25Ω

## EQU3 ## Z ₀₂ ′ = Z ₀₄ ′ = Z ₀₅ ′ = Z ₀₆ ′ = 50Ω.

In the fourth embodiment configured as described above, the impedance value Zx (complex value) of the DUT 10 can be measured using the following equation.

[0031]

Equation 4] _{Zx = V DUT / I DUT =} [V · exp {j (2πl e1) / λ}] / [I · exp {-j (2πl e2) / λ}] = (V / I) exp { j · 2π ( _le1 + _le2 ) / λ}

Here, V _DUT : voltage applied to _DUT 10 (complex value), I _DUT : current flowing through _DUT 10 (complex value), V: measured value of voltmeter 32 (complex value), I: ammeter 34 Measured value (complex value), l _e1 : electrical length of a pair of three-wire coaxial cables 1a, 1b, l _e2 : electrical length of a pair of coaxial cables 2a, 2b, λ: signal used in the voltage signal source 32 It is the wavelength of the frequency.

In the fourth embodiment, in addition to the functions and effects of the third embodiment, each coaxial cable 1
Since the other ends of a, 1b, 2a, and 2b are terminated,

## EQU5 ## Z _on ′ = Z _on , n = 1, 2, 3, 4, 5, 6 The standing wave in each coaxial cable 1a, 1b, 2a, 2b can be suppressed, and Has a flat frequency characteristic, and the impedance can be measured with high accuracy even in a very high frequency band.

As described above, according to the first to fourth embodiments, the harmful voltage Ve at a high frequency can be reduced, and the impedance can be measured with higher accuracy than the conventional example. A terminal trio measuring device can be provided. According to this measuring device, for example, a measuring end face having a pencil-type probe can be formed at the tip of a flexible extension cable, and not only impedance measurement of a single electronic component such as a resistor or a capacitor, but also measurement It can also measure the input / output impedance of line-grounded amplifiers and the impedance of components, circuits, and materials placed in a thermostatic chamber atmosphere.

[0035]

As described above in detail, according to the two-terminal trio measuring apparatus of the first aspect of the present invention, the first conductor constituting the center conductor and the second conductor covering the first conductor are formed. And a third conductor further covering the second conductor, and the first, second, and third conductors are connected in parallel such that they are connected to each other at one end. The device under test connected to the pair of first and second three-wire coaxial cables and the first and third conductors on one end side of the pair of first and second three-wire coaxial cables, respectively. A pair of connection terminals for connecting devices, a voltage signal source connected to first and second conductors at the other end of the second three-wire coaxial cable, and the first three-wire coaxial cable The other end of the first
And a voltmeter connected to the second conductor, and a voltage amplifier for amplifying a voltage between the second and third conductors at the other end of the first three-wire coaxial cable and outputting an amplified signal. And a third coaxial cable having a center conductor and a ground conductor respectively connected to the second conductor and the third conductor at each end of the pair of first and second three-wire coaxial cables. Between the center conductor on the other end of the third coaxial cable and the ground conductor,
A variable current source for controlling an output current according to a signal output from the voltage amplifier is connected to an ammeter. According to the present invention, it is possible to provide a two-terminal trio measuring device capable of reducing the harmful voltage Ve at a high frequency and measuring the impedance with higher accuracy than the conventional example.

Further, according to the two-terminal trio measuring apparatus of the present invention, the first conductor constituting the center conductor, the second conductor covering the first conductor, and the second conductor A pair of first and second conductors respectively formed by a third conductor further covering the second conductor, and connected in parallel such that the first, second and third conductors are connected to each other at respective one ends. And a pair of the first and second three-wire coaxial cables.
A pair of connection terminals respectively connected to the first conductor and the third conductor on one end of the wire coaxial cable for connecting a device under test, and the other end of the first three wire coaxial cable A voltage signal source connected to the first and second conductors; a voltmeter connected to the first and second conductors on the other end of the second three-wire coaxial cable; A voltage amplifier for amplifying a voltage between the second and third conductors at the other end of the linear coaxial cable and outputting an amplified signal; and a pair of the first and second three-wire coaxial cables. A third coaxial cable having a center conductor and a ground conductor connected to the second conductor and the third conductor at one end, respectively; and a center conductor and a ground conductor at the other end of the third coaxial cable. A variable current source that controls an output current according to a signal output from the voltage amplifier; and an ammeter. It is connected. According to the present invention, it is possible to provide a two-terminal trio measuring device capable of reducing the harmful voltage Ve at a high frequency and measuring the impedance with higher accuracy than the conventional example.

Further, according to the two-terminal trio measuring apparatus according to claim 3 of the present invention, the first conductor constituting the center conductor, the second conductor covering the first conductor, and the second conductor A pair of first and second conductors respectively formed in parallel so that the first, second and third conductors are connected to each other at one end thereof.
And the second three-wire coaxial cable, and the device under test connected to the first and third conductors at one end of each of the pair of first and second three-wire coaxial cables. Terminal, a voltage signal source connected to the first and second conductors on the other end of the second three-wire coaxial cable, and another end of the first three-wire coaxial cable Voltmeter connected to the first and second conductors, and a center connected to the second and third conductors at one end of each of the pair of first and second three-wire coaxial cables. A third and a fourth coaxial cable having a conductor and a ground conductor, respectively, and amplifying a voltage between the center conductor and the ground conductor on the other end of the third coaxial cable to output an amplified signal. And a voltage amplifier.
A variable current source for controlling an output current in accordance with a signal output from the voltage amplifier and an ammeter are connected between the center conductor and the ground conductor on the other end of the coaxial cable.
According to the present invention, it is possible to provide a two-terminal trio measuring device capable of reducing the harmful voltage Ve at a high frequency and measuring the impedance with higher accuracy than the conventional example.

Further, according to the two-terminal trio measuring device according to the fourth aspect, in the two-terminal trio measuring device according to the third aspect, the first and second terminals on the other end side of the first three-wire coaxial cable. Between the conductors, between the second and third conductors on the other end of the first three-wire coaxial cable, and on the other end of the second three-wire coaxial cable, the first conductor and the voltage signal source; Between the second and third conductors at the other end of the second three-wire coaxial cable, between the center conductor and the ground conductor at the other end of the third coaxial cable, A resistor for terminating in a state of impedance matching is inserted and connected between the center conductor and the ground conductor at the other end of the coaxial cable. According to the present invention, it is possible to provide a two-terminal trio measuring device capable of reducing the harmful voltage Ve at a high frequency and measuring the impedance with higher accuracy than the conventional example. Furthermore, since the other end of each coaxial cable is terminated, standing waves in each coaxial cable can be suppressed, and the frequency characteristics of the measuring device become flat, and high accuracy can be achieved even in an extremely high frequency band. Impedance can be measured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring device according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring device according to a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a first conventional example of an ammeter floating type two-terminal trio measuring apparatus.

FIG. 6 is a circuit diagram showing the configuration of a second conventional example of an ammeter floating type two-terminal trio measuring apparatus.

FIG. 7 is a circuit diagram showing a configuration of a third conventional example of a voltmeter floating type two-terminal trio measuring apparatus.

FIG. 8 is a circuit diagram showing the configuration of a fourth conventional voltmeter floating type two-terminal trio measuring apparatus.

FIG. 9 is a circuit diagram showing a problem in the third conventional example of FIG. 7;

[Explanation of symbols]

 1a, 1b: 3-wire coaxial cable, 2, 2a, 2b: coaxial cable, 10: device under test (DUT), 10a, 10b: device under test (DUT) connection terminal, 31: voltage signal source, 32: voltmeter 33, variable current source, 34, ammeter, 35, voltage amplifier, 41, 51, 52, 53, 54, 55 ... resistor

[Procedure amendment]

[Submission date] July 5, 2000 (2007.5.5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

First, consider the operation at a low frequency where the cable lengths of the three-wire coaxial cables 1a and 1b are sufficiently short with respect to the wavelength. The potential of the second conductor of FIGS. 5 and 6 is substantially equal to the voltage applied to the DUT 10, while the potential of the second conductor of FIGS.
As a result of the negative feedback control, the potential becomes almost the ground potential. When any of the configurations shown in FIGS. 5 to 8 is adopted, a circuit block connected between the first conductor and the second conductor (the circuits 33, 34, 35 in FIGS. 5 and 6, FIGS. 8, 31) and 32) require insulation levitation from the ground, and the magnitude of the AC potential at the levitation portion greatly affects circuit feasibility. Considering that the AC potential divided by the levitation impedance between the grounds is a disturbance that occurs in the system,
7 and 8 with lower potentials are shown in FIGS. 5 and 6.
It is presumed that it is more forgiving than that of and is convenient in terms of circuit configuration.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

In FIG. 2, as compared with the circuit configuration of the first embodiment shown in FIG. 1, the position of the voltmeter 32 and the position of the series circuit of the voltage signal source 31 and the resistor 41 are switched. The other circuit configuration is the same.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

Here, the variable current source 33 and the ammeter 34 in the fourth conventional example shown in FIG. 8 are detached from the other end of the second three-wire coaxial cable 1b, and the other end of the third coaxial cable 2 is removed. Since the current flowing from the variable current source 33 does not flow through the second conductor of the three-wire coaxial cable 1b, the harmful voltage Ve is applied to the second and third conductors of the second three-wire coaxial cable 1b. Does not occur during That is, since the floating potential of the voltage signal source 31 and the voltmeter 32 can be made equal to the ground potential, the harmful voltage Ve can be obtained even at a high frequency.
Does not occur, and the impedance can be measured with higher accuracy than in the conventional example.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

<Fourth Embodiment> FIG. 4 is a circuit diagram showing a configuration of a voltmeter floating type two-terminal trio measuring apparatus according to a fourth embodiment of the present invention, which is the same as FIG. 1 and FIG. Are given the same reference numerals. The two-terminal trio measuring apparatus of the fourth embodiment differs from the third embodiment of FIG. 3 in that the impedance matching terminating resistors 51 to 55 are inserted and connected as follows. (A) A resistor 52 having a resistance value Z ₀₂ ′ for terminating in an impedance matching state is inserted and connected between the first and second conductors at the other end of the first three-wire coaxial cable 1a. . (B) A resistor 51 having a resistance value Z ₀₁ ′ for terminating in an impedance matching state is inserted and connected between the second and third conductors at the other end of the first three-wire coaxial cable 1a. . (C) A resistance value R for terminating in an impedance matching state between the first conductor at the other end of the second three-wire coaxial cable 1b and the voltage signal source 31, as in the third embodiment.
A resistor 41 having p = Z ₀₄ ′ is inserted and connected. Here, the resistor 41 is a resistor corresponding to the internal resistance of the voltage signal source 31. (D) A resistor 53 having a resistance value Z ₀₃ ′ for terminating in an impedance matching state is inserted and connected between the second and third conductors at the other end of the second three-wire coaxial cable 1b. . (E) A resistor 54 having a resistance value Z ₀₅ ′ for terminating in an impedance matching state is inserted and connected between the center conductor on the other end side of the third coaxial cable 2a and the ground conductor. (F) A resistor 55 having a resistance value Z ₀₆ ′ for terminating in an impedance matching state is inserted and connected between the center conductor on the other end side of the fourth coaxial cable 2b and the ground conductor.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

Here, V _DUT : voltage applied to _DUT 10 (complex value), I _DUT : current flowing through _DUT 10 (complex value), V: measured value of voltmeter 32 (complex value), I: ammeter 34 Measured value (complex value), l _e1 : electrical length of a pair of three-wire coaxial cables 1a and 1b, l _e2 : electrical length of a pair of coaxial cables 2a and 2b, λ: signal used by the voltage signal source 31 It is the wavelength of the frequency.

[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Claims (4)

[Claims] A first conductor that forms a central conductor, a second conductor that covers the first conductor, and a third conductor that further covers the second conductor,
A pair of first and second three-wire coaxial cables connected in parallel such that the first, second, and third conductors are connected to each other at respective one ends; and the pair of first and second coaxial cables. A pair of connection terminals respectively connected to the first conductor and the third conductor on one end side of the three-wire coaxial cable for connecting a device under test; A voltage signal source connected to the first and second conductors on the end side; a voltmeter connected to the first and second conductors on the other end side of the first three-wire coaxial cable; A voltage amplifier for amplifying the voltage between the second and third conductors at the other end of the three-wire coaxial cable and outputting the amplified signal; and the pair of first and second three-wire coaxial cables. And a third coaxial cable having a center conductor and a ground conductor connected to the second conductor and the third conductor, respectively, at one end of the cable. A variable current source for controlling an output current according to a signal output from the voltage amplifier and an ammeter are connected between a center conductor on the other end of the third coaxial cable and a ground conductor. Two-terminal trio measuring device. 2. A first conductor that forms a center conductor, a second conductor that covers the first conductor, and a third conductor that further covers the second conductor,
A pair of first and second three-wire coaxial cables connected in parallel such that the first, second, and third conductors are connected to each other at respective one ends; and the pair of first and second coaxial cables. A pair of connecting terminals respectively connected to the first conductor and the third conductor on one end side of the three-wire coaxial cable for connecting a device under test; A voltage signal source connected to the first and second conductors on the end side; a voltmeter connected to the first and second conductors on the other end side of the second three-wire coaxial cable; A voltage amplifier for amplifying the voltage between the second and third conductors at the other end of the three-wire coaxial cable and outputting the amplified signal; and the pair of first and second three-wire coaxial cables. And a third coaxial cable having a center conductor and a ground conductor connected to the second conductor and the third conductor, respectively, at one end of the cable. A variable current source for controlling an output current according to a signal output from the voltage amplifier and an ammeter are connected between a center conductor on the other end of the third coaxial cable and a ground conductor. Two-terminal trio measuring device. 3. A first conductor that forms a center conductor, a second conductor that covers the first conductor, and a third conductor that further covers the second conductor,
A pair of first and second three-wire coaxial cables connected in parallel such that the first, second, and third conductors are connected to each other at respective one ends; and the pair of first and second coaxial cables. A pair of connection terminals respectively connected to the first conductor and the third conductor on one end side of the three-wire coaxial cable for connecting a device under test; A voltage signal source connected to the first and second conductors on the end side; a voltmeter connected to the first and second conductors on the other end side of the first three-wire coaxial cable; A third and a fourth coaxial cable having a center conductor and a ground conductor respectively connected to the second conductor and the third conductor on one end side of each of the first and second three-wire coaxial cables; A voltage for amplifying the voltage between the center conductor on the other end of the third coaxial cable and the ground conductor and outputting the amplified signal. An amplifier; and a variable current source for controlling an output current according to a signal output from the voltage amplifier, and an ammeter connected between the center conductor and the ground conductor on the other end of the fourth coaxial cable. A two-terminal trio measuring device, characterized in that: 4. The two-terminal trio measuring apparatus according to claim 3, wherein the first three-wire coaxial cable is connected between the first and second conductors at the other end of the first three-wire coaxial cable, and the other of the first three-wire coaxial cable. Between the second and third conductors at the end; between the first conductor at the other end of the second three-wire coaxial cable and the voltage signal source; the other end of the second three-wire coaxial cable Between the second and third conductors on the other side, between the center conductor on the other end of the third coaxial cable and the ground conductor, and between the center conductor on the other end of the fourth coaxial cable and the ground conductor. A two-terminal trio measuring apparatus, characterized in that a resistor for terminating in an impedance matching state is inserted and connected between the two terminals.