JPH0835998A - Measuring instrument probe and voltage measuring method - Google Patents

Abstract

(57) [Abstract] [Purpose] A probe for a measuring instrument that enables an improved measurement method and that enables measurement with sufficient reliability not only for high frequencies but also for low-frequency polyphase signals such as three-phase AC. To provide a voltage measuring method. [Structure] The measuring instrument probe includes an optical modulator 5, conductors 3 and 4, an input optical fiber 12, and an output optical fiber 15.
And a photodetector 16. The light modulator 5 changes the intensity of light passing near the electrodes depending on the voltage applied between the two electrodes. The conductors 3 and 4 have one end connected to the electrode and the other end provided with detection terminals 1 and 2. The input optical fiber 12 propagates the light from the light source to the optical modulator 5. The output optical fiber 15 propagates the optical output from the optical modulator. The photodetector 16 has an output optical fiber 15
And a coaxial connector 17 for connecting an electric output to an oscilloscope 19 which is an asymmetric measuring instrument. This measuring instrument probe has a function of contacting or holding the detection terminals 1 and 2 at any two points in the electric circuit which are the points to be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe and a measuring method for measuring a voltage in an electric circuit or the like.

[0002]

2. Description of the Related Art Conventionally, an oscilloscope measuring probe has been used between measurement targets for measuring voltage waveforms inside an electric circuit or the like. This probe directly guides the signal at the detection end to an oscilloscope and measures the voltage waveform. It is widely used.

[0003]

In an asymmetrical measuring instrument such as an oscilloscope which is connected by a coaxial cable from a conventional electric probe and which measures the point under measurement by distinguishing it between the measuring instrument ground and the signal line, the measuring instrument and the ground level are different from each other. When observing different electrical circuits or voltage waveforms between two points that are not grounded, the effects of grounding, signal sneaking,
Furthermore, due to the capacitance of the probe and other factors, accurate measurement is difficult, and unnecessary information may be measured. This problem remains unsolved especially when the measurement target is high frequency.

The technical problem of the present invention is to solve such a long-awaited problem, to enable an improved measuring method, and to have a sufficient reliability not only for high frequencies but also for low frequency polyphase signals such as three-phase alternating current. An object of the present invention is to provide a measuring instrument probe and a voltage measuring method that enable accurate measurement.

[0005]

As means for solving the above problems, in the present invention, a voltage to be measured is applied to an electrode of an optical modulator, passes through the vicinity of the electrode, and is dependent on the voltage to be measured. After converting the intensity of the changed light into an electric signal,
It is a voltage measuring method characterized by measuring using an asymmetrical measuring device.

The measuring instrument probe of the present invention has an optical modulator for changing the intensity of light passing through the vicinity of the electrode depending on the voltage applied between the two electrodes, and one end of which is connected to the electrode. Connected to a conductor having a detection terminal at the other end, an optical input section for propagating light from a light source to the optical modulator, an optical output section for propagating an optical output from the optical modulator, and the optical output section A photodetector having a coaxial connector for connecting the electrical output to an asymmetrical measuring instrument, and having a function of contacting or holding the detection terminal at any two points in the electrical circuit which is the measured point. It has a feature.

Further, the probe for a measuring instrument according to the present invention is a light which is incident from one end face, passes through the vicinity of two electrodes to which a voltage is applied, is reflected by the other end face, and is then emitted from the end face which is incident upon. Optical modulator having an optical modulator whose intensity changes depending on the applied voltage, a conductor having one end connected to the electrode and a detection terminal at the other end, and a coaxial connector for connecting to the asymmetric measuring instrument. Device and an optical directional separator each provided with a light source for the light, and an optical propagation section having an input and output transmission function for connecting the optical directional separator and the optical modulator, and the detection terminal It is characterized by having a function of contacting or holding two arbitrary points in the electric circuit, which is a measured point.

The measuring instrument probe of the present invention is characterized in that the optical modulator is housed in a container made of a non-metallic material.

Further, in the measuring instrument probe of the present invention, the optical modulator is a Mach-Zehnder interferometric optical modulator.

[0010]

According to the measuring method of the present invention, the light passing through the vicinity of the two electrodes to which a voltage is applied is detected as a change in the intensity of the light depending on the voltage, and this is converted into an electric signal. It measures and processes. Since the measured point is completely electrically separated from the measuring instrument, all the effects of grounding and electrical sneak-up described above are avoided.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram showing a configuration example of a probe for a measuring instrument for measuring a voltage waveform according to the present invention. 2 is an enlarged view of the optical modulator shown in FIG.
As shown in FIG. 1, the probe for a measuring instrument includes conductors 3 and 4 having two detection terminals 1 and 2, an optical modulator 5 connected to the conductors 3 and 4, and a light source 11 that is housed in a container 20. , An input optical fiber 12 as an optical input section for connecting one end of the optical modulator 5 and the light source 11, a power source 21 connected to the light source 11,
A photodetector 16, a coaxial cable 18 having an output optical fiber 15 as an optical output section for connecting the other end of the optical modulator 5 and the photodetector 16, an oscilloscope 19, and a coaxial connector 17 connected to the photodetector 16. Is equipped with.

As shown in FIG. 2, the optical modulator 5 uses a substrate 6 made of lithium niobate crystal exhibiting an electro-optical effect, and optical waveguides 9 and 10 are formed on the surface of the substrate 6, respectively. A pair of electrodes 7, 8 so as to cover the surface of the
Are formed by overlapping. The phase shift optical waveguides 9 and 10 are formed by branching from the incident optical waveguide 13 while being connected to the input optical fiber 12, joined again to the outgoing waveguide 14, and connected to the output optical fiber 15. Further, the conductors 3 and 4 are respectively connected to the pair of electrodes to form a Mach-Zehnder optical interferometer.

Referring to FIGS. 1 and 2, the signals under measurement input from the two detection terminals 1 and 2 are guided to the electrodes 7 and 8 of the optical modulator 5 by the conductors 3 and 4. The light source 11 includes a semiconductor laser, is guided by an optical fiber 12 to an incident optical waveguide 13 of an optical modulator 5, is branched by two phase shift optical waveguides 9 and 10, passes near the electrodes 7 and 8, and is an emission waveguide. Join 14 The voltage to be measured introduced from the detection terminals 1 and 2 generates an electric field in the two phase shift optical waveguides 9 and 10 via the electrodes 7 and 8 and locally causes a change in the refractive index. Therefore, a phase difference occurs in the light passing through these two phase shift optical waveguides 9 and 10, and in the output optical waveguide 14 where these merge, they interfere with each other and become light having an intensity change depending on the applied voltage. Therefore, the change in the light intensity is converted into an electric signal by the photodetector 16 via the output optical fiber 15, and is transmitted to the asymmetrical measuring device such as the coaxial cable 18 having the coaxial connector 17, the oscilloscope 19 and the like and processed. .

The size of the optical modulator 5 used in the first embodiment of the present invention is approximately 50 mm in length, 3 mm in width, and 0.
It is 5 mm, has no moving parts, does not require a power supply, and is so-called maintenance-free. Therefore, as shown in FIG. 1, the optical modulator 5 can be used for measurement while being housed in a thin cylindrical container 20 made of a resin of an organic polymer material. The voltage probe in the high-frequency circuit was measured by using the measuring instrument probe with this configuration and the oscilloscope 19 which is an asymmetrical measuring instrument, that is, by the configuration of the measuring system in FIG. 1, and frequently occurred when the conventional electric probe was used. There were no problems at all, and the results were sufficiently reliable.

(Embodiment 2) FIG. 3 is a view showing the arrangement of a measuring instrument probe according to Embodiment 2 of the present invention. The measuring instrument probe shown in FIG. 3 is configured using a so-called reflection type optical modulator.

As shown in FIG. 3, the measuring instrument probe is
Conductors 3 and 4 having two detection terminals 1 and 2, and conductors 3 and 4.
4, an optical modulator 25 housed in a container 20,
Light source 11, power source 21 connected to light source 11, optical circulator 28 connected to light source 11, optical circulator 2
8, a polarization maintaining fiber 12 ', which is an optical input / output unit connecting the optical modulator 25 and the optical modulator 25, a photodetector 16 connected to the optical circulator 28, an oscilloscope 19, and a photodetector
And a coaxial cable 18 having a coaxial connector 17 for connecting the oscilloscope 19 and the oscilloscope 19. The optical modulator 25 according to the second embodiment has a different structure from that of the first embodiment, but has the same function and principle.

FIG. 4 is an enlarged schematic view of the optical modulator 25 used in FIG. As shown in FIG. 4, on the substrate 24 made of lithium niobate crystal having an electro-optical effect, the phase-shifted optical waveguide 22 branched into two,
23 is formed. This phase shift optical waveguide 22,
A total reflection film 26 is attached to the end face of 23. Due to the presence of the total reflection film 26, a Mach-Zehnder optical interferometer using an optical waveguide is formed. The input light to the optical modulator 25 and the output light by reflection are transmitted by one polarization maintaining fiber 12 '. With reference to FIGS. 3 and 4, the input light from the light source 11 and the output light guided from the optical modulator 25 to the photodetector 16 by the polarization maintaining fiber 12 'serve as an optical circulator 28 as an optical direction separator. Are separated from each other. The light from the light source 11 enters the optical modulator 1 stored in the container 20 through the optical circulator 28 and the polarization maintaining fiber 12 '. The light branched to the two phase shift optical waveguides 9 and 10 passes through the vicinity of the electrodes 7 and 8 and is then reflected by the total reflection film 26, and returns along the same optical path.

On the other hand, the voltage to be measured introduced from the detection terminal 3 is transmitted through the electrodes 7 and 8 to the two phase shift optical waveguides 22 and
An electric field is generated at 23, causing a local change in the refractive index. Therefore, the light passing through the phase shift optical waveguides 22 and 23 has a phase difference in the reciprocating process, and the optical waveguides 27 where these merge are interfered with each other and have intensity changes depending on the applied voltage. Become light. The change in light intensity is converted into an electric signal by the photodetector 16 via the optical circulator 28 by the polarization maintaining fiber 12 ',
It is transmitted to an asymmetrical measuring device such as an oscilloscope 19 by the coaxial cable 18 and processed.

The size of the optical modulator used in the second embodiment of the present invention is approximately 25 mm in length, 3 mm in width, and 0.5 in thickness.
mm. In addition, as shown in FIG. 3, the optical modulator / modulator can be used as it is stored in a thin cylindrical container 20 made of a resin of an organic polymer material. As in the modification shown in Fig. 1, one of the detection terminals 1 is fixed to the tip of the container, and the other one has a detection terminal having a flexible conductor (conductor wire). , Also used for voltage measurement. Further, in Example 2 of the present invention, the same effect was obtained by using an optical directional coupler instead of the optical circulator 17.

Compared to the first embodiment, the second embodiment has one input / output optical fiber and is connected to only one side of the optical modulator, so that it is easy to handle and easy to manufacture. Further, since the length of the modulator for obtaining the same sensitivity is halved, the size can be reduced. Further, when compared with the same sensitivity, the electrode capacitance is halved, so that a higher speed waveform can be observed.

(Embodiment 3) FIG. 6 is a diagram showing a schematic configuration of a measuring instrument probe according to a third embodiment of the present invention, and FIG. 7 is a diagram showing a configuration of the optical modulator of FIG. As shown in FIG. 6, the optical modulator 30 has the same configuration as that of the first embodiment except that a Pockels element 31 that utilizes the property that the birefringence changes depending on the applied voltage is used. That is, as shown in FIG. 6, the measuring instrument probe is connected to the conductors 3 and 4 having the two detection terminals 1 and 2, and the conductors 3 and 4, and is connected to the container 20.
Light modulator 30, light source 11, and light modulator 30 housed in
Optical fiber 12 for connecting one end of the light source 11 to the light source 11, a power supply 21 connected to the light source 11, a photodetector 16, an output optical fiber 15 for connecting the other end of the optical modulator 30 to the photodetector 16, an oscilloscope 19, and a coaxial cable 18 having a coaxial connector 17 connected to the photodetector 16.

As shown in FIG. 7, the optical modulator 30 of the measuring instrument probe according to the third embodiment of the present invention uses a BGO crystal (chemical formula Bi ₁₂ GeO ₂₀ ) as the Pockels element 31. This Pockels element 31 has a hexahedral structure, and has electrodes 28 and 29 on two opposing surfaces, and a polarizer 33 on the incident surface side on the other two opposing optical surfaces.
A wave plate 34 and an analyzer 35 are sequentially arranged on the emission surface side.

Referring again to FIGS. 6 and 7, the light from the light source 11 passing through the input optical fiber 12 is converged by the lens 32, passes through the polarizer 33, becomes linearly polarized light, and enters the Pockels element 31. The outgoing light that has passed through the Pockels element 31 and has become elliptically polarized light becomes linearly polarized light that is intensity-modulated by the wave plate 34 and the analyzer 35. further,
This linearly polarized light is converged through the lens 36, is incident on the output optical fiber 15, is transmitted to the photodetector 16 by the output optical fiber 15, and is converted into an electric signal here.
It is transmitted through the coaxial cable 18 to an asymmetrical measuring device such as an oscilloscope 19 and processed.

In the third embodiment of the present invention, the optical modulator 30 includes the Pockels element 3 in the container 20 made of resin.
It is constructed by constructing optical elements such as a lens 34 including 1 and a polarizer 32.

[0026]

As described above, the measurement probe according to the present invention enables measurement with sufficient reliability from a high frequency region to a low frequency region, as easily as a measurement probe of an oscilloscope.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a measurement probe according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of the optical modulator shown in FIG.

FIG. 3 is a configuration diagram of a measurement probe according to a second embodiment of the present invention.

FIG. 4 is an enlarged view of the optical modulator of FIG.

5 is a diagram showing a modified example in which the optical modulator shown in FIG. 4 is housed in another container.

FIG. 6 is a configuration diagram of a measurement probe according to a third embodiment of the present invention.

FIG. 7 is an enlarged view of the optical modulator of FIG.

[Explanation of symbols]

 1, 2 Detection terminal 3, 4 Conductor 5, 25, 30 Optical modulator 6, 24 Substrate 7, 8 Electrode 9, 10 Optical waveguide 11 Light source 12 'Polarization maintaining fiber 12 Incident optical fiber 13 Incident optical waveguide 14 Emitting optical waveguide 15 Output optical fiber 16 Photodetector 17 Coaxial connector 18 Coaxial cable 19 Oscilloscope 20 Container 21 Light source power source 22, 23 Phase shift optical waveguide 26 Total reflection film 28 Optical circulator 31 Pockels element 32, 36 Lens 33 Polarizer 34 Wave plate 35 Analyzer

Claims (5)

[Claims] 1. An optical modulator for changing the intensity of light passing through the vicinity of the electrode depending on a voltage applied between the two electrodes, and one end connected to the electrode and a detection terminal at the other end. A conductor, an optical input section for propagating light from a light source to the optical modulator, an optical output section for propagating an optical output from the optical modulator, and an asymmetric measuring instrument for electrical output connected to the optical output section. And a photodetector with a coaxial connector for connection to
A probe for a measuring instrument, which has a function of contacting or holding the detection terminal at any two points in an electric circuit which is a measured point. 2. The intensity of light which is incident from one end face, passes through the vicinity of two electrodes to which a voltage is applied, is reflected by the other end face, and then is emitted from the end face which is incident on the other end face is equal to the applied voltage. An optical modulator that changes depending on the light source, a conductor having one end connected to the electrode and a detection terminal at the other end, a photodetector having a coaxial connector for connecting to the asymmetric measuring instrument, and the light source for the light, respectively. In an electric circuit having an attached optical directional separator and an optical propagation section having an input and output transmission function for connecting between the optical directional separator and the optical modulator, and having the detection terminal as a point to be measured. A probe for a measuring instrument, which has a function of contacting or holding any two points of 3. The measuring instrument probe according to claim 1 or 2, wherein the optical modulator is housed in a container made of a non-metallic material. 4. The measuring instrument probe according to claim 1, wherein the optical modulator is a Mach-Zehnder interferometric optical modulator. 5. A voltage to be measured is applied to an electrode of an optical modulator, the intensity of light passing through the vicinity of the electrode and changed depending on the voltage is converted into an electric signal, and then an asymmetric measuring device is used. A voltage measuring method characterized by using and measuring.