JPH0886808A - High voltage probe - Google Patents

Abstract

PURPOSE: To keep an insulating material from melting by a dielectric loss in a high frequency operation just like a gelatinous silicon is used as insulating material by housing a resistor in a through hole of an insulating structural body comprising a solid insulating material to be insulated from a conducting ring, an electroconductive member and a shield body. CONSTITUTION: A resistor 36 is housed in a through hole provided in an insulating structural body 26 with one end thereof connected electrically to a probe tip sticking out from the insulating structural body and the other end to a connector for an output and a conducting ring 38 surrounding the perimeter of the insulating structural body is connected electrically to the other end of the resistor with electroconductive members 40 and 48 at a position corresponding to the resistor. The insulating structural body, the electroconductive ring and a conductor are wrapped with a shield body 56 at least in a range of the resistor existing and the insulating structural body and the shield body are wrapped with an insulating cover member with the probe tip exposed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to high voltage probes for measuring high voltages.

[0002]

2. Description of the Related Art FIG. 5 is a side view showing an inner body 100 of a conventional high voltage probe. In a normal use state, the inner main body 100 is housed in a plastic outer cover having a handle attached to one end. The inner main body 100 includes a rod-shaped resistor 104 having a high resistance value in a case 102 formed of a transparent resin such as polycarbonate.
including. One end of the resistor 104 has a probe tip 106.
To one end of the conductive support 106 is attached to the other end. The support 106 extends along the resistor 104, and a ring 108 surrounding the resistor 104 in a contactless manner is attached to the other end. The ring 108 forms a capacitance with the resistor 104, and a capacitor is equivalently connected in parallel with the resistor 104. The other end of the resistor 104 and the other end of the support 106 are commonly connected to the internal conductor of the connector 110. A shield body 112 is arranged around the case 102, and the shield body 112 is supplied with a ground potential via a lead wire of the probe.

Up to 10 kV on the probe tip 106
Since a high voltage is input, the case 102 is filled with an insulator that prevents discharge between the resistor 104 and the other metal parts 106, 108 and 112. Previously, CFC gas was used as this insulator, but it is not used now because of environmental problems, and gel silicon 114 is used instead. Gel Silicon 114
Has an advantage that it can be filled even if the internal structure of the case 102 is complicated.

[0004]

The silicon 114 filled in the case 102 works well as an insulator when the input voltage is direct current or low frequency. However, a dielectric such as silicon has a large dielectric loss tangent as the frequency of the applied voltage increases, and the energy loss, that is, the dielectric loss increases in proportion thereto. When a high voltage having a frequency of 10 MHz or higher is actually applied to a high voltage probe using silicon, heat is generated due to energy loss, and when the voltage is further increased, the gel silicon is melted and the resistor 104 and other components are formed. The problem of causing element damage arises.

As shown in FIG. 6, the output of the probe head, ie the output of the inner body 100, is input to the oscilloscope via the coaxial cable 116 and the compensation circuit 118.
The inner body 100 includes the resistor 104 and the capacitor 120 equivalently connected in parallel with the resistor 104 as described above. The value of this capacitor 120 is fixed, determined by the length of the support 106 along the resistor 104 and the diameter of the ring 108. A resistor having a high resistance value of 100 MΩ or more is used as the resistor 104 in order to reduce the load effect, but the resistor having a high resistance value has a relatively large parasitic capacitance. The oscilloscope has an input impedance by an input resistor 122 and a capacitor 124 which are connected in parallel to the input terminal, and this value differs depending on the oscilloscope.

The compensating circuit 118 includes a plurality of impedance adjusting circuits 126a to 126d each connected in parallel to the probe cable 116, each of which is formed by connecting a variable resistor and a variable capacitor in series, and the left and right side of the cable 116. Variable resistor 1 for adjusting the voltage dividing ratio to adjust the voltage dividing ratio
28 and a high frequency region compensating resistor 130.
The impedance adjustment circuits 126a to 126c are for fine adjustment used to compensate for impedance changes due to the parasitic capacitance of the resistor 104 during high frequency operation, and the impedance adjustment circuit 126d compensates for changes in the input impedance of the oscilloscope. It is for coarse adjustment used to When the impedance adjustment circuit 126d is adjusted according to the change in the input impedance of the oscilloscope from a state in which each circuit in the compensation circuit is adjusted in a good balance so that an accurate waveform is obtained and the voltage division ratio is kept constant, the correction circuit The balance of each circuit in 118 is lost. Again, a lot of adjustments are needed to get it in balance.

If the capacitor 120 in the internal body 100 is a variable capacitor, the value of this capacitor can be adjusted to compensate for changes in the input impedance of the oscilloscope. However, in the probe of FIG. 5, since the value of the capacitor 120 is fixed, adjustment within the correction circuit 118 is necessary.

Therefore, it is an object of the present invention to provide a high voltage probe which can satisfactorily insulate in a probe without using gel silicon.

Another object of the present invention is to provide a high voltage probe which has good insulation within the probe and a variable capacitance.

[0010]

A first high voltage probe according to the present invention comprises an insulating structure having a through hole in the axial direction, and a probe housed in the through hole of the insulator and having one end protruding from the insulating structure. A resistor electrically connected to the chip and the other end electrically connected to the output connector, and a conductive ring surrounding the insulating structure at a position corresponding to the resistor,
By exposing the conductor member electrically connecting the other end of the resistor and the conductive ring, the shield body surrounding the insulating structure, the conductive ring and the conductor, and the probe tip to the extent that at least the resistor exists. And an insulating cover member that surrounds at least the shield body.

A second high-voltage probe according to the present invention is electrically connected to an insulating structure having a through hole in the axial direction and a probe tip housed in the through hole of the insulator and having one end protruding from the insulating structure. A resistor having the other end electrically connected to the output connector, a conductive ring surrounding the periphery of the insulating structure at a position corresponding to the resistor, and the other end electrically connected to the resistor. A support member electrically connected to the conductive ring and slidably supporting the conductive ring along the insulating structure; a guide pin mechanically coupled to the conductive ring; and at least a range where the resistor is present. Enclose the insulating structure, conductive ring, and support member with
A shield body having an elongated hole through which the pin passes, an insulating cover member that exposes the probe tip and surrounds at least the shield body, and has an elongated hole through which the guide pin is exposed, and slidable on the cover member. And a ring position adjusting means attached to the guide pin for pressing the guide pin to adjust the position of the conductive ring with respect to the resistor.

A third high-voltage probe according to the present invention has an insulating structure made of a solid insulating material having a through hole in the axial direction, and an electric probe probe that is housed in the through hole of the insulator and protrudes from the insulating structure. -Shaped electrode member having a metal electrode and a rod-shaped insulator connected to the metal electrode, a conductive ring surrounding the insulating structure at a position corresponding to the rod-shaped electrode member, and a conductive ring electrically connected to the conductive ring. A support member that is connected and slidably supports the conductive ring along the insulating structure, a guide pin mechanically coupled to the conductive ring, and an insulating structure at least in the range where the rod-shaped electrode member is present, Enclosing the conductive ring and the support member,
A shield body having an elongated hole for passing the guide pin, an insulating cover member having an elongated hole for exposing the probe tip to surround at least the shield body and exposing the guide pin, and slidable on the cover member And a ring position adjusting means which is attached to the base plate and is capable of adjusting the position of the conductive ring with respect to the rod-shaped electrode member by pressing the guide pin.

[0013]

In the first high voltage probe, the resistor is housed in the through hole of the insulating structure made of a solid insulating material having a small dielectric loss tangent and insulated from the conductive ring, the conductive member and the shield. Therefore, unlike the case where gel-like silicon is used as the insulating material, the insulating material does not melt due to dielectric loss during high frequency operation.

In the second high voltage probe, the same effect as that of the first high voltage probe is obtained, and the ring position adjusting means changes the position of the ring through the guide pin to equivalently make the resistor. Since the value of the capacitor connected in parallel with can be adjusted, complicated adjustment of the impedance adjustment circuit in the compensation circuit can be omitted each time the input impedance of the oscilloscope changes.

In the third high voltage probe, a rod-shaped electrode member composed of a metal electrode and a rod-shaped insulating member connected to the metal electrode is used instead of the resistor to change the ring position and adjust the value of the capacitor to adjust the voltage division ratio. An adjustable, AC-coupled probe suitable for measuring higher frequency signals than when using resistors is obtained.

[0016]

1 is an exploded perspective view of a high voltage probe 10 of the present invention, FIG. 2 is a perspective view of the probe 10 in an assembled state, and FIG. 3 is a sectional view of the probe 10 taken along the line A--A in FIG. is there.
The cover 12 made of a plastic insulating material has a cylindrical portion 14 and a skirt portion 16 extending radially from one end of the cylindrical portion, and an internal thread is formed on the inner surface of the one end. A male screw 18 is formed on a part of the outer surface of the cylindrical portion 14, and a pair of slots (elongated holes) 20 are formed along the axial direction at symmetrical positions with respect to the center. Further, near the other end of the cylindrical portion 14, there is provided a passage hole 21 through which a ground lead 22 having an alligator clip connected to one end thereof passes. The pair of adjusting ring screws 23 and 24 are screwed into the threaded portion 18 of the cylindrical portion 14 and are rotated to rotate the cylindrical portion 1.
4 can be moved in the axial direction.

The insulating structure 26 is preferably made of fluororesin as an insulating material having a small dielectric loss tangent. In particular,
Polytetrafluoroethylene (Teflon trademark) has a dielectric loss tangent of about 1/10 that of silicon resin, and its high-frequency withstand voltage is significantly higher than that of silicon resin. Therefore, when polytetrafluoroethylene is used for the insulating structure 26, The probe enables input of high voltage of 10 MHz or more. The insulating structure 26 has a head portion 28 composed of two substantially cylindrical portions having different diameters and an inclined portion connecting them, and a sleeve portion 30 extending from the large diameter cylindrical portion along the axis.
A collar 29 is formed around the end of the large diameter cylinder of head 28. The sleeve portion 30 is formed by forming a pair of opposed surfaces extending in the axial direction on the peripheral surface of a cylinder having a diameter smaller than that of the cylinder portion having a large diameter of the head portion 28. Insulation structure 26
Has a constant diameter in the sleeve portion 30 and gradually decreases in diameter in the head portion 28 toward the tip thereof.
Two are provided. The conductive shaft 34 has a length substantially equal to that of the head portion 28, and has a central portion shaped to fit into the through hole 32 in the head portion 28 and a pair of screw portions provided at both ends of the central portion. When the shaft 34 is fitted in the through hole 32, one screw portion projects from the head portion 28 and the other screw portion extends into the through hole 32 in the sleeve portion 30. Head 28
A probe tip (not shown) suitable for the object to be measured is screwed onto one of the threaded portions protruding from. Sleeve part 3
A resistor 36 having female threads on both ends is housed in the through-hole 32 in 0, and one end of the resistor 36 is screwed to the other threaded portion of the conductive shaft 34. The resistor 36 determines the voltage division ratio in relation to the input impedance of the oscilloscope connecting the probe, and has a resistance value of 100 MΩ, for example.

Around the sleeve portion 30 of the insulating structure 26, a conductive correction ring 38 which is slidable in the axial direction of the sleeve portion 30 is arranged. The correction ring 38 has a pair of flat parts symmetrically with respect to the center, and the flat parts are internally threaded. A conductive contact plate 40 and an insulating guide plate 42, which are laminated in the same rectangular shape, are fixed to each flat surface portion of the correction ring 38 by a fixing screw 44 via an opening provided at one end thereof. Contact plate 40 and guide plate 42
Extends from the correction ring 38 in the opposite direction to the head 28. The fixing screw 44 slightly protrudes inside the correction ring 38 and prevents the correction ring 38 from rotating with respect to the sleeve portion 30. A screw hole into which a guide pin 46 is screwed is provided at a substantially central portion of the guide plate 42 as described later.

The conductive contact 48 has a mounting plate having an opening, and a pair of leaf spring portions extending in parallel with each other and having a curved contact portion at the tip thereof. Fixing screw 5
Reference numeral 2 indicates that a nut is attached to a rod-shaped bolt, and the bolt is screwed into the female screw at the other end of the resistor 36 through the washer 50 and the opening of the attachment plate of the contact 46, and the nut 48 is tightened. It is fixed to the resistor 36. Contact 4
The contact part of 8 electrically contacts the contact plate 40 from the inside,
The pair of leaf spring portions of the correction ring 38, the contact plate 40, and the contactor 48 generate a capacitance between the correction ring 38, the contact plate 40, and the resistor 36 via the insulating structure 26, and equivalently, the capacitor 120 ′ is parallel to the resistor 36. (FIG. 6) are connected. This capacitance varies with the position of the compensation ring 38 along the sleeve portion 30. The resistor 36 is insulated from the correction ring 38, the contact plate 40 and the pair of leaf spring portions of the contact 48 by the insulating structure 26.

Fixing ring 54 internally threaded
Is fitted into a large diameter cylindrical portion of the head portion 28 of the insulating structure 26 and locked by the collar portion 29. Ground pipe 56, which is a shield body in which male threads are cut on the outer surfaces of both ends of the cylinder.
Are arranged to accommodate the components mounted around the insulating structure 26 and its sleeve 30 and are attached at one end to the fixing ring 54 by screwing. The ground pipe 56 has a pair of axially extending slots 58 at opposite positions on the periphery, and connects the ground pipe 56 to the fixing ring 54.
Mounted on the guide plate 4,
Aligned with 2. That is, the screw hole provided in the guide plate 42 can be seen from the slot 58. The ground pipe 56 is connected to the ground lead 2 when the probe is assembled.
2 supplies the ground potential. The resistor 36 and the ground pipe 56 are insulated by the insulating structure 26.

The signal conductive plate 60 has a screw hole at the center,
It is screwed to the exposed bolt portion of the fixing screw 52 via the insulating washer 62. The other end of the resistor 36 and the contact 48 are now connected to the signal conductive plate 60. The insulating washer 62 insulates between the ground pipe 56 and the signal conductive plate 60. By attaching one end of the spacer 68 to the conductive plate 64 with a screw hole provided in the plane of the grounding conductive plate 64 and the fixing screw 66 and attaching the conductive plate 60 to the other end of the spacer 68 with the fixing screw 70, 64 are spaced apart. The outer conductor of the connector 70 is fitted into the opening provided at the center of the conductive plate 64. The center conductor of the connector 70 is electrically connected to the signal conductive plate 60. A fixing ring 72, which is internally threaded, houses the components 60-68 and is attached to the other end of the ground pipe 56 by screwing. The connector 70 has a fixing screw 72.
, And is connected to a receptacle provided at one end of the signal line 74.

The components 26 to 72 assembled as described above
The inner body of the probe, consisting of (excluding guide pins 46), is inserted into the cover 12. The cylindrical handle portion 76 has an external thread at one end on the outer surface thereof, and has a slot 20 of the cover portion 12 and a slot 58 of the ground pipe 56.
Is attached to the handle portion 76 by screwing. The handle portion 76 presses the inner body to prevent the inner body from rotating within the cover portion 12. The guide pin 46 is vertically attached to the guide plate 42 by screwing the slots of the cover portion 12 and the ground pipe 56 into the screw holes of the guide plate 42.
The guide pin 46 passes through the slot 20 and the cover portion 1
2 slightly protrudes to the outside.

The adjusting ring screws 23 and 24 have grooves 78 on their opposite surfaces for abutting the guide pins 46. Guide either one of the adjustment rings 23 and 24
By contacting the pin 46 and rotating it,
The pin 46 moves within the slot 20, thereby changing the position of the compensation ring 38 with respect to the resistor 36, and equivalently changing the value of the capacitor 120 'connected in parallel with the resistor 36. The value of the capacitor 120 is adjusted by inputting a pulse having a predetermined speed into the probe and observing the waveform with an oscilloscope. When this adjustment is completed, the other of the adjustment ring screws 23 and 24 is advanced to one side, and the guide pin 46 is sandwiched and fixed by both. In this way, since the capacitor 120 'in the probe can be adjusted, it is possible to compensate for the change in the input impedance of the oscilloscope on the probe side by adjusting the capacitor 120'. Therefore, it is possible to omit the complicated adjustment of the adjustment circuits 126a to 126d in the compensation circuit 118 of FIG. 6 every time the input impedance of the oscilloscope changes.

The high voltage probe described above does not use a gel-like silicon material to insulate the resistor but houses the resistor 35 in an insulating structure made of a solid insulating material. High voltage measurement of frequency becomes possible. However, when measuring higher frequency voltage,
A problem arises due to the resistor 36. The resistor 36 is a high withstand voltage resistor in which a resistance element is inserted in a shield tube. Since the resistance element is relatively large, the stray capacitance between the resistance element and the shield tube is relatively large. Therefore, when the input signal has a high frequency of, for example, 14 MHz, the input signal supplied to the resistor 36 is bypassed and grounded on the way without passing through the entire resistor 36. As a result, a large current flows through a part of the resistor 36, and heat generated thereby causes the resistor 36 to
Will be destroyed.

It is considered that the voltage division of the probe is a voltage division completely due to the capacitance for the high frequency signal, and the resistor 36 does not contribute to the signal transmission at all. Therefore,
If direct current and low frequency (20 kHz or less) transmission is not required, the resistor 36 can be omitted so that the probe has only a capacitive component. Therefore, the rod-shaped electrode member 8 in which the rod-shaped insulator 82 is connected to the metal electrode 80 shown in FIG.
4 is used in place of resistor 36. Rod-shaped electrode member 84
Has the same shape as the resistor 36, and has female threads on both ends similarly to the resistor 36. The metal electrode 80 is screwed onto the threaded portion of the conductive shaft 34, and the high voltage probe is assembled as shown in FIG. , The variable capacitor having the insulating structure 26 and the rod-shaped insulator 82 interposed therebetween is formed, and the probe 10 is A
It becomes a C-coupled probe. By changing the position of the correction ring 38 with the adjusting rings 23 and 24, the value of the variable capacitor is changed and the voltage dividing ratio can be adjusted.

[0026]

In the first high voltage probe, the resistor is housed in the through hole of the insulating structure made of a solid insulating material,
It is insulated from the conductive ring, the conductive member and the shield body. Therefore, unlike the case where gel-like silicon is used as the insulating material, the insulating material does not melt due to dielectric loss during high frequency operation. In the second high voltage probe, the same effect as that of the first high voltage probe is obtained, and the position of the ring is changed by the ring position adjusting means via the guide pin so that it is equivalently parallel to the resistor. Since the value of the connected capacitor can be adjusted, complicated adjustment of the impedance adjustment circuit in the compensation circuit can be omitted every time the input impedance of the oscilloscope changes. In the third high-voltage probe, a rod-shaped electrode member composed of a metal electrode and a rod-shaped insulating member connected to the metal electrode is used instead of the resistor, so that the ring position can be changed and the value of the capacitor can be adjusted to adjust the voltage division ratio. An AC-coupled probe that is more suitable for measuring high-frequency signals than when using resistors is obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a high voltage probe of the present invention.

FIG. 2 is a perspective view showing an assembled state of the probe shown in FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a perspective view showing a rod-shaped electrode member.

FIG. 5 is a side view showing an internal body of a conventional high voltage probe.

FIG. 6 is a circuit diagram showing an equivalent circuit including a probe and an oscilloscope.

[Explanation of symbols]

 12 cover member 23, 24 ring position adjusting means 26 insulating structure 36 resistor 38 conductive ring 40, 48 conductor member, support member 46 guide pin 56 shield body 70 output connector

Claims (3)

[Claims] 1. An insulating structure made of a solid insulating material having a through hole in the axial direction, and an insulator housed in the through hole of the insulator and having one end electrically connected to a probe tip protruding from the insulating structure. ,
A resistor whose other end is electrically connected to the output connector, a conductive ring surrounding the periphery of the insulating structure at a position corresponding to the resistor, and the other end of the resistor and the conductive ring are electrically connected. A conductive member that is electrically connected, a shield member that surrounds the insulating structure, the conductive ring, and the conductor in a range where at least the resistor is present, and at least the shield member that exposes the probe tip. A high-voltage probe, characterized by comprising an insulating cover member surrounding the. 2. An insulating structure made of a solid insulating material having a through hole in the axial direction, and an insulator housed in the through hole of the insulator and electrically connected to a probe tip protruding from the insulating structure at one end. A resistor having the other end electrically connected to the output connector, a conductive ring surrounding the periphery of the insulating structure at a position corresponding to the resistor, and electrically connected to the other end of the resistor. A support member electrically connected to the conductive ring and slidably supporting the conductive ring along the insulating structure; and a guide pin mechanically coupled to the conductive ring. A shield body having an elongated hole that surrounds the insulating structure, the conductive ring, and the support member, and has an elongated hole through which the guide pin passes, at least in a range where the resistor exists. An insulative cover member that extends and surrounds at least the shield body and has an elongated hole that exposes the guide pin; A high-voltage probe, comprising ring position adjusting means capable of adjusting the position of the ring with respect to the resistor. 3. An insulating structure made of a solid insulating material having a through hole in the axial direction, and a metal housed in the through hole of the insulator and electrically connected to a probe tip protruding from the insulating structure. An electrode and a rod-shaped electrode member having a rod-shaped insulator connected to the metal electrode, a conductive ring surrounding the periphery of the insulating structure at a position corresponding to the rod-shaped electrode member, and electrically connected to the conductive ring. In addition, a supporting member that slidably supports the conductive ring along the insulating structure, a guide pin mechanically coupled to the conductive ring, and at least a range in which the rod-shaped electrode member exists, the insulation is formed. Surrounding the structure, the conductive ring and the support member,
A shield body having an elongated hole for allowing the guide pin to pass therethrough; an insulating cover member having an elongated hole for exposing the probe tip to surround at least the shield body and exposing the guide pin; A high voltage probe, comprising ring position adjusting means slidably attached to a member and capable of adjusting the position of the conductive ring with respect to the rod-shaped electrode member by pressing the guide pin.