Passive voltage probe and measurement system

Abstract

This invention provides a passive voltage probe, including a first connecting terminal, a second connecting terminal, a coaxial cable, and a capacitance compensation module. The capacitance compensation module includes a housing, a circuit board, a capacitance switch assembly, and a turntable. The housing has an observation window. The turntable has a rotating part that controls the position of the capacitance switch assembly and a display part that displays second digital information of the compensation capacitance corresponding to each position. The display part rotates together with the rotating part. The passive voltage probe provided by this invention allows for convenient, tool-free, and low-cost adjustment of the compensation capacitance via the turntable.

Description

[Technical Field]

[0001] This utility model relates to the field of electronic testing and measurement equipment, and in particular to a passive voltage probe and measurement system. [Background Technology]

[0002] Digital oscilloscopes are essential instruments in electronic engineering for visualizing electrical signals, facilitating engineers' study of the changing processes of various electrical phenomena. Passive voltage probes, as electronic components connecting the circuit under test to the input of the digital oscilloscope, are indispensable parts of both the oscilloscope and the measurement system.

[0003] Please see Figure 1 , Figure 1 The diagram shows the circuit connection of an existing test system. The system includes the equivalent circuit of an oscilloscope input and the equivalent circuit of a passive voltage probe, as shown. The passive voltage probe contains a first capacitor and a second capacitor, while the oscilloscope's input equivalent circuit contains a third capacitor. If these two capacitors are not compatible, it will cause errors in the waveform displayed on the oscilloscope, such as... Figure 2 As shown, Figure 2 This is a waveform diagram displayed when a passive voltage probe is connected to the oscilloscope's test channel. The oscilloscope comes with a standard square wave signal source for calibration. When the oscilloscope is matched with the capacitor inside the passive voltage probe, the displayed test waveform is as follows. Figure 3 As shown, Figure 2 and Figure 3 The comparison shows that the accuracy of the capacitance adapter in detecting signals is very important; otherwise, serious measurement errors will occur.

[0004] In existing technologies, to address error issues, compensation circuits are added to both the oscilloscope and the passive voltage probe to achieve capacitance compatibility. Among these, US Patent 11408916B2 proposes a modular probe concept. By adding a compensation adjustment circuit to the passive voltage probe, users can adjust the capacitance value according to the connected oscilloscope and cable length, thus adapting the passive voltage probe to the oscilloscope.

[0005] Typically, this adjustment requires the use of a specialized miniature non-contact screwdriver to adjust the fine-tuning capacitor inside the passive voltage probe. Because it requires a specific tool not commonly found in tool kits, situations often arise where the tool is lost and adjustment becomes impossible. Furthermore, this adjustment method necessitates connecting the passive voltage probe to a standard square wave signal source on an oscilloscope, and judging whether the adjustment is complete by observing changes in the test waveform displayed on the oscilloscope. If the compensation is insufficient after adjustment, the waveform will exhibit… Figure 2 The state shown will display if there is overcompensation. Figure 4 The state only occurs when... Figure 3 The waveform shown indicates that the adjustment is complete. This process relies entirely on visual observation and adjustment by engineers, which is prone to errors.

[0006] Furthermore, engineers repeatedly inserted and adjusted the non-contact screwdriver, which easily caused wear and tear on the switching components of the compensation circuit, rendering it unusable and causing significant inconvenience. Moreover, the exposed switching components of the compensation circuit are also susceptible to environmental factors, leading to measurement errors.

[0007] Therefore, there is an urgent need for a passive voltage probe and measurement system that allows for convenient, tool-free, and low-cost adjustment of the compensation capacitor. It eliminates the need to connect the passive voltage probe to a standard square wave signal source to observe the waveform for accurate waveform observation, thus achieving capacitance matching between the probe and the oscilloscope. [Utility Model Content]

[0008] This invention provides a passive voltage probe for solving the above-mentioned problems.

[0009] This invention provides a passive voltage probe for use with an oscilloscope to achieve precise capacitance compensation. The oscilloscope panel displays the equivalent capacitance value of the input terminal, defined as first digital information. The passive voltage probe includes a first connection terminal, a second connection terminal, a coaxial cable, and a capacitance compensation module. The capacitance compensation module is located between the first and second connection terminals via the coaxial cable. The capacitance compensation module includes a housing, a circuit board, a capacitance switch assembly, and a turntable. The housing has an observation window. The capacitance switch assembly is soldered onto the circuit board and housed within the housing, providing compensation capacitance. The turntable has a rotating part that controls the position of the capacitance switch assembly and a display part that displays the second digital information of the compensation capacitance corresponding to each position. The display part rotates with the rotating part. When the second digital information displayed in the observation window is equal to the first digital information, the passive voltage probe is capacitance-matched with the oscilloscope. This eliminates the need to connect the passive voltage probe to a standard square wave signal source to observe the waveform for capacitance matching with the oscilloscope.

[0010] Furthermore, the housing has a first opening, a second opening, a third opening, and a fourth opening. The first connecting end is electrically connected to the circuit board through the first opening via the coaxial cable. The second connecting end is electrically connected to the circuit board through the second switch via the coaxial cable. The rotating part protrudes from the third opening, and the third opening or the fourth opening is set as the observation window, correspondingly displaying at least one of the second digital information in the display unit.

[0011] Furthermore, the housing includes a first part and a second part, with corresponding notches provided on the first part and the second part respectively. When connected, they form a symmetrically arranged first opening, a second opening, and a third opening arranged relative to the turntable. The rotating part extends outward through the third opening.

[0012] Furthermore, the fourth opening is set as the observation window, the rotating part is parallel to the circuit board and is disposed near the first part, the display part is located between the rotating part and the first part, and the first part opens the fourth opening relative to at least one of the second digital information positions in the display part;

[0013] Furthermore, the third opening is set as the observation window, the rotating part and the display part have the same structure, the second digital information is engraved on the periphery of the rotating part, and the second digital information is displayed outward through the third opening.

[0014] Furthermore, the capacitor switch assembly has a protruding first connecting post, and the turntable also includes a connecting part, which is a groove structure located at the center of the rotating part. The first connecting post is engaged with the turntable through the connecting part.

[0015] Furthermore, the first connecting post is provided with a foolproof structure, and the connecting part is provided with a groove structure that matches the foolproof structure.

[0016] Furthermore, the capacitive switch assembly includes an 8421 binary rotary encoder.

[0017] Furthermore, the capacitor switch assembly also includes a base capacitor, which is connected in parallel with the capacitor bank in the 8421 binary rotary encoder on the circuit board, and the compensation capacitor is equal to the sum of the base capacitor and the capacitor bank in the 8421 binary rotary encoder.

[0018] This utility model provides a measurement system including an oscilloscope and a passive voltage probe. The oscilloscope includes at least one signal channel as its input terminal. The passive voltage probe is detachably connected to the signal channel, the circuit under test, and ground. The passive voltage probe is used to adapt to the oscilloscope to achieve precise capacitance compensation. The oscilloscope panel displays the equivalent capacitance value of the input terminal, defined as first digital information. The passive voltage probe includes a first connection terminal, a second connection terminal, a coaxial cable, and a capacitance compensation module. The capacitance compensation module is located between the first connection terminal and the second connection terminal via the coaxial cable. The capacitance compensation module includes a housing, a circuit board, a capacitance switch assembly, and a turntable. The housing has an observation window. The capacitance switch assembly is soldered onto the circuit board and housed within the housing, providing compensation capacitance. The turntable has a rotating part that controls the range of the capacitance switch assembly and a display part that displays the second digital information of the compensation capacitance corresponding to the range. The display part rotates with the rotating part. When the second digital information displayed in the observation window is equal to the first digital information, the passive voltage probe is capacitance-matched with the oscilloscope.

[0019] Compared with the prior art, the passive voltage probe provided in this application, through a capacitor compensation module with a capacitor switch and a turntable, achieves capacitor compensation for the passive voltage probe, and has the following beneficial effects:

[0020] 1. Tool-free adjustment, simple operation, avoiding loss or damage of tools;

[0021] 2. Set the parameters directly according to the oscilloscope's specifications; there is no need to connect an oscilloscope and a standard square wave signal source to observe the waveform, thus improving efficiency.

[0022] 3. High compensation accuracy, wide applicability, and compatible with various oscilloscope models;

[0023] 4. Simple structure, low cost, and high reliability.

[0024] The voltage detection system provided in this application reduces user adjustment time by using the passive voltage probe, can quickly match the passive voltage probe with the oscilloscope, and ensures that the detected waveform is not distorted. [Attached Image Description]

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0026] Figure 1 This is the equivalent circuit diagram of a passive voltage probe;

[0027] Figure 2 This is an undercompensated waveform displayed when a passive voltage probe is connected to a standard square wave source on an oscilloscope.

[0028] Figure 3 This is the correct waveform displayed when a passive voltage probe is connected to a standard square wave source on an oscilloscope;

[0029] Figure 4 This is the overcompensation waveform displayed when a passive voltage probe is connected to a standard square wave source on an oscilloscope;

[0030] Figure 5 This is a connection diagram of the measurement system provided by this utility model;

[0031] Figure 6 This is a three-dimensional structural schematic diagram of the passive voltage probe provided by this utility model;

[0032] Figure 7 This is a cross-sectional view of the passive voltage probe provided by this utility model;

[0033] Figure 8 This is a three-dimensional structural diagram of the capacitor compensation module in the passive voltage probe provided by this utility model;

[0034] Figure 9 This is a three-dimensional exploded view of the capacitor compensation module in the passive voltage probe provided by this utility model;

[0035] Figure 10 yes Figure 8 A three-dimensional enlarged view of the turntable shown;

[0036] Figure 11 This is a front view of the capacitor compensation module described in another embodiment of the passive voltage probe provided by this utility model;

[0037] Figure 12 This is the schematic diagram of the equivalent circuit of the compensation capacitor provided by this utility model.

Detailed Implementation Methods

[0038] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0039] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0040] Furthermore, in this utility model, the use of terms such as "first," "second," etc., is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this utility model, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0042] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0043] Please also refer to Figure 1 , Figures 5 to 7 , Figure 5 This is a block diagram of the connection structure of the measurement system 100 provided by this utility model. The measurement system 100 includes an oscilloscope 30 and a passive voltage probe 10. The oscilloscope 30 includes at least one signal channel, which serves as the input terminal of the oscilloscope 30 for connecting to the passive voltage probe 10. Figure 5As shown, the oscilloscope 30 typically has four signal channels. Although the internal circuit structures of various types of oscilloscopes 30 differ, they all form equivalent circuits within the corresponding signal channels. These equivalent circuits include a third capacitor C301 and a second resistor R2, with the third capacitor C301 and the second resistor R2 connected in parallel to ground. The value of the third capacitor C301 may vary between different oscilloscope models 30, and is usually indicated on the oscilloscope panel, such as 1MΩ / / 17pF, meaning the third capacitor C301 is 17pF and the second resistor R2 is 1MΩ. The oscilloscope panel displays the equivalent third capacitor C301 at the input terminal, defining its capacitance value (in pF) as the first digital information. Currently, the second resistor R2 is 1MΩ across different oscilloscope manufacturers; only the third capacitor C301 differs, typically ranging from 10-20pF. To inform users, oscilloscope manufacturers typically display the first digital information on the panel. This application proposes to set a different third capacitor C301 for oscilloscope 30, based on the premise that the second resistor R2 is 1MΩ.

[0044] The passive voltage probe 10 is detachably connected to the signal channel, the circuit under test (DUT), and ground on the oscilloscope 30. While transmitting the measurement signal, it also adapts to the oscilloscope 30 to achieve precise capacitance compensation. The passive voltage probe 10 includes a first connection terminal 1 and a second connection terminal 3. The first connection terminal 1 is detachably connected to the signal channel, and the second connection terminal 3 is used to connect to the DUT and ground, thereby enabling the measurement of the signal from the DUT. The first connection terminal 1 uses a BNC connector, allowing for compatibility with existing oscilloscopes 30. The second connection terminal 3 provides a high-resistance resistor (R1) to reduce the load effect, and simultaneously connects an accelerating capacitor (C101) in parallel.

[0045] The first connection end 1 and the second connection end 3 are connected by a coaxial cable 5 to extend the measurement distance. During use, the coaxial cable 5 forms an equivalent capacitance, namely the second capacitor C201. The value of the second capacitor C201 is related to the specific settings of the coaxial cable 5; for example, different settings such as length or thickness will result in different values ​​for the second capacitor C201.

[0046] It should be noted that the values ​​of the first capacitor C101, the second capacitor C201, and the first resistor R1 may all be obtained during the manufacturing process by testing with the passive voltage probe 10; there are no restrictions on the specific values. Furthermore, as... Figure 5 As shown, the second connection terminal 3 typically includes a probe front end, and a signal input terminal and a grounding terminal are set from the probe front end. The relevant settings are all common technologies and will not be described in detail here.

[0047] Please continue reading. Figure 8 , Figure 9 and Figure 10 To ensure the accuracy of the measurement system 100, the passive voltage probe 10 of this application is equipped with a capacitance compensation module 7, which is located between the first connection terminal 1 and the second connection terminal 3. In this embodiment, the capacitance compensation module 7 includes a housing 71, a circuit board 73, a capacitance switch assembly 75, and a turntable 77. The housing has an observation window, and the capacitance switch assembly 75 is soldered onto the circuit board 73, both housed within the housing 71. The capacitance switch assembly 75 provides a compensation capacitor C401, and by adjusting the state of the capacitance switch assembly 75, different compensation values ​​of the compensation capacitor C401 can be provided.

[0048] The turntable 77 is equipped with a rotating part 771 for controlling the positions of the capacitor switch assembly 75 and a display part 773. The display part 773 shows second digital information 7731 corresponding to the position and the value of the compensation capacitor C401. The display part 773 rotates together with the rotating part 771. When the second digital information 7731 displayed in the observation window is equal to the first digital information, the passive voltage probe 10 is capacitively matched with the oscilloscope 30.

[0049] To meet the value of the compensation capacitor C401 for the rotation adjustment of the turntable 77, the capacitor switch assembly 75 may include an 8421 rotary DIP switch or other similar DIP switches. The 8421 rotary DIP switch is an 8421 binary rotary encoder, such as the GSDR-16S model rotary DIP switch. The capacitor switch assembly 75 incorporates a capacitor bank Cx consisting of four capacitors connected in parallel, such as... Figure 12 As shown, the capacitance values ​​of the four capacitors are set to 1pF, 2pF, 4pF and 8pF respectively. Each capacitor is connected in series with a switch. The capacitor switch assembly 75 can adjust the capacitance value range of the capacitor group Cx from 0pF to 15pF by controlling the conduction state of the corresponding series-connected switches of the four capacitors, so as to achieve precise setting of the compensation capacitor C401.

[0050] The adjustment principle of the rotary DIP switch is explained simply as follows:

[0051] When the capacitance value to be compensated is 7pF, the series connection switches for capacitors with capacitance values ​​of 1pF, 2pF, and 4pF are simultaneously turned on, while the series connection switch for capacitor with capacitance value of 8pF is turned off. Since the capacitors are connected in parallel, the compensation capacitance value should be the sum of the capacitance values ​​of the capacitors turned on in the circuit, that is, 1pF + 2pF + 4pF = 7pF, thus achieving the adjustment of the compensation capacitance. Of course, any capacitance value between 0pF and 15pF can be adjusted by controlling the on and off states of the four capacitor series connection switches, which will not be elaborated here.

[0052] The turntable 77 is connected to the capacitor switch assembly 75. Rotation of the rotating part 771 changes the position of the capacitor switch assembly 75, thereby changing the value of the compensation capacitor C401. The value of the compensation capacitor C401 is visualized through the display part 773 and the observation window in the housing 71. When the second digital information 7731 displayed in the observation window equals the first digital information, rotation of the turntable 77 stops. At this point, it is ensured that the passive voltage probe 10 is adjusted and compatible with the oscilloscope 30 displaying the first digital information, and that an accurate waveform can be displayed on the oscilloscope 30.

[0053] Please continue reading. Figure 8 , Figure 9 and Figure 10 In one embodiment, the housing 71 has a first opening 701, a second opening 703, a third opening 705, and a fourth opening 707. The first connecting end 1 and the second connecting end 3 are respectively connected to the circuit board 73 via coaxial cables 5 passing through the first opening 701 and the second opening 703. The capacitor switch assembly 75 is connected in parallel in the circuit, providing a compensation capacitor C401. The turntable 77 includes a rotating part 771, a display part 773, and a connecting part 775. The connecting part 775 is a groove structure located at the center of the rotating part 771. The capacitor switch assembly 75 has a protruding first connecting post 751. The first connecting post 751 can be rotated to adjust the position of the capacitor switch assembly 75. The first connecting post 751 engages with the connecting part 775 in the turntable 77. The groove structure of the first connecting post 751 and the connecting part 775 are adapted to each other and are not cylindrical structures, so as to ensure that the rotating part 771 can drive the first connecting post 751 to rotate relative to the housing 71, thereby controlling the capacitor switch assembly 75 and adjusting the compensation capacitor C401.

[0054] The non-cylindrical structure refers to the first connecting post 751 having a foolproof structure, and the connecting part 775 having a corresponding groove structure in place to match the foolproof structure. Specifically, the first connecting post 751 is designed as a combination of a flat surface and a curved surface, forming a connecting structure with a defined orientation. Correspondingly, the connecting part 775 has a corresponding groove structure, and the first connecting post 751 has a unique installation method, thereby confirming the positional relationship between the turntable 77 and the capacitive switch assembly. Of course, the first connecting post 751 and the connecting part 775 can also be designed as other structures with a unique installation position, and after installation, the display part 773 in the turntable 77 can be set according to the correspondence between the gear position and the second digital information 7731 corresponding to the compensation capacitor C401 value.

[0055] A rotating part 771 protrudes from the third opening 705. The display part 773 is fixedly connected to the rotating part 771 and can rotate together with the rotating part 771. The fourth opening 707 is set as an observation window, and the second digital information 7731 in the display part 773 is set corresponding to the fourth opening 707, so that the second digital information 7731 can be observed through the outside of the housing 71. During use, the user manually rotates the rotating part 771, causing the display part 773 and the first connecting post 751 to rotate together. While setting the compensation capacitor C401, the user can observe the specifically set second digital information 7731 through the fourth opening 707.

[0056] Please see Figure 11 In another embodiment, the third opening 703 can also be set as an observation window, the rotating part 771 and the display part 773 have the same structure, the rotating part 771 is engraved with second digital information 7731 on its periphery, and the second digital information 7731 is displayed outward through the third opening 703.

[0057] Both the second digital information 7731 and the first digital information are Arabic numerals. The size of the compensation capacitor C401 provided by the capacitor switch assembly 75 can be accurately confirmed by observing the second digital information 7731 through the fourth opening 707 or the third opening 703, thereby achieving accurate compensation.

[0058] Please continue to refer to the following: Figure 8 and Figure 9 For ease of assembly, the housing 71 includes a first portion 711 and a second portion 713. The first portion 711 and the second portion 713 are connected and fixed by means of snap-fit, screw fixing, or adhesive. The circuit board 73 is sandwiched between the first portion 711 and the second portion 713. The first portion 711 and the second portion 713 are respectively provided with corresponding notches, which, when connected, form a symmetrically arranged first opening 701 and second opening 703 for housing the coaxial cable 5, and a third opening 705 arranged opposite the turntable 77. Part of the structure of the turntable 77 extends outward through the third opening 705, mainly the rotating part 771 extending outward through the third opening 705. The rotating part 771 is configured as a gear structure, parallel to the circuit board 73 and close to the first portion 711, and is engaged with the connecting part 775 by a first connecting post 751 to achieve relative position fixation.

[0059] When the fourth opening 707 is set as an observation window, the rotating part 771 is parallel to the circuit board 73 and positioned close to the first part 771. The display part 773 is located between the rotating part 771 and the first part 711, with the fourth opening 707 positioned relative to at least one second digital information 7731 in the display part 773. The position of the fourth opening 707 should be set with reference to the compensation capacitor reference table to ensure that the second digital information 7731 displayed through the fourth opening 707 corresponds to the third capacitor C301 marked on the oscilloscope 30 panel. It should be noted that the rotating part 771 and the display part 773 can be integrated, or they can be connected and fixed by means of snap-fit, screw fixing, or adhesive to ensure that they rotate together. The specific setting method is not limited.

[0060] Of course, in another embodiment, the rotating part 771 and the display part 773 can be the same structure. Only the second digital information 7731 needs to be imprinted on the periphery of the rotating part 771, and the second digital information 7731 can be displayed outwards through the third opening 705. This arrangement eliminates the need for a fourth opening 707; rotation control and the display of the second digital information 7731 can be achieved solely through the third opening 705. A specific configuration can be referenced from a combination lock structure, where the displayed second digital information 7731 is switched by rotating and adjusting the compensation capacitor C401.

[0061] Compared with the prior art, the passive voltage probe 10 provided in this application achieves capacitance compensation of the passive voltage probe 10 through the capacitance compensation module 7 having a capacitor switch assembly 75 and a turntable 77, which has the following beneficial effects:

[0062] 1. Tool-free adjustment, simple operation, avoiding loss or damage of tools;

[0063] 2. Set the parameters directly according to the oscilloscope 30 markings, without needing to connect the oscilloscope 30 and a standard square wave signal source to observe the waveform, thus improving efficiency;

[0064] 3. High compensation accuracy and wide applicability; compatible with various oscilloscope 30 models.

[0065] 4. Simple structure, low cost, and high reliability.

[0066] Please continue to combine Figure 1 , Figures 5 to 11 The voltage detection system provided in this application reduces the user's adjustment time by using a passive voltage probe 10, can quickly match the passive voltage probe 10 with the oscilloscope 30, and ensures that the detected waveform is not distorted.

[0067] On the other hand, based on the passive voltage probe 10, this application also provides a capacitance compensation method for the passive voltage probe 10, which specifically includes the following steps:

[0068] A passive voltage probe 10 is provided. The passive voltage probe 10 includes a first connection terminal 1, a second connection terminal 3, a coaxial cable 5, and a capacitor compensation module 7. The capacitor compensation module 7 is located between the first connection terminal 1 and the second connection terminal 3 via the coaxial cable 5. The first connection terminal 1 is used to connect to an oscilloscope 30, and the second connection terminal 3 is used to connect to the circuit under test.

[0069] A capacitor compensation module 7 is configured. The capacitor compensation module 7 includes a housing 71, a circuit board 73, a capacitor switch assembly 75, and a turntable 77. The capacitor switch assembly 75 is soldered onto the circuit board 73 and together housed in the housing 71. The capacitor switch assembly 75 has an adjustable range for providing a variable compensation capacitor C401.

[0070] The turntable 77 includes a rotating part 771 and a display part 773. The rotating part 771 is mounted on the capacitor switch assembly 75 and is used to switch the gear of the capacitor switch assembly 75. The display part 773 is used to display the second digital information 7731 corresponding to the gear and the compensation capacitor value C401. The display part 773 is fixedly connected to the rotating part 771 and rotates together with the rotating part 771. The housing 71 has an observation window for displaying the second digital information 7731.

[0071] Rotate the turntable 77 so that the second digital information 7731 displayed in the observation window is equal to the first digital information displayed on the oscilloscope 30 panel. At this time, the passive voltage probe 10 is capacitor-matched with the oscilloscope 30 to test the accurate waveform.

[0072] Furthermore, in order to ensure that the passive voltage probe 10 and the oscilloscope 30 are capacitor-matched when the second digital information 7731 displayed in the observation window is equal to the first digital information displayed on the oscilloscope 30 panel, when the turntable 77 is installed on the capacitor switch assembly 75, the compensation capacitor C401 corresponding to each range has a one-to-one correspondence with the second digital information 7731 displayed in the observation window and the first digital information displayed on the oscilloscope 30 input panel.

[0073] The establishment of this correspondence also includes the following steps:

[0074] Obtain the equivalent parameters corresponding to the equivalent circuits of the passive voltage probe 10 and the input terminal of the oscilloscope 30, and establish a compensation capacitor lookup table. The equivalent parameters include the first resistor R1 and the first capacitor C101 corresponding to the second connection terminal 3, the second capacitor C201 corresponding to the coaxial cable 5, and the second resistor R2 and the third capacitor C301 corresponding to the input terminal of the oscilloscope 30. The compensation capacitor lookup table includes the third capacitor C301 at the input terminal of the oscilloscope 30, the second digital information 7731 displayed in the observation window, and the correspondence between the third capacitor C301 and the actual required compensation capacitor C401 calculated based on the third capacitor C301.

[0075] According to the compensation capacitor reference table, the capacitor compensation module 7 is set up. When the turntable 77 is installed on the capacitor switch assembly 75, the correspondence between the compensation capacitor C401 corresponding to each position and the second digital information 7731 displayed in the observation window conforms to the correspondence in the compensation capacitor reference table.

[0076] To facilitate user adjustments, the passive voltage probe 10 acquires the values ​​of the first resistor R1, the second resistor R2, the first capacitor C101, and the second capacitor C201 at the initial setup stage. Combined with the values ​​of the third capacitor C301 and the second resistor R2 indicated on the oscilloscope panel of the capacitor switch assembly 75 and the oscilloscope 30, a compensation capacitor reference table is established.

[0077] The compatibility between the oscilloscope 30 and the passive voltage probe 10 is primarily based on the principle that the time constant of the capacitance multiplied by the resistance is equal, thus achieving capacitance compensation. Specifically, the product of the first capacitor C101 and the first resistor R1 equals the product of the second capacitor C201, the third capacitor C301, and the compensation capacitor C401, plus the second resistor R2. Under this principle, compensating capacitor C401 ensures that the waveform displayed by the oscilloscope 30 is accurate and distortion-free.

[0078] The calculation formula is as follows:

[0079] C101*R1=(C201+C301+C401)*R2

[0080] Using the known parameters, the relationship between the compensation capacitor C401 and the third capacitor C301 can be directly calculated.

[0081] Based on the model parameters of the capacitor switch assembly 75, the turntable 77 is set according to the corresponding compensation capacitor reference table. When the turntable 77 is rotated so that the capacitor switch assembly 75 provides the corresponding compensation capacitor C401 value, the second digital information 7731 observed in the observation window corresponds to the calculated compensation capacitor C401. Of course, the correspondence here means that it is easy for the user to confirm the one-to-one correspondence between the second digital information 7731 and the compensation capacitor C401 value. For example, in this embodiment, it is preferable to directly use a digital display to ensure that the two are consistent. The user can directly set the corresponding second digital information 7731 through the turntable 77 according to the compensation capacitor C401 value, thereby ensuring that the adjusted capacitor switch assembly 75 can provide the required compensation capacitor C401 value.

[0082] After the passive voltage probe 10 is set according to the compensation capacitor reference table, rotate the turntable 77 so that the second digital information 7731 displayed in the observation window is equal to the first digital information displayed on the oscilloscope panel. At this time, the passive voltage probe 10 and the oscilloscope 30 are capacitor-matched and can be directly connected to the circuit under test to test the accurate waveform.

[0083] The specific establishment method and calculation steps are illustrated below using an oscilloscope 30 with a 10:1 attenuation ratio and a passive voltage probe 10 as an example:

[0084] Wherein, the second resistor R2 is 1MΩ, a fixed value; the first resistor R1 is set to 9MΩ; the first capacitor C101 is measured to be 15pF; and the second capacitor C201 is measured to be 100pF. Substituting these parameters into the formula for calculation, a unique correspondence can be obtained between the third capacitor C301 and the compensation capacitor C401:

[0085] 15pF*9M=(100pF+C301+C401)*1M

[0086] 135pF = (100pF + C301 + C401)

[0087] 35pF = C301 + C401

[0088] Please refer to the following: Figure 12 The third capacitor C301 in the existing oscilloscope 30 is typically between 10pF and 20pF. To meet the setting requirements, the capacitor switch assembly 75 should have at least 10 selectable positions. The GSDR-16S DIP switch typically has 16 selectable positions, which meets the requirements of the capacitor switch assembly 75. Since the GSDR-16S DIP switch uses 8421 encoding settings, the adjustment range is between 0pF and 15pF. Based on the calculation formula, the value of the compensation capacitor C401 will be higher than this range. To meet the adjustment requirements, the capacitor compensation module 7 also includes the following steps:

[0089] The capacitive switch assembly 73 also includes a base capacitor C0, which is connected in parallel with the capacitor group Cx in the 8421 binary rotary encoder on the circuit board. The compensation capacitor C401 is equal to the sum of the base capacitor C0 and the capacitor group Cx in the 8421 binary rotary encoder, thereby making the adjustment range of the capacitive switch assembly 75 correspond to the range required by the compensation capacitor C401.

[0090] The value of the base capacitor C0 can be set within a certain range as needed. Based on the principle that the compensation capacitor C401 is equal to the sum of the base capacitor C0 and the capacitor group Cx in the 8421 binary rotary encoder, the base capacitor C0 is set according to the setting range of the compensation capacitor C401.

[0091] In this embodiment, the base capacitor C0 is set to 15pF. After the base capacitor C0 is connected in parallel with the capacitor in the GSDR-16S DIP switch, the adjustment range of the capacitor switch assembly 75 is 15pF to 30pF. This setting method can be adapted to various types of existing oscilloscopes 30 and has a wide range of applications.

[0092] By setting the base capacitor C0, the adjustment range of the capacitor switch assembly 75 can be supplemented. This setting method allows the passive voltage probe capacitor compensation method to be adapted to various types of oscilloscopes 30, increasing the applicable scenarios.

[0093] A compensation capacitor lookup table is established based on the above correspondence. The details are shown in the table below:

[0094] The table shows a one-to-one correspondence between the third capacitor C301, the compensation capacitor C401, and the second digital information 7731. Specifically, when the turntable 77 is installed on the capacitor switch assembly 75, there is a one-to-one correspondence between the compensation capacitor C401 for each setting, the second digital information 7731 displayed in the observation window, and the first digital information displayed on the oscilloscope input panel. Based on this correspondence, the installation position and method of the turntable 77 can be directly set. When the user observes that the value of the third capacitor C301 marked on the oscilloscope 30 panel is 17pF, the actual compensation capacitor C401 required is 18pF. The user rotates the turntable 77, and when the second digital information 7731 observed in the observation window displays the number 17, the adjustment is complete. At this point, the user does not need to know the value of the compensation capacitor C401. They only need to adjust the dial 77 according to the value of the third capacitor C301 marked on the oscilloscope 30 panel, which is the first digital information, so that the second digital information 7731 displayed in the observation window is equal to the first digital information displayed on the oscilloscope 30 panel, and thus obtain the accurate value of the compensation capacitor C401.

[0095] To facilitate installation and adjustment, the capacitor compensation module 7 also includes:

[0096] A housing 71 is provided, which has a first opening 701, a second opening 703, a third opening 705 and a fourth opening 707. A first connecting end 1 and a second connecting end 3 are respectively connected to the circuit board 73 through the first opening 701 and the second opening 703 via a coaxial cable 5. A capacitor switch assembly 75 is connected in parallel in the circuit, and a compensation capacitor C401 is provided.

[0097] A capacitor switch assembly 75 is provided, and a first connecting post 751 is provided protruding from the capacitor switch assembly 75;

[0098] A turntable 77 is provided, and the turntable 77 also includes a connecting part 775. The connecting part 775 is a groove structure located at the center of the rotating part 771. The first connecting post 751 is engaged with the turntable 77 through the connecting part 775 to complete the installation of the turntable 77. At this time, the rotating part 771 protrudes from the third opening 705. The third opening 705 or the fourth opening 707 is set as an observation window to display the second digital information 7731 in the display part 773.

[0099] The installation of the turntable 77 also includes marking the position of the fourth opening 707 in the display unit 773, consulting the compensation capacitor reference table, and rotating the turntable 77 to the corresponding installation position according to the current position of the capacitor switch assembly 75 and the corresponding relationship in the compensation capacitor reference table. Then, the first connecting post 751 is engaged and connected through the connecting part 775 to complete the installation.

[0100] Of course, in order to make it easier to determine the position of the turntable 77, the installation of the turntable 77 also includes setting a foolproof structure in the first connecting post 751 according to the position information in the display part 773 corresponding to the marked fourth opening 707, the compensation capacitor reference table, and the correspondence between the current position of the capacitor switch assembly 75 and the compensation capacitor reference table, and setting a matching groove structure in the connecting part 775 to the position corresponding to the foolproof structure, and rotating the turntable 77 to the position corresponding to the foolproof structure for direct installation.

[0101] For ease of assembly, the housing 71 includes a first portion 711 and a second portion 713. The first portion 711 and the second portion 713 are connected and fixed by means of snap-fit, screw fixing, or adhesive. The circuit board 73 is sandwiched between the first portion 711 and the second portion 713. The first portion 711 and the second portion 713 are respectively provided with corresponding notches, forming symmetrically arranged first openings 701 and second openings 703 after connection, for housing the coaxial cable 5, and a third opening 705 disposed opposite the turntable 77. A portion of the structure of the turntable 77 extends outward through the third opening 705. The third opening 705 or the fourth opening 707 is configured as an observation window, corresponding to the display unit 773 displaying the second digital information 7731, including:

[0102] When the fourth opening 707 is set as an observation window, the rotating part 771 is parallel to the circuit board 73 and is set close to the first part 711. The display part 773 is located between the rotating part 771 and the first part 711. The first part 711 opens the fourth opening 707 relative to the position of the second digital information 7731 in the display part 773.

[0103] When the third opening 705 is set as an observation window, the rotating part 771 and the display part 773 have the same structure. The second digital information 7731 is printed on the periphery of the rotating part 771, and the second digital information 7731 is displayed outward through the third opening 705.

[0104] Compared with existing technologies, the passive voltage probe capacitance compensation method provided by this utility model achieves connection detection with the oscilloscope 30 and the circuit under test by providing a passive voltage probe 10 with a capacitance compensation module 7, and provides capacitance compensation to achieve waveform adjustment. During use, the user only needs to observe the first digital information displayed on the oscilloscope 30 panel, rotate the dial 77 until the second digital information 7731 displayed in the observation window is equal to the first digital information displayed on the oscilloscope 30 panel, and the compensation adjustment process is completed. There is no need to connect a standard square wave signal source to the oscilloscope to observe the correctness of the waveform. The operation is simple and error-free, effectively improving the efficiency of capacitance compensation adjustment.

[0105] Furthermore, the passive voltage probe capacitance compensation method provided by this utility model utilizes the relationship between the compensation capacitor C401 corresponding to each position in the capacitor switch assembly 75 and the first digital information and second digital information 7731 to set up the turntable 77, observation window, and capacitor switch assembly 75. Based on the principle of equal capacitor resistance time constants, a corresponding compensation capacitor reference table is constructed, which facilitates the setting of a passive voltage probe 10 that meets the requirements. The setting method is simple and accurate, and uses fewer structures and has low cost. The passive voltage probe capacitance compensation method achieves capacitance compensation while being easy to operate, eliminating the dependence on tools, and does not require waveform display and adjustment via oscilloscope 30. It has high compensation accuracy, wide applicability, and can conveniently, tool-free, and low-costly adjust the compensation capacitor C401.

[0106] The above description is merely an embodiment of this utility model. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of this utility model, but these improvements all fall within the protection scope of this utility model.

Claims

1. A passive voltage probe for use with an oscilloscope to achieve precise capacitance compensation, wherein the oscilloscope panel displays the equivalent capacitance value at the input terminal, defined as first digital information, characterized in that... include: First connection end; Second connection end; Coaxial cable; and A capacitance compensation module is disposed between the first connection terminal and the second connection terminal via the coaxial cable. The capacitance compensation module includes: The housing has an observation window. Circuit board; A capacitor switch assembly, soldered onto the circuit board and housed within the housing, provides compensation capacitance; and A turntable, which is provided with a rotating part and a display part for controlling the gear position of the capacitor switch assembly. The display part displays second digital information corresponding to the gear position and the compensation capacitor value. The display part is rotated together with the rotating part. Specifically, when the second digital information displayed in the observation window is equal to the first digital information, the passive voltage probe is matched with the capacitance of the oscilloscope.

2. The passive voltage probe of claim 1, wherein, The housing has the following openings: The first opening, the first connection end is electrically connected to the circuit board through the coaxial cable passing through the first opening; The second opening, the second connection end is electrically connected to the circuit board through the coaxial cable passing through the second opening; The third and fourth openings are provided, with the rotating part protruding from the third opening. The third or fourth opening is set as the observation window, which displays the second digital information in the display unit.

3. The passive voltage probe of claim 2, wherein, The housing includes a first part and a second part, with corresponding notches provided on the first part and the second part respectively. When connected, they form a first opening and a second opening that are symmetrically arranged, as well as a third opening that is arranged opposite to the turntable. The rotating part extends outward through the third opening.

4. The passive voltage probe of claim 3, wherein, The fourth opening is set as the observation window. The rotating part is parallel to the circuit board and is located near the first part. The display part is located between the rotating part and the first part. The first part opens the fourth opening relative to at least one of the second digital information positions in the display part.

5. The passive voltage probe of claim 3, wherein, The third opening is set as the observation window. The rotating part and the display part have the same structure. The second digital information is printed on the periphery of the rotating part. The second digital information is displayed outward through the third opening.

6. The passive voltage probe of claim 2, wherein, The capacitor switch assembly has a protruding first connecting post, and the turntable also includes a connecting part, which is a groove structure located at the center of the rotating part. The first connecting post is engaged with the turntable through the connecting part.

7. The passive voltage probe of claim 6, wherein, The first connecting post is provided with a foolproof structure, and the connecting part is provided with a groove structure that matches the foolproof structure.

8. The passive voltage probe of claim 1, wherein, The capacitive switching assembly includes an 8421 binary rotary encoder.

9. The passive voltage probe of claim 8, wherein, The capacitor switch assembly also includes a base capacitor, which is connected in parallel with the capacitor bank in the 8421 binary rotary encoder on the circuit board. The compensation capacitor is equal to the sum of the base capacitor and the capacitor bank in the 8421 binary rotary encoder.

10. A measurement system characterized by, include: An oscilloscope, the oscilloscope including at least one signal channel as an input terminal of the oscilloscope; and The passive voltage probe as claimed in any one of claims 1 to 9, which is detachably connected to the signal channel, the circuit under test and the ground.

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