LCR test board card based on self-balancing bridge method

Abstract

The utility model discloses an LCR test board card based on a self-balancing bridge method, which relates to the technical field of electrical measurement and comprises a to-be-tested element, the to-be-tested element receives current signals of a signal generation module, voltage signals at two ends of the to-be-tested element are transmitted to a self-balancing bridge module, and the self-balancing bridge module is connected with the to-be-tested element. Waveforms generated by the self-balancing bridge module are transmitted to the single-chip microcomputer module through the acquisition module, and the power supply conversion module supplies power to other modules. The beneficial effects of the utility model are that signals are raised to be all positive by utilizing the adjustable bias characteristic of the instrumentation amplifier at the first stage of the instrumentation amplifier, so that a cheap unipolar ADC can be used. The ADC collects data and then sends the data to the single-chip microcomputer for processing, the single-chip microcomputer can eliminate direct-current bias interference by calculating an alternating-current effective value, and then the testing precision is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of electrical measurement, in particular to an LCR test board based on the self-balancing bridge method. Background Art

[0002] As the most basic components in a circuit, resistors, capacitors, and inductors play a crucial role in electronic design. The true value of these components is important for the performance design and evaluation of electronic circuits. Therefore, LCR measurement is undoubtedly an important module in the field of electronic measurement, and there are various measurement methods, including the self-balancing bridge method, resonance method, network analysis method, volt-ampere method, etc. Among them, the self-balancing bridge method is widely used in current LCR test products.

[0003] There are many LCR test products on the market, but products that can perform high-precision LCR tests within a wide range are generally expensive, and products with lower prices cannot meet the requirements of most users in terms of measurement range and accuracy.

[0004] Therefore, an LCR test board based on the self-balancing bridge method is needed to solve the above problems. Summary of the Utility Model

[0005] In this part, as well as in the abstract and title of the specification of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this part, the abstract, and the title, but such simplifications or omissions shall not be used to limit the scope of the utility model.

[0006] In view of the problems existing in the above or prior art, the present utility model is proposed.

[0007] Therefore, the purpose of the present utility model is to provide an LCR test board based on the self-balancing bridge method, which can solve the problem that existing LCR test products cannot measure high-precision resistor-capacitor-inductor products at low cost.

[0008] To solve the above technical problems, the present utility model provides the following technical solution: An LCR test board based on the self-balancing bridge method, which includes a component under test. The component under test receives the current signal from the signal generation module, and the voltage signal at both ends of the component under test is transmitted to the self-balancing bridge module. The waveform generated by the self-balancing bridge module is transmitted to the single-chip microcomputer module through the acquisition module.

[0009] As a preferred embodiment of the LCR test board based on the self-balancing bridge method of the present utility model, the signal generation module includes a first chip and a second chip. The first chip is connected to the component under test through a first analog switch and a first relay, and the second chip is connected to the component under test through the first relay.

[0010] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: the self - balancing bridge module includes a first follower, and the first follower is arranged between the first chip and the first analog switch.

[0011] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: the self - balancing bridge module further includes a core amplifier. The inverting input terminal of the core amplifier is connected to the element under test through a second relay, the non - inverting input terminal is grounded, and the output terminal is connected to the acquisition module through a second follower;

[0012] A second analog switch is also connected across the inverting input terminal and the output terminal of the core amplifier.

[0013] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: the self - balancing bridge module further includes a third follower and a fourth follower. One ends of the third follower and the fourth follower are respectively connected to the element under test, and the other ends are connected to the acquisition module.

[0014] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: the acquisition module includes a first instrumentation amplifier. One end of the first instrumentation amplifier is respectively connected to the second follower and the third follower, and the other end is connected to the single - chip microcomputer module through a first analog - to - digital conversion chip.

[0015] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: the acquisition module further includes a second instrumentation amplifier. One end of the second instrumentation amplifier is respectively connected to the third follower and the fourth follower, and the other end is connected to the single - chip microcomputer module through a second analog - to - digital conversion chip.

[0016] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: a power conversion module is further included. The power conversion module is connected to an external 5V power supply and supplies power to the element under test, the self - balancing bridge module, the acquisition module and the single - chip microcomputer module respectively.

[0017] As a preferred solution of the LCR test board card based on the self - balancing bridge method of the present utility model, wherein: the power conversion module converts the external 5V power supply into voltages of 5.5V, ±5V, 2.5V, and 3.3V.

[0018] Advantages of the present utility model: By utilizing the adjustable bias characteristic of the instrumentation amplifier at the first stage of the instrumentation amplifier, the present utility model raises the signal to all positive values, so as to use an inexpensive unipolar ADC. After the ADC collects data, it is handed over to the single-chip microcomputer for processing. The single-chip microcomputer can eliminate the DC bias interference by calculating the AC effective value, thereby improving the test accuracy. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0020] Figure 1 It is the overall circuit connection diagram of the LCR test board based on the self-balancing bridge method.

[0021] Figure 2 It is the circuit connection diagram of the LCR test board based on the self-balancing bridge method connected to an external power supply through TYPEC.

[0022] Figure 3 It is the circuit schematic diagram of converting 5V to 2.5V of the LCR test board based on the self-balancing bridge method.

[0023] Figure 4 It is the circuit schematic diagram of converting 5V to 3.3V of the LCR test board based on the self-balancing bridge method.

[0024] Figure 5 It is the circuit schematic diagram of converting 5V to 5.5V of the LCR test board based on the self-balancing bridge method.

[0025] Figure 6 It is the circuit schematic diagram of converting 5V to ±5V of the LCR test board based on the self-balancing bridge method.

[0026] Figure 7 It is the schematic diagram of the first chip and its peripheral circuit of the LCR test board based on the self-balancing bridge method.

[0027] Figure 8 It is the schematic diagram of the second chip and its peripheral circuit of the LCR test board based on the self-balancing bridge method.

[0028] Figure 9 It is the power supply diagram of the first chip and the second chip of the LCR test board based on the self-balancing bridge method and an external 5V power supply.

[0029] Figure 10Connection diagram of the first instrumentation amplifier, the first analog-to-digital conversion chip and their peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0030] Figure 11 Connection diagram of the second instrumentation amplifier, the second analog-to-digital conversion chip and their peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0031] Figure 12 Connection diagram of the ADR4550BRZ reference level chip and its peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0032] Figure 13 Connection diagram of the ADR4525BRZ reference level chip and its peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0033] Figure 14 Connection diagram of the first analog switch and its peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0034] Figure 15 Connection diagram of the second analog switch and its peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0035] Figure 16 Connection diagram of the Darlington tube and its peripheral circuits for the LCR test board based on the self-balancing bridge method.

[0036] Figure 17 Connection diagram of the relay and its peripheral circuits for the LCR test board based on the self-balancing bridge method. Detailed implementation manners

[0037] To make the above objects, features and advantages of the present utility model more obvious and understandable, the following will describe the detailed implementation manners of the present utility model in conjunction with the drawings of the specification.

[0038] In the following description, many specific details are set forth to fully understand the present utility model. However, the present utility model can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present utility model. Therefore, the present utility model is not limited by the specific embodiments disclosed below.

[0039] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation manner of the present utility model. The "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is separate or selectively exclusive of other embodiments.

[0040] Embodiment 1

[0041] Reference Figures 1 to 6 、 Figures 12 to 17 This is the first embodiment of the present utility model. This embodiment provides an LCR test board based on the self - balancing bridge method, which includes a power conversion module 500 that mainly converts the external power supply voltage to supply power to the chips of each unit. It includes TPS55340RTER, LM27762DSSR, LP5907MFX - 2.5 / NOPB, TPS54202DDCR, ADR4550BRZ, ADR4525BRZ and their peripheral circuits. Among them, TPS55340RTER and TPS54202DDCR are connected to the 5V external power supply through TYPE - C. TPS55340RTER and its peripheral circuit output a 5.5V voltage, and TPS54202DDCR and its peripheral circuit output a 3.3V voltage. The signal generation module 100, the relay and the Darlington tube circuit for controlling the relay are directly powered by the 5V external power supply.

[0042] Furthermore, LM27762DSSR is connected to the power supply output terminal of TPS55340RTER to convert the 5.5V voltage into ±5V voltage for power supply. LM27762DSSR provides ±5V power supply for LP5907MFX - 2.5 / NOPB, AD8065 and its peripheral circuits, AD8253 and its peripheral circuits, and ADG1212 and its peripheral circuits.

[0043] Furthermore, LP5907MFX - 2.5 / NOPB converts the ±5V voltage into 2.5V voltage to provide 2.5V voltage for AD7980 and its peripheral circuits.

[0044] Furthermore, the power supply output terminal of TPS55340RTER is also respectively connected to the power supply pins of ADR4550BRZ and ADR4525BRZ. ADR4550BRZ and ADR4525BRZ are reference level chips. ADR4550BRZ outputs a 5V voltage to provide a 5V reference voltage for AD7980 and its peripheral circuits, and ADR4525BRZ outputs a 2.5V voltage to provide a 2.5V reference voltage for AD8253 and its peripheral circuits.

[0045] Furthermore, TPS54202DDCR outputs a 3.3V voltage to provide 3.3V power supply for AD7980 and its peripheral circuits, OT322525MJBA4SL and CH32F205RBT6 and their peripheral circuits.

[0046] The power conversion module 500 converts the external power supply into the voltages required by each chip on the circuit board to supply power to each chip, specifically converting into 2.5V, 3.3V, and ±5V voltages.

[0047] Further, the relay is a G6K-2F-Y circuit. One relay has two switches. One switch is used to select the AC source / current source, and the other is used to select the self-balancing bridge or ground. The Darlington tube circuit for controlling the relay is a ULN2001 circuit, and the Darlington tube circuit drives the relay to control the on / off signal. When the V- pin of G6K-2F-Y is at a high level, SA = SA1, SB = SB1; when the V- pin is at a low level, SA = SA2, SB = SB2.

[0048] In summary, the power conversion module 500 provides voltage for each chip. The relay and the Darlington tube circuit connected to the component under test Z are used to select a suitable signal source according to the impedance of the component under test Z. For small resistors below 10R, the current range is selected, and for others, the AC signal range is selected.

[0049] Embodiment 2

[0050] Referring to Figure 1 、 Figures 7 to 10 , this is the second embodiment of the present utility model. It further provides an LCR test board based on the self-balancing bridge method, including a signal generation module 100. The component under test Z receives the current signal of the signal generation module 100, and the voltage signal at both ends of the component under test Z is transmitted to the self-balancing bridge module 200. The waveform generated by the self-balancing bridge module 200 is transmitted to the single-chip microcomputer module 400 through the acquisition module 300.

[0051] Further, the component under test Z is a resistor, capacitor or inductor to be measured. Both ends of the component under test Z are respectively connected to the first relay KT1 and the second relay KT2.

[0052] Further, the signal generation module 100 includes a first chip 101 and a second chip 102. The first chip 101 is connected to the component under test Z through the first analog switch S1 and the first relay KT1, and the second chip 102 is connected to the component under test Z through the first relay KT1.

[0053] Further, the self-balancing bridge module 200 includes a first follower 201. The first follower 201 is arranged between the first chip 101 and the analog switch S1. It also includes a core amplifier 202. The inverting input terminal of the core amplifier 202 is connected to the component under test Z through the second relay KT2, the non-inverting input terminal is grounded, and the output terminal is connected to the acquisition module 300 through the second follower 203; a second analog switch S2 is also connected in parallel between the inverting input terminal and the output terminal of the core amplifier 202;

[0054] The self-balancing bridge module 200 further includes a third follower 204 and a fourth follower 205. One ends of the third follower 204 and the fourth follower 205 are respectively connected to the element under test Z, and the other ends are connected to the acquisition module 300.

[0055] Further, the acquisition module 300 includes a first instrumentation amplifier 301. One end of the first instrumentation amplifier 301 is respectively connected to the second follower 203 and the third follower 204, and the other end is connected to the single-chip microcomputer module 400 through a first analog-to-digital conversion chip 303.

[0056] Further, the acquisition module 300 further includes a second instrumentation amplifier 302. One end of the second instrumentation amplifier 302 is respectively connected to the third follower 204 and the fourth follower 205, and the other end is connected to the single-chip microcomputer module 400 through a second analog-to-digital conversion chip 304.

[0057] The working process of this test board is divided into three steps. First, select a suitable measurement source and range according to the type and size of the element under test. Then, after the internal modules of the board measure the data, the data is output through the single-chip microcomputer. Finally, the size of the element under test is calculated based on the obtained test data.

[0058] Specifically, in the first step, connect the element under test Z to the board in a four-wire system to ensure good contact, and select a suitable measurement source and range according to the property (resistance, capacitance or inductance) and size of the element under test Z. For small resistors below 10R, select a current source of 200mA, and for the rest, select an AC signal source. The frequency of the AC signal source is obtained through I2C configuration in the single-chip microcomputer CH32F205RBT6. The test signal frequency for resistance is 500Hz, the test signal frequencies for capacitance are 100Hz, 1kHz, and 10kHz, and the test signal frequencies for inductance are 1kHz, 10kHz, and 100kHz. The LCR test board has four ranges, namely RG = RF = 100R, 1k, 10k, and 500k. Select the range according to the impedance size of the element under test. Generally, the impedance value of the element under test Z is more accurately measured within the range of RF / 10 to 10 * RF.

[0059] Step 2: The measurement processes corresponding to different measurement sources are different. When selecting the 200 mA current range to measure a small resistor, the first relay KT1 selects the second chip 102, and the second relay KT2 selects grounding. At this time, the Darlington tube circuit controls the second relay KT2 to select the small resistor measurement circuit and the grounding gear. The second chip 102 is a current source chip, and its model is LT3092. The voltage across the element under test Z is sent to the differential input terminals of the first instrumentation amplifier 301 and the second instrumentation amplifier 303 after passing through the third follower 204 and the fourth follower 205, and the output signal is sent to the microcontroller module 400 after passing through the sampling module 300. The microcontroller module 400 is the CH32F205RBT6 chip and its peripheral circuits. When selecting the AC range for measurement, according to the "virtual short, virtual open" of the operational amplifier, it can be known that the currents on the matching resistor RG, the element under test Z, and the feedback resistor RF are equal. The voltages VZ_S+ and VZ_S- across the element under test Z are sent to the differential input terminal of the second instrumentation amplifier -303 after passing through the third follower 204 and the fourth follower 205. The output of the second instrumentation amplifier 303 is the voltage VZ on the element under test Z plus a 2.5 V DC bias. The output CORE_VOUT of the core amplifier 202, after passing through the second follower 203, together with the output of VZ_S- after passing through the third follower 204 and the fourth follower 205, is sent to the differential input terminal of the first instrumentation amplifier 301. The output of the first instrumentation amplifier 301 can be regarded as the voltage VOUT on the feedback resistor RF plus a 2.5 V DC bias. After the first analog-to-digital conversion chip 302 and the second analog-to-digital conversion 304 collect the biased analog signals VZ and VOUT, the digital data is sent to the microcontroller CH32F205RBT6 for processing.

[0060] Step 3 is for the microcontroller CH32F205RBT6 to process the collected digital data internally. It includes the following situations:

[0061] 1. When selecting the DC range to measure a small resistor, the microcontroller calculates the DC component VZ of the collected signal. According to the following equation

[0062]

[0063] the size of the resistor under test R can be obtained, where I is the output current size of the first chip 102, that is, the current source LT3092.

[0064] 2. When selecting the AC range to measure resistors, capacitors, and inductors, the microcontroller calculates the effective values of the collected biased VZ and VOUT, clears the interference of the DC component. According to the "virtual short" and "virtual open" of the operational amplifier, it can be known that the currents on the matching resistor RG, the element under test Z, and the feedback resistor RF are equal, and the current size is

[0065]

[0066] where VZ and VOUT are the effective AC values. According to the above equation, we can obtain

[0067]

[0068] When the component Z to be measured is a resistor, Z = R; when the component Z to be measured is a capacitor,

[0069]

[0070] When the component Z to be measured is an inductor,

[0071] Z = 2 * pi * f * L

[0072] It should be noted that the f in the above equation for measuring the component to be measured in the AC range is the frequency of the AC signal.

[0073] In summary, through the above work process, according to different components to be measured, different measurement ranges are selected, and the digital data collected is processed by a single-chip microcomputer, and finally the accurate data of the component to be measured is calculated.

[0074] Embodiment 3

[0075] Referring to Figures 1 to 17 , this is the third embodiment of the present invention. What is different from the previous two embodiments is that in this embodiment, according to the test processes of the previous two embodiments, specific experiments are carried out, and a large amount of data of 0.1R - 1M resistors and 20p - 100u capacitors are actually measured as follows:

[0076] Table 1. Measurement using a 1M resistor

[0077]

[0078] Table 2. Measurement using a 2K resistor

[0079]

[0080]

[0081] Table 3. Measurement using a 100R resistor

[0082]

[0083] Table 4. Measurement using a 1R resistor

[0084]

[0085] Table 5. Measurement using a capacitor

[0086]

[0087]

[0088] The results from Tables 1 to 5 show that the resistance accuracy above 500R can reach 99.9% under most test conditions, and the accuracy of resistors and capacitors below 500R can also reach over 99%.

[0089] In summary, when testing resistors, capacitors and inductors, it is necessary to change the signal frequency, and the highest frequency can reach 100KHZ. To ensure that the signal is not distorted, the sampling rate of the ADC is required to be above 200KHz; at the same time, to ensure high data accuracy, the resolution of the ADC is also required to be high, above 12bit; the positive and negative nature of the AC signal requires a bipolar ADC for the ADC. Through analysis, by utilizing the adjustable bias characteristic of the instrumentation amplifier at the first stage of the instrumentation amplifier, the signal is raised to all positive values, so as to use an inexpensive unipolar ADC. After the ADC collects the data, it is handed over to the single-chip microcomputer for processing. The single-chip microcomputer can eliminate the DC bias interference by calculating the AC effective value. This test board can meet the measurement requirements of most resistors, capacitors and inductors on the market, and keep the error below 1%, greatly improving the test accuracy.

[0090] Importantly, it should be noted that the construction and arrangement of the present application shown in multiple different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who refer to this disclosure should easily understand that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in this application (for example, the dimensions, scales, structures, shapes and proportions of various components, as well as parameter values (such as temperature, pressure, etc.), installation arrangements, use of materials, color, orientation changes, etc.). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature, number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. In the claims, any "means-plus-function" clause is intended to cover the structure that performs the recited function herein, and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present invention. Therefore, the present invention is not limited to a specific embodiment, but extends to various modifications that still fall within the scope of the appended claims.

[0091] In addition, in order to provide a concise description of the exemplary embodiments, not all features of the actual embodiments may be described (i.e., those features that are not relevant to the currently considered best mode of implementing the present invention, or those features that are not relevant to the implementation of the present invention).

[0092] It should be understood that, during the development of any actual implementation, such as in any engineering or design project, numerous specific implementation decisions can be made. Such development efforts may be complex and time-consuming, but for those of ordinary skill in the art who benefit from this disclosure, without undue experimentation, the development efforts will be routine work of design, manufacture, and production.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. An LCR test board based on the self - balancing bridge method, characterized in that: Including, a device under test (Z), which receives the current signal from the signal generation module (100), and the voltage signal across the device under test (Z) is transmitted to the self-balancing bridge module (200), and the waveform generated by the self-balancing bridge module (200) is transmitted to the single-chip microcomputer module (400) through the acquisition module (300).

2. The LCR test board based on the self - balancing bridge method according to claim 1, characterized in that: The signal generation module (100) includes a first chip (101) and a second chip (102). The first chip (101) is connected to the device under test (Z) through a first analog switch (S1) and a first relay (KT1), and the second chip (102) is connected to the device under test (Z) through the first relay (KT1).

3. The LCR test board based on the self - balancing bridge method according to claim 2, characterized in that: The self-balancing bridge module (200) includes a first follower (201), and the first follower (201) is arranged between the first chip (101) and the first analog switch (S1).

4. The LCR test board based on the self-balancing bridge method according to claim 3, characterized in that: The self-balancing bridge module (200) further includes a core amplifier (202). The inverting input terminal of the core amplifier (202) is connected to the device under test (Z) through a second relay (KT2), the non-inverting input terminal is grounded, and the output terminal is connected to the acquisition module (300) through a second follower (203).

5. The LCR test board based on the self - balancing bridge method according to claim 4, characterized in that: A second analog switch (S2) is also connected across the inverting input terminal and the output terminal of the core amplifier (202).

6. The LCR test board based on the self - balancing bridge method according to claim 5, characterized in that: The self-balancing bridge module (200) further includes a third follower (204) and a fourth follower (205). One ends of the third follower (204) and the fourth follower (205) are respectively connected to the device under test (Z), and the other ends are connected to the acquisition module (300).

7. The LCR test board based on the self-balancing bridge method according to claim 6, wherein: The acquisition module (300) includes a first instrumentation amplifier (301). One end of the first instrumentation amplifier (301) is respectively connected to the second follower (203) and the third follower (204), and the other end is connected to the single-chip microcomputer module (400) through a first analog-to-digital conversion chip (303).

8. The LCR test board based on the self-balancing bridge method according to claim 7, characterized in that: The acquisition module (300) further includes a second instrumentation amplifier (302). One end of the second instrumentation amplifier (302) is respectively connected to the third follower (204) and the fourth follower (205), and the other end is connected to the single-chip microcomputer module (400) through a second analog-to-digital conversion chip (304).

9. The LCR test board based on the self-balancing bridge method according to claim 8, wherein: Also included is a power conversion module (500), which is connected to an external 5V power supply and supplies power to the device under test (Z), the self-balancing bridge module (200), the acquisition module (300), and the single-chip microcomputer module (400) respectively.

10. The LCR test board based on the self-balancing bridge method according to claim 9, characterized in that: The power conversion module (500) converts the external 5V power supply into voltages of 5.5V, ±5V, 2.5V, and 3.3V.

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