CN216285489U

CN216285489U - Miniaturized digital LCR meter

Info

Publication number: CN216285489U
Application number: CN202220334267.4U
Authority: CN
Inventors: 刘洋; 崔文良; 陈锦伟; 丘伟鹏; 貌土锋; 陈余
Original assignee: Guangzhou Silinger Technology Co ltd
Current assignee: Guangzhou Silinger Technology Co ltd
Priority date: 2022-02-19
Filing date: 2022-02-19
Publication date: 2022-04-12
Anticipated expiration: 2032-02-19

Abstract

The utility model discloses a miniaturized digital LCR meter, which comprises a main control system, wherein the main control system is modularized into an FPGA control panel, an LCR panel and a test bottom plate which are mutually independent; the number of the LCR boards is N, N is larger than or equal to 1, the LCR boards are connected with the FPGA control board through a control bus, and the test bottom board is electrically connected with the FPGA control board and the LCR boards. The digital LCR meter is of a modular design structure, and the FPGA control panel and the LCR panel are separately designed, so that the digital LCR meter is convenient to customize, small in size, flexible and easy to use, and more suitable for application in industrial automation measurement fields.

Description

Miniaturized digital LCR meter

Technical Field

The utility model relates to the technical field of LCR meter design, in particular to a miniaturized digital LCR meter.

Background

With the rapid development of the global electronic information industry, the rapid updating and iteration of electronic products, the requirements of electronic components on the precision of measurement parameters are continuously increased. The LCR meter is a necessary measuring instrument in the electronic information industry, and the stability and the accuracy of the measurement are very important for the whole process of product research and development and production. In addition, the high-precision impedance measuring instrument is one of hot spots developed at home and abroad.

Impedance is an important parameter of a passive element, and is defined as the frequency domain ratio of voltage to current. The basic idea of impedance measurement is to measure the real and imaginary parts of the impedance vector and then convert them to the required parameters. The measurement principle of the digital LCR meter is that a sinusoidal signal with adjustable frequency and amplitude is generated by an excitation signal source, the signal is applied to a component to be measured (DUT) to generate current to reach an inverting input end of an amplifier, and the current flowing through the DUT completely flows through a feedback resistor of the amplifier according to the virtual ground and virtual break principle because the inverting input end is grounded. The voltage at the output end of the amplifier and the voltage at the two ends of the element to be measured are measured, and the impedance Z of the element to be measured (DUT) can be calculated through a formula.

The research and development of domestic impedance measuring instruments are relatively late. In an industrial automation test field, multiple instruments are generally required to be completed in a space stacking mode, so that the space of the test field is easily insufficient, and sometimes even multiple large-volume instruments are placed everywhere, so that the measurement work cannot be carried out.

In summary, there is a need in the industry to develop a digital LCR meter which has a small size and low cost and can meet the requirements of high-precision and broadband measurement.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome the defects of the prior art and provides a miniaturized digital LCR meter which is small in size and high in running speed.

The purpose of the utility model is realized by the following technical scheme:

a miniaturized digital LCR meter comprises a main control system, wherein the main control system is modularized into an FPGA control panel, an LCR panel and a test bottom plate which are mutually independent; the number of the LCR plates is N, and N is more than or equal to 1; the LCR board is connected with the FPGA control board through a control bus, and the testing bottom board is electrically connected with the FPGA control board and the LCR board.

Preferably, the control bus comprises: the I2C bus and the SPI bus.

Preferably, the analog signal of the LCR board is disposed in a first region of the LCR board, the digital signal of the LCR board is disposed in a second region of the LCR board, and the miniaturized digital LCR meter further includes a shield for sealing the analog signal.

Preferably, the shielding case is made of copper.

Preferably, the LCR board includes an excitation signal circuit, a signal amplification circuit, a filter circuit, an analog-to-digital conversion circuit, and a digital-to-analog conversion circuit; the excitation signal circuit, the signal amplification circuit and the filter circuit are sequentially connected, and the analog-to-digital conversion circuit and the digital-to-analog conversion circuit are connected with the FPGA control panel.

Preferably, the analog-to-digital conversion circuit and the digital-to-analog conversion circuit are both multi-channel devices or a single chip containing a plurality of operational amplifiers.

Preferably, the LCR sheet is a laminated structure of multilayer sheets.

Preferably, an EEPROM and a temperature sensor are arranged in the LCR board, and both the EEPROM and the temperature sensor are connected with the FPGA control board.

Preferably, the test backplane comprises at least one of a BNC connector, an RJ45 port, a power interface, and an AMP board-to-board connector.

What need to say, what this application need protect is with FPGA control panel and LCR board independent setting for a FPGA control panel can carry on N this kind of structural style of LCR board, and this kind of structural style of this application makes the customization convenient, and the volume reduces, and is nimble easy-to-use, is fit for the application on industrial automation measurement scene more. The FPGA control board, the LCR board and the test bottom board can be realized by adopting the existing products or circuit boards and are not in the protection scope of the application.

Compared with the prior art, the utility model has the following advantages:

the digital LCR meter is of a modular design structure, the FPGA control panel and the LCR panel are separately designed, and one FPGA control panel can carry N LCR panels, so that the digital LCR meter is convenient to customize, small in size, flexible and easy to use, and more suitable for application in industrial automatic measurement fields. The utility model adopts the FPGA control panel, not only bears the control function of the LCR panel through the control bus, but also carries out operation and processing on high-speed data which is transmitted from the analog-digital converter on the LCR panel in parallel. The digital LCR meter meets the requirements of high-precision and wide-band measurement, has small volume and high running speed, is greatly convenient for users to carry out automatic measurement and is beneficial to the development of industrial automatic test sites.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the utility model and, together with the description, serve to explain the utility model and not to limit the utility model. In the drawings:

FIG. 1 is a block diagram of a master control system for a miniaturized digital LCR meter according to the present invention.

Detailed Description

The utility model is further illustrated by the following figures and examples.

Referring to fig. 1, a miniaturized digital LCR meter includes a main control system modularized into an FPGA control board, an LCR board, and a test backplane that are independent of each other; the LCR board is connected with the FPGA control board through a control bus, and the testing bottom board is electrically connected with the FPGA control board and the LCR board. The number of the LCR plates is N, and N is more than or equal to 1;

the FPGA control panel adopts an FPGA chip and is responsible for processing signals from the LCR board and controlling an analog-digital converter and a digital-analog converter on the LCR board. The test bottom plate is mainly used for interconnection of the LCR plate and the FPGA control plate, has a switching function, and is convenient to debug and calibrate. Therefore, the FPGA control board and the digital LCR board are independent, so that the customization is convenient and the cost is saved.

In this embodiment, the test backplane includes a BNC connector, an RJ45 port, a power interface, and an AMP board-to-board connector. The testing bottom plate is used for connecting the FPGA control panel and the LCR panel and is mainly used for debugging and calibrating. And the LCR board and the FPGA control board are respectively butted with the test bottom board by adopting an AMP connector.

The embedded modular design is adopted in the structural design, the functions of the instrument are independently designed into a module and then integrated into a main control system of the whole instrument, the integration of the embedded instrument is really realized, and various instruments are not simply stacked. And the functions and the gears can be completed in a customized mode according to the requirements of a test field, so that unnecessary functions and gears can be reduced, and the aims of optimizing cost and reducing volume are fulfilled. Particularly, the FPGA control board and the LCR board are separated, so that the FPGA control board and the LCR board are convenient to customize. For example, one FPGA control panel can be matched with a plurality of LCR boards to work simultaneously, so that the industrial automation measurement field with a large amount of impedance measurement requirements is met, and the problem that the existing FPGA control panel and the LCR boards are not independent and a plurality of independent circuit boards in the form of FPGA and LCR have to be adopted when a large amount of impedance measurement requirements exist on the same board is solved.

In this embodiment, the control bus includes: the I2C bus and the SPI bus. The digital LCR meter is controlled by serially transmitting data through a chip-level control bus I2C and an SPI (serial peripheral interface). The I2C is used here for reading and writing EEPROM, reading temperature sensor data, controlling a CAT9555 IO expansion chip, controlling a digital-to-analog converter, and realizing calibration data storage, version information storage, board card identity number storage, board card temperature reading, direct current offset signal generation control, and the like. The SPI bus is used to control a DDS (direct frequency synthesis) chip to synthesize a sine wave signal of a required frequency and amplitude as an excitation signal to be applied to the device under test, and to control the analog-to-digital converter to obtain a voltage at two ends of the device under test and a voltage converted from a current flowing through the device under test.

In this embodiment, the analog signal of the LCR board is disposed in the first region of the LCR board, the digital signal of the LCR board is disposed in the second region of the LCR board, and the miniaturized digital LCR meter further includes a shield for sealing the analog signal. The shielding cover is made of copper materials. Therefore, the electromagnetic compatibility and the anti-electromagnetic interference performance of the LCR board can be improved, the analog signals and the digital signals are separately distributed, and the influence of the digital signals on the analog signals is reduced. In addition, the analog signal is sealed in a shielding case made of cupronickel, so that the interference of the external complex environment is further reduced. In addition, the Guard ring technology is adopted to play a role in shielding and protecting by draining unnecessary noise. The two modes act simultaneously, and the electromagnetic compatibility and the anti-electromagnetic interference performance of the LCR board are improved.

In this embodiment, the LCR board includes an excitation signal circuit, a signal amplification circuit, a filter circuit, an analog-to-digital conversion circuit, and a digital-to-analog conversion circuit; the excitation signal circuit, the signal amplification circuit and the filter circuit are sequentially connected, and the analog-to-digital conversion circuit and the digital-to-analog conversion circuit are connected with the FPGA control panel. The signal amplification circuit comprises an operational amplifier. The operational amplifier is one of important devices forming the LCR meter, can select a proper operational amplifier in different application scenes and is beneficial to efficiently and smoothly finishing work. The AD8066 high-performance operational amplifier with high slew rate, wide frequency band and low bias is selected in the disclosure, so that the obvious effect is achieved in various application scenes.

In this embodiment, the analog-to-digital conversion circuit and the digital-to-analog conversion circuit are both multi-channel devices or a single chip including a plurality of operational amplifiers. The FPGA control board is used for processing various tasks, including the control of the LCR board card and the processing and calculation of digital signals. Finally, the size of the LCR plate is controlled within 175mm in length and 113mm in width.

In this embodiment, the LCR board is a 6-layer board stacked structure, which makes full use of the space of the PCB board for layout and routing, and avoids the use of plug-in components as much as possible. Finally, the size of the LCR plate is controlled within 175mm in length and 113mm in width.

In this embodiment, an EEPROM and a temperature sensor are built in the LCR board, and both the EEPROM and the temperature sensor are connected with the FPGA control board.

The overall panel size of the final LCR panel was 175mm in length and 113mm in width. Firstly, the precision of an excitation signal (sine wave) is verified, and under an open-circuit mode, the frequency range of an HC end is 1 kHz-2 MHz through measurement of a standard instrument, and the frequency precision reaches 0.01%. The HC end outputs a level range of 5mVrms to 2Vrms, and the level range can be increased and decreased by taking 1mVrms as a step length. The result shows that the frequency of the sine wave signal output by the HC end is stable, the frequency band is wide, the resolution of the output level is high, and the range is wide. Further ensuring the stability of the measuring result.

Finally, after calibration, under the state of a measuring level of 1Vrms, a certain frequency of 1 kHz-2 MHz is selected as a measuring frequency, the alternating current impedance measuring range of the resistor and the corresponding measuring precision thereof are shown in table 1, the alternating current impedance measuring range of the capacitor and the measuring precision thereof are shown in table 2, and the alternating current impedance measuring range of the inductor and the measuring precision thereof are shown in table 3.

TABLE 1 measurement of the AC impedance of the resistors

TABLE 2 measurement of the AC impedance of the capacitors

TABLE 3 measurement of the AC impedance of the inductor

The data of the above table show that the digital LCR meter has the functional characteristics of wide frequency band, high precision and small volume of alternating current impedance measurement. The measuring result is stable and reliable, and meets the condition of application in an industrial automatic measuring field.

In conclusion, the FPGA control panel and the LCR panel are separated, so that the device is convenient to customize, small in size, flexible and easy to use, and more suitable for application in an industrial automation measurement field. The FPGA control board is adopted to not only bear the control function of the LCR board through the I2C and the SPI bus, but also carry out operation and processing on high-speed data transmitted in parallel from the analog-to-digital converter on the LCR board.

The above-mentioned embodiments are preferred embodiments of the present invention, and the present invention is not limited thereto, and any other modifications or equivalent substitutions that do not depart from the technical spirit of the present invention are included in the scope of the present invention.

Claims

1. A miniaturized digital LCR meter is characterized by comprising a main control system, wherein the main control system is modularized into an FPGA control board, an LCR board and a test bottom board which are mutually independent;

the number of the LCR plates is N, and N is more than or equal to 1;

the LCR board is connected with the FPGA control board through a control bus, and the testing bottom board is electrically connected with the FPGA control board and the LCR board.

2. The miniaturized digital LCR meter of claim 1, wherein the control bus comprises: the I2C bus and the SPI bus.

3. The miniaturized digital LCR meter of claim 1, wherein the analog signal of the LCR board is disposed in a first area of the LCR board, the digital signal of the LCR board is disposed in a second area of the LCR board, and the miniaturized digital LCR meter further comprises a shield for sealing the analog signal.

4. The miniaturized digital LCR meter of claim 3, wherein the shield is a copper shield.

5. The miniaturized digital LCR meter according to claim 1, wherein the LCR board includes an excitation signal circuit, a signal amplification circuit, a filter circuit, an analog-to-digital conversion circuit, and a digital-to-analog conversion circuit;

the excitation signal circuit, the signal amplification circuit and the filter circuit are sequentially connected, and the analog-to-digital conversion circuit and the digital-to-analog conversion circuit are connected with the FPGA control panel.

6. The miniaturized digital LCR meter according to claim 5, wherein the analog-to-digital conversion circuit and the digital-to-analog conversion circuit are each a multi-channel device or a single chip containing a plurality of operational amplifiers.

7. The miniaturized digital LCR meter of claim 1, wherein the LCR board is a laminated structure of multiple boards.

8. The miniaturized digital LCR meter of claim 1, wherein the LCR board has built-in EEPROM and temperature sensors, both of which are connected to the FPGA control board.

9. The miniaturized digital LCR meter of claim 1, wherein the test chassis includes at least one of a BNC connector, an RJ45 port, a power interface, an AMP board-to-board connector.