Intelligent signal distortion measuring instrument

Abstract

The utility model discloses a kind of signal distortion degree intelligent measuring instrument, including microcontroller, AGC circuit, conditioning circuit and display screen;AGC circuit is automatic gain control circuit;The input end of AGC circuit is used to connect input signal Vin, and the signal output end VOUT of AGC circuit is connected with the ACD port of microcontroller through conditioning circuit;Display screen is TFT serial port screen, and display screen is connected with the UART0 serial port of microcontroller;AGC circuit is the AGC circuit based on VCA821 chip;Conditioning circuit is ADC front conditioning circuit;Microcontroller is DSP processor.The utility model discloses signal distortion degree intelligent measuring instrument can realize signal distortion degree detection, and circuit realizes simply, easy to implement.

Description

Technical Field

[0001] This utility model relates to an intelligent signal distortion measuring instrument. Background Technology

[0002] A signal distortion meter is an instrument used to assess the degree of signal distortion during signal transmission. As a primary device for distortion testing, the distortion meter is widely used in various fields such as electronic measurement, instrument calibration, signal transmission and control.

[0003] Signal distortion is a significant problem in modern digital communication systems, caused by a variety of factors, including nonlinearity of the transmission medium, noise, clock skew, and non-ideal characteristics in signal processing circuits. To ensure accurate and consistent distortion measurements, both domestically and internationally, standard distortion signal generators with known distortion levels are commonly used to calibrate instruments with distortion measurement capabilities. ] .

[0004] Distortion measurement involves a wide range of instrument accuracy issues. Traditional methods mostly rely on analog approaches, whose core mechanism revolves around the construction of specially designed filters. These filters aim to remove the fundamental frequency component from the input signal in order to detect and quantify each harmonic component individually. [4] The measurement precision achieved by this design method is directly and significantly affected by the performance of the selected filter; simultaneously, its hardware configuration exhibits relatively high complexity. With the continuous advancement of electronic technology, THD (Total Harmonic Distortion) measurement techniques have gradually undergone a transformation and upgrade from traditional analog technology to the field of digital signal processing. When measuring nonlinear distortion, the spectrum analysis method transforms the input signal into the frequency domain through Fourier transform and then analyzes the harmonic components in the spectrum. The frequency of the original signal is called the fundamental frequency, and frequency components above the fundamental frequency are called harmonics. Nonlinear distortion generates additional harmonics beyond the fundamental frequency; the presence and intensity of these harmonics can be used to quantify the degree of nonlinear distortion. Therefore, the spectrum analysis method can detect and quantify nonlinear distortion by identifying and measuring these harmonics. Typically, distortion measurement devices use a spectrum analyzer to measure each harmonic and then determine the degree of waveform distortion. Although this method has high accuracy, its instrumentation is relatively complex.

[0005] When measuring signal distortion, sampling is limited by frequency and amplitude range. Therefore, conditioning the signal may not completely avoid introducing harmonic components, leading to errors in distortion measurement. This is due to the combined effect of frequency and amplitude limitations during sampling. Currently, there are some commercially available signal distortion measurement instruments that can measure distortion over a wide frequency range, but they are expensive.

[0006] Chinese patent publication number 217060341U discloses a signal distortion measurement system, which includes an electronic switch, a multiplier, a filter, a DDS module, an automatic gain amplifier circuit (AGC), an adder, a microcontroller, and a display (LCD). The system structure is relatively complex.

[0007] Therefore, it is necessary to design an intelligent signal distortion measuring instrument. Utility Model Content

[0008] The technical problem to be solved by this utility model is to provide an intelligent signal distortion measuring instrument, which has a simple structure and is easy to implement.

[0009] The technical solution of the utility model is as follows: An intelligent signal distortion measuring instrument includes a microcontroller, an AGC circuit, a conditioning circuit, and a display screen; the AGC circuit is an automatic gain control circuit. The input terminal of the AGC circuit is used to connect to the input signal Vin, and the signal output terminal VOUT of the AGC circuit is connected to the ACD port of the microcontroller through the conditioning circuit. The display screen is a TFT serial port screen, and the display screen is connected to the UART0 serial port of the microcontroller; The AGC circuit is an AGC circuit based on the VCA821 chip; The conditioning circuit is the ADC front-end conditioning circuit; The microcontroller is a DSP processor.

[0010] The AGC circuit includes chip U1, an amplifier based on chip U2, and an integrator based on chip U3; U1 is a VCA821 chip, U2 is an operational amplifier chip OPA695, and U3 is an operational amplifier chip OPA820. The signal input terminal +Vin of U1 is connected to the input signal Vin; the feedback terminal FB of U1 is connected to the signal output terminal VOUT of U1 through resistor RF; the signal output terminal VOUT of U1 is connected to the input terminal of the amplifier through resistor R4; the output terminal of the integrator is connected to the VG terminal of U1. Amplifier circuit: The input terminal of the amplifier is the non-inverting input terminal of U2; the inverting input terminal of U2 is grounded through resistor R6; a resistor R5 is connected between the inverting input terminal and the output terminal of U2. Integrator circuit: The output of U2 is connected to the inverting input of U3 via a series diode D1 and resistor R9; the non-inverting input of U3 is connected to the sliding terminal of rheostat R11, the first terminal of rheostat R11 is grounded, the second terminal of rheostat R11 is connected to a +5V DC power supply via resistor R10; the third terminal of rheostat R11 is the aforementioned sliding terminal; a capacitor C2 is connected across the output of U3 and the inverting input; the output of U3 is connected to the VG terminal of U1 via resistor R6. A resistor R7 is connected between the overall output terminals Vo1 and U2 of the AGC circuit.

[0011] C2 is 0.1uF, and R9 is 1k ohm.

[0012] The conditioning circuit includes a first voltage follower, a second voltage follower, and a DC bias circuit; The first voltage follower and the second voltage follower are implemented using an operational amplifier OPA211; the first voltage follower and the second voltage follower are cascaded through capacitor C3; The DC bias circuit uses the REF3030 chip and a voltage divider circuit based on resistors R15 and R16; the output of the REF3030 chip is grounded through resistors R15 and R16 connected in series, and the connection point of resistors R15 and R16 (i.e. the voltage divider point) is connected to the input of the second voltage follower.

[0013] It also includes a Bluetooth module; the Bluetooth module is used to communicate with smartphones and is connected to the microcontroller's UART1 serial port.

[0014] The microcontroller used is an MSP432P401R chip. Beneficial effects

[0015] The intelligent signal distortion measuring instrument of this invention has a simple overall structure. It adopts an AGC circuit with feedback to realize automatic gain adjustment and a conditioning circuit to adjust the level, ensuring accurate signal acquisition and conversion. The intelligent signal distortion measuring instrument of this invention uses few components and can guarantee the accuracy of detection. Attached Figure Description

[0016] Figure 1 This is a block diagram illustrating the overall principle of the intelligent signal distortion measuring instrument. Figure 2 This is a schematic diagram of an AGC circuit based on VCA821. Figure 3 This is the schematic diagram of the ADC front-end conditioning circuit. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example

[0018] like Figure 1 A signal distortion intelligent measuring instrument includes a microcontroller, an AGC circuit, a conditioning circuit, and a display screen; the AGC circuit is an automatic gain control circuit. The input terminal of the AGC circuit is used to connect to the input signal Vin, and the signal output terminal VOUT of the AGC circuit is connected to the ACD port of the microcontroller through the conditioning circuit. The display screen is a TFT serial port screen, and the display screen is connected to the UART0 serial port of the microcontroller; The AGC circuit is an AGC circuit based on the VCA821 chip; The conditioning circuit is the ADC front-end conditioning circuit; The microcontroller is a DSP processor.

[0019] AGC circuit based on VCA821: The AGC circuit based on VCA821 is a crucial component of the intelligent signal distortion measuring instrument. The AGC (Automatic Gain Control) circuit maintains a constant output power for the input signal by dynamically adjusting the amplifier gain, thus ensuring normal operation of the system under different input signal strengths. Based on the above scheme design and principle analysis, and through parameter calculation and actual debugging, the AGC circuit based on VCA821 was designed as follows: Figure 2 As shown. When calibration of dynamic signal amplitude is required, the AGC (Automatic Gain Control) loop can perform instantaneous gain adjustment. The signal generated by the VCA821 then passes through the OPA695 amplifier to enhance its ability to drive the load. Next, the signal is processed by the OPA820 integrator and finally connected to the VG pin of the VCA821, forming a closed feedback loop. The time constant characteristics of this loop are determined by the specific values ​​of capacitor C2 and resistor R9, as shown in the circuit diagram. Figure 2 As shown.

[0020] Specifically, the AGC circuit includes chip U1, an amplifier based on chip U2, and an integrator based on chip U3; U1 is a VCA821 chip, U2 is an operational amplifier chip OPA695, and U3 is an operational amplifier chip OPA820. The signal input terminal +Vin of U1 is connected to the input signal Vin; the feedback terminal FB of U1 is connected to the signal output terminal VOUT of U1 through resistor RF; the signal output terminal VOUT of U1 is connected to the input terminal of the amplifier through resistor R4; the output terminal of the integrator is connected to the VG terminal of U1. Amplifier circuit: The input terminal of the amplifier is the non-inverting input terminal of U2; the inverting input terminal of U2 is grounded through resistor R6; a resistor R5 is connected between the inverting input terminal and the output terminal of U2. Integrator circuit: The output of U2 is connected to the inverting input of U3 via a series diode D1 and resistor R9; the non-inverting input of U3 is connected to the sliding terminal of rheostat R11, the first terminal of rheostat R11 is grounded, the second terminal of rheostat R11 is connected to a +5V DC power supply via resistor R10; the third terminal of rheostat R11 is the aforementioned sliding terminal; a capacitor C2 is connected across the output of U3 and the inverting input; the output of U3 is connected to the VG terminal of U1 via resistor R6. A resistor R7 is connected between the overall output terminals Vo1 and U2 of the AGC circuit.

[0021] C2 is 0.1uF, and R9 is 1k ohm.

[0022] ADC front-end conditioning circuit: The ADC front-end conditioning circuit is a crucial component of the intelligent signal distortion measurement instrument, responsible for converting analog signals into digital signals and performing preliminary processing. In this circuit, we selected a high-quality ADC chip to ensure accurate signal acquisition and conversion. Simultaneously, to improve system stability and anti-interference capabilities, we designed a sophisticated signal conditioning circuit, including modules such as filters and amplifiers. These modules effectively remove noise and interference signals, guaranteeing the accuracy and reliability of the measurement results.

[0023] To ensure the input signal matches the on-chip ADC's voltage input range (0~3.3V), the initial signal conditioning stage is crucial. This design adopts the OPA211 as the core component of the voltage follower, aiming to achieve signal buffering, independence, and enhanced load driving capability. Subsequently, a REF3030 chip is introduced to generate a +3V reference voltage. Through a resistor divider network configuration, a stable +1.65V DC bias is incorporated into the original signal. This strategy facilitates a comprehensive and accurate signal sampling process for the ADC. The specific circuit layout is as follows... Figure 3 As shown.

[0024] Specifically, the conditioning circuit includes a first voltage follower, a second voltage follower, and a DC bias circuit; The first voltage follower and the second voltage follower are implemented using an operational amplifier OPA211; the first voltage follower and the second voltage follower are cascaded through capacitor C3; The DC bias circuit uses the REF3030 chip and a voltage divider circuit based on resistors R15 and R16; the output of the REF3030 chip is grounded through resistors R15 and R16 connected in series, and the connection point of resistors R15 and R16 (i.e. the voltage divider point) is connected to the input of the second voltage follower.

[0025] It also includes a Bluetooth module; the Bluetooth module is used to communicate with smartphones and is connected to the microcontroller's UART1 serial port.

[0026] The microcontroller used is an MSP432P401R chip.

[0027] Main control chip: MSP432 microcontroller The MSP432P401R microcontroller series is a mixed-signal MCU from TI, employing an ARM Cortex-M4 processor with a working frequency up to 48MHz. It provides a high-performance, low-cost platform with excellent computing performance and system interrupt response capabilities. It features a tightly coupled floating-point unit (FPU) supporting various mathematical operations and data format conversions. It offers a rich selection of peripheral devices to meet data processing and low-power operation requirements. Power consumption is controlled between 1.62V and 3.7V, with a normal mode current of 80μA / MHz and 83μA at low frequencies (128kHz). Power control management (PCM) can control device operating mode switching to meet power and performance requirements. It also enables 8-channel DMA, allowing simultaneous data transfer across multiple channels without CPU intervention, thus reducing power consumption. It supports C-style assembly language and is compatible with standard C, simplifying development. In summary, the MSP432P401R meets the system's requirements for high cost-effectiveness and low power consumption.

[0028] This signal distortion measurement device consists of an MSP432P401R, an operational amplifier gain module, a 5V regulated power supply, a serial port screen display, and a Bluetooth module. The system first performs pre-processing on the input periodic signal using an AGC circuit, then combines this with the ADC front-end conditioning circuit to adjust the signal to the ADC's acquisition range. Next, it uses the MSP432's internal ADC for sequential sampling, and then performs internal processing on the sampled values ​​(the specific processing procedure is existing technology) to obtain the Total Harmonic Distortion (THD) index. Finally, the system displays the results on the serial port screen and a mobile app.

[0029] The actual test results of this intelligent signal distortion measuring instrument show that when the input THD is 5%~50%, and the fundamental frequency is changed from 1kHz to 500kHz, the peak-to-peak value of the input signal is 10mV-900mV, and the absolute error of the measured THDx is less than 3%.

[0030] After the HC-05 Bluetooth module is wirelessly connected to the mobile phone, THD measurements, normalized amplitudes of the fundamental and subharmonics, and signal waveforms can all be correctly displayed on the local LCD screen and the mobile phone.

Claims

1. An intelligent signal distortion measuring instrument, characterized in that, Includes a microcontroller, AGC circuit, conditioning circuit, and display screen; the AGC circuit is an automatic gain control circuit. The input terminal of the AGC circuit is used to connect to the input signal Vin, and the signal output terminal VOUT of the AGC circuit is connected to the ACD port of the microcontroller through the conditioning circuit. The display screen is a TFT serial port screen, and the display screen is connected to the UART0 serial port of the microcontroller; The AGC circuit is an AGC circuit based on the VCA821 chip; The conditioning circuit is the ADC front-end conditioning circuit; The microcontroller is a DSP processor.

2. The intelligent signal distortion measuring instrument according to claim 1, characterized in that, The AGC circuit includes chip U1, an amplifier based on chip U2, and an integrator based on chip U3; U1 is a VCA821 chip, U2 is an operational amplifier chip OPA695, and U3 is an operational amplifier chip OPA820. The signal input terminal +Vin of U1 is connected to the input signal Vin; the feedback terminal FB of U1 is connected to the signal output terminal VOUT of U1 through resistor RF; the signal output terminal VOUT of U1 is connected to the input terminal of the amplifier through resistor R4; the output terminal of the integrator is connected to the VG terminal of U1. Amplifier circuit: The input terminal of the amplifier is the non-inverting input terminal of U2; the inverting input terminal of U2 is grounded through resistor R6; a resistor R5 is connected between the inverting input terminal and the output terminal of U2. Integrator circuit: The output of U2 is connected to the inverting input of U3 via a series diode D1 and resistor R9; the non-inverting input of U3 is connected to the sliding terminal of rheostat R11, the first terminal of rheostat R11 is grounded, the second terminal of rheostat R11 is connected to a +5V DC power supply via resistor R10; the third terminal of rheostat R11 is the aforementioned sliding terminal; a capacitor C2 is connected across the output of U3 and the inverting input; the output of U3 is connected to the VG terminal of U1 via resistor R6. A resistor R7 is connected between the overall output terminals Vo1 and U2 of the AGC circuit.

3. The intelligent signal distortion measuring instrument according to claim 2, characterized in that, C2 is 0.1uF, and R9 is 1k ohms.

4. The intelligent signal distortion measuring instrument according to claim 1, characterized in that, The conditioning circuit includes a first voltage follower, a second voltage follower, and a DC bias circuit; The first voltage follower and the second voltage follower are implemented using an operational amplifier OPA211; the first voltage follower and the second voltage follower are cascaded through capacitor C3; The DC bias circuit uses the REF3030 chip and a voltage divider circuit based on resistors R15 and R16; the output of the REF3030 chip is grounded through resistors R15 and R16 connected in series, and the connection point of resistors R15 and R16 is connected to the input of the second voltage follower.

5. The intelligent signal distortion measuring instrument according to claim 1, characterized in that, It also includes a Bluetooth module; the Bluetooth module is used to communicate with smartphones and is connected to the microcontroller's UART1 serial port.

6. The intelligent signal distortion measuring instrument according to any one of claims 1-5, characterized in that, The microcontroller used is an MSP432P401R chip.

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