Alternating electric field intensity detection circuit

Abstract

The utility model discloses a field intensity detection circuit of an alternating electric field, which relates to the technical field of field intensity detection of a power grid in space, and comprises an antenna, an anti-aliasing filter, a band-pass filter and an MCU (Microprogrammed Control Unit), the anti-aliasing filter prevents frequency spectrum aliasing during digital sampling and filters out low-frequency and high-frequency noise, the band-pass filtering transmission band is narrower, out-of-band signals are further filtered out, and the anti-aliasing filter is electrically connected with the MCU. The device is used for detecting the field intensity of an alternating electric field in a space, converting the field intensity into field intensity through a circuit, and then displaying the field intensity; the device can be used for field intensity detection of a power grid in space, namely, the device is suitable for a 220 / 380V50Hz high-voltage system and a 110V60Hz low-voltage system of a power frequency network; the circuit provided by the utility model can be used for detecting the field intensity level of the voltage, and can also be used for detecting the safety field intensity of power grid equipment maintainers.

Description

Technical Field

[0001] The utility model relates to the technical field of field strength detection of a power grid in space, in particular to an alternating electric field strength detection circuit. Background Art

[0002] Electric field strength measurement refers to the measurement of electric field strength at the receiving location to obtain various propagation data and parameters for proper wireless circuit design. This measurement is also crucial for resolving electromagnetic compatibility issues. Current alternating electric field strength detection circuits are complex to design, resulting in insufficient reliability and stability during actual detection operations and inability to adapt to varying voltage levels. Therefore, we offer an alternating electric field detection solution with high circuit integration, high noise tolerance, compact size, and low power consumption. Utility Model Content

[0003] The utility model provides an alternating electric field strength detection circuit, which solves the existing problems.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solution: an alternating electric field strength detection circuit, including an antenna, an anti-aliasing filter, a bandpass filter, and an MCU. The antenna obtains an alternating induced voltage through electromagnetic induction and provides it to subsequent circuits for signal processing and detection. The anti-aliasing filter prevents spectrum aliasing during digital sampling and filters out low-frequency and high-frequency noise. The bandpass filter has a narrower passband and further filters out out-of-band signals. The anti-aliasing filter is electrically connected to the MCU.

[0005] Preferably, the MCU includes a variable gain amplifier, an analog-to-digital converter, a comparator, an integrator, and a control module. The variable gain amplifier uses a digitally controlled variable gain amplifier to adjust the amplification factor of the signal path.

[0006] Preferably, the analog-to-digital converter converts the detected electric field signal from an analog signal to a digital signal to improve accuracy and noise tolerance.

[0007] Preferably, the electric field signals are compared in a parallel circuit of the comparators to obtain a synchronous square wave for controlling the start and reset of the digital integrator.

[0008] Preferably, the integrator integrates the digital electric field signal to further reduce the influence of noise and interference and improve the accuracy of electric field detection.

[0009] Preferably, the control module determines whether the signal chain is in a linear state by reading the value of the integrator. If it is in amplification saturation, the amplification factor of the variable gain amplifier is reduced until it is in the optimal linear amplification state, and then numerical calculations are performed to output the detected field strength.

[0010] Preferably, the input of the anti-aliasing filter is Vi, the output is Vo, R1 and C1 form a low-pass filter link, R2 and C2 form a high-pass link, and the two together form a bandpass function. In the passband, the intermediate frequency gain A1 of the anti-aliasing filter is mainly determined by the ratio of R3 and R4, that is, A1=R4 / R3.

[0011] Preferably, the bandwidth of the bandpass filter is set to 30-80 Hz

[0012] The beneficial effects of the utility model are:

[0013] (1) Anti-aliasing filters and bandpass filters are used to filter out noise and interference outside the power frequency band, thereby improving the reliability and stability of electronic systems.

[0014] (2) The gain of the variable amplifier is set by algorithms and software, and it can adapt to different voltage levels such as 110V, 220V, 380V, 10kV, 35kV, etc.

[0015] (3) The signal integration method is used to further smooth the output waveform, greatly reduce data reading errors, improve system accuracy, and reduce data fluctuations.

[0016] (4) The variable gain amplifier, comparator, analog-to-digital converter, integrator and control module are all integrated inside the MCU. Signal processing mainly adopts digital signal processing. The overall circuit has high integration and large noise tolerance, which can realize a compact and low-power alternating electric field detection solution.

[0017] In summary, the present invention provides an alternating electric field strength detection circuit for detecting alternating electric field strength in space, converting it into field strength through the circuit, and then displaying it. The present invention can be used to detect field strength in power grids in space, namely, for high-voltage systems (220 / 380V 50Hz) and low-voltage systems (110V 60Hz) operating at power frequency networks. The circuit of the present invention can detect voltage field strength levels and can also be used for safety field strength testing by power grid equipment maintenance personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the framework structure of the present utility model.

[0019] Figure 2 This is a circuit diagram of the anti-aliasing filter of the present utility model.

[0020] Figure 3 This is a circuit diagram of the bandpass filter of the present utility model.

[0021] Figure 4 It is a schematic diagram of the amplification and frequency response path of the overall circuit of the utility model.

[0022] Figure 5 This is a schematic diagram showing that the integrator of the present invention operates in the digital domain.

[0023] Figure 6 This is a schematic diagram of the signal output in the circuit path of the utility model. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0025] Reference Figure 1-Figure 5 As shown, the utility model provides an alternating electric field strength detection circuit, which mainly includes modules such as an antenna, an anti-aliasing filter, a bandpass filter, a variable gain amplifier, an analog-to-digital converter, a comparator, an integrator, and a control module.

[0026] Antenna: According to the principle of electromagnetic field, the alternating electric field and magnetic field in space will generate induced voltage in the antenna segment. If the alternating electric field is generated by the industrial frequency, then the induced voltage generated in the antenna is also alternating, and the frequency is the same as the industrial frequency. The main function of the antenna is to obtain the alternating induced voltage through electromagnetic induction and provide it to the subsequent circuit for signal processing and detection. The antenna is implemented by a monopole antenna.

[0027] Anti-aliasing filter: The anti-aliasing filter prevents spectrum aliasing during digital sampling, filters out low-frequency and high-frequency noise, and provides a certain gain;

[0028] The circuit diagram of the anti-aliasing filter is as follows Figure 2 As shown in the figure, the anti-aliasing filter is a bandpass filter with a wide bandwidth. The input is Vi and the output is Vo. R1 and C1 form a low-pass filter link, and R2 and C2 form a high-pass link. The two together form a bandpass function.

[0029] In the passband, the intermediate frequency gain A1 of the anti-aliasing filter is mainly determined by the ratio of R3 to R4, that is, A1 = R4 / R3.

[0030] Bandpass filtering: The passband is narrower, further filtering out out-of-band signals and providing gain.

[0031] Bandpass filter circuits such as Figure 3 , providing a narrower bandwidth and higher Q value bandpass filtering function, further filtering out out-of-band interference and screening out electric field induced voltage. The bandwidth of the bandpass filter is set to 30-80Hz, meeting 50Hz and 60Hz power frequency environments and adapting to a wider range of power supply scenarios. The input of the bandpass filter is Vin, and the output is Vout. R1 forms a proportional amplification with the equivalent impedance of the band-stop unit, and R2 is the balancing resistor of the amplifier;

[0032] The band-stop unit, comprised of an RC twin-T network, provides a high-Q notch filter. Rb1, Rb2, and Cb1 form a low-pass circuit, while Cb2, Cb3, and Rb3 form a high-pass circuit. These two elements, connected in parallel, form the twin-T band-stop circuit. The band-stop unit is located in the feedback branch of the entire band-pass filter, forming a voltage-parallel negative feedback circuit. During signal feedback, due to the presence of the band-stop circuit, the 30-80 Hz power frequency passband in the Vout signal spectrum is not fed back to the input node. Therefore, out-of-band signals are suppressed throughout the entire circuit. From the perspective of the entire band-pass filter circuit, only signals between 30 and 80 Hz can be amplified, providing a large amplification factor A2. This allows detection of weak alternating electric field signals and output of a pure power frequency signal.

[0033] Variable gain amplifier: A digitally controlled variable gain amplifier is used to adjust the amplification factor of the signal path to ensure that the input to output is in the linear amplification region, so that the intensity of the electric field can be measured more accurately.

[0034] The variable gain amplifier is used to adjust the overall amplification factor of the signal chain. The amplification factor A3 of the variable gain amplifier is digitally controlled. The amplification factor range of A3 is set to -40 to 40dB, that is, the amplification factor is 0.01 to 100. That is, if the received signal is strong, the variable gain amplifier will attenuate it; if the received signal is weak, the variable gain amplifier will amplify it, so that the received signal amplitude is adjusted to the appropriate linear amplification range;

[0035] Therefore, the overall circuit amplification and frequency response path is as follows Figure 4 As shown, in terms of passband width, the anti-aliasing filter provides a wider passband frequency range. After passing through the bandpass filter, the passband frequency range is f1 to f2, specifically set to f1 = 30 Hz, f2 = 80 Hz, ensuring that both 50 Hz and 60 Hz power frequency electric fields are applicable. In terms of the gain of the signal chain, the overall gain of the circuit is G = A1A2A3, which is the product of the anti-aliasing filter, bandpass filtering, and the variable gain amplifier amplification factor, ensuring that the electric field induced voltage can be linearly amplified in the signal path.

[0036] Analog-to-digital converter: Converts the detected electric field signal from analog to digital to improve accuracy and noise tolerance.

[0037] Comparator: Compares the electric field signal to obtain a synchronous square wave, which is used to control the start and reset of the digital integrator.

[0038] Integrator: Integrates the digital electric field signal to further reduce the impact of noise and interference and improve the accuracy of electric field detection.

[0039] After the signal is conditioned by the front-end circuit, it is converted into digital by the analog-to-digital converter and then digital signal processing is performed. Figure 5 The integrators shown all operate in the digital domain. Their application primarily assumes that the mathematical expectation of noise and interference is zero (average value). Their primary function is to further suppress noise and interference, enabling accurate estimation of electric field strength.

[0040] Figure 5 The signal conditioning output is the analog-to-digital converted signal, a 50Hz or 60Hz power frequency signal. The synchronous square wave is the integration-clearing signal generated by the comparator. This integration-clearing synchronization signal strictly matches the input frequency, ensuring no frequency error during integration. On the rising edge of the synchronization signal, the integrator clears and begins integration; on the next rising edge of the synchronization signal, it clears and integrates again, ensuring no cumulative integration error.

[0041] Since the input signal is conditioned, if it is linearly amplified, it is ideally a sine wave, and the sine wave is integrated to form a cosine signal. Therefore, the integrator integrates at time t0, the integrator output reaches the maximum at time t1, and the integral value returns to zero at time t2. At the same time, in order to prevent integration error, the integration of the next cycle is cleared.

[0042] The mathematical expression is as follows:

[0043]

[0044] At this time, the sine becomes cosine after integration, and the maximum value of the integrated signal is 2 A m , by detecting A m The value of the alternating electric field can be calculated by antenna induction (standard electric field calibration) and the gain of the signal path.

[0045] When the circuit is working, the controller controls the gain of the signal chain to a larger value to ensure that weak field strength can also be detected. If the signal path amplification factor is too large, the output of the signal conditioning is saturated, that is, close to a square wave. At this time, after integration by the integrator, the output of the integrator is close to a triangle wave. At this time, the controller determines that the integrator is saturated and reduces the gain of the variable gain amplifier until the signal is in linear amplification in the circuit path (such as Figure 6 shown).

[0046] Control module: By reading the value of the integrator, it determines whether the signal chain is in a linear state. If it is in amplification saturation, the amplification factor of the variable gain amplifier is reduced until it is in the optimal linear amplification state, and then numerical calculations are performed to output the detected field strength.

[0047] The main principle of the alternating electric field strength detection circuit is as follows: the monopole antenna senses the alternating electric field and outputs the induced voltage to the anti-aliasing filter. After anti-aliasing filtering, the power frequency electric field signal is filtered out by a bandpass filter and amplified. The variable gain amplifier then adjusts the amplification factor to condition the signal.

[0048] The conditioned signal is passed through a comparator to obtain the synchronous square wave required for the integrator to work, that is, the integration-clear signal. On the other hand, it is converted into a digital signal for processing.

[0049] The integrator is controlled by the integration-clear signal to integrate and clear the signal. The integrated signal is processed by the controller. If the signal is saturated, the variable gain amplifier is lowered until the entire signal chain is in a linear amplification state.

[0050] If the signal is not saturated, it is determined that the signal is not linearly amplified, and the field strength is calculated and output.

[0051] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An alternating electric field strength detection circuit, characterized in that: It includes an antenna, an anti-aliasing filter, a bandpass filter, and an MCU. The antenna obtains an alternating induced voltage through electromagnetic induction, which is used for subsequent circuit signal processing and detection. The anti-aliasing filter is used to filter out low-frequency and high-frequency noise. The bandpass filter is used to filter out out-of-band signals. The anti-aliasing filter is electrically connected to the MCU.

2. The alternating electric field strength detection circuit according to claim 1, characterized in that: The MCU includes a variable gain amplifier, an analog-to-digital converter, a comparator, an integrator, a control module, and an analog-to-digital converter. The variable gain amplifier adopts a digitally controlled variable gain amplifier to adjust the amplification factor of the signal path.

3. The alternating electric field strength detection circuit according to claim 2, characterized in that: The analog-to-digital converter converts the detected electric field signal from an analog signal to a digital signal, thereby improving accuracy and noise tolerance.

4. The alternating electric field strength detection circuit according to claim 2, characterized in that: The electric field signals are compared in the parallel circuit of the comparators to obtain synchronous square waves for controlling the start and reset of the digital integrator.

5. The alternating electric field strength detection circuit according to claim 2, characterized in that: The integrator integrates the digital electric field signal to further reduce the influence of noise and interference and improve the accuracy of electric field detection.

6. The alternating electric field strength detection circuit according to claim 2, characterized in that: The control module determines whether the signal chain is in a linear state by reading the value of the integrator. If it is in amplification saturation, the amplification factor of the variable gain amplifier is reduced until it is in the optimal linear amplification state, and then numerical calculation is performed to output the detected field strength.

7. The alternating electric field strength detection circuit according to claim 1, characterized in that: The input of the anti-aliasing filter is Vi, and the output is Vo. R1 and C1 form a low-pass filter link, and R2 and C2 form a high-pass link. The two together form a bandpass function. In the passband, the intermediate frequency gain A1 of the anti-aliasing filter is mainly determined by the ratio of R3 and R4, that is, A1=R4 / R3.

8. The alternating electric field strength detection circuit according to claim 1, characterized in that: The bandwidth of the bandpass filter is set to 30-80 Hz.

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