Self-calibrating digital measurement system and its measure-as-you-calibrate method

Abstract

The application provides a self-calibration digital measurement system and a method for self-calibration and measurement. The digital measurement system comprises a standard signal source, an ADC conversion module, a high-precision clock reference, a digital engine, a switch circuit and a phase-locked unit. The digital engine is connected with the standard signal source, the ADC conversion module, the switch circuit, the high-precision clock reference and the phase-locked unit, and is configured to receive data after the ADC conversion module performs analog-digital conversion on an alternating voltage reference signal of different conversion channels, and perform linear fitting, so as to obtain calibration parameters of the corresponding channel ADC. The digital engine is also configured to receive data after the ADC conversion module performs analog-digital conversion on a to-be-measured alternating voltage signal of different conversion channels, and call the calibration parameters of the corresponding conversion channel to correct the to-be-measured alternating voltage signal, so as to realize self-calibration and self-calibration and measurement of the system.

Description

Technical Field

[0001] This invention relates to the field of metrology, and more specifically, to a self-calibrating digital measurement system and its instant calibration and measurement method. Background Technology

[0002] In the field of metrology and calibration, various electrical measuring devices used to measure voltage, current, and electrical energy require regular calibration or verification to ensure their measurement accuracy meets requirements. The industry typically uses standards with higher accuracy levels to calibrate or verify electrical measuring devices according to the methods specified in relevant calibration / verification procedures. From a calibration or verification perspective, the methods and standards used have a decisive impact on the accuracy of the calibration or verification results. The desired method is to minimize the influence of environmental factors on the calibration or verification process and avoid introducing excessive uncertainty. The grade of the standard used for calibration or verification determines the accuracy level and error range of the measuring devices that can be used for calibration or verification.

[0003] Currently, digital measurement equipment has gradually replaced traditional analog measurement equipment as the industry's preferred choice. Digital measurement equipment typically includes an analog-to-digital converter (ADC) to convert analog signals into digital signals. The ADC in digital measurement equipment usually introduces a certain conversion error during the analog-to-digital conversion process, causing a deviation between the measured value and the true value. This is a significant source of measurement error inherent in digital measurement equipment. Regarding voltage measurement, the industry has adopted quantum voltage references as the highest-level standard for traceability. Existing technology has attempted to use a quantum voltage ladder wave synthesized by a programmable Josephson quantum array chip as a standard reference signal, achieving accurate measurement of AC voltage through differential sampling. The differential sampling method synchronously samples the difference between the measured AC voltage signal and the quantum voltage ladder wave signal. Its measurement accuracy is closely related to the magnitude of the differential signal, and the relative phase difference between the measured AC signal and the ladder wave signal must be kept stable to ensure the stability of the differential signal.

[0004] Although existing differential sampling methods utilize the highest-level standards, they still have shortcomings. On the one hand, differential sampling systems do not consider the conversion error of the ADC itself in the circuit or device used to measure the differential signal, and cannot correct the ADC's conversion error while performing differential sampling. Moreover, since differential signals are usually small, they must be amplified using a gain module, which inevitably introduces some error. On the other hand, because differential sampling methods require the measured AC signal and the stepped wave signal to have the same frequency to maintain a stable relative phase difference, noise in the measured AC signal cannot be attenuated by conventional frequency doubling sampling. This greatly limits the accuracy of the measurement equipment and also limits the frequency range of signals suitable for calibration with high-level standards such as quantum voltage references.

[0005] As is well known, the accuracy of voltage, current, and electrical energy measurements is ultimately closely related to the accuracy of voltage measurement. This is because the measurement of the current component in a current signal or electrical energy pulse can be converted into a voltage signal through a precision current-to-voltage conversion module. In practice, calibrating electrical measuring equipment separately is neither time-efficient nor cost-effective. Therefore, the industry urgently needs measurement systems and new measurement methods with self-calibration capabilities. The desired outcome is that these systems can instantly correct measurement errors introduced by the conversion error of the measurement system's ADC itself, and effectively attenuate noise in the measured AC voltage signal over a wide frequency range. Summary of the Invention

[0006] According to one aspect of the present invention, a self-calibrating digital measurement system is provided, comprising a standard signal source, an ADC conversion module, a switching circuit, a phase-locked loop unit, a digital engine, and a high-precision clock reference. The standard signal source is connected to the ADC conversion module through the switching circuit. The ADC conversion module is connected to the phase-locked loop unit and the digital engine, respectively. The digital engine is connected to the phase-locked loop unit and the high-precision clock reference, respectively.

[0007] A standard signal source is used to generate an AC voltage reference signal. The AC voltage reference signal is a signal with the same amplitude as the AC voltage signal to be measured, but with a period that is N times larger. A high-precision clock reference is used to provide the digital measurement system with the same time and frequency reference as the device that generates the AC voltage signal to be measured; N is an integer greater than or equal to 2.

[0008] The switching circuit is used to control the alternating input of the AC voltage reference signal and the AC voltage signal under test in two different conversion channels of the ADC conversion module by switching the switch position. When the phase-locked unit locks the zero phase point of the AC voltage reference signal, the digital engine performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal in the ADC conversion module from its zero phase point for an integer cycle, and obtains the calibration parameters of the current conversion channel of the AC voltage reference signal. When the phase-locked unit locks the zero phase point of the AC voltage signal under test, the digital engine calls the calibration parameters of the current conversion channel of the AC voltage signal under test for correction on the data obtained after sampling and analog-to-digital conversion of the AC voltage signal under test in the ADC conversion module from its zero phase point for N times the cycle, and obtains the corrected measurement value of the AC voltage signal under test.

[0009] The aforementioned self-calibrating digital measurement system accurately measures the conversion error of the ADC itself through a standard signal source, a phase-locked loop unit, and a digital engine. Furthermore, when the phase-locked loop unit locks the zero-phase point of the AC voltage signal under test, it calls the calibration parameters of the corresponding conversion channel to correct the AC voltage signal under test, achieving immediate correction of measurement errors introduced by the ADC's own conversion error. Simultaneously, the system achieves instant calibration and measurement through zero-delay switching of the switching circuit. Moreover, it effectively attenuates noise in the AC signal under test through frequency doubling sampling, achieving effective noise reduction in the AC voltage signal under test over a wide frequency range. The AC voltage reference signal and the AC voltage signal under test can be directly input into the ADC for sampling and analog-to-digital conversion without the need for an additional gain module, thus avoiding the gain error introduced by an additional gain module.

[0010] According to another aspect of the present invention, a method for instant calibration and testing of a digital measurement system is provided. Based on the above-described digital measurement system, the method includes the following steps:

[0011] In the current measurement, the AC voltage reference signal and the AC voltage signal to be measured are input into two different conversion channels in the ADC conversion module through the switching circuit; the AC voltage reference signal is a signal with the same amplitude as the AC voltage signal to be measured and a period that is N times larger, where N is an integer greater than or equal to 2;

[0012] Determine the locking status of the phase-locked unit for signals in two different conversion channels of the ADC conversion module;

[0013] When the phase-locked unit locks the zero phase point of the AC voltage reference signal, the digital engine performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal in the ADC conversion module from its zero phase point for an entire cycle, and obtains the calibration parameters of the current conversion channel of the AC voltage reference signal.

[0014] When the phase-locked unit locks the zero-phase point of the AC voltage signal under test, the digital engine uses the data obtained by sampling and analog-to-digital conversion of the AC voltage signal under test in the ADC conversion module from its zero-phase point for N times the period to call the calibration parameters of the conversion channel where the AC voltage signal under test is currently located to correct it, and obtain the corrected measurement value of the AC voltage signal under test.

[0015] After the input signals of two different conversion channels in the ADC conversion module are swapped by the switching circuit, the process jumps to the step of judging the locking state of the phase-locked unit for the signals in the two different conversion channels in the ADC conversion module, and then proceeds to the next measurement.

[0016] In a preferred embodiment provided according to various aspects of the present invention, the ADC conversion module is a dual-channel ADC. When the switching circuit is in a first switching state, it connects the AC voltage reference signal to the first conversion channel of the dual-channel ADC and connects the AC voltage signal to be measured to the second conversion channel of the dual-channel ADC. When the switching circuit is in a second switching state, it connects the AC voltage signal to be measured to the first conversion channel of the dual-channel ADC and connects the AC voltage reference signal to the second conversion channel of the dual-channel ADC.

[0017] In a preferred embodiment provided by various aspects of the present invention, the ADC conversion module includes at least two dual-channel ADCs, the number of switching branches of the switching circuit is matched with the number of conversion channels of the dual-channel ADCs, the two input terminals of each switching branch are respectively used to connect an AC voltage reference signal and an AC voltage signal to be measured, the output terminal of each switching branch is connected to a corresponding conversion channel, and each switching branch includes a first switching state and a second switching state.

[0018] In a preferred embodiment provided according to various aspects of the present invention, the digital engine includes a data processing unit and a storage unit that are communicatively connected, the data processing unit being respectively connected to an ADC conversion module, a phase-locked loop unit and a high-precision clock reference;

[0019] The data processing unit is used to perform linear fitting and store the obtained calibration parameters into the storage unit, and to call the calibration parameters of the current conversion channel of the AC voltage signal under test to correct the AC voltage signal under test.

[0020] In preferred embodiments provided according to various aspects of the present invention, the dual-channel ADC in the ADC conversion module is a 24-bit high-speed, high-precision ADC, and the high-precision clock reference in the digital measurement system has a clock stability of 10. -12 A rubidium atomic clock of the order of magnitude.

[0021] In a preferred embodiment provided according to various aspects of the invention, the period of the AC voltage reference signal generated by the standard signal source is at least 5 times the period of the AC voltage signal to be measured.

[0022] In a preferred embodiment provided according to various aspects of the present invention, the standard signal source is a programmable Josephson voltage standard, and the generated AC voltage reference signal is a step-wave quantum voltage signal.

[0023] In preferred embodiments provided according to various aspects of the present invention, the standard signal source is a pulse-driven AC Josephson voltage standard, and the generated AC voltage reference signal is a sinusoidal quantum voltage signal.

[0024] In preferred embodiments provided according to various aspects of the present invention, the above-described digital measurement system further includes a display device connected to a data processing unit, the display device being used to display the measured value, corrected measured value, and correction amount of the AC signal under test. Attached Figure Description

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

[0026] Figure 1 A schematic block diagram of a self-calibrating digital measurement system provided by an embodiment of the present invention is shown.

[0027] Figure 2 A circuit block diagram of a self-calibrating digital measurement system provided in an embodiment of the present invention is shown.

[0028] Figure 3 This is a flowchart of the instant calibration and testing method for the digital measurement system provided in the embodiments of the present invention;

[0029] Figure 4 This is an application flowchart of the instant calibration and testing method of the digital measurement system provided in the embodiments of the present invention;

[0030] Figure 5 This is an exemplary calibration-measurement timing diagram of the on-demand calibration method for a digital measurement system provided in an embodiment of the present invention. Detailed Implementation

[0031] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, so as to provide a thorough understanding of embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0032] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "connection," "linkage," etc., should be interpreted broadly. For example, "connection" can be a physical connection, an electrical connection, or a wireless communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0036] In one embodiment, Figure 1 A schematic block diagram of a self-calibrating digital measurement system 100 provided in an embodiment of the present invention is shown. Figure 1 As shown, the digital measurement system 100 includes: a standard signal source 1, a switching circuit 3, an ADC conversion module 4, a high-precision clock reference 5, a phase-locked loop (PLL) unit 6, and a digital engine 7. The standard signal source 1 is connected to the ADC conversion module 4 via the switching circuit 3. The ADC conversion module 4 is connected to both the PLL unit 6 and the digital engine 7. The digital engine 7 is connected to both the PLL unit 6 and the high-precision clock reference 5. The standard signal source 1 generates an AC voltage reference signal, which is a signal with the same amplitude as the AC voltage signal to be measured but with a period increased by a factor of N. The high-precision clock reference 5 provides the digital measurement system 100 with the same time-frequency reference as the device 200 generating the AC voltage signal to be measured; N is an integer greater than or equal to 2.

[0037] Switching circuit 3 is used to control the alternating input of AC voltage reference signal and AC voltage signal under test in two different conversion channels of ADC conversion module 4 by switching the switch position. When phase-locked unit 6 locks the zero phase point of AC voltage reference signal, digital engine 7 performs linear fitting on the data obtained after sampling and analog-to-digital conversion of AC voltage reference signal in ADC conversion module 4 from its zero phase point for an integer cycle, and obtains the calibration parameters of the current conversion channel of AC voltage reference signal. When phase-locked unit 6 locks the zero phase point of AC voltage signal under test, digital engine 7 calls the calibration parameters of the current conversion channel of AC voltage signal under test for correction on the data obtained after sampling and analog-to-digital conversion of AC voltage signal under test in ADC conversion module 4 from its zero phase point for N times the cycle, and obtains the corrected measurement value of AC voltage signal under test.

[0038] It can be understood that the standard signal source 1 is used to generate an AC voltage reference signal with the same amplitude and a period N times larger than the AC voltage signal to be measured; the signal input module 2 (the connection line at the front end of the switching circuit 3) includes at least one signal input subunit, each of which includes two input lines, used to input the AC voltage reference signal and the AC voltage signal to be measured, respectively; the ADC conversion module 4 has at least two different conversion channels, for example, it can be implemented in hardware using an ADC converter that integrates at least two ADC conversion channels, or it can be implemented in hardware using at least two parallel single-channel ADC converters, or it can be implemented in hardware using at least one dual-channel ADC.

[0039] For the switching circuit 3, which controls the alternating input of AC voltage reference signal and AC voltage signal to be measured into two different conversion channels in the ADC conversion module 4 by switching the switch position, for ease of explanation, a dual-channel ADC is used as an example. It is configured in pairs with the signal input subunit and includes a first conversion channel and a second conversion channel. The switching circuit 3, which is connected between the signal input module 2 and the ADC conversion module 4, includes a switching branch corresponding to each signal input subunit and the dual-channel ADC. The switching branch can have two switching states, namely a first switching state and a second switching state (corresponding to the signal access state under two switching positions). In the first switching state of the switching branch, the first conversion channel and the second conversion channel of the dual-channel ADC receive the AC voltage reference signal and the AC voltage signal to be measured, respectively. In the second switching state of the switching branch, the first conversion channel and the second conversion channel of the dual-channel ADC receive the AC voltage signal to be measured and the AC voltage reference signal, respectively (i.e., the two different conversion channels are input alternately).

[0040] A high-precision clock reference 5 is configured to serve as a common time and frequency reference for the digital measurement system 100, the AC voltage signal generator 200 under test, and the standard signal source 1. A phase-locked unit 6, connected to the ADC conversion module 4, is configured to lock the zero-phase point of the AC voltage reference signal and the AC voltage signal under test. A digital engine 7, connected to the standard signal source 1, the ADC conversion module 4, the switching circuit 3, the high-precision clock reference 5, and the phase-locked unit 6, is configured to perform linear fitting of the data from the corresponding conversion channels to obtain the corresponding calibration parameters, and to perform correction processing of the AC voltage signal under test in the conversion channels.

[0041] The aforementioned self-calibrating digital measurement system 100 accurately measures the conversion error of the ADC itself in the system through a standard signal source, a phase-locked loop unit, and a digital engine. Furthermore, when the phase-locked loop unit locks the zero-phase point of the AC voltage signal under test, it calls the calibration parameters of the corresponding conversion channel to correct the AC voltage signal under test, achieving immediate correction of the measurement error introduced by the ADC's own conversion error. Simultaneously, it achieves the purpose of immediate calibration and measurement through the delay-free switching of the switching circuit, and effectively attenuates noise in the AC signal under test through frequency doubling sampling, achieving effective noise attenuation in the AC voltage signal under test over a wide frequency range. The AC voltage reference signal and the AC voltage signal under test can be directly input into the ADC for sampling and analog-to-digital conversion without the need for an additional gain module, thus avoiding the gain error caused by an additional gain module.

[0042] In one embodiment, such as Figure 2 As shown, the ADC conversion module 4 is a dual-channel ADC. When the switching circuit 3 is in the first switching state, it connects the AC voltage reference signal to the first conversion channel of the dual-channel ADC and the AC voltage signal to be measured to the second conversion channel of the dual-channel ADC. When the switching circuit 3 is in the second switching state, it connects the AC voltage signal to be measured to the first conversion channel of the dual-channel ADC and the AC voltage reference signal to the second conversion channel of the dual-channel ADC.

[0043] It is understood that this embodiment uses a dual-channel ADC to implement the ADC conversion module 4. By directly applying the dual-channel ADC, the circuit complexity of the system is reduced with a simple ADC circuit structure.

[0044] In one embodiment, such as Figure 2 As shown, the ADC conversion module 4 includes at least two dual-channel ADCs. The number of switching branches of the switching circuit 3 is matched with the number of conversion channels of the dual-channel ADCs. The two input terminals of each switching branch are used to connect the AC voltage reference signal and the AC voltage signal to be measured, respectively. The output terminal of each switching branch is connected to a corresponding conversion channel. Each switching branch includes a first switching state and a second switching state.

[0045] It is understood that in this embodiment, multiple measurement paths for immediate calibration and testing can be expanded according to actual measurement needs. Furthermore, each switch branch of the switch circuit 3 can adopt a switch circuit structure with dual-ended input and single-ended output. For example, but not limited to, multiplexers or MOS transistor switches can be used to implement the hardware of each switch branch of the switch circuit 3, thereby achieving efficient signal transmission path control with a simple switch circuit structure.

[0046] In one embodiment, such as Figure 2 As shown, the digital engine 7 includes a data processing unit and a storage unit connected via communication. The data processing unit is connected to the ADC conversion module, the phase-locked loop unit, and the high-precision clock reference, respectively. The data processing unit is used to perform linear fitting and store the obtained calibration parameters in the storage unit, as well as to call the calibration parameters of the current conversion channel of the AC voltage signal under test to correct the AC voltage signal under test.

[0047] Specifically, the digital engine 7 includes a data processing unit and a storage unit connected by communication. The digital engine 7 is configured such that, when the switching branch is in the first switching state, and when it is determined that the phase-locked unit 6 has locked the zero phase point of the AC voltage reference signal, the digital engine 7 performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal from its zero phase point for an entire cycle for the first conversion channel of the dual-channel ADC, obtains the calibration parameters of the first conversion channel of the dual-channel ADC, and stores them in the storage unit. When the switching branch is in the second switching state, and when the digital engine 7 determines that the phase-locked unit 6 has locked the zero phase point of the AC voltage reference signal, the digital engine 7 performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal from its zero phase point for an entire cycle for the second conversion channel of the dual-channel ADC, obtains the calibration parameters of the second conversion channel of the dual-channel ADC, and stores them in the storage unit.

[0048] The digital engine 7 is also configured to, when the switching branch is in the first switching state, when it is determined that the phase-locked unit 6 has locked the zero-phase point of the AC voltage signal under test, for the data obtained by sampling and analog-to-digital conversion of the AC voltage signal under test from its zero-phase point by N times the period from its zero-phase point using the second conversion channel of the dual-channel ADC, call the calibration parameters of the second conversion channel of the dual-channel ADC stored in the storage unit to correct it, and obtain the corrected measurement value of the AC voltage signal under test. And when the switching branch is in the second switching state, when the digital engine 7 determines that the phase-locked unit 6 has locked the zero-phase point of the AC voltage signal under test, for the data obtained by sampling and analog-to-digital conversion of the AC voltage signal under test by N times the period from its zero-phase point using the first conversion channel of the dual-channel ADC, call the calibration parameters of the first conversion channel of the dual-channel ADC stored in the storage unit to correct it, and obtain the corrected measurement value of the AC voltage signal under test.

[0049] In one embodiment, such as Figure 2 As shown, the digital measurement system 100 described above may also include a display device 300, which is connected to the data processing unit and is used to display the measured value, corrected measured value, and correction amount of the AC signal under test.

[0050] It is understood that in this embodiment, the digital measurement system 100 can be connected to the display device 300 to display the measured value, corrected measured value, and correction amount of the AC signal under test. Optionally, the display device 300 can also be integrated into the digital measurement system 100, and the display device 300 can be a touch-screen or non-touch-screen display.

[0051] It should be noted that, depending on the actual measurement requirements, the signal input module 2 may include one, two, four, or six signal input subunits. Correspondingly, the ADC conversion module 4 includes one, two, four, or six dual-channel ADCs configured in pairs with the signal input subunits. As a non-limiting example, Figure 2 The signal input module 2 shown includes two signal input subunits 21 and 22, and the ADC conversion module 4 includes a first dual-channel ADC 41 and a second dual-channel ADC 42 configured in pairs with the signal input subunits 21 and 22. Each signal input subunit 21 and 22 includes two input lines, used to input an AC voltage reference signal generated by the standard signal source 1 and a measured AC voltage signal generated by the measured AC voltage signal generation device 200, respectively. The switching elements in the switching branch can be, but are not limited to, low-delay relay switches, optocoupler switches, or MOSFET switches. It should be noted that the "low-delay" requirement for the switching elements in this invention means that both their turn-on and turn-off times are less than 0.05 times the period of the measured AC voltage signal. Preferably, the turn-on and turn-off times of the switching elements are both less than 0.01 times the period of the measured AC voltage signal.

[0052] The device 200 for generating the AC voltage signal to be measured can consist of an AC signal source 201 and signal conversion modules 202 and 203. The AC signal source 201 may include, but is not limited to, a voltage source, a current source, or a power source. The signal conversion modules 202 and 203 may correspondingly include a voltage / voltage conversion module, a current / voltage conversion module, or both. The signal conversion modules 202 and 203 are configured to convert the voltage signal and / or the current signal into a nominal voltage signal that matches the rated amplitude of the AC voltage reference signal at a certain ratio. The standard signal source 1 can generate an AC voltage reference signal with an equal amplitude and an integer multiple larger period compared to the nominal voltage signal to be measured. According to... Figure 2In the provided embodiment, the amplitudes of the nominal voltage signal and the AC voltage reference signal are within the linear operating range of the dual-channel ADC, allowing the two signals to be directly input into the dual-channel ADC for sampling and analog-to-digital conversion without the need for an additional gain module, thereby avoiding the corresponding gain error caused by an additional gain module.

[0053] According to an embodiment of the present invention, the digital measurement system 100 is a high-precision measurement facility, wherein the dual-channel ADC adopts a high-speed, high-precision ADC, and the correspondingly configured high-precision clock reference has a clock stability of 10. -12 A rubidium atomic clock of the order of magnitude.

[0054] As a preferred option, the standard signal source 1 can be an AC quantum voltage standard. This is because quantum voltage is based on a natural constant, and its reference value remains constant, unaffected by time and external environment. It has the advantages of good stability, high reproducibility accuracy, and ease of replication. Choosing the AC quantum voltage standard as the calibration signal source allows for accurate measurement of the conversion error of the ADC in the digital measurement system 100. Consequently, when measuring the signal under test, the measurement error of each conversion channel of the dual-channel ADC can be corrected, resulting in a more accurate measurement value.

[0055] As is known to those skilled in the art, AC quantum voltage standards are divided into two schemes: programmable Josephson AC quantum voltage standards and pulse-driven AC quantum voltage standards. One is the programmable Josephson voltage standard (PJVS), which works by changing the number of Josephson junctions in operation to synthesize an AC waveform approximating a voltage step. The other is the pulse-driven Josephson AC voltage standard (JAWS), which synthesizes the desired voltage waveform by changing the frequency of microwaves. JAWS utilizes the principle of magnetic flux quantum, employing a series of high-speed current pulses to drive the Josephson junction array. The uncertainty of the synthesized voltage effective value of both of these AC quantum voltage standards is better than 1 × 10⁻⁶. -6 Both can be used in this invention as AC quantum voltage signals to measure the conversion error of each conversion channel of a dual-channel ADC in a digital measurement system. The difference lies in that when PJVS is used as the standard signal source, the generated AC quantum voltage signal is a stepped-wave quantum voltage; when JAWS is used as the standard signal source, the generated AC quantum voltage signal is a sinusoidal quantum voltage.

[0056] According to a preferred embodiment of the present invention, the period of the AC quantum voltage signal generated by the standard signal source 1 is at least five times the period of the AC voltage signal to be measured generated by the AC voltage signal generation device 200. This greatly avoids the influence of environmental noise on the measurement results, thereby improving the measurement accuracy of the measurement system 100, and also expands the frequency range of signals suitable for calibration by high-level standards such as quantum voltage references.

[0057] The following is based on Figure 2 The AC signal source 201 shown is a single-phase AC power source, which is used as a non-limiting example to further illustrate the connection method between the switching circuit 3 of the present invention, the device for generating the AC voltage signal to be measured 200, and the standard signal source 1. The switching circuit 3 includes eight switching elements S1, S2, S3, S4, S5, S6, S7, and S8 connected between the signal input module 2 and the ADC conversion module 4. Switching elements S1, S2, S3, and S4 form the corresponding switching branch between the signal input subunit 21 and the first dual-channel ADC 41, while switching elements S5, S6, S7, and S8 form the corresponding switching branch between the signal input subunit 22 and the second dual-channel ADC 42. The device for generating the AC voltage signal to be measured 200 includes an AC signal source 201 configured as a single-phase AC power source, a signal conversion module 202 configured as a precision voltage / voltage conversion module, and a signal conversion module 203 configured as a precision current / voltage conversion module. Signal conversion module 202 is used to convert the voltage component in the power signal output by AC signal source 201 into a nominal voltage signal that matches the rated amplitude (e.g., 1V) of the AC voltage reference signal of standard signal source 1, while signal conversion module 203 is used to convert the current component in the power signal output by AC signal source 201 into a nominal voltage signal that matches the rated amplitude of the AC voltage reference signal of standard signal source 1, in a certain proportion.

[0058] The voltage signal output from the signal conversion module 202 is the first voltage signal to be measured. It can be input to one of the two input lines of the input signal input subunit 21, and then connected to the switching elements S2 and S3 in the switching circuit 3 via a 1-to-2 splitter. The AC voltage reference signal generated by the standard signal source 1 is input to the other of the two input lines of the input signal input subunit 21, and then connected to the switching elements S1 and S4 in the switching circuit 3 via a 1-to-2 splitter. In the first switching state of the switching branch composed of switching elements S1, S2, S3 and S4, switching elements S1 and S3 are turned on while switching elements S2 and S4 are turned off. The first conversion channel CH1 and the second conversion channel CH2 of the first dual-channel ADC 41 receive the AC voltage reference signal and the AC voltage signal to be measured, respectively. In the second switching state of this switching branch, switching elements S2 and S4 are turned on while switching elements S1 and S3 are turned off. The first conversion channel CH1 and the second conversion channel CH2 of the first dual-channel ADC 41 receive the AC voltage signal to be measured and the AC voltage reference signal, respectively.

[0059] Similarly, the voltage signal output from the signal conversion module 203 is the second voltage signal to be measured. It can be input to one of the two input lines of the input signal input subunit 22, and then connected to the switching elements S6 and S7 in the switching circuit 3 via a splitter. The AC voltage reference signal generated by the standard signal source 1 is input to the other of the two input lines of the input signal input subunit 22, and then connected to the switching elements S5 and S8 in the switching circuit 3 via a splitter. In the first switching state of the switching branch composed of switching elements S5, S6, S7 and S8, switching elements S5 and S7 are turned on while switching elements S6 and S8 are turned off. The first conversion channel CH1' and the second conversion channel CH2' of the second dual-channel ADC 42 receive the AC voltage reference signal and the AC voltage signal to be measured, respectively. In the second switching state of this switching branch, switching elements S6 and S8 are turned on while switching elements S5 and S7 are turned off. The first conversion channel CH1' and the second conversion channel CH2' of the second dual-channel ADC 42 receive the AC voltage signal to be measured and the AC voltage reference signal, respectively.

[0060] In one embodiment, a method for simultaneous calibration and testing of a digital measurement system is also provided. Based on the aforementioned digital measurement system, it can be understood that the following references... Figures 1-4 This section describes the steps, flow, and calibration-measurement sequence of the on-demand calibration method for the digital measurement system 100 provided in embodiments of the present invention. For example... Figure 3As shown, the instant calibration and testing method of the digital measurement system 100 includes the following steps:

[0061] S11, In the current measurement, the AC voltage reference signal and the AC voltage signal to be measured are respectively input into two different conversion channels in the ADC conversion module through the switching circuit;

[0062] S13, determine the locking status of the phase-locked unit for signals in two different conversion channels in the ADC conversion module;

[0063] S15, when the phase-locked unit locks the zero phase point of the AC voltage reference signal, the digital engine performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal in the ADC conversion module from its zero phase point for an integer cycle, and obtains the calibration parameters of the current conversion channel of the AC voltage reference signal.

[0064] S17, when the phase-locked unit locks the zero phase point of the AC voltage signal under test, the digital engine uses the data obtained by sampling and analog-to-digital conversion of the AC voltage signal under test in the ADC conversion module from its zero phase point for N times the period to call the calibration parameters of the conversion channel where the AC voltage signal under test is currently located to correct it, and obtain the corrected measurement value of the AC voltage signal under test.

[0065] S19: After swapping the input signals of two different conversion channels in the ADC conversion module through the switching circuit, jump to step S13 and proceed to the next measurement.

[0066] It is understandable that in practical applications, such as Figure 4 As shown (using a dual-channel ADC as an example; other types of ADCs are similar):

[0067] S10, the digital measurement system 100 is connected to the AC voltage signal generator 200 under test. Under the control of the digital engine 7 of the digital measurement system 100, the high-precision clock reference 5 of the digital measurement system 100 is configured to serve as a common time and frequency reference for the digital measurement system 100, the AC voltage signal generator 200 under test, and the standard signal source 1.

[0068] S20, the device 200 that generates the AC voltage signal to be measured generates the AC voltage signal to be measured, and the standard signal source 1 generates an AC voltage reference signal with the same amplitude and a period that is N times larger than the AC voltage signal to be measured.

[0069] S30, the digital engine 7 of the digital measurement system 100 controls the switching branch in the switching circuit 3 of the digital measurement system 100 corresponding to the signal input subunit 21 and the first dual-channel ADC 41 to switch to the first switching state, that is, the switching elements S1 and S3 are turned on while the switching elements S2 and S4 are turned off, so that the first conversion channel CH1 of the first dual-channel ADC 41 receives the AC voltage reference signal and the second conversion channel CH2 of the first dual-channel ADC 41 receives the first voltage signal to be measured.

[0070] S40, when the digital engine 7 determines that the phase-locked unit 6 of the digital measurement system 100 has locked the zero phase point of the AC voltage reference signal, the first conversion channel CH1 of the first dual-channel ADC 41 performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal from its zero phase point for an entire cycle, and obtains the calibration parameters of the first conversion channel CH1 of the first dual-channel ADC 41.

[0071] S50, the calibration parameters of the first conversion channel CH1 of the first dual-channel ADC 41 are stored in the storage unit of the digital engine 7.

[0072] S60, the digital engine 7 controls the switch branch to switch to the second switch state, that is, switch element S2 and switch element S4 are turned on while switch element S1 and switch element S3 are turned off, so that the first conversion channel CH1 of the first dual-channel ADC 41 receives the AC voltage signal to be measured and the second conversion channel CH2 of the first dual-channel ADC 41 receives the AC voltage reference signal.

[0073] S70, when the digital engine 7 determines that the phase-locked unit 6 of the digital measurement system 100 has locked the zero phase point of the AC voltage reference signal, it performs linear fitting on the data obtained by sampling and analog-to-digital conversion of the AC voltage reference signal from its zero phase point for an integer cycle for the second conversion channel CH2 of the first dual-channel ADC 41, and obtains the calibration parameters of the second conversion channel CH2 of the first dual-channel ADC 41.

[0074] S80 stores the calibration parameters of the second conversion channel CH2 of the first dual-channel ADC 41 in the storage unit of the digital engine 7.

[0075] The method also includes step S41, which occurs after step S80: when the switch branch is in the first switch state, when the digital engine 7 determines that the phase-locked unit 6 has locked the zero phase point of the first voltage signal to be measured, the calibration parameters of the second conversion channel CH2 of the first dual-channel ADC 41 stored in the storage unit are called to correct the data obtained by sampling and analog-to-digital conversion of the first voltage signal from its zero phase point using the second conversion channel CH2 of the first dual-channel ADC 41. The corrected measurement value of the first voltage signal is obtained.

[0076] The method may further include step S71, which occurs after step S60: when the switching branch is in the second switching state, when the digital engine 7 determines that the phase-locked unit 6 has locked the zero phase point of the first voltage signal to be measured, the data obtained by sampling and analog-to-digital conversion of the first voltage signal from its zero phase point by the first conversion channel CH1 of the first dual-channel ADC 41 is corrected by calling the calibration parameters of the first conversion channel CH1 of the first dual-channel ADC 41 stored in the storage unit, so as to obtain the corrected measurement value of the first voltage signal.

[0077] In particular, Figure 5 The first timing diagram in the provided exemplary calibration-measurement timing diagram (where the horizontal axis represents time t, and the timing diagrams below are similar) shows that: in the case where PJVS is used as the standard signal source 1 to generate a stepped wave quantum voltage as an AC voltage reference signal, in step S40, after the phase-locked unit 6 of the digital measurement system 100 locks the zero phase point of the stepped wave quantum voltage, the digital engine 7 of the digital measurement system 100 performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the stepped wave quantum voltage from its zero phase point for an integer period for the first conversion channel CH1 of the first dual-channel ADC 41. Then, after steps 50 and 60, in step S71, for the data obtained after sampling and analog-to-digital conversion of the first voltage signal to be measured for a multiple period from its zero phase point for the first conversion channel CH1 of the first dual-channel ADC 41, the calibration parameters of the first conversion channel CH1 of the first dual-channel ADC 41 stored in the storage unit are called to correct the data, and the corrected measurement value of the first voltage signal is obtained.

[0078] Accordingly, Figure 5The second timing diagram in the provided exemplary calibration-measurement timing diagram shows that: in step S70, after the phase-locked unit 6 locks the zero phase point of the step wave quantum voltage, the digital engine 7 performs linear fitting on the data obtained by sampling and analog-to-digital conversion of the step wave quantum voltage from its zero phase point for an integer period for the second conversion channel CH2 of the first dual-channel ADC 41. Then, after steps 80 and 30, in step S41, for the data obtained by sampling and analog-to-digital conversion of the first voltage signal to be measured for a multiple period from its zero phase point for a multiple period for the second conversion channel CH2 of the first dual-channel ADC 41, the calibration parameters of the second conversion channel CH2 of the first dual-channel ADC 41 stored in the storage unit are called to correct the data, and the corrected measurement value of the first voltage signal is obtained.

[0079] Thus, through accurate clock control and almost zero-delay switching of the switching state, the first conversion channel CH1 and the second conversion channel CH2 of the first dual-channel ADC 41 of the digital measurement system 100 can measure and correct the voltage signal under test immediately after being calibrated by the quantum voltage generated by the standard signal source 1, thereby achieving the purpose of immediate calibration and measurement (i.e., immediate calibration and immediate measurement).

[0080] Figure 5 The third and fourth timing sequences in the provided exemplary calibration-measurement timing diagram further illustrate the sampling timing of the first conversion channel CH1' and the second conversion channel CH2' of the second dual-channel ADC 42 for the stepped quantum voltage and the second voltage signal to be measured. The overall step sequence is similar to that of the sampling of the first conversion channel CH1 and the second conversion channel CH2 of the first dual-channel ADC 41. Through accurate clock control and almost no delay in switching states, the first conversion channel CH1' and the second conversion channel CH2' of the second dual-channel ADC 42 of the digital measurement system 100 can measure and correct the voltage signal to be measured immediately after calibration by the quantum voltage generated by the standard signal source 1, thereby achieving the purpose of calibration and measurement at the same time. The specific process will not be described in detail here.

[0081] exist Figure 5 In the illustrated embodiment, the total cycle length of the stepped-wave quantum voltage is equal to three times the cycle length of the voltage signal under test, and the switching elements S1-S8 are also controlled to switch once every three times the cycle length of the voltage signal under test. In practice, the switching cycle of the switching elements S1-S8 can be adjusted by the data engine according to preset time parameters and the requirements of the calibration cycle.

[0082] It should be noted that in steps S40 and S70 of the on-demand calibration method of the digital measurement system 100 provided according to an embodiment of the present invention, the least squares method is used to perform linear regression analysis and line fitting on the data after analog-to-digital conversion of the AC voltage reference signal, thereby obtaining the calibration parameters of each conversion channel of the dual-channel ADC. If the equation of the fitted line is y = a*x + b, the formula for the linear regression derivation is as follows:

[0083]

[0084] Where, {y1, y2, ..., y n} represents the data values ​​of the corresponding sampling points obtained by analog-to-digital conversion after the first conversion channel of the dual-channel ADC performs integer-cycle sampling on the AC voltage reference signal. {x1, x2, ..., x} n} represents the ideal data value corresponding to the sampling point of the AC voltage reference signal, x avg and y avg They are {x 1， x2, ..., x n} and {y 1， y2, ..., y n The average value of}.

[0085] Based on the above formulas (1-1) and (1-2), the grouped data points (x1, y1), (x2, y2), ..., (x n ,y n By performing a line fitting operation, the slope 'a' and intercept 'b' of the best-fitting line can be found. Specifically, select... Figure 1 The first dual-channel ADC 41 shown is used as an example to illustrate the derivation process of the calibration parameters of its first conversion channel CH1 and second conversion channel CH2. Assuming that PJVS is used as the standard signal source 1 to generate a stepped quantum voltage, in the first switching state of the switching branch, when the phase-locked unit 6 of the digital measurement system 100 locks the zero phase point of the AC quantum voltage signal, the digital engine 7 of the digital measurement system 100 performs linear fitting on the discrete data values ​​obtained by sampling the quantum voltage signal from the zero phase point (the sampling points are all controlled in the middle of each quantum voltage step) and converting the first conversion channel CH1 of the first dual-channel ADC 41. The expression of the fitted line is set as y=k*x+c. According to the above formulas (1-1) and (1-2), the calibration parameters k and c of the first conversion channel CH1 of the first dual-channel ADC 41 can be obtained.

[0086] Similarly, in the second switching state of the switching branch, when the phase-locked unit 6 of the digital measurement system 100 locks the zero phase point of the AC quantum voltage signal, the digital engine 7 performs linear fitting on the discrete data values ​​obtained by sampling the quantum voltage signal from the zero phase point for an entire cycle (the sampling points are all controlled in the middle of each quantum voltage step) and converting it for the second conversion channel CH2 of the first dual-channel ADC 41. The expression of the fitted line is set as y=m*x+d. According to the above formulas (1-1) and (1-2), the calibration parameters m and d of the second conversion channel CH2 of the first dual-channel ADC 41 can be obtained.

[0087] As mentioned above, the calibration parameters k and c of the first conversion channel CH1 and the calibration parameters m and d of the second conversion channel CH2 of the first dual-channel ADC 41 can be stored in the storage unit of the digital engine 7. This is used to correct the measured values ​​of the voltages to be measured input to the first conversion channel CH1 and the second conversion channel CH2. The purpose of calibration and measurement is achieved through the high-precision clock reference 5 and the time-delay switching of the switching element.

[0088] The self-calibrating digital measurement system 100 and its calibration-and-measurement method provided by the present invention can produce the following beneficial effects: (1) The present invention can use a high-precision clock reference as a common time and frequency reference for the digital measurement system, the generator of the AC voltage signal to be measured, and the standard signal source. By controlling the switching element that switches instantly through the digital engine of the measurement system, the self-calibration and calibration-and-measurement of the digital measurement system can be realized. Compared with separate calibration, it is more efficient in terms of time and cost; (2) The present invention can use the mainstream AC quantum voltage reference on the market as the highest level standard, which greatly improves the accuracy of calibration and measurement; (3) The calibration-and-measurement method adopted by the present invention can attenuate the noise in the AC signal under test by frequency doubling sampling, reduce the influence of environmental factors on the calibration and measurement process, further improve the accuracy of calibration and measurement, and at the same time expand the frequency range of signals suitable for calibration and measurement with high-level standards such as quantum voltage references.

[0089] Those skilled in the art will understand that the modules, units, and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can employ different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0090] If a module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the power quality detection method embodiments for each of the above-described distributed photovoltaic grid-connected devices. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0091] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A self-calibrating digital measurement system, comprising a standard signal source, an ADC conversion module, a switching circuit, a phase-locked loop unit, a digital engine, and a high-precision clock reference, wherein the standard signal source is connected to the ADC conversion module through the switching circuit, the ADC conversion module is connected to the phase-locked loop unit and the digital engine, and the digital engine is connected to the phase-locked loop unit and the high-precision clock reference. The standard signal source is used to generate an AC voltage reference signal. The AC voltage reference signal is a signal with the same amplitude as the AC voltage signal to be measured and a period that is N times larger. The high-precision clock reference is used to provide the digital measurement system with the same time and frequency reference as the device that generates the AC voltage signal to be measured, where N is an integer greater than or equal to 2. The switching circuit is used to control the alternating input of the AC voltage reference signal and the AC voltage signal under test into two different conversion channels in the ADC conversion module by switching the switch position. When the phase-locked unit locks the zero phase point of the AC voltage reference signal, the digital engine performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal in the ADC conversion module from its zero phase point for an integer cycle, and obtains the calibration parameters of the conversion channel where the AC voltage reference signal is currently located. When the phase-locked unit locks the zero phase point of the AC voltage signal under test, the digital engine calls the calibration parameters of the conversion channel where the AC voltage signal under test is currently located to correct the data obtained after sampling and analog-to-digital conversion of the AC voltage signal under test in the ADC conversion module from its zero phase point for N times the cycle, and obtains the corrected measurement value of the AC voltage signal under test.

2. The digital measurement system according to claim 1, characterized in that, The ADC conversion module is a dual-channel ADC. When the switching circuit is in the first switching state, it connects the AC voltage reference signal to the first conversion channel of the dual-channel ADC and connects the AC voltage signal to be measured to the second conversion channel of the dual-channel ADC. When the switching circuit is in the second switching state, it connects the AC voltage signal to be measured to the first conversion channel of the dual-channel ADC, and connects the AC voltage reference signal to the second conversion channel of the dual-channel ADC.

3. The digital measurement system according to claim 2, characterized in that, The ADC conversion module includes at least two dual-channel ADCs. The number of switching branches of the switching circuit matches the number of conversion channels of the dual-channel ADC. The two input terminals of each switching branch are respectively used to connect the AC voltage reference signal and the AC voltage signal to be measured. The output terminal of each switching branch is connected to a corresponding conversion channel. Each switching branch includes a first switching state and a second switching state.

4. The digital measurement system according to any one of claims 1 to 3, characterized in that, The digital engine includes a data processing unit and a storage unit that are connected in communication. The data processing unit is connected to the ADC conversion module, the phase-locked unit and the high-precision clock reference, respectively. The data processing unit is used to perform linear fitting and store the obtained calibration parameters into the storage unit, and to call the calibration parameters of the current conversion channel of the AC voltage signal under test to correct the AC voltage signal under test.

5. The digital measurement system according to claim 2, characterized in that, The dual-channel ADC in the ADC conversion module is a 24-bit high-speed, high-precision ADC, and the high-precision clock reference has a clock stability of 10. -12 A rubidium atomic clock of the order of magnitude.

6. The digital measurement system according to claim 1, characterized in that, The period of the AC voltage reference signal generated by the standard signal source is at least 5 times the period of the AC voltage signal to be measured.

7. The digital measurement system according to claim 1 or 6, characterized in that, The standard signal source is a programmable Josephson voltage standard, and the generated AC voltage reference signal is a step-wave quantum voltage signal.

8. The digital measurement system according to claim 1 or 6, characterized in that, The standard signal source is a pulse-driven AC Josephson voltage standard, and the generated AC voltage reference signal is a sinusoidal quantum voltage signal.

9. The digital measurement system according to claim 4, characterized in that, It also includes a display device connected to the data processing unit, the display device being used to display the measured value, corrected measured value, and correction amount of the AC signal under test.

10. A method for simultaneous calibration and measurement of a digital measurement system, characterized in that, Based on the digital measurement system according to any one of claims 1 to 9, the instant calibration and measurement method includes the following steps: In the current measurement, the AC voltage reference signal and the AC voltage signal to be measured are respectively input into two different conversion channels in the ADC conversion module through the switching circuit; the AC voltage reference signal is a signal with the same amplitude as the AC voltage signal to be measured and a period that is N times larger, where N is an integer greater than or equal to 2; Determine the locking status of the phase-locked unit for signals in two different conversion channels of the ADC conversion module; When the phase-locked unit locks the zero phase point of the AC voltage reference signal, the digital engine performs linear fitting on the data obtained after sampling and analog-to-digital conversion of the AC voltage reference signal in the ADC conversion module from its zero phase point for an integer cycle, and obtains the calibration parameters of the current conversion channel of the AC voltage reference signal. When the phase-locked unit locks the zero phase point of the AC voltage signal under test, the digital engine uses the data obtained by sampling and analog-to-digital conversion of the AC voltage signal under test in the ADC conversion module from its zero phase point at N times the period to call the calibration parameters of the conversion channel where the AC voltage signal under test is currently located to correct it, and obtain the corrected measurement value of the AC voltage signal under test. After the input signals of two different conversion channels in the ADC conversion module are swapped by the switching circuit, the process jumps to the step of determining the locking state of the phase-locked unit for the signals in the two different conversion channels in the ADC conversion module, and then proceeds to the next measurement.

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