Automatic range switching method and system for electric measuring instrument

Abstract

The invention discloses an automatic measuring range switching method and system for an electric measuring instrument, and relates to the technical field of electronic measurement, and the method comprises the steps that a measuring range control module analyzes a measuring range instruction and calculates a relay control time sequence of a target measuring range gear; and the execution driving module drives the multi-path relay group to be switched to the target range gear according to the relay control time sequence. According to the invention, the execution driving module is configured with a multi-path relay group composed of a high-precision relay channel, a power relay channel and a high-voltage relay channel, and a heterogeneous hardware design concept of a special relay is adopted for different measurement requirements. Therefore, one instrument can give consideration to the precision requirement of micro-parameter measurement and the safety requirements of power and high-voltage measurement at the same time, the limitation of measuring range design of a traditional instrument is fundamentally broken through, and the application scene and the comprehensive testing capability of the electric measuring instrument are greatly widened. And a solid hardware foundation is provided for developing a multifunctional and wide-range general electric measurement platform.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic measurement technology, in particular to an automatic range switching method and system for an electrical measuring instrument. BACKGROUND

[0002] With the continuous upgrading of the demand for fine and efficient electrical parameter measurement in the fields of industrial automation, electronic manufacturing and power system operation and maintenance, the automatic switching and intelligent adaptation capability of the range of various electrical measuring instruments, such as resistance testers, voltmeters, high-precision current sources or tables, has become a core factor determining the measurement accuracy, stability and test efficiency. In a wide range of electrical parameter measurement, the dynamic range of the signal to be measured is extremely wide - from the small signal of microvolts or microamperes to the large signal of kilovolts or amperes, which requires the instrument to have wide range and high precision measurement capability. However, the traditional range switching technology, whether it is manual switching at the initial stage or automatic switching based on fixed threshold at the later stage, is difficult to cope with the challenges in complex working conditions.

[0003] The traditional range switching method has the following common defects: first, its decision-making logic is single, and it is only based on the instantaneous amplitude of the measured parameter for judgment, ignoring the influence of key factors such as environmental temperature fluctuations, load power changes, circuit noise and signal frequency characteristics. For example, in resistance measurement, thermal drift caused by high temperature may be misjudged as resistance value change, causing mis-switching; in AC voltage or current measurement, different frequency response characteristics may also cause amplitude measurement error. Secondly, the relay switching timing design is simple, mostly using fixed delay, without considering key phase information such as AC signal zero-crossing point, which is easy to produce electric arc at the switching moment, not only damaging the relay contact and shortening the service life, but also introducing transient interference, affecting the accuracy of measurement data. Thirdly, the hardware channel lacks targeted design, usually using the same size relay to cope with different ranges, resulting in contact resistance error in small signal measurement and safety risk of insufficient current carrying capacity or insufficient insulation voltage in large current or high voltage measurement.

[0004] Therefore, it is necessary to invent an automatic range switching method and system for an electrical measuring instrument to solve the above problems. SUMMARY

[0005] The present application aims to provide an automatic range switching method and system for an electrical measuring instrument to solve the problems raised in the background.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: an automatic range switching method for an electrical measuring instrument, specifically comprising the following steps: S1, the data acquisition module collects the original electrical characteristic data of the object to be measured to form an electrical characteristic data set; the electrical characteristic data set includes original parameter values, environmental temperature data and load power values; S2, the signal conditioning module performs multi-frequency point impedance spectrum scanning on the original parameter values to generate an enhanced characteristic data set containing phase angles and frequency domain response amplitudes; S3, the feature analysis module performs time-frequency domain fusion analysis on the electrical characteristic data set and the enhanced characteristic data set to obtain stability coefficients, load characteristic coefficients and environmental drift coefficients, and inputs the stability coefficients, load characteristic coefficients and environmental drift coefficients into an adaptive range decision model to output a range switching index; S4, the model decision module generates a range instruction according to the comparison result of the range switching index and the preset threshold interval; S5, the range control module analyzes the range instruction and calculates the relay control timing of the target range gear; S6, the execution driving module drives the multi-way relay group to switch to the target range gear according to the relay control timing.

[0007] Preferably, the original parameter value is an original resistance value R0, including measurement values collected at 10 Hz, 1 kHz and 100 kHz frequencies; the environmental temperature data includes contact point temperature values T j and environmental temperature values T a ; the load power value P l includes the product of the output current I s of the constant current source and the voltage V r across the resistance to be measured, and is subjected to noise suppression processing, and the calculation formula is: wherein f is the real-time detected circuit noise frequency, and f n is the preset noise cutoff frequency.

[0008] Preferably, the calculation formula of the stability coefficient is: , wherein is the standard deviation of R0 in N sampling periods, is the arithmetic mean of R0, k R is a resistance dispersion compensation coefficient, k T is a temperature sensitivity coefficient, and △T is the contact point temperature fluctuation value, specifically △T = max(T j ) - min(T j ), wherein T j is the contact point temperature value, max is the maximum value function, and min is the minimum value function.

[0009] Preferably, the calculation formula of the load characteristic coefficient is: , wherein P l is the load power value, P nom is the rated power setting value, A f is the response amplitude value at 100 kHz frequency point, f c is the critical frequency setting value, ln is the natural logarithm with e as the base, and e is the natural constant.

[0010] Preferably, the calculation formula of the environmental drift coefficient is as follows: , wherein T a is the environmental temperature value, T max is the maximum allowable operating temperature, T ref is the reference temperature, min is the minimum function, π is the circular constant, and cos is the cosine function.

[0011] Preferably, the adaptive range decision model is specifically as follows: , wherein Q is the range switching index, α is the stability coefficient, β is the load characteristic coefficient, γ is the environmental drift coefficient, λ is the smoothing factor, ω1 and ω2 are dynamic weight coefficients, ω1 + ω2 = 1 and ω1 and ω2 ∈ [0, 1].

[0012] Preferably, the range instruction is as follows: when the range switching index Q > Q1, a first-grade range instruction is generated; when the range switching index Q2 ≤ Q ≤ Q1, a second-grade range instruction is generated; when the range switching index Q < Q2, a third-grade range instruction is generated.

[0013] Preferably, the relay control time sequence comprises: A1, disconnecting the current range relay group; A2, delaying wherein t d is the relay switching delay time, f0 is the phase angle zero-crossing point frequency, and π is the circular constant; A3, closing the target range relay group; A4, applying a pre-charge current .

[0014] Preferably, the multiple relay groups comprise: a high-precision relay channel with a contact resistance less than 10 mΩ, used for the first-grade range; a power relay channel with a current-carrying capacity greater than 3 A, used for the second-grade range; High-voltage relay channel with insulation withstand voltage greater than 300V, used for the third range.

[0015] An automatic range switching system for electrical measuring instrument, comprising a data acquisition module, a signal conditioning module, a feature analysis module, a model decision module, a range control module and an execution driving module, wherein: The data acquisition module is used for acquiring original electrical characteristic data of the object to be measured to form an electrical characteristic data set; the electrical characteristic data set comprises original parameter values, environmental temperature data and load power values; The signal conditioning module is used for performing multi-frequency point impedance spectrum scanning on the original parameter values to generate an enhanced characteristic data set comprising phase angles and frequency domain response amplitudes; The feature analysis module is used for performing time-frequency domain fusion analysis on the electrical characteristic data set and the enhanced characteristic data set to obtain stability coefficients, load characteristic coefficients and environmental drift coefficients, and inputting the stability coefficients, load characteristic coefficients and environmental drift coefficients into an adaptive range decision model to output a range switching index; The model decision module is used for generating a range instruction according to the comparison result of the range switching index and a preset threshold interval; The range control module is used for analyzing the range instruction and calculating a relay control timing of a target range gear; The execution driving module is used for driving a plurality of relay groups to switch to the target range gear according to the relay control timing.

[0016] The technical effects and advantages of the present application are as follows: 1. The feature analysis module is used for performing time-frequency domain fusion analysis on the original electrical characteristic data set and the enhanced characteristic data set, extracting stability, load characteristic and environmental drift coefficients, and inputting the coefficients into an adaptive decision model to generate a range switching index. This intelligent decision mechanism based on multi-dimensional feature fusion overcomes the limitations of traditional single parameter threshold method, can effectively distinguish the real changes of parameters and environmental disturbances, and significantly improves the accuracy and intelligent adaptability of range switching of the electrical measuring instrument under various complex working conditions. 2. After the range control module analyzes the instruction, the relay control timing based on the dynamic delay of the phase angle zero-crossing frequency and the pre-charge current is executed. This timing strategy can ensure that the relay contact moves near the zero-crossing of current or voltage, greatly suppresses the arc discharge phenomenon, reduces the contact wear, prolongs the mechanical and electrical life of the relay, and at the same time, the pre-charge current smoothes the circuit impact at the switching moment, improves the stability of the entire range switching process and the accuracy of the measurement data. This advantage has universal reliability and safety value for any electrical measuring instrument using relays for range switching. 3. This invention configures a multi-channel relay group consisting of a high-precision relay channel, a power relay channel, and a high-voltage relay channel through an execution drive module. This heterogeneous hardware design concept, which uses dedicated relays for different measurement needs, enables a single instrument to simultaneously meet the accuracy requirements of microparameter measurement and the safety requirements of power and high-voltage measurement. This fundamentally breaks through the limitations of traditional instrument range design, greatly expands the application scenarios and comprehensive testing capabilities of electrical measuring instruments, and provides a solid hardware foundation for developing a multi-functional, wide-range general-purpose electrical measurement platform. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the method steps of the present invention.

[0018] Figure 2 This is a timing diagram of the relay of the present invention.

[0019] Figure 3 This is a schematic diagram of the system structure of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides, for example Figure 1 The automatic range switching method for electrical measuring instruments shown includes the following steps: S1. The resistance acquisition module acquires the original electrical characteristic data of the object under test to form an electrical characteristic dataset; the electrical characteristic dataset includes original parameter values, ambient temperature data, and load power values; Furthermore, in the above technical solution, the original parameter value is the original resistance value R0, including measured values ​​collected at frequencies of 10Hz, 1kHz, and 100kHz; the ambient temperature data includes the contact point temperature value T. j and ambient temperature value T a The load power value P l Including the constant current source output current I s With the voltage V at the end of the resistor to be measured r The product of the base values, after noise suppression processing, is calculated using the following formula: Where f is the frequency of the circuit noise detected in real time, f n This is the preset noise cutoff frequency.

[0022] It is to be known that the original resistance value R0 is obtained by a constant current source excitation circuit combined with a four-wire measurement method, specifically, a precise constant current source applies an excitation current with a frequency adjustable at 10 Hz, 1 kHz and 100 kHz to the resistance to be measured, and a 24-bit high-precision ADC synchronously collects the terminal voltage V r of the resistance to be measured according to Ohm's law R0 = V r / I s , wherein the constant current source output current I s is converted into a voltage signal through a 0.1Ω precise sampling resistor connected in series in the excitation loop, and the voltage signal is input into the ADC after being amplified by an instrument amplifier INA128. The contact point temperature value T j is collected by a Pt1000 platinum resistance temperature sensor attached to the base of the test probe, the sensor is in thermal connection with the probe through an alumina ceramic substrate, a three-wire compensation circuit powered by a constant current source is used to eliminate the influence of wire resistance, the original data is obtained by a 24-bit∑-△ ADC at a sampling rate of 10 times per second, and the resistance value is converted into the temperature value by a lookup table method. The ambient temperature value T a is detected by an NTC thermistor installed in the ventilation port of the equipment cabinet, the sensor is physically isolated from the metal heat sink and covered with a dustproof filter screen, the resistance change is converted into a voltage signal by a voltage dividing circuit, the ADC sampling data is processed by a sliding average filtering algorithm, the ambient temperature value is updated every 30 seconds, and the measurement range covers the industrial temperature range of-40℃ to +85℃. The circuit noise frequency f detected in real time is obtained by sampling the V r signal for 256 points by a high-speed ADC, and the main noise frequency component is obtained by applying FFT spectrum analysis, specifically, the ARM processor performs Hanning window weighting processing and calculates the power spectral density, automatically identifies the 50Hz or 60Hz power frequency and the high-frequency switching noise spectrum peak position, and the detection frequency range covers 10Hz~100kHz. The preset noise cutoff frequency f n is dynamically set according to the real-time spectrum analysis result: when the main noise frequency component is detected as 50Hz or 60Hz power frequency interference, f n =200Hz; when there is high-frequency switching noise, i.e., >10kHz, f n =20kHz; in other scenarios, it is adaptively adjusted according to the 3dB point of the noise power spectral density and is constrained within the range of 200Hz to 20kHz, so as to achieve the optimal balance between noise suppression and signal fidelity.

[0023] S2, the signal conditioning module performs multi-frequency point impedance spectrum scanning on the original resistance value, and generates an enhanced characteristic data set containing phase angle and frequency domain response amplitude; The execution process of the signal conditioning module is to sequentially apply excitation currents of three characteristic frequencies of 10 Hz, 1 kHz and 100 kHz to the resistance to be measured through a programmable constant current source, and to synchronously collect the resistance terminal voltage signals at each frequency point by using a four-wire measurement method combined with a 24-bit high-precision ADC; the digital phase-locked loop technology is applied to the collected time-domain voltage signals to extract the quadrature components with the same frequency as the excitation current, and the phase angle data at each frequency point is calculated, and the phase resolution is 0.01 degrees; at the same time, the voltage signals are subjected to 256-point FFT spectrum analysis, and the power spectral density is calculated after Hanning window weighting processing, and the response amplitudes at the characteristic frequencies in the frequency band of 10 Hz to 100 kHz are obtained; finally, the three-frequency point phase angles and the corresponding frequency domain response amplitudes are integrated into structured data to form an enhanced characteristic data set, wherein the phase angle data is used to represent the dielectric characteristics of the resistance material, and the frequency domain response amplitude is used to reveal the nonlinear characteristics of the impedance with the change of frequency, and the data set is stored in the form of a matrix and output to the characteristic analysis module.

[0024] S3, the characteristic analysis module performs time-frequency domain fusion analysis on the electrical characteristic data set and the enhanced characteristic data set to obtain stability coefficients, load characteristic coefficients and environmental drift coefficients, and inputs the stability coefficients, load characteristic coefficients and environmental drift coefficients into an adaptive range decision model to output a range switching index; Further, in the above technical solution, the calculation formula of the stability coefficient is: , wherein, is the standard deviation of R0 in N sampling periods, is the arithmetic mean of R0, k R is a resistance dispersion compensation coefficient, k T is a temperature sensitivity coefficient, and ΔT is a contact point temperature fluctuation value, specifically ΔT = max(T j ) - min(T j ), wherein T j is a contact point temperature value, max is a maximum value function, and min is a minimum value function.

[0025] It should be noted that max(T j ) is the maximum value of the contact point temperature T j in N consecutive sampling periods, and min(T j ) is the minimum value of the contact point temperature T j in N consecutive sampling periods; The resistance dispersion compensation coefficient k R is determined according to the expected measurement accuracy of the measured resistance and the material characteristics, and is preferably set to k R= 0.003, which is calibrated by repeatedly measuring the standard resistor and analyzing its discrete distribution characteristics, and is used to effectively balance the influence of resistance inherent discreteness and measurement system noise on standard deviation in stability coefficient calculation. The temperature sensitivity coefficient k T is set by comprehensively considering the temperature coefficient of the resistance to be measured and the thermal conduction characteristics of the contact point, and is preferably k T = 0.05Ω / ℃, which is obtained by measuring the proportional relationship between the contact point temperature fluctuation ΔT and the resistance value drift through thermal shock test, and is used to quantify the equivalent influence degree of unit temperature fluctuation on resistance measurement stability, and to ensure that the environmental temperature change is accurately compensated in the stability coefficient.

[0026] Further, in the above technical solution, the calculation formula of the load characteristic coefficient is: , Where P l is the load power value, P nom is the rated power set value, A f is the response amplitude at 100kHz frequency point, f c is the critical frequency set value, and ln is the logarithm with base e, and e is the natural constant.

[0027] It should be noted that the response amplitude A f at the 100kHz frequency point is obtained by multi-frequency point impedance spectrum scanning of the signal conditioning module: a programmable constant current source applies an excitation current of 100kHz characteristic frequency to the resistance to be measured, and a four-wire measurement method is combined with a 24-bit ADC to collect the time domain signal of the resistance terminal voltage; the collected data is applied to digital phase-locked loop technology to extract the orthogonal component with the same frequency as the excitation current, and then the power spectrum density is calculated through 256-point FFT spectrum analysis after Hanning window weighting, and finally the response amplitude at the 100kHz characteristic frequency is extracted from the 10Hz-100kHz frequency band, which together with the phase angle constitutes the enhanced characteristic data set, which is used to reveal the high-frequency impedance characteristics and nonlinear load effect of the resistance; The rated power set value P nom is determined according to the safety working area characteristics of the resistance to be measured, specifically the maximum allowable power consumption of the resistor under the reference temperature T ref , and its setting needs to comprehensively consider the physical size of the resistance to be measured, the material heat capacity and the thermal conduction characteristics of the test environment; preferably, P nom is not greater than 70% of the nominal power value in the resistance manufacturer's specification, and under high temperature environment, i.e. T a > 60℃, P nom needs to be dynamically adjusted according to the adjustment coefficient, and the adjustment coefficient is k derate = 1-0.015×(T​a -25), to ensure that the resistance test process is always in a safe working zone; The critical frequency setting value f c The setting is calibrated based on the frequency response characteristics of the resistance to be tested through impedance spectrum scanning experiments, specifically by performing multi-frequency excitation in the 10Hz to 100kHz frequency band and identifying the turning point where the impedance amplitude significantly decays with increasing frequency. The value is preset as a typical value such as 20kHz according to the dielectric constant of the resistance material and the structural design parameters, and is calibrated by verifying the frequency position where the impedance amplitude drops by 3dB on a standard resistance sample, to ensure that the effects of high-frequency noise and parasitic parameters on the non-linear characteristics of the resistance are effectively quantified in the load characteristic coefficient, thereby optimizing the adaptability of the range decision model.

[0028] Further, in the above technical solution, the calculation formula of the environmental drift coefficient is: , Where T a is the ambient temperature value, T max is the maximum allowable operating temperature, T ref is the reference temperature, min is the minimum function, π is the circular constant, and cos is the cosine function.

[0029] It is known that the maximum allowable operating temperature T max is determined by the safety working boundary of the core electronic components of the intelligent resistance tester, including the multi-channel relay group, the signal conditioning circuit, and the temperature sensor. Specifically, it is determined by the maximum junction temperature parameter in the specification book provided by the component supplier, combined with the internal thermal simulation model and high-temperature aging test results. This temperature value needs to ensure that the contact resistance stability of the relay contact, the heat resistance of the insulating material, and the working drift of the operational amplifier in the signal conditioning circuit are within a controllable range, while considering the thermal resistance characteristics of the device heat dissipation structure and the heat dissipation capacity of the forced air cooling system. Its typical value is set to 85℃, and it is used as the critical upper limit of temperature standardization processing in the calculation of the environmental drift coefficient. When the ambient temperature T a approaches T max , the environmental drift coefficient γ approaches 0, triggering the range decision model to switch to the high insulation voltage range to ensure test safety; The reference temperature T ref is determined based on the standard test conditions of the resistance to be tested and the thermal design parameters of the device itself. Specifically, it needs to be associated with the measurement reference of the contact temperature T j and the rated working environment of the resistance tester, where T ref serves as the normalization reference of the environmental drift coefficient. Its typical value is set to 25℃, and at the same time, this value needs to be consistent with the calibration reference point of the device temperature sensor, and its consistency is verified through thermal equilibrium experiments.max -T ref The linearity error in the temperature difference interval is less than ±0.5%, when the ambient temperature T a The ambient drift coefficient γ approaches 1 when T ref The ambient drift coefficient γ approaches 1 when T

[0030] Further, in the technical solution, the adaptive range decision model specifically comprises: , wherein, Q is a range switching index, α is a stability coefficient, β is a load characteristic coefficient, γ is an ambient drift coefficient, λ is a smoothing factor, ω1 and ω2 are dynamic weight coefficients, ω1+ω2=1 and ω1 and ω2∈[0, 1].

[0031] It is to be known that the dynamic weight coefficients ω1 and ω2 are set as ω1=0.7 and ω2=0.3 when the stability coefficient α<0.9 or the contact point temperature fluctuation value ΔT>5℃ is detected by the feature analysis module, so as to strengthen the weight of the resistance stability and the temperature drift compensation in the range decision; when the load characteristic coefficient β<0.8 or the 100kHz frequency point response amplitude A f is less than 30% of the reference value, ω1=0.4 and ω2=0.6 are set, and the influence of the load nonlinear effect and the high frequency characteristic on the range decision is emphasized; in the normal working condition, i.e. α≥0.9, β≥0.8 and ΔT≤5℃, ω1=0.5 and ω2=0.5 are adopted in the balanced configuration.

[0032] S4, the model decision module generates a range instruction according to the comparison result of the range switching index and the preset threshold interval; Further, in the technical solution, the range instruction comprises: when the range switching index Q>Q1, a first range instruction is generated; when the range switching index Q2≤Q≤Q1, a second range instruction is generated; when the range switching index Q<Q2, a third range instruction is generated.

[0033] It is to be known that Q1 and Q2 are preset thresholds of the range switching index, and the setting thereof needs to be optimized and configured in combination with the resistance measurement range, the test accuracy requirement and the load power characteristics, and is determined according to the correlation between the range switching index Q output by the adaptive range decision model and the physical characteristics of the three range gears. Q1 is taken as the demarcation threshold between the first range and the second range, and the setting thereof needs to meet the error constraint condition of high-precision small-resistance measurement: when Q>Q1, the system switches to the high-precision relay channel with a contact resistance less than 10 mΩ, and the threshold needs to ensure that the fusion calculation result of the stability coefficient a and the load characteristic coefficient β can accurately trigger the high-sensitivity range when the resistance value is lower than 10 Ω and the load power dynamically fluctuates. Q2 is taken as the demarcation threshold between the second range and the third range, and the setting thereof needs to adapt to the safety switching boundary of the power relay and the high-voltage relay: when Q<Q2, the system automatically enables the high-voltage relay channel with an insulation withstand voltage greater than 300 V, and the threshold needs to ensure that the downward trend of the environmental drift coefficient γ can timely trigger the high-isolation range when the resistance value is higher than 1 kΩ or there is a high-voltage test demand. Preferably, Q1 and Q2 are dynamically calibrated through calibration experiments: under the condition of the reference temperature 25℃, 10 Ω±1% and 1 kΩ±1% standard resistance samples are respectively used, the load power is tested with a step change from 10% to 90% of the rated value, the measurement error in the range switching process is limited to not more than ±0.2%, the relay switching arc energy is limited to less than 5 mJ as the constraint condition, the initial values of Q1=0.85±0.03 and Q2=0.65±0.03 are determined through an iterative optimization algorithm, and ±0.05 dynamic compensation is performed in actual application according to the environmental temperature fluctuation range (-40℃~+85℃) and the noise spectrum characteristics (10 Hz~100 kHz), so as to ensure the test accuracy while realizing the safe and reliable switching of the multi-channel relay group; The first range instruction corresponds to the first range, specifically a 10 mΩ~10 Ω range gear; The second range instruction corresponds to the second range, specifically a 10 Ω~1 kΩ range gear; The third range instruction corresponds to the third range, specifically a 1 kΩ~100 kΩ range gear.

[0034] S5, the range control module parses the range instruction and calculates the relay control time sequence of the target range gear; Further, in the above technical solution, the relay control time sequence is as shown in Figure 2 , and includes: A1, disconnecting the current range relay group; A2, delaying , wherein t d is the relay switching delay time, f0 is the phase angle zero-crossing frequency, and π is the circular constant; A3, closing the target range relay group; A4, applying a pre-charge current .

[0035] It should be noted that the acquisition of the phase angle zero-crossing point frequency f0 is realized by a signal conditioning module: the module performs continuous frequency point analysis on the phase angle data obtained in the multi-frequency point impedance spectrum scan, and in the process of applying a step-scan excitation of 10 Hz to 100 kHz, the critical frequency position where the phase angle between adjacent frequency points changes from positive to negative is detected in real time, and a linear interpolation algorithm is used to calculate the accurate frequency value of the zero-crossing point between the two continuous frequency points where the phase angle sign changes.

[0036] S6, the execution driving module drives the multi-relay group to switch to the target range position according to the relay control timing.

[0037] Further, in the above technical solution, the multi-relay group comprises: a high-precision relay channel with a contact resistance less than 10 mΩ, used for the first range; a power relay channel with a current-carrying capacity greater than 3 A, used for the second range; a high-voltage relay channel with an insulation withstand voltage greater than 300 V, used for the third range.

[0038] It should be noted that for the first range, a high-precision magnetic latching relay with a contact resistance less than 10 mΩ is used to ensure that the contact voltage drop does not affect the measurement accuracy of the micro-resistor; for the second range, a power relay with a current-carrying capacity greater than 3 A is selected, and the silver-plated contact and the heat dissipation substrate design can bear the maximum output current of the constant current source; for the third range, a high-voltage dry reed relay with an insulation withstand voltage greater than 300 V is configured, and its ceramic sealing structure provides sufficient dielectric strength to isolate the high-voltage test signal; The high-precision relay selects Panasonic TQ2-5V type magnetic latching relay, and its coil driving circuit is connected in series with the low-power output channel of the range control module; the power relay selects TE EA2-12NJ type power relay, which is driven by a Darlington transistor array and is configured with an RC snubber circuit; the high-voltage relay selects Standex-Meder SIL05-1A72 type dry reed relay, which is controlled by optical coupling isolation to avoid high-voltage crosstalk.

[0039] An automatic range switching system for an electrical measuring instrument, as shown in Figure 3 , comprises a data acquisition module, a signal conditioning module, a feature analysis module, a model decision module, a range control module, and an execution driving module, wherein: The data acquisition module is used to acquire the original electrical characteristic data of the object to be measured, forming an electrical characteristic data set; the electrical characteristic data set includes original parameter values, environmental temperature data, and load power values; A signal conditioning module is configured to perform multi-frequency point impedance spectrum scanning on the original parameter value to generate an enhanced characteristic data set containing phase angle and frequency domain response amplitude; A feature analysis module is configured to perform time-frequency domain fusion analysis on the electrical characteristic data set and the enhanced characteristic data set to obtain a stability coefficient, a load characteristic coefficient and an environmental drift coefficient, and input the stability coefficient, the load characteristic coefficient and the environmental drift coefficient into an adaptive range decision model to output a range switching index; A model decision module is configured to generate a range instruction according to a comparison result of the range switching index and a preset threshold interval; A range control module is configured to analyze the range instruction and calculate a relay control timing of a target range gear; An execution driving module is configured to drive a multi-way relay group to switch to the target range gear according to the relay control timing.

[0040] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing embodiments of the present application have been described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included within the scope of the present application.

Claims

1. An automatic range switching method for electrical measuring instruments, characterized in that, Specifically, it includes the following steps: S1. The data acquisition module acquires the original electrical characteristic data of the object to be measured, forming an electrical characteristic data set; the electrical characteristic data set includes original parameter values, ambient temperature data, and load power values; S2. The signal conditioning module performs multi-frequency point impedance spectrum scanning on the original parameter values, generating an enhanced characteristic data set containing phase angles and frequency-domain response amplitudes; S3. The feature analysis module performs time-frequency domain fusion analysis on the electrical characteristic data set and the enhanced characteristic data set, obtaining a stability coefficient, a load characteristic coefficient, and an environmental drift coefficient, and inputs the stability coefficient, the load characteristic coefficient, and the environmental drift coefficient into the adaptive range decision model to output a range switching index; S4. The model decision module generates a range command according to the comparison result between the range switching index and a preset threshold interval; S5. The range control module analyzes the range command and calculates the relay control timing of the target range gear; S6. The execution drive module drives the multi-channel relay group to switch to the target range gear according to the relay control timing.

2. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The original parameter values ​​are the original resistance value R0, including measured values ​​collected at frequencies of 10Hz, 1kHz, and 100kHz; the ambient temperature data includes the contact point temperature value T. j and ambient temperature value T a The load power value P l Including the constant current source output current I s With the voltage V at the end of the resistor to be measured r The product of the base values, after noise suppression processing, is calculated using the following formula: Where f is the frequency of the circuit noise detected in real time, f n This is the preset noise cutoff frequency.

3. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The calculation formula for the stability coefficient is: ， in, Let R0 be the standard deviation over N sampling periods. Let k be the arithmetic mean of R0. R k is the resistance dispersion compensation coefficient. T Here, ΔT is the temperature sensitivity coefficient, and ΔT is the temperature fluctuation value at the contact point, specifically ΔT = max(T j )-min(T j ), where T j Let be the contact point temperature value, max be the maximum value function, and min be the minimum value function.

4. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The calculation formula for the load characteristic coefficient is: ， Among them, P l P represents the load power value. nom A is the rated power setting value. f f is the response amplitude at a frequency of 100kHz. c The critical frequency is set, where ln is the logarithm to the base e, and e is the natural constant.

5. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The calculation formula for the environmental drift coefficient is: ， Among them, T a T represents the ambient temperature value. max To allow for the highest operating temperature, T ref Let be the reference temperature, min be the minimum value function, π be the value of pi, and cos be the cosine function.

6. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The adaptive range decision model is specifically: ， Where Q is the range switching index, α is the stability coefficient, β is the load characteristic coefficient, γ is the environmental drift coefficient, λ is the smoothing factor, ω1 and ω2 are dynamic weight coefficients, ω1 + ω2 = 1 and ω1 and ω2 ∈ [0, 1].

7. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The range command is: When the range switching index Q > Q1, generate a first gear range command; When the range switching index Q2 ≤ Q ≤ Q1, generate a second gear range command; When the range switching index Q < Q2, generate a third gear range command.

8. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The relay control timing includes: A1. Disconnect the current range relay group; A2, Delay , where t d f0 is the relay switching delay time, f0 is the zero-crossing frequency of the phase angle, and π is pi. A3. Close the target range relay group; A4. Apply pre-charging current .

9. The automatic range switching method for an electrical measuring instrument according to claim 1, characterized in that, The multi-channel relay group includes: A high-precision relay channel with a contact resistance less than 10 mΩ, for the first gear range; A power relay channel with a current-carrying capacity greater than 3 A, for the second gear range; A high-voltage relay channel with an insulation withstand voltage greater than 300 V, for the third gear range.

10. An automatic range switching system for an electrical measuring instrument, applied to the automatic range switching method for an electrical measuring instrument as described in any one of claims 1-9, characterized in that, It includes a data acquisition module, a signal conditioning module, a feature analysis module, a model decision module, a range control module, and an execution drive module, where: The data acquisition module is used to acquire the original electrical characteristic data of the object to be measured, forming an electrical characteristic data set; the electrical characteristic data set includes original parameter values, ambient temperature data, and load power values; The signal conditioning module is used to perform multi-frequency point impedance spectrum scanning on the original parameter values, generating an enhanced characteristic data set containing phase angles and frequency-domain response amplitudes; The feature analysis module is used to perform time-frequency domain fusion analysis on the electrical characteristic data set and the enhanced characteristic data set, obtaining a stability coefficient, a load characteristic coefficient, and an environmental drift coefficient, and inputs the stability coefficient, the load characteristic coefficient, and the environmental drift coefficient into the adaptive range decision model to output a range switching index; The model decision module is used to generate a range command according to the comparison result between the range switching index and a preset threshold interval; The range control module is used to parse the range command and calculate the relay control timing of the target range. The execution drive module is used to drive multiple relay groups to switch to the target range according to the relay control timing.

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