Switching-free high-precision wide-range current measuring device and signal processing method

Abstract

The invention belongs to the field of precision test technologies and instruments, and the traditional non-contact current detection meets the basic requirements of power monitoring to a certain extent, but the limitation gradually appears in the face of complex and changeable measurement environments and increasing measurement precision requirements. According to the non-switching high-precision wide-range current measuring device and the signal processing method, high-precision sampling of micro-current analog signals is achieved through the high-sensitivity signal sampling unit, and two-stage passive filter circuits are added to the signal sampling unit to filter most clutters in the analog signals, so that high-precision sampling of the micro-current analog signals is achieved. A digital signal processing method is used in the MCU to filter digital current data with higher precision, a digital signal processing technology is applied to the field of current detection, and high-precision and high-efficiency current measurement is realized by optimizing a detection circuit structure and a signal processing flow.

Description

Technical Field

[0001] The present invention belongs to the field of precision testing technology and instruments, and in particular relates to a non-switching high-precision large-range current measuring device and a signal processing method. Background Art

[0002] With the rapid development of the power industry and the in-depth advancement of smart grid construction, current detection technology, as an indispensable component of the power system, has become increasingly important, especially in the fields of modern industrial production, scientific research experiments, and power monitoring, which put forward higher requirements for the accuracy, real-time and safety of current detection. Although traditional current detection devices, such as electromagnetic current sensors, meet the needs of power monitoring to a certain extent, there are still many shortcomings in practical applications. Due to the limitations of its structure and working principle, traditional electromagnetic current sensors have problems such as easy saturation of the core and difficulty in insulation. When the current is too large or there are harmonics, the saturation of the core will lead to a decrease in measurement accuracy, and the difficulty of insulation increases the safety hazards of the equipment. In order to overcome the shortcomings of traditional current detection devices, non-contact current detection equipment came into being. Non-contact current detection equipment uses the principle of electromagnetic induction to indirectly measure the current value by detecting the magnetic field generated by the current. Compared with traditional electromagnetic current sensors, it has the advantages of non-contact measurement, wide dynamic range, electrical isolation, and digital output. However, although traditional non-contact current detection meets the basic needs of power monitoring to a certain extent, its limitations gradually emerge when facing complex and changing measurement environments and increasing measurement accuracy requirements. Therefore, developing a new type of high-precision, high-efficiency non-contact current detection equipment combined with digital signal processing technology has become an important innovation direction in the current power industry.

[0003] Traditional non-contact current detection devices, such as sensors based on the Hall effect or magnetoresistive effect, indirectly measure the current value by detecting the magnetic field generated by the current. However, these devices are often affected by various factors during the measurement process, such as ambient temperature, magnetic field interference, etc., resulting in low measurement accuracy and poor stability. In addition, traditional devices have deficiencies in signal processing and data analysis, and are difficult to adapt to complex and changing measurement environments. The non-contact current detection devices on the current market mainly include products from Fluke in the United States and Uni-Tek in China. The products on the current market need to be switched in grades according to the measurement range; the highest current measurement resolution of Fluke products in the United States is 0.01A at the 40A range, and the highest current resolution is 0.1A at the 600A range; the highest measurement accuracy is 1.5% + 5 times the resolution; the products of domestic Uni-Tek and other companies have lower measurement accuracy and stability at the same measurement resolution. Summary of the invention

[0004] In order to overcome the limitations of traditional non-contact current detection equipment, the present invention proposes a non-switching high-precision and large-range current measurement device and a signal processing method, which combines digital signal processing technology with non-contact current detection, applies digital signal processing technology to the field of current detection, and achieves high-precision and high-efficiency current measurement by optimizing the detection circuit structure and signal processing flow.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A non-switching high-precision and large-range current measuring device comprises a main measuring unit, a signal acquisition unit, a signal amplification and filtering circuit unit, a high-precision AD conversion unit, an MCU for collecting high-precision data, and a digital signal processing unit, wherein:

[0007] The main measuring unit includes two Hall current sensors, which are respectively located at the two ends of the opening and closing clamp heads of the current clamp, and the Hall potential generated by the magnetic flux density at the gap is detected by the two Hall current sensors;

[0008] The signal input end of the signal acquisition unit is connected to the signal output end of the main measurement unit, and the influence of the lateral offset and the longitudinal displacement on the detection accuracy is reduced by the Wheatstone bridge circuit. The lateral offset represents the offset distance of the detected wire harness in the direction of the axis of the wire harness itself relative to the central axis of the magnetic core gap, and the longitudinal displacement represents the displacement distance of the detected wire harness in the direction of the axis of the wire harness itself relative to the magnetic core gap.

[0009] The signal amplification and filtering circuit unit includes a signal amplification part and a signal filtering part, the input end of the signal amplification part is connected to the output end of the signal acquisition unit, and the output signal of the signal acquisition unit is transmitted to the signal filtering part after signal amplification to obtain a smooth Hall potential signal;

[0010] The high-precision AD conversion unit converts the Hall potential analog signal output by the signal amplification and filtering circuit unit into a digital signal that meets the accuracy requirements through a programmable high-precision conversion unit, achieving a current resolution of 0.001A within a 200A range; and uses the MCU to collect high-precision data after the signal conversion has been completed;

[0011] The digital signal processing unit filters the high-precision data collected by the MCU to obtain a stable digital signal, and performs data calibration to obtain an accurate current signal.

[0012] Furthermore, it also includes a wireless transmission and display unit, and the wireless transmission unit sends the acquired accurate current signal data to the host computer through the wireless transmission unit, and displays the current signal data in the host computer.

[0013] Further, the signal acquisition unit includes four resistors and two sliding rheostats, the output terminal OUT- and the output terminal OUT+ of the Hall current sensor U4 are respectively connected to the resistor R17 and the resistor R18, the other ends of the resistor R17 and the resistor R18 are respectively connected to the fixed resistance end of the sliding rheostat RP3, and the sliding end of the sliding rheostat RP3 is connected to the positive input end of the operational amplifier U1.1 as the first output end Uin1 of the Wheatstone bridge circuit;

[0014] The output terminal OUT- and the output terminal OUT+ of the Hall current sensor U3 are connected to the resistor R19 and the resistor R20 respectively. The other ends of the resistor R19 and the resistor R20 are respectively connected to the fixed resistance ends of the sliding resistor RP4. The sliding end of the sliding resistor RP4 serves as the second output terminal Uin2 of the Wheatstone bridge circuit and is connected to the positive input terminal of the operational amplifier U1.4; the two output terminals of the Wheatstone bridge circuit are filtered by capacitors C13 and C14 respectively.

[0015] A signal processing method for a non-switching high-precision and large-range current measuring device is provided. Based on the non-switching high-precision and large-range current measuring device, in the MCU of the non-switching high-precision and large-range current measuring device, the current input value at the current moment is estimated according to the current input value at the previous moment, and the accuracy of the current input value at the current moment is judged, and the output value is predicted and updated to filter out the interference of noise on the true value. The method specifically includes the following steps:

[0016] Step 1. Set the parameters of the circuit system according to the non-switching high-precision large-range current measurement device: process noise Q, sensor measurement noise R, and initial estimate value X 0 ;

[0017] Step 2. Based on the parameters set in step 1, calculate the current estimated value X according to the following formula: i :

[0018] X i =X' i-1 +Q

[0019] Among them, X' i-1 Indicates the estimated value after the last moment update, based on the current moment estimated value X i Calculate the gain K of the circuit system g :

[0020]

[0021] Gain K g Indicates the proportion of the current estimate in the sum of the sensor measurement noise R and the current estimate, which serves as the weight of the current estimate and the measurement data;

[0022] Step 3. Calculate the current output value out based on the gain obtained in step 2 i :

[0023] out i =out i-1 +K g (input i -out i-1 )

[0024] Among them, input i is the input value at the current moment, out i-1 is the output value of the previous moment, and out 0 is 0; and the estimated value X' at the current moment is updated according to the following formula i Calculation for the next moment:

[0025] X' i =(1-K g )X i ;

[0026] Step 4. Repeat steps 2 and 3 to estimate the dynamic response of the circuit system in a recursive manner to reduce the error between the estimated value and the true value, so that effective noise filtering can be achieved under the condition of interference without switching the high-precision and large-range current measurement device.

[0027] In summary, the invention has the following beneficial effects:

[0028] The present invention adopts an open-loop design to achieve the measurement of 0-200A current without switching the range. The measurement resolution is 0.001A, and the measurement accuracy can reach 1%±6mA, realizing the independence of domestic high-precision measurement equipment. The Hall current sensor is used as the main measurement unit, which can accurately detect the magnetic field generated by the current, and through the optimized circuit structure and signal processing flow, the noise interference is effectively filtered out, thereby improving the measurement accuracy. At the same time, the high-precision AD conversion unit and the digital signal processing unit are used to further process the collected data in a fine manner to ensure the accuracy of the output current signal.

[0029] The present invention uses a symmetrical Hall chip design, a Wheatstone bridge circuit design, and a differential input amplifier circuit design to cancel external magnetic field interference signals, so that only the magnetic field signal generated by the current change is collected and converted with high precision and then sent to the MCU for processing, thereby improving the measurement accuracy and data stability of the present invention; the present invention combines a hardware filtering circuit with a digital filtering method to ensure the stability of the measurement data of the measuring device.

[0030] The present invention realizes high-precision sampling of tiny current analog signals through a high-sensitivity signal sampling unit, and adds a two-stage passive filtering circuit in the signal sampling unit to filter out most of the noise in the analog signal. The digital signal processing method is used in the MCU to filter the digital current data with higher precision, and the digital signal processing technology is applied to the field of current detection. By optimizing the detection circuit structure and signal processing flow, high-precision and high-efficiency current measurement is achieved. The present invention can adapt to complex and changeable measurement environments and the increasing measurement accuracy requirements, and provides an efficient and reliable current detection solution for the power industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of the detection method of the present invention;

[0032] Figure 2 is a block diagram of the detection system of the present invention;

[0033] Figure 3 This is a circuit diagram of the signal acquisition part of the present invention;

[0034] Figure 4 This is the differential amplifier circuit diagram;

[0035] Figure 5 This is the passive filter circuit diagram;

[0036] Figure 6 It is a comparison diagram of the data after filtering by the signal processing method of the present invention (the red curve in the figure) and the original data without filtering (the blue curve in the figure). DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0038] It should be noted that, for the sake of convenience, the directions described below are consistent with the directions of the drawings themselves, but do not limit the structure of the present invention.

[0039] like Figures 1 to 6 As shown, the present invention discloses a non-switching high-precision and large-range current measuring device, comprising a main measuring unit, a signal acquisition unit, a signal amplification and filtering circuit unit, a high-precision AD conversion unit, an MCU for collecting high-precision data, and a digital signal processing unit. The main measuring unit comprises two Hall current sensors, and the two Hall current sensors are respectively located at the two ends of the opening and closing clamp heads of the current clamp. In this embodiment, the two Hall current sensors are respectively placed at the air gaps at the two ends of the opening and closing clamp heads to collect the magnetic flux density generated by the leakage magnetic field at the gap, thereby generating a Hall potential, and the Hall potential generated by the magnetic flux density at the gap is detected by the two Hall current sensors.

[0040] The signal input end of the signal acquisition unit is connected to the signal output end of the main measurement unit, and the influence of lateral offset and longitudinal displacement on the detection accuracy is reduced through the Wheatstone bridge circuit. The lateral offset represents the offset distance of the detected wiring harness relative to the central axis of the magnetic core gap in the axial direction of the wiring harness itself, and the longitudinal displacement represents the displacement distance of the detected wiring harness relative to the magnetic core gap in the axial direction of the wiring harness itself, so as to avoid the influence of the potential change caused by the Hall current sensor at one end and the Hall current sensor at the other end on the measurement value; the signal acquisition unit includes four resistors and two sliding rheostats, and the output end OUT- and the output end OUT+ of the Hall current sensor U4 are connected to the resistor R17 and the resistor R18 respectively, and the resistor R 17 and the other end of resistor R18 are respectively connected to the fixed resistance end of sliding rheostat RP3, and the sliding end of sliding rheostat RP3 is connected to the positive input end of operational amplifier U1.1 as the first output end Uin1 of Wheatstone bridge circuit; the output end OUT- and output end OUT+ of Hall current sensor U3 are respectively connected to resistor R19 and resistor R20, and the other ends of resistor R19 and resistor R20 are respectively connected to the fixed resistance end of sliding rheostat RP4, and the sliding end of sliding rheostat RP4 is connected to the positive input end of operational amplifier U1.4 as the second output end Uin2 of Wheatstone bridge circuit; the two output ends of Wheatstone bridge circuit are filtered through capacitor C13 and capacitor C14 respectively. The bridge structure reduces the accuracy drift problem of Hall current sensor caused by temperature change, superimposes the potential change of two Hall current sensors, and greatly reduces the accuracy impact caused by the lateral offset and longitudinal displacement of the wire harness at the gap of clamp head magnetic core, thereby improving the collection sensitivity of the circuit.

[0041] The signal amplification and filtering circuit unit includes a signal amplification part and a signal filtering part. The input end of the signal amplification part is connected to the output end of the signal acquisition unit. The output signal of the signal acquisition unit is transmitted to the signal filtering part after signal amplification to obtain a smooth Hall potential signal. The operational amplifier of the signal amplification and filtering circuit unit adopts a dual power supply mode, which is suitable for the high-sensitivity signal generated by the above-mentioned signal acquisition unit. The signal amplification part is divided into two stages. The first stage constitutes a unit gain follower to amplify the differential voltage gain coefficient and increase the common mode rejection ratio. The second stage constitutes a differential amplifier circuit to filter out the common mode interference in the signal and increase the sensitivity of the signal acquisition system. The signal filtering part is divided into two stages. The first stage filters the signal collected by the above-mentioned signal amplification part to obtain a relatively smooth Hall potential signal. The second stage amplifies the above-mentioned smooth Hall potential signal and filters it again to finally obtain a smoother Hall potential signal.

[0042] The high-precision AD conversion unit converts the analog signal of the Hall potential signal output by the signal amplification and filtering circuit unit into a digital signal that meets the accuracy requirement through a programmable high-precision conversion unit, thereby achieving a current resolution of 0.001A within a range of 200A. The current resolution of the present invention is significantly better than that of existing products, and the conversion of the waveform signal of the analog quantity to the high-precision data of the digital quantity is completed; the high-precision data of the signal conversion is collected by using the MCU; in this embodiment, the current resolution is 0.001A, and the high-precision AD conversion unit adopts a programmable high-precision conversion unit to meet the accuracy requirement. In this embodiment, the programmable high-precision conversion unit adopts ADS1263.

[0043] The digital signal processing unit filters the high-precision data converted by the MCU to obtain a stable digital signal, and performs data calibration to obtain an accurate current signal. Due to the high-precision AD conversion, the tiny fluctuations in the signal will become huge with the accuracy of the acquisition. The digital signal processing unit will filter the huge tiny fluctuations to obtain a stable digital signal, and perform data calibration to obtain an accurate current signal.

[0044] The non-switching high-precision and large-range current measuring device also includes a wireless transmission and display unit. The wireless transmission unit sends the acquired accurate current signal data to the host computer through the wireless transmission unit, and displays the current signal data in the host computer. In this embodiment, wireless WiFi is used to send data to a computer host or a mobile phone or other device that can realize wireless communication. The data can be displayed on the acquisition device, and the data can also be sent to the host computer wirelessly, and the host computer can perform operations such as storage, display, and data query.

[0045] Figure 3It is a signal acquisition and Hall element power supply unit, wherein the right end circuit of Hall current sensor U3 and Hall current sensor U4 is a Hall element constant current source power supply circuit, wherein the voltage VDD+ is connected to the positive power supply terminal of operational amplifier U2, and GND is connected to the negative power supply terminal of operational amplifier U2, forming a single power supply mode, so that the output range of operational amplifier U2 is within the reference voltage. The voltage VCC1.2V is the reference voltage, wherein resistor R28 and resistor R16 are voltage divider resistors, and the clutter after the voltage VCC1.2V voltage division is filtered out by filter capacitor C10. Since the output of operational amplifier U2 is affected by the input voltage, the output end of operational amplifier U2 can also obtain a stable output voltage. Among them, capacitor C21 and capacitor C22 are also filter capacitors, which provide a stable output voltage for operational amplifier U2. According to the concept of virtual short and virtual disconnection, resistor R15 is a current limiting resistor, and the size of resistor R15 can limit the current value of the constant current source. The left ends of Hall current sensor U3 and Hall current sensor U4 are connected to the signal output end of the main measurement unit through a Wheatstone bridge circuit. Due to the limitations of the manufacturing process of the Hall current sensor, there are some errors in the internal resistance and it is also easily affected by temperature. When the power supply part of the circuit is turned on, when the input signal is zero, the output Hall electromotive force is not zero. Therefore, it is necessary to design a zero adjustment circuit to suppress temperature drift and zero drift and achieve zero input and zero output. Among them, the resistors R17, R18, R19, and R20 and the sliding rheostats RP3 and RP4 form a Wheatstone bridge structure, and the two Hall elements are connected to the two input ends of the Wheatstone bridge respectively. This structure can offset the temperature drift of the Hall current sensor and superimpose the Hall potential changes of the Hall elements, thereby improving the sensitivity of the circuit system. The output ends of the sliding rheostats RP3 and RP4 can be zeroed under zero input to compensate for the internal defects of the Hall current sensor. The function of capacitors C13 and C14 is filtering, providing stable analog signals for subsequent circuits.

[0046] Figure 4It is a differential amplifier circuit structure, connected to the output end of the Wheatstone bridge circuit, wherein the capacitors C17, C18, C19, and C20 function as filters, providing stable voltages for the operational amplifiers of the differential amplifier circuit and the active filter circuit. The power supply mode of the differential amplifier circuit is a dual power supply mode, which is commonly used in high-precision, high-performance circuits to improve the stability and reliability of the circuit. The feedback end of the output of the operational amplifier U1.4 uses a parallel structure of resistor R21 and capacitor C15, which can improve the stability of the operational amplifier. The connection mode of the operational amplifier U1.1 and the capacitor C16 and resistor R22 is similar to that of the operational amplifier U1.4. The structure of the operational amplifier U1.1, the operational amplifier U1.4, and the resistor R23 constitutes a unit gain follower. The common mode signal passes through the input follower with a unit gain, the gain coefficient of the differential voltage is amplified, and the common mode rejection ratio of the circuit is increased. The outputs of operational amplifier U1.1 and operational amplifier U1.2 respectively pass through resistors R24 and R25 to enter the input end of operational amplifier U1.2, forming a differential amplifier circuit to filter out common-mode interference in the signal and increase the sensitivity of the signal acquisition system. After filtering out common-mode interference, the signal Uout1 passes through resistor R35 and enters a two-stage passive filtering circuit, that is, resistor R35, resistor R36, capacitor C7, and capacitor C8 form a first-stage passive filter. After the filtered signal is amplified by a multiple of R34 / R33 through the amplifier circuit formed by operational amplifier U1.3, it is output to a high-precision AD conversion unit after passing through a second-stage passive filter of resistors R31, resistor R32, capacitor C23, and capacitor C24. Figure 4 The differential amplifier circuit and Figure 5 In the passive filtering circuit, the power supply connection method of the four operational amplifiers is the same. In actual use, a device in which four operational amplifiers are integrated in one chip can be used.

[0047] The present invention also discloses a signal processing method for a non-switching high-precision and large-range current measuring device. Based on the non-switching high-precision and large-range current measuring device, in the MCU of the non-switching high-precision and large-range current measuring device, the current input value at the current moment is estimated according to the current input value at the previous moment, and the accuracy of the current input value at the current moment is judged, and the output value is predicted and updated to filter out the interference of noise on the true value. Specifically, the method includes the following steps:

[0048] Step 1. Set the parameters of the circuit system according to the non-switching high-precision large-range current measurement device: process noise Q, sensor measurement noise R, and initial estimate value X 0 The three parameters can be adjusted according to the specific settings of the circuit system. The sensor measurement noise R is an estimated value, that is, the size of R is estimated by comparing the sensor measurement value with the standard current source setting value.

[0049] Step 2. Based on the parameters set in step 1, calculate the current estimated value X according to the following formula: i :

[0050] X i =X' i-1 +Q

[0051] Among them, X' i-1 Indicates the estimated value after the last moment update, based on the current moment estimated value X i Calculate the gain K of the circuit system g :

[0052]

[0053] Gain K g Indicates the proportion of the current estimate in the sum of the sensor measurement noise R and the current estimate, which serves as the weight of the current estimate and the measurement data;

[0054] Step 3. Calculate the current output value out based on the gain obtained in step 2 i :

[0055] out i =out i-1 +K g (input i -out i-1 )

[0056] Among them, input i is the input value at the current moment, out i-1 is the output value of the previous moment, and out 0 is 0, that is, the output is 0 when there is no input signal; and the estimated value X' at the current moment is updated according to the following formula i Calculation for the next moment:

[0057] X' i =(1-K g )X i ;

[0058] Step 4. Repeat steps 2 and 3 to estimate the dynamic response of the circuit system in a recursive manner to reduce the error between the estimated value and the true value. The output value is corrected and continuously updated based on the difference and gain between the measurement data obtained by the sensor and the input and output, so that effective noise filtering can be achieved without switching the high-precision and large-range current measurement device in the presence of interference.

[0059] like Figure 6As shown, by comparing the data filtered by the signal processing method of the present invention (the red curve in the figure) with the original data without filtering (the blue curve in the figure), it can be clearly seen that the method of the present invention eliminates the spike signal in the signal. Compared with the original data, the curve trend is obviously flat, and the noise is effectively filtered out. The present invention realizes the accurate collection and efficient processing of a wide range of current signals, and improves the accuracy and stability of the non-switching high-precision and large-range current measurement device of the present invention.

[0060] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A non-switching high-precision large-range current measuring device, characterized in that: It includes a main measurement unit, a signal acquisition unit, a signal amplification and filtering circuit unit, a high-precision AD conversion unit, an MCU for collecting high-precision data, and a digital signal processing unit, among which: The main measuring unit includes two Hall current sensors, which are respectively located at the two ends of the opening and closing clamp heads of the current clamp, and the Hall potential generated by the magnetic flux density at the gap is detected by the two Hall current sensors; The signal input end of the signal acquisition unit is connected to the signal output end of the main measurement unit, and the influence of the lateral offset and the longitudinal displacement on the detection accuracy is reduced by the Wheatstone bridge circuit. The lateral offset represents the offset distance of the detected wire harness in the direction of the axis of the wire harness itself relative to the central axis of the magnetic core gap, and the longitudinal displacement represents the displacement distance of the detected wire harness in the direction of the axis of the wire harness itself relative to the magnetic core gap. The signal amplification and filtering circuit unit includes a signal amplification part and a signal filtering part, the input end of the signal amplification part is connected to the output end of the signal acquisition unit, and the output signal of the signal acquisition unit is transmitted to the signal filtering part after signal amplification to obtain a smooth Hall potential signal; The high-precision AD conversion unit converts the Hall potential analog signal output by the signal amplification and filtering circuit unit into a digital signal that meets the accuracy requirements through a programmable high-precision conversion unit, achieving a current resolution of 0.001A within a 200A range; and uses the MCU to collect high-precision data after the signal conversion has been completed; The digital signal processing unit filters the high-precision data collected by the MCU to obtain a stable digital signal, and performs data calibration to obtain an accurate current signal.

2. The non-switching high-precision and large-range current measuring device according to claim 1, characterized in that: It also includes a wireless transmission and display unit, which sends the acquired accurate current signal data to a host computer through the wireless transmission unit, and displays the current signal data in the host computer.

3. The non-switching high-precision and large-range current measuring device according to claim 1, characterized in that: The signal acquisition unit includes four resistors and two sliding rheostats. The output terminal OUT- and the output terminal OUT+ of the Hall current sensor U4 are connected to the resistor R17 and the resistor R18 respectively. The other ends of the resistors R17 and R18 are connected to the fixed resistance ends of the sliding rheostat RP3 respectively. The sliding end of the sliding rheostat RP3 is connected to the positive input end of the operational amplifier U1.1 as the first output end Uin1 of the Wheatstone bridge circuit. The output terminal OUT- and the output terminal OUT+ of the Hall current sensor U3 are connected to the resistor R19 and the resistor R20 respectively. The other ends of the resistor R19 and the resistor R20 are respectively connected to the fixed resistance ends of the sliding resistor RP4. The sliding end of the sliding resistor RP4 serves as the second output terminal Uin2 of the Wheatstone bridge circuit and is connected to the positive input terminal of the operational amplifier U1.4; the two output terminals of the Wheatstone bridge circuit are filtered by capacitors C13 and C14 respectively.

4. A signal processing method for a non-switching high-precision large-range current measuring device, based on the non-switching high-precision large-range current measuring device according to any one of claims 1 to 3, characterized in that: In the MCU of the non-switching high-precision large-range current measurement device, the current input value at the current moment is estimated based on the current input value at the previous moment, and the accuracy of the current input value at the current moment is judged, and the output value is predicted and updated to filter out the interference of noise on the true value. Specifically, the following steps are included: Step 1. Set the parameters of the circuit system according to the non-switching high-precision large-range current measurement device: process noise Q, sensor measurement noise R, and initial estimation value X0; Step 2. Based on the parameters set in step 1, calculate the current estimated value X according to the following formula: i : X i =X’ i-1 +Q Among them, X' i-1 Indicates the estimated value after the last moment update, based on the current moment estimated value X i Calculate the gain K of the circuit system g : Gain K g Indicates the proportion of the current estimate in the sum of the sensor measurement noise R and the current estimate, which serves as the weight of the current estimate and the measurement data; Step 3. Calculate the current output value out based on the gain obtained in step 2 i : out i =out i-1 +K g (input i -out i-1 ) Among them, input i is the input value at the current moment, out i-1 is the output value of the previous moment, and out0 is 0; and the estimated value X' of the current moment is updated according to the following formula i Calculation for the next moment: X’ i =(1-K g )X i ; Step 4. Repeat steps 2 and 3 to estimate the dynamic response of the circuit system in a recursive manner to reduce the error between the estimated value and the true value, so that effective noise filtering can be achieved under the condition of interference without switching the high-precision and large-range current measurement device.

Images