Measurement device, measurement method, and program

Abstract

This measurement device comprises a first input circuit provided with a first input terminal to which a first signal indicating the magnitude of a potential generated in a measurement object is input, an input resistor having one end connected to the first input terminal, and a first resistor having one end connected to the other end of the input resistor and the other end connected to a reference potential. The measurement device further comprises a second input circuit provided with a second input terminal to which a second signal indicating the magnitude of a current flowing to the measurement object is input, and calculates a physical quantity of the measurement object on the basis of the output signals of the first input circuit and the second input circuit. The measurement device performs processing for compensating for the capacitance parasitic to the input resistance and the frequency characteristics of a filter composed of the input resistor and the first resistor, with respect to the output signal of the second input circuit.

Description

Measurement device, measurement method, and program

[0001] The present invention relates to a measurement device, a measurement method, and a program for calculating a physical quantity of a measurement object.

[0002] JP2008-175532A discloses a measuring device that calculates power based on a voltage signal output from a voltage detection unit and a current signal output from a current detection unit.

[0003] Among the measuring devices described above, there are some in which the amplitude level of the voltage signal is larger than the amplitude level of the current signal, and such measuring devices often have an input resistor arranged as an attenuator to attenuate the amplitude level of the input voltage signal.

[0004] However, increasing the resistance of the attenuator increases the effect of the frequency characteristics of the filter formed by the resistance and parasitic capacitance of the attenuator, impairing the frequency characteristics of the voltage signal. As a result, in the band where the frequency characteristics of the voltage signal are impaired, a phase shift occurs between the voltage signal output from the voltage detection unit and input to the measurement device through the attenuator and the current signal output from the current detection unit and input directly to the measurement device, resulting in a problem of reduced measurement accuracy of the physical quantities calculated from the voltage signal and the current signal.

[0005] The present invention has been made in view of these problems, and has as its object to suppress a decrease in measurement accuracy caused by a parasitic capacitance in an input resistor such as an attenuator.

[0006] According to one aspect of the present invention, a measurement device includes a first input circuit having a first input terminal to which a first signal indicating the magnitude of a potential generated in an object to be measured is input, an input resistor having one end connected to the first input terminal, and a first resistor having one end connected to the other end of the input resistor and the other end connected to a reference potential.The measurement device further includes a second input circuit having a second input terminal to which a second signal indicating the magnitude of a current flowing through the object to be measured is input, and a calculation means for calculating a physical quantity of the object to be measured based on output signals from the first input circuit and the second input circuit.The measurement device also includes a compensation means for processing the output signal from the second input circuit to compensate for a parasitic capacitance of the input resistor and the frequency characteristics of a filter formed by the input resistor and the first resistor.

[0007] According to the above aspect, the compensation means adds the frequency characteristics of the filter constituted by the input resistance, the first resistance, and the parasitic capacitance of the first input circuit to the output signal of the second input circuit, thereby reducing the difference in frequency characteristics between the first input circuit and the second input circuit.

[0008] Therefore, the phase shift between the output signal of the first input circuit and the output signal of the second input circuit used in the calculation of the physical quantity is reduced, and the physical quantity of the measurement target can be measured with high accuracy. In other words, it is possible to suppress a decrease in measurement accuracy caused by the parasitic capacitance of an input resistor such as an attenuator.

[0009] FIG. 1 is a diagram showing the configuration of a measurement device according to a first embodiment. FIG. 2 is a circuit diagram showing the circuit configuration of two channel input sections of the measurement device. FIG. 3 is a circuit diagram showing an example configuration of an LPF circuit in the two channel input sections. FIG. 4 is a diagram for explaining the frequency characteristics of a compensation circuit provided in a second input section that compensates for deterioration in frequency characteristics due to parasitic capacitance of an input resistor provided in a first input section. FIG. 5 is a flowchart showing an example of a measurement method executed by the measurement device. FIG. 6 is a diagram showing the configuration of a measurement device according to a second embodiment. FIG. 7 is a circuit diagram showing an example configuration of a compensation LPF circuit provided in the second input section. FIG. 8 is a diagram showing the configuration of a measurement device according to a third embodiment. FIG. 9 is a diagram showing the configuration of a measurement device according to a fourth embodiment.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this specification, the same or equivalent elements are designated by the same reference numerals throughout.

[0011] First Embodiment FIG. 1 is a circuit diagram showing the circuit configuration of a measurement device according to a first embodiment.

[0012] The measurement device 1 of the first embodiment is a device for measuring electrical signals input to multiple channels, and measures the physical quantity of a measurement object. Examples of the measurement object include an electric wire that transmits electric power, a power conversion device, and a power supply device. The measurement object in the first embodiment is an electric wire.

[0013] The physical quantity (measurement quantity) measured by the measurement device 1 includes the power and power efficiency of the measurement target, the impedance of the measurement target, and the phase difference between input signals. In the first embodiment, the measurement quantity is the magnitude of the power transmitted to the electric wire.

[0014] The measuring device 1 is a computer configured with a processor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, and a bus connecting these to each other, etc. Examples of the processor include a CPU (Central Processing Unit) and an MPU (Micro Processor Unit).

[0015] The measurement device 1 includes a voltage channel input unit 10 , a current channel input unit 20 , a processing unit 30 , a storage unit 40 , a display unit 50 , and an operation unit 60 .

[0016] The voltage channel input unit 10 converts an analog input signal, which indicates the magnitude of the potential generated in the measurement target, into a digital signal, and outputs the converted digital signal to the processing unit 30 as voltage measurement data.

[0017] The current channel input section 20 converts an analog input signal indicating the magnitude of the current flowing through the object to be measured into a digital signal, and outputs the converted digital signal to the processing section 30 as current measurement data.

[0018] The processing unit 30 calculates the physical quantity of the measurement target based on the output signals of the voltage channel input unit 10 and the current channel input unit 20. The processing unit 30 of the first embodiment calculates the power transmitted to the electric wire that is the measurement target. The processing unit 30 is configured with one or more processors.

[0019] The storage unit 40 stores, for example, the calculation results obtained by the processing unit 30, the measurement conditions, etc. The storage unit 40 also stores a program for controlling the operation of the measurement device 1. The storage unit 40 is a computer-readable recording medium on which the program is recorded, and is composed of a ROM and a RAM.

[0020] The display unit 50 displays the measurement results or measurement conditions. The display unit 50 is configured, for example, as a touch panel so that the user can view information and operate it. Alternatively, the display unit 50 may be configured as a liquid crystal display, an LED display, or the like.

[0021] The operation unit 60 is configured by a plurality of push buttons provided around the display screen, a touch sensor arranged within the display screen, a keyboard, a mouse, etc. The operation unit 60 receives input operations from the user and generates an operation signal indicating the content of the received input operation.

[0022] Examples of input operations include pressing the power button, setting measurement conditions and display conditions, and issuing an instruction to start or end the measurement process. The operation unit 60 outputs the generated operation signal to the processing unit 30.

[0023] FIG. 2 is a circuit diagram showing an example of the circuit configuration of the voltage channel input section 10 and the current channel input section 20. As shown in FIG.

[0024] As shown in FIG. 2, a voltage signal Sv is input to the voltage channel input section 10 of the first embodiment, and a current signal Si is input to the current channel input section 20.

[0025] The voltage signal Sv is a first signal that indicates the magnitude of the potential generated in the measurement object. In the first embodiment, the voltage signal Sv is a voltage detection signal that is output from a clip or a terminal that extracts the voltage of the electric wire. In the first embodiment, the amplitude level of the voltage signal Sv is larger than the amplitude level of the current signal Si.

[0026] The current signal Si is a second signal indicating the magnitude of the current flowing through the object to be measured. In the first embodiment, the current signal Si is a current detection signal output from a current sensor that detects the current flowing through the electric wire to be measured. For example, a current sensor that detects the current flowing through the electric wire in a non-contact manner while the electric wire is clamped is used as the current sensor.

[0027] The voltage terminal 1A of the voltage channel input unit 10 is a first input terminal to which a voltage signal Sv is input, and the current terminal 1B of the current channel input unit 20 is a second input terminal to which a current signal Si is input.

[0028] A voltage signal Sv having a frequency of, for example, 1 Hz to several MHz is input to the voltage terminal 1A. The magnitude of the voltage signal Sv in the first embodiment is a high voltage of several hundred V to several kV.

[0029] The voltage channel input unit 10 receives a voltage signal Sv, converts the analog voltage signal Sv into a digital voltage value, and outputs voltage measurement data. The voltage channel input unit 10 of the first embodiment includes an input circuit 11, an LPF circuit 12, and an AD converter 13.

[0030] The input circuit 11 is a first input circuit that includes a voltage terminal 1A to which a voltage signal Sv from a voltage sensor is input, an input resistor 111 having one end connected to the voltage terminal 1A, and a first resistor 112 having one end connected to one end of the input resistor 111 and the other end connected to a reference potential G.

[0031] The input circuit 11 of the first embodiment functions as a voltage measurement circuit that measures the output voltage of a voltage sensor, and includes an input resistor 111 , a first resistor 112 , and a buffer circuit 113 .

[0032] The input resistor 111 is an electric resistor to which the voltage signal Sv is input from the voltage terminal 1A, and a parasitic capacitance Cp that is parasitic on the input resistor 111 is added to the input resistor 111 .

[0033] Since the amplitude level of the voltage signal Sv is larger than that of the current signal Si, the input resistor 111 is used to attenuate the amplitude level of the voltage signal Sv so that the amplitude level of the voltage signal Sv falls within the input range of the buffer circuit 113. The resistance values ​​of the input resistor 111 and the first resistor 112 in the first embodiment are determined to be magnitudes such that the signal level of the voltage signal Sv is attenuated to a level equivalent to the input level of the input circuit 21.

[0034] The input resistor 111 is composed of one or more resistive elements, and is realized by, for example, a general resistor or a high-voltage resistor that can be used at a voltage higher than the withstand voltage of a general resistor. The input resistor 111 in the first embodiment is configured by a high-voltage resistor having a resistance value in the range of several hundred kΩ to several MΩ.

[0035] In order to increase the resistance value, the high-voltage resistor described above has a serpentine resistor pattern with many folded portions between the electrodes so that the path of the resistor pattern is long. As a result, many capacitive couplings are continuously distributed between the many folded portions formed in the resistor pattern and the reference potential G, like a distributed constant circuit.

[0036] In this way, in the high-voltage resistor, many parasitic capacitance components are continuously formed between the electrodes, and therefore, the combined capacitance resulting from the combination of many capacitive couplings is shown as parasitic capacitance Cp in Fig. 1. The combined value of the parasitic capacitance Cp in the first embodiment has a capacitance value of, for example, several pF.

[0037] The presence of this parasitic capacitance Cp impairs the frequency characteristics of the input resistor 111. Specifically, the flatness of the frequency characteristics of the voltage channel input unit 10 deteriorates due to the frequency characteristics of the filter (RC circuit) formed by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112. For example, the frequency characteristics of the voltage channel input unit 10 deteriorate from around several hundred kHz or several MHz.

[0038] The frequency characteristics referred to here include frequency characteristics of amplitude and phase. In the following, the filter formed by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 is also referred to as a parasitic filter.

[0039] The first resistor 112 is an electrical resistor for dividing the voltage signal Sv. The resistance value of the first resistor 112 is designed according to the resistance value of the input resistor 111 so that the level of the attenuated voltage signal Sv divided by the input resistors 111 and 112 is within the input range of the buffer circuit 113. The resistance value of the first resistor 112 in the first embodiment is set to a magnitude within a range of, for example, several hundred Ω to one hundred kΩ.

[0040] The buffer circuit 113 amplifies the voltage generated across the first resistor 112 as an attenuated voltage signal Sv with a predetermined gain for converting the detected value into a measured value, and outputs the amplified voltage signal Sv to the LPF circuit 12 as a voltage measurement signal.

[0041] Next, a description will be given of the connection configuration of the input circuit 11. In the input circuit 11, the voltage terminal 1A is connected to one end of an input resistor 111, which is an input terminal, and the other end of the input resistor 111, which is an output terminal, is connected to one end of a first resistor 112 and an input terminal of a buffer circuit 113. The other end of the first resistor 112 is connected to a reference potential G.

[0042] The LPF circuit 12 is an analog circuit that functions as a first filter means that performs low-pass filtering on the output signal of the input circuit 11. The LPF circuit 12 is connected to the output terminal of the input circuit 11 and is a filter circuit intended to suppress aliasing noise (anti-aliasing).

[0043] The LPF circuit 12 of the first embodiment is an anti-aliasing filter that serves to suppress the generation of aliasing noise in the AD converter 13. The LPF circuit 12 is configured by, for example, a second-order low-pass filter circuit. In the first embodiment, the LPF circuit 12 is realized by an active filter having an active element.

[0044] For example, the LPF circuit 12 is configured by a second-order VCVS (Voltage Controlled Voltage Source) filter. An example of the configuration of the LPF circuit 12 will be described later with reference to Fig. 3. The LPF circuit 12 outputs the voltage measurement signal after low-pass filtering to the AD converter 13.

[0045] The AD converter 13 converts the output signal of the LPF circuit 12 from an analog signal to a digital signal, and outputs the converted digital signal indicating the measurement value of the voltage signal Sv to the processing unit 30 as voltage measurement data.

[0046] Next, the configuration of the current channel input section 20 will be described.

[0047] The current channel input unit 20 receives the current signal Si, converts the analog current signal Si into a digital voltage value, and outputs the resulting current measurement data. The current channel input unit 20 of the first embodiment includes an input circuit 21, a compensation circuit 22, an LPF circuit 23, and an AD converter 24.

[0048] The input circuit 21 is a second input circuit including a current terminal 1B to which a current signal Si from the current sensor is input. The input circuit 21 of the first embodiment functions as a measurement circuit that measures the output voltage of the current sensor, and includes a buffer circuit 211.

[0049] The buffer circuit 211 amplifies the voltage generated across the first resistor 112 as a current signal Si with a predetermined gain for converting the detected value into a measured value, and outputs the amplified current signal Si to the compensation circuit 22 as a current measurement signal.

[0050] As for the connection configuration of the input circuit 21, the input terminal of a buffer circuit 211 is connected to the current terminal 1B, and the output terminal of the buffer circuit 211 constitutes the output terminal of the input circuit 21.

[0051] The circuit constants of the buffer circuit 211 of the first embodiment are designed so that the frequency characteristics are equivalent to those of the buffer circuit 113. The input circuit 21 may be configured using a shunt resistor instead of the buffer circuit 211. A resistive element may be connected between the input terminal of the buffer circuit 211 and the reference potential G.

[0052] The compensation circuit 22 functions as a compensation means that performs processing on the output signal of the input circuit 21 to compensate for the parasitic capacitance Cp that is parasitic on the input resistor 111 of the input circuit 11, and the frequency characteristics of the parasitic filter formed by the input resistor 111 and the first resistor 112.

[0053] The compensation circuit 22 in the first embodiment is realized by an analog LPF circuit. It is desirable that the compensation circuit 22 be realized by an active filter that performs first-order low-pass filtering on the input signal so as to reduce the difference in frequency characteristics between the output signals of the input circuits 11 and 21 caused by the parasitic capacitance Cp.

[0054] As a specific example, the compensation circuit 22 shown in FIG. 2 includes a resistor element 221 , a capacitor 222 , and a buffer circuit 223 .

[0055] The resistance value of the resistor element 221 and the capacitance value of the capacitor 222 are determined so that the frequency characteristics of the compensation circuit 22 match the frequency characteristics of the parasitic filter made up of the parasitic capacitance Cp, the input resistor 111 and the first resistor 112 .

[0056] For example, the resistance value of the resistor element 221 is set to a value within a range from several kΩ to several tens of kΩ so as to suppress the generation of thermal noise in the resistor element 221. On the other hand, the capacitance value of the capacitor 222 is set to a value of, for example, several tens of pF according to the resistance value of the resistor element 221 so that the frequency characteristics of the compensation circuit 22 are equivalent to the frequency characteristics of the parasitic filter.

[0057] As a specific example, when the circuit constants are designed so that the cutoff frequency of the compensation circuit 22 is 720 kHz, the resistance value of the resistor element 221 is set to 10 kΩ and the capacitance value of the capacitor 222 is set to 22 pF.

[0058] The compensation circuit 22 is connected in such a manner that one end of a resistor element 221 is connected to the output end of a buffer circuit 211 of the input circuit 21, and the other end of the resistor element 221 is connected to one end of a capacitor 222 and the input end of a buffer circuit 223. The other end of the capacitor 222 is connected to a reference potential G.

[0059] The compensation circuit 22 performs a first-order low-pass filtering process on the current measurement signal output from the input circuit 21. The compensation circuit 22 then outputs the processed current measurement signal to the LPF circuit .

[0060] The LPF circuit 23 is an analog circuit that performs low-pass filtering on the output signal of the compensation circuit 22. Like the LPF circuit 12, the LPF circuit 23 serves as an anti-aliasing filter.

[0061] The configuration of the LPF circuit 23 in the first embodiment is the same as the configuration of the LPF circuit 12. The LPF circuit 23 outputs to the AD converter 24 a current measurement signal that has been subjected to low-pass filtering.

[0062] The AD converter 24 converts the output signal of the LPF circuit 23 from an analog signal to a digital signal, and outputs the converted digital signal indicating the measurement value of the current signal Si to the processing unit 30 as current measurement data.

[0063] The processing unit 30 functions as a calculation means for calculating the physical quantity of the measurement object based on the output signals of the input circuit 11 and the input circuit 21 .

[0064] The processing unit 30 of the first embodiment calculates the physical quantity of the object to be measured based on the voltage measurement data output from the voltage channel input unit 10 and the current measurement data output from the current channel input unit 20. Specifically, the processing unit 30 calculates the magnitude of the transmission power of the electric wire to be measured using the voltage value indicated in the voltage measurement data and the current value indicated in the current measurement data.

[0065] Furthermore, the processing unit 30 may calculate the phase difference between the voltage signal Sv and the current signal Si using the voltage value indicated in the voltage measurement data and the current value indicated in the current measurement data.

[0066] For example, when the measurement target is an electric storage device such as a secondary battery or a fuel cell, the processing unit 30 may calculate the internal impedance of the electric storage device using the voltage measurement data and the current measurement data.

[0067] In addition, the compensation circuit 22 in the first embodiment is configured as an RC circuit having a resistive element 221 and a capacitor 222, but it may also be configured as an RL circuit having a resistor and a coil, or may be configured by combining a resistive element, a capacitor, and a coil.

[0068] Next, the LPF circuit 12 and the LPF circuit 23 will be described with reference to Fig. 3. As described above, the circuit configuration of the LPF circuit 12 and the circuit configuration of the LPF circuit 23 are the same, and therefore the circuit configurations are shown in the same drawing.

[0069] 3 is a circuit diagram showing the circuit configuration of the LPF circuits 12 and 23. Each of the LPF circuits 12 and 23 includes a resistor element 121, a resistor element 122, a capacitor 123, a capacitor 124, and an operational amplifier 125.

[0070] First, in the LPF circuit 12, one end of the resistor element 121 is connected to the output terminal of the buffer circuit 113, and the other end of the resistor element 121 is connected to one end of the resistor element 122 and one end of the capacitor 123. The other end of the resistor element 122 is connected to one end of the capacitor 124 and the non-inverting input terminal (+) of the operational amplifier 125, and the other end of the capacitor 124 is connected to the reference potential G.

[0071] The other end of the capacitor 123 is connected to the inverting input terminal (−) and output terminal of an operational amplifier 125 , and the output terminal of the operational amplifier 125 is connected to the input terminal of the AD converter 13 .

[0072] Next, the LPF circuit 23 has the same connection configuration as the LPF circuit 12 described above, except that one end of the resistor element 121 is connected to the buffer circuit 211 and the output terminal of the operational amplifier 125 is connected to the AD converter 24.

[0073] In the first embodiment, the resistance value of each of the resistor elements 121 and 122 is set to several kΩ, and the capacitance value of each of the capacitors 123 and 124 is set to several hundred pF.

[0074] As a specific example, when the circuit constants are designed so that the cutoff frequency of the LPF circuits 12 and 23 is 1 MHz and the Q value is 0.70, the resistance values ​​of the resistive elements 121 and 122 are set to 1 kΩ, the capacitance value of the capacitor 123 is set to approximately 200 pF, and the capacitance value of the capacitor 124 is set to approximately 100 pF.

[0075] In the first embodiment, the voltage channel input section 10 and the current channel input section 20 are provided with the LPF circuits 12 and 23, respectively, to suppress the occurrence of aliasing noise, but these may be omitted. For example, if the circuit configuration is such that aliasing does not occur, the LPF circuits 12 and 23 can be omitted.

[0076] Next, the frequency characteristics of the input circuit 11 obtained by simulation analysis will be described with reference to FIG.

[0077] FIG. 4 is a diagram showing the frequency characteristics of the output signals of the input circuit 11 and the compensation circuit 22. As shown in FIG.

[0078] The simulation conditions for the input circuit 11 were as follows: for the input resistor 111 having five resistor elements connected in series, the capacitance values ​​of the parasitic capacitance connected in parallel to each resistor element and the parasitic capacitance occurring between each resistor element and the reference potential G were both 0.4 pF, and the capacitance value of the parasitic capacitance connected in parallel to the first resistor 112 was 0.4 pF. In addition, the resistance values ​​of each resistor element and the first resistor 112 were both 100 kΩ.

[0079] The simulation conditions for the compensation circuit 22 were that the resistance value of the resistor element 221 was 10 kΩ and the capacitance value of the capacitor 222 was 22 pF.

[0080] In Figure 4, the frequency characteristics of the amplitude and phase of the output signal from input circuit 11 are shown by thick dashed lines and thin dashed lines, respectively, and the frequency characteristics of the amplitude and phase of the output signal from compensation circuit 22 are shown by thick solid lines and thin solid lines, respectively.

[0081] As a comparative example, the frequency characteristics of the amplitude and phase of the output signal of the input circuit 21 before compensation processing for the frequency characteristics caused by the parasitic capacitance Cp is shown by a thick dashed line and a thin dashed line, respectively.

[0082] As shown in FIG. 4, the frequency characteristics of the output signal of the input circuit 11, indicated by the dashed line, are attenuated in the high frequency band compared to the frequency characteristics of the output signal of the input circuit 21, which has not been subjected to compensation processing, indicated by the dotted line as a comparative example.

[0083] To address this issue, the output signal of the input circuit 21 is filtered by the compensation circuit 22, which constitutes a primary low-pass filter, so that the frequency characteristics of the output signal of the compensation circuit 22, shown by the solid line, roughly match the frequency characteristics of the output signal of the input circuit 11.

[0084] The frequency characteristics of the output signal of the input circuit 11 correspond to the frequency characteristics of a parasitic filter composed of the parasitic capacitance Cp, the input resistor 111, and the first resistor 112, and the frequency characteristics of this parasitic filter are accurately approximated by configuring the compensation circuit 22 as a first-order low-pass filter.

[0085] Therefore, the inventors have found that the frequency characteristics of the parasitic filter in the input circuit 11 can be realized with at least the frequency characteristics of a first-order low-pass filter.

[0086] In this way, in the first embodiment, by configuring the compensation circuit 22 with a first-order low-pass filter, it is possible to compensate for the frequency characteristics of the parasitic filter in the output signal of the input circuit 21 so that the frequency characteristics of the parasitic filter are taken into account in the current channel input section 20.

[0087] Next, the operation of the measurement device 1 in the first embodiment will be described with reference to FIG.

[0088] 5 is a flowchart showing an example of the processing procedure of the measurement method executed by the measurement device 1. Here, the voltage sensor outputs a voltage signal Sv indicating the magnitude of the voltage generated in the object to be measured, and the current sensor outputs a current signal Si indicating the magnitude of the current flowing through the object to be measured.

[0089] In step S1, a voltage signal Sv output from a voltage sensor is input to a voltage terminal 1A connected to the input end of the input resistor 111 of the input circuit 11 including the input resistor 111 and the first resistor 112 in the measuring device 1.

[0090] In step S2, the current signal Si output from the current sensor is input to the current terminal 1B of the input circuit 21 in the measuring device 1.

[0091] In step S3, the measurement device 1 performs compensation processing on the output signal of the input circuit 21 to compensate for the parasitic capacitance Cp parasitic on the input resistor 111 and the frequency characteristics of a parasitic filter formed by the input resistor 111 and the first resistor 112. The measurement device 1 of the first embodiment performs first-order low-pass filtering on the output signal of the input circuit 21 as compensation processing.

[0092] In step S4, the measurement device 1 calculates the physical quantity of the measurement object based on the output signal of the input circuit 11 and the output signal of the input circuit 21 that has been subjected to compensation processing in step S3.

[0093] In the first embodiment, the measurement device 1 performs low-pass filtering on the output signal of the input circuit 11 using the LPF circuit 12, and converts the output signal after low-pass filtering into a digital signal using the AD converter 13 to generate voltage measurement data.

[0094] The measuring device 1 then performs low-pass filtering on the compensated output signal of the input circuit 21 using the LPF circuit 23, and converts the low-pass filtered output signal into a digital signal using the AD converter 24 to generate current measurement data. Furthermore, the measuring device 1 uses the generated voltage measurement data and current measurement data to calculate the magnitude of the power transmitted to the electric wire being measured.

[0095] When the process of step S4 is completed, the series of processing steps of the measurement method according to the first embodiment is completed.

[0096] Next, the effects of the first embodiment will be described.

[0097] In the first embodiment, the measurement device 1 includes an input circuit 11, an input circuit 21, and a processing unit 30. The input circuit 11 configures a first input circuit including a voltage terminal 1A corresponding to a first input terminal to which a voltage signal Sv is input as a first signal indicating the magnitude of the potential generated in the measurement object, an input resistor 111 having one end connected to the voltage terminal 1A, and a first resistor 112 having one end connected to the other end of the input resistor 111 and the other end connected to a reference potential G.

[0098] The input circuit 21 constitutes a second input circuit including a current terminal 1B corresponding to a second input terminal to which a current signal Si is input as a second signal indicating the magnitude of a current flowing through the object to be measured. The processing unit 30 functions as a calculation means for calculating the physical quantity of the object to be measured based on the output signals of the input circuit 11 and the input circuit 21.

[0099] The measuring device 1 further includes a compensation circuit 22 that functions as a compensation means for performing processing on the output signal of the input circuit 21 to compensate for the parasitic capacitance Cp that is parasitic on the input resistor 111 and the frequency characteristics of the filter formed by the input resistor 111.

[0100] Moreover, in the first embodiment, the measurement method includes a first input step (S1) in which a voltage signal Sv is input as a first signal to the input terminal of the input resistor 111 of the input circuit 11 having the input resistor 111 and the first resistor 112, and a second input step (S2) in which a current signal Si is input as a second signal to the input circuit 21.

[0101] The measurement method further includes a compensation step (S3) of processing the output signal of the input circuit 21 to compensate for the frequency characteristics of the filter formed by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112, and a calculation step (S4) of calculating the physical quantity of the object to be measured based on the output signal of the input circuit 11 and the output signal of the input circuit 21 processed in the compensation step (S3).

[0102] Furthermore, the computer of the measuring device 1 that executes the program in the first embodiment acquires an output signal from the input circuit 11 to which the voltage signal Sv is input as a first signal to the input terminal of the input resistor 111, and an output signal from the input circuit 21 to which the current signal Si is input as a second signal. The above program is a program for causing the computer of the measuring device 1 to execute the compensation step (S3) and the calculation step (S4) described above.

[0103] According to these configurations, the compensation circuit 22 or the compensation step (S3) adds the frequency characteristics of the filter formed by the input resistance 111, the first resistance 112, and the parasitic capacitance Cp of the input circuit 11 to the output signal of the input circuit 21. This makes it possible to reduce the difference in frequency characteristics between the input circuit 11 and the input circuit 21.

[0104] Therefore, the phase shift between the output signal of the input circuit 11 and the output signal of the input circuit 21 used in the calculation of the physical quantity is reduced, and the physical quantity of the measurement target can be measured with high accuracy. In other words, the deterioration of measurement accuracy caused by the parasitic capacitance Cp of the input resistor 111 can be suppressed.

[0105] Furthermore, the compensation circuit 22 of the first embodiment performs first-order low-pass filtering on the output signal of the input circuit 21 .

[0106] The reason for this configuration will be briefly explained. In the input circuit 11, although the frequency characteristics of the input resistor 111 are deteriorated due to the presence of the parasitic capacitance Cp, it is possible to accurately approximate this with a first-order low-pass filter, as shown in FIG.

[0107] Therefore, as described above, by employing a first-order low-pass filter as compensation circuit 22, it is possible to improve the degree of agreement between the frequency characteristics of the output signal of compensation circuit 22 and the frequency characteristics of the output signal of input circuit 21, compared to a case in which a first-order low-pass filter is not employed. Therefore, it is possible to suppress the phase shift between the measured amount of voltage signal Sv and the measured amount of current signal Si.

[0108] Furthermore, the resistance values ​​of the input resistor 111 and the first resistor 112 in the first embodiment are set to magnitudes such that the input level of the input circuit 11 (voltage signal Sv) is attenuated to a level equivalent to the input level of the input circuit 21 (current signal Si) when output from the other end of the input resistor 111 by voltage division by the input resistor 111 and the first resistor 112.

[0109] This configuration eliminates the need to attenuate the input signal in the compensation circuit 22, and also makes it possible to use the same element values ​​of the LPF circuit 23 as those of the LPF circuit 12 in the voltage channel input unit 10, and to use the same AD converter 24 as the AD converter 13 in the voltage channel input unit 10. This facilitates the circuit design of the compensation circuit 22, the LPF circuit 23, and the AD converter 24.

[0110] Second Embodiment Next, a measurement device according to a second embodiment will be described with reference to FIG.

[0111] 6 is a circuit diagram showing the circuit configuration of a measurement device 2 according to the second embodiment. The second embodiment differs from the first embodiment in that the function of the compensation circuit 22 of the first embodiment is integrated into an LPF circuit 23.

[0112] The measuring device 2 includes a current channel input unit 20A instead of the current channel input unit 20 shown in Fig. 1. Note that the same components as those in the measuring device 1 of the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0113] The current channel input section 20A includes an input circuit 21 having the same configuration as that of the first embodiment, and also includes a compensation LPF circuit 25 instead of the compensation circuit 22 and LPF circuit 23 of the first embodiment.

[0114] The compensation LPF circuit 25 functions as a compensation unit that performs a process to compensate for the frequency characteristics of a parasitic filter formed by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112, similar to the compensation circuit 22 of the first embodiment.

[0115] The compensation LPF circuit 25 of the second embodiment performs low-pass filtering of an order (N+1) that is one order larger than the order N of the LPF circuit 12 serving as the first filter means, on the output signal of the input circuit 21. Note that N, which indicates the order, is a positive integer.

[0116] The compensation LPF circuit 25 is an active filter circuit connected to the output terminal of the input circuit 21 and having an operational amplifier as an active element. The LPF circuit 12 of the second embodiment is configured by a second-order low-pass filter circuit as shown in FIG.

[0117] For example, the compensation LPF circuit 25 is configured by a third-order Geffe-type low-pass filter circuit which is one order larger than the order of the LPF circuit 12. An example of the configuration of the compensation LPF circuit 25 will be described with reference to FIG.

[0118] FIG. 7 is a circuit diagram showing an example of the circuit configuration of the compensation LPF circuit 25. As shown in FIG.

[0119] As shown in FIG. 7, the compensation LPF circuit 25 includes a resistor element 251 and a capacitor 252 in addition to the configuration of the LPF circuit 23 of the first embodiment shown in FIG.

[0120] The circuit constants of the compensation LPF circuit 25 are designed based on the cutoff frequency of the first transfer function representing the frequency characteristics of the compensation circuit 22 of the first embodiment shown in FIG. 1 and the cutoff frequency and Q value of the second transfer function representing the frequency characteristics of the LPF circuit 12.

[0121] Specifically, a third-order transfer function is obtained using the cutoff frequency of the first-order transfer function of the compensation circuit 22 and the cutoff frequency and Q value of the second-order transfer function of the LPF circuit 12. Then, the circuit constants of the compensation LPF circuit 25 are determined using the cutoff frequency and Q value of the third-order transfer function.

[0122] For example, the resistance value of each of the resistor elements 121, 122, and 251 is set to several kΩ, the capacitance value of each of the capacitors 123 and 252 is set to several hundred pF, and the capacitance value of the capacitor 124 is set to several tens pF.

[0123] As a specific example, it is assumed that the circuit constants are designed so that the cutoff frequency of the first-order characteristic of compensation circuit 22 is 720 kΩ, the cutoff frequency of the second-order characteristic of LPF circuit 12 is 1 MHz, and the Q value is 0.70. In this case, the resistance values ​​of resistor elements 121, 122, and 251 are each set to 1 kΩ, the capacitance value of capacitor 123 is set to approximately 350 pF, the capacitance value of capacitor 124 is set to approximately 60 pF, and the capacitance value of capacitor 252 is set to approximately 260 pF.

[0124] The compensation LPF circuit 25 of the second embodiment may be configured with a coil and a resistance element instead of the resistance element 251 and the capacitor 252, or may be configured with a circuit that combines a resistance element, a capacitor, and a coil.

[0125] Next, the effects of the second embodiment will be described.

[0126] The measurement device 2 of the second embodiment includes, as in the first embodiment, an input circuit 11 and an input circuit 21. The measurement device 2 further includes an LPF circuit 12 and a compensation LPF circuit 25.

[0127] At this time, the LPF circuit 12 functions as a first filter means that performs low-pass filtering on the output signal of the input circuit 11. Furthermore, the compensation LPF circuit 25 functions as a compensation means that performs low-pass filtering on the output signal of the input circuit 21, the order of which is one higher than that of the LPF circuit 12.

[0128] According to this configuration, the compensation LPF circuit 25 has an order one higher than that of the LPF circuit 12, and therefore it is possible to take into account the frequency characteristics of a first-order parasitic filter composed of the parasitic capacitance Cp, the input resistance 111, and the first resistance 112 in relation to the frequency characteristics of the LPF circuit 12.

[0129] This allows the output signal of the input circuit 21 to be subjected to low-pass filtering equivalent to that of the LPF circuit 12, while taking into account the frequency characteristics of the parasitic filter. Therefore, as in the first embodiment, the difference between the frequency characteristics of the output signal of the compensation LPF circuit 25 and the frequency characteristics of the output signal of the LPF circuit 12 is reduced, thereby improving measurement accuracy.

[0130] In the second embodiment, the LPF circuit 12 is a filter circuit connected to the input circuit 11 to suppress the generation of aliasing noise, and the compensating LPF circuit 25 is an active filter circuit connected to the input circuit 21 and having an operational amplifier 125 as an active element.

[0131] According to this configuration, the LPF circuit 12 suppresses the occurrence of aliasing noise, while the compensating LPF circuit 25 suppresses the influence of the parasitic capacitance Cp, thereby improving measurement accuracy.

[0132] In addition, by employing an active filter circuit as the compensation LPF circuit 25, it is possible to form complex frequency characteristics. Therefore, even if the LPF circuit 12 has a frequency characteristic of second order or higher, it is possible to accurately approximate the frequency characteristics of the output signal of the LPF circuit 12. Therefore, it is possible to suppress a decrease in measurement accuracy due to the inaccuracy in adjusting the frequency characteristics of the compensation LPF circuit 25.

[0133] More specifically, in the second embodiment, the LPF circuit 12 is configured as a second-order low-pass filter circuit, and the compensation LPF circuit 25 is configured as a third-order Geffe-type low-pass filter circuit.

[0134] According to this configuration, the compensation LPF circuit 25 can be realized by including only one operational amplifier 125 as an active element, as shown in Fig. 7. In contrast, the compensation circuit 22 and LPF circuit 23 (see Fig. 2) of the first embodiment, which have the two functions of the compensation LPF circuit 25, require two active elements: a buffer circuit 223 and an operational amplifier 125.

[0135] In this way, by employing a third-order Geffe-type low-pass filter circuit as the compensation LPF circuit 25, the number of active elements is reduced compared to the circuit configuration of the first embodiment, making it possible to reduce an increase in offset within the circuit and the introduction of noise. In addition, because the number of active elements can be minimized, it is possible to reduce the size of the measuring device 2 and suppress increases in manufacturing costs.

[0136] Third Embodiment Next, a measurement device according to a third embodiment will be described with reference to Fig. 8. The third embodiment differs from the first embodiment in that the compensation circuit 22, the LPF circuit 12, and the LPF circuit 23 of the first embodiment shown in Fig. 1 are omitted, and the function of the compensation circuit 22 is provided in a processing unit 30.

[0137] FIG. 8 is a diagram showing the configuration of a measurement device 3 according to the third embodiment.

[0138] The measurement device 3 includes a voltage channel input unit 10A from which the LPF circuit 12 of the first embodiment has been eliminated, a current channel input unit 20B from which the compensation circuit 22 and the LPF circuit 23 of the first embodiment have been eliminated, and a processing unit 30A having the functions of the compensation circuit 22. In the following, to avoid redundant description, only the functional configuration of the processing unit 30A will be described.

[0139] The processing unit 30A is configured by one or more processors that perform digital processing. The processing unit 30A of the third embodiment includes a compensation unit 31 and a measurement amount calculation unit 32.

[0140] The compensation unit 31 functions as a compensation means that performs processing on the output signal of the input circuit 21 to compensate for the parasitic capacitance Cp that is parasitic on the input resistor 111 of the input circuit 11, and the frequency characteristics of the parasitic filter formed by the input resistor 111 and the first resistor 112.

[0141] Similar to the first embodiment, the compensator 31 of the third embodiment performs first-order low-pass filtering on the measured current data output from the current channel input unit 20B. For example, the compensator 31 executes compensation processing equivalent to the processing performed by the circuit configuration of the compensation circuit 22 shown in FIG. 1. The compensator 31 outputs the compensated measured current data to the measured quantity calculator 32.

[0142] The measurement quantity calculation unit 32 functions as a calculation means for calculating the physical quantity of the measurement object based on the output signals of the input circuit 11 and the input circuit 21 .

[0143] In the third embodiment, the measured quantity calculation unit 32 acquires voltage measurement data from the voltage channel input unit 10A and acquires compensated current measurement data from the compensation unit 31. Then, the measured quantity calculation unit 32 calculates the magnitude of power transmitted to the electric wire to be measured, using the voltage value indicated in the voltage measurement data and the current value indicated in the compensated current measurement data.

[0144] Furthermore, the measured quantity calculation unit 32 may calculate the phase difference between the voltage signal Sv and the current signal Si using the voltage value indicated in the voltage measurement data and the current value indicated in the compensated current measurement data. For example, if the measurement target is an energy storage device, the measured quantity calculation unit 32 may calculate the internal impedance of the energy storage device using the voltage measurement data and the compensated current measurement data.

[0145] Next, the effects of the third embodiment will be described.

[0146] The measuring device 3 of the third embodiment includes an input circuit 11, an input circuit 21, and a processing unit 30A including a compensation unit 31 and a measured quantity calculation unit 32. The measured quantity calculation unit 32 functions as a calculation means that calculates a physical quantity of the measurement object based on output signals from the input circuit 11 and the input circuit 21. The compensation unit 31 functions as a compensation means that performs processing on the output signal of the input circuit 21 that is input to the measured quantity calculation unit 32 to compensate for the frequency characteristics of a parasitic filter formed by the parasitic capacitance Cp, the input resistance 111, and the first resistance 112.

[0147] According to this configuration, similar to the first embodiment, it is possible to suppress the decrease in measurement accuracy caused by the parasitic capacitance Cp of the input resistor 111 compared to a functional configuration in which the compensation unit 31 does not perform compensation processing.

[0148] In addition, since the processing of the compensation circuit 22 is performed in the processing unit 30A that performs digital processing, unlike the first embodiment, there is no need to provide the compensation circuit 22. Therefore, increases in the size and manufacturing costs of the measurement device 3 can be suppressed.

[0149] Fourth Embodiment Next, a measurement device according to a fourth embodiment will be described with reference to Fig. 9. The fourth embodiment differs from the third embodiment in that, in addition to the functional configuration of the processing unit 30A of the third embodiment, a functional configuration is added that performs low-pass filtering on both the voltage measurement data and the current measurement data.

[0150] FIG. 9 is a diagram showing the configuration of a measurement device 4 according to the fourth embodiment.

[0151] The measuring device 4 includes a processing unit 30B instead of the processing unit 30A of the measuring device 3 of the third embodiment shown in Fig. 8. The processing unit 30B includes an LPF unit 311 and a compensation LPF unit 312 instead of the compensation unit 31 of the processing unit 30A. Note that the same components of the measuring device 4 as those of the measuring device 3 of the third embodiment shown in Fig. 8 are designated by the same reference numerals, and redundant explanations will be omitted.

[0152] The LPF unit 311 functions as a first filter means that performs low-pass filtering on the output signal of the input circuit 11. The LPF unit 311 plays a role in removing high-frequency noise contained in the voltage measurement data.

[0153] The LPF unit 311 of the fourth embodiment performs second-order low-pass filtering on the voltage measurement data output from the voltage channel input unit 10 A. As a specific example, the LPF unit 311 performs low-pass filtering on the voltage measurement data using the same circuit configuration as the LPF circuit 12 of the first embodiment.

[0154] The compensation LPF unit 312 functions as a compensation unit that performs processing to compensate for the frequency characteristics of the parasitic filter formed by the parasitic capacitance Cp, the input resistor 111 and the first resistor 112 on the output signal of the input circuit 21 .

[0155] For example, the compensation LPF unit 312 performs low-pass filtering on the output signal of the input circuit 21 with an order that is one order greater than the order of the LPF unit 311. As a specific example, the compensation LPF unit 312 performs low-pass filtering similar to that performed by a third-order Geffe-type low-pass filter circuit.

[0156] Next, the effects of the fourth embodiment will be described.

[0157] In the fourth embodiment, the LPF unit 311 functions as a first filter means that performs low-pass filtering on the output signal of the input circuit 11. The compensation LPF unit 312 functions as a compensation means that performs low-pass filtering on the output signal of the input circuit 21, the order of which is one order larger than that of the LPF unit 311.

[0158] According to this configuration, the LPF unit 311 can remove high-frequency noise that mixes into the output signal of the input circuit 11 from around the electric wire to be measured, or high-frequency noise that occurs in the input resistor 111 and the AD converter 24. Therefore, the measurement accuracy can be improved compared to a configuration that does not have the function of the LPF unit 311.

[0159] In addition, as in the second embodiment, the compensation LPF unit 312 applies low-pass filtering to the output signal of the input circuit 21 in the same manner as the LPF unit 311, and also takes into account the frequency characteristics of the parasitic filter caused by the parasitic capacitance Cp of the input resistor 111.

[0160] This removes high-frequency noise from each of the output signals of the input circuits 11 and 21, and reduces the phase shift between the output data of the LPF unit 311 and the compensation LPF unit 312 compared to the phase shift between the output signals of the input circuits 11 and 21. This makes it possible to improve the measurement accuracy of the physical quantity calculated based on the output signals of the input circuits 11 and 21.

[0161] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0162] For example, in the above embodiment, the number of current channel input units 20, 20A, or 20B is one, but multiple current channel input units 20, 20A, or 20B may be provided. Even in this case, phase shift between the multiple current channel input units 20, 20A, or 20B or the processing unit 30A or 30B and the voltage channel input unit 10 or 10A is suppressed, so that it is possible to accurately calculate the measured quantity.

[0163] Furthermore, although the compensation circuit 22 and the compensation LPF circuit 25 are configured with active filters in the first and second embodiments, this is not limiting. For example, if a passive filter can be used to approximate the frequency characteristics of the compensation circuit 22 and the compensation LPF circuit 25 to the frequency characteristics of a parasitic filter formed by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112, the compensation circuit 22 and the compensation LPF circuit 25 may be a passive filter.

[0164] Furthermore, in the first and second embodiments, the LPF circuit 12 is configured as a second-order low-pass filter, but this is not limiting, and a third-order or higher-order low-pass filter may be used as the LPF circuit 12. In this case, the compensation LPF circuit 25 may be a fourth-order or higher-order low-pass filter, and a low-pass filter other than a Geffe type may be used.

[0165] This application claims priority based on Japanese Patent Application No. 2023-122599, filed with the Japan Patent Office on July 27, 2023, the entire contents of which are incorporated herein by reference.

[0166] 1 to 4 Measuring device 1A Voltage terminal (first input terminal) 1B Current terminal (second input terminal) 11 Input circuit (first input circuit) 111 Input resistance 112 First resistance Cp Parasitic capacitance (capacitance parasitic on input resistance) 12 LPF circuit (first filter means, filter circuit, second-order low-pass filter circuit) 21 Input circuit (second input circuit) 22 Compensation circuit (compensation means) 25 Compensation LPF circuit (compensation means, active filter circuit, third-order Geffen-type low-pass filter circuit) 30, 30A, 30B Processing unit (computation means) 31 Compensation unit (compensation means) 32 Measurement quantity computation unit (computation means) 311 LPF unit (first filter means) 312 Compensation LPF unit (compensation means) S1 to S4 (first input step, second input step, compensation step, computation step)

Claims

1. A measuring device comprising: a first input circuit having a first input terminal to which a first signal indicating the magnitude of the potential generated in an object to be measured is input, an input resistor having one end connected to the first input terminal, and a first resistor having one end connected to the other end of the input resistor and the other end connected to a reference potential; a second input circuit having a second input terminal to which a second signal indicating the magnitude of a current flowing through the object to be measured is input; and a calculation means for calculating a physical quantity of the object to be measured based on output signals from the first input circuit and the second input circuit, and further comprising a compensation means for applying a process to the output signal from the second input circuit to compensate for a capacitance parasitic to the input resistor and a frequency characteristic of a filter formed by the input resistor and the first resistor.

2. A measuring device according to claim 1, wherein said compensation means performs a first-order low-pass filter process on the output signal of said second input circuit.

3. A measuring device as claimed in claim 1, further comprising a first filter means for applying low-pass filtering to the output signal of said first input circuit, and said compensation means for applying low-pass filtering to the output signal of said second input circuit, the order of which is one higher than that of said first filter means.

4. A measuring device according to claim 3, wherein the first filter means is a filter circuit connected to the first input circuit for suppressing aliasing noise, and the compensation means is an active filter circuit connected to the second input circuit and having an active element.

5. The measuring device according to claim 4, wherein the filter circuit is a second-order low-pass filter circuit, and the active filter circuit is a third-order Geffe-type low-pass filter circuit.

6. A measuring device according to any one of claims 1 to 3, wherein the compensation means is a processor that performs low-pass filtering on the output signal of the second input circuit as a process for compensating for the frequency characteristics of the filter.

7. A measuring device according to any one of claims 1 to 6, wherein the resistance values ​​of the input resistor and the first resistor are determined to be such that the input level of the first signal is attenuated to a level equivalent to the input level of the second input circuit when it is output from the other end of the input resistor.

8. A measurement method comprising: a first input step in which a first signal indicating a magnitude of a potential generated in an object to be measured is input to an end of an input resistor of a first input circuit having an input resistor and a first resistor having one end connected to one end of the input resistor and the other end connected to a reference potential; a second input step in which a second signal indicating a magnitude of a current flowing through the object to be measured is input to a second input circuit; a compensation step in which an output signal of the second input circuit is processed to compensate for a capacitance parasitic to the input resistor and a frequency characteristic of a filter formed by the input resistor and the first resistor; and a calculation step in which a physical quantity of the object to be measured is calculated based on the output signal of the first input circuit and the output signal of the second input circuit that has been processed in the compensation step.

9. A program for causing a computer to acquire an output signal from a first input circuit, which comprises an input resistor and a first resistor having one end connected to one end of the input resistor and the other end connected to a reference potential, and in which a first signal indicating the magnitude of a potential generated in an object to be measured is input to the other end of the input resistor, and an output signal from a second input circuit to which a second signal indicating the magnitude of a current flowing through the object to be measured is input, the program causing a computer to execute the following steps: a compensation step of performing a process on the output signal from the second input circuit to compensate for a capacitance parasitic to the input resistor and a frequency characteristic of a filter formed by the input resistor and the first resistor; and a calculation step of calculating a physical quantity of the object to be measured based on the output signal from the first input circuit and the output signal from the second input circuit that has been subjected to the process in the compensation step.

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