Measurement device, measurement method, and program

Abstract

A measurement device includes a first input circuit including: a first input terminal to which a first signal indicating a 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, one end of which is connected to the other end of the input resistor and the other end of which is connected to a reference potential. Furthermore, the measurement device includes a second input circuit including a second input terminal into which a second signal indicating a magnitude of a current flowing through the measurement object is input, and calculates a physical quantity of the measurement object on the basis of output signals of the first input circuit and the second input circuit. The measurement device performs processing for compensating for the frequency characteristics of a filter configured from the capacitance parasitizing the input resistor, the input resistor, and the first resistor on the output signal of the second input circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to a measurement device that operates a physical quantity of a measurement object, a measurement method, and a program. BACKGROUND

[0002] A measurement device disclosed in JP 2008-175532 A calculates electric power based on a voltage signal output from a voltage detection section and a current signal output from a current detection section. SUMMARY

[0003] In the measurement device described above, there is a measurement device in which the amplitude level of the voltage signal is larger than the amplitude level of the current signal, and in such a measurement device, an input resistor is often provided as an attenuator for attenuating the amplitude level of the input voltage signal.

[0004] However, if the resistance value of the attenuator is increased, the influence of the frequency characteristics of the filter composed of the resistance of the attenuator and the parasitic capacitance becomes large, and the frequency characteristics of the voltage signal are impaired. As a result, there is a problem in that a phase shift occurs between the voltage signal output from the voltage detection section and input to the measurement device through the attenuator and the current signal output from the current detection section and directly input to the measurement device in a frequency band in which the frequency characteristics of the voltage signal are impaired, and the measurement accuracy of the physical quantity calculated from the voltage signal and the current signal decreases.

[0005] The present application is completed in view of such a problem, and aims to suppress the decrease in measurement accuracy caused by the capacitance parasitic to the input resistor such as the attenuator.

[0006] According to one aspect of the present application, a measurement device includes a first input circuit including a first input terminal into which a first signal representing the magnitude of the potential generated at 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 also includes a second input circuit including a second input terminal into which a second signal representing the magnitude of the current flowing through the measurement object is input, and an operation unit that operates a physical quantity of the measurement object based on the output signals of the first input circuit and the second input circuit. The measurement device also includes a compensation unit that compensates the output signal of the second input circuit for the frequency characteristics of a filter composed of the capacitance parasitic to the input resistor, the input resistor, and the first resistor.

[0007] According to the above-described aspect, the frequency characteristic of the filter composed of the input resistance of the first input circuit, the first resistance, and the parasitic capacitance is added to the output signal of the second input circuit by the compensation unit, and thus the shift in the frequency characteristic between the first input circuit and the second input circuit can be reduced.

[0008] Therefore, the phase shift between the output signal of the first input circuit and the output signal of the second input circuit for the operation of the physical quantity is reduced, and thus the physical quantity of the measurement target can be measured with high accuracy. That is, the reduction in the measurement accuracy caused by the parasitic capacitance of the input resistance such as an attenuator can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a diagram showing the configuration of the measurement device of the first embodiment.

[0010] Figure 2 is a circuit diagram showing the circuit configuration of the two-channel input section of the measurement device.

[0011] Figure 3 is a circuit diagram showing a configuration example of the LPF circuit of the two-channel input section.

[0012] Figure 4 is a diagram for explaining the frequency characteristic of the compensation circuit provided in the second input section for compensating for the deterioration of the frequency characteristic caused by the parasitic capacitance of the input resistance provided in the first input section.

[0013] Figure 5 is a flowchart showing one example of the measurement method performed by the measurement device.

[0014] Figure 6 is a diagram showing the configuration of the measurement device of the second embodiment.

[0015] Figure 7 is a circuit diagram showing a configuration example of the compensation LPF circuit provided in the second input section.

[0016] Figure 8 is a diagram showing the configuration of the measurement device of the third embodiment.

[0017] Figure 9 is a diagram showing the configuration of the measurement device of the fourth embodiment. DETAILED DESCRIPTION

[0018] Hereinafter, each embodiment of the present application will be described with reference to the accompanying drawings. In the present specification, the same reference numerals are assigned to the same or equivalent elements throughout the specification.

[0019] (First embodiment) Figure 1is a circuit diagram showing a circuit configuration of the measurement device of the first embodiment.

[0020] The measurement device 1 of the first embodiment is a device for measuring an electric signal input to a plurality of channels, and measures a physical quantity of a measurement target. As the measurement target, for example, an electric wire, a power conversion device, a power supply device, and the like can be listed. The measurement target of the first embodiment is an electric wire.

[0021] As the physical quantity (measurement quantity) measured by the measurement device 1, a power and a power efficiency of the measurement target, an impedance of the measurement target, a phase difference between input signals, and the like can be listed. The measurement quantity of the first embodiment is a magnitude of a power transmitted to the electric wire.

[0022] The measurement device 1 is a computer configured of a processor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, a bus, and the like that connect them to each other. As the processor, a CPU (Central Processing Unit) or an MPU (Micro Processor Unit), and the like can be listed.

[0023] The measurement device 1 includes a voltage channel input section 10, a current channel input section 20, a processing section 30, a storage section 40, a display section 50, and an operation section 60.

[0024] The voltage channel input section 10 converts an analog input signal that represents a magnitude of an electric potential generated in the measurement target into a digital signal. The voltage channel input section 10 outputs the converted digital signal to the processing section 30 as voltage measurement data.

[0025] The current channel input section 20 converts an analog input signal that represents a magnitude of a current flowing through the measurement target into a digital signal. The current channel input section 20 outputs the converted digital signal to the processing section 30 as current measurement data.

[0026] The processing section 30 calculates a physical quantity of the measurement target on the basis of the output signals of the voltage channel input section 10 and the current channel input section 20. The processing section 30 of the first embodiment calculates a power transmitted to the electric wire that becomes the measurement target. The processing section 30 is configured of one or a plurality of processors.

[0027] The storage section 40 stores, for example, a calculation result and a measurement condition obtained by the processing section 30, and the like. Further, a program for controlling an operation of the measurement device 1 is stored in the storage section 40. The storage section 40 is a computer-readable recording medium in which the above program is recorded, and is configured of a ROM and a RAM.

[0028] The display section 50 displays the above-described measurement results or measurement conditions, and the like. The display section 50 is constituted of, for example, a touch panel so that a user can visually confirm information and the user can perform an operation. Alternatively, the display section 50 can be constituted of a liquid crystal display or an LED (Light-Emitting Diode) display, and the like.

[0029] The operation section 60 is constituted of a plurality of push-type buttons provided around a display screen, a touch sensor or a keyboard and a mouse disposed within the display screen, and the like. The operation section 60 accepts an input operation of a user, and generates an operation signal indicating the content of the accepted input operation.

[0030] As the input operation, for example, an operation of pressing a power button, an operation of setting a measurement condition and a display condition, and an operation of instructing the start or end of a measurement process, and the like can be cited. The operation section 60 outputs the generated operation signal to the processing section 30.

[0031] Figure 2 is a circuit diagram indicating one example of a circuit configuration of the voltage channel input section 10 and the current channel input section 20.

[0032] As shown in Figure 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.

[0033] The voltage signal Sv is a first signal indicating the magnitude of a potential generated at a measurement object. The voltage signal Sv of the first embodiment is a voltage detection signal output from a jig or a terminal, and the like that extracts the voltage of a wire. In the first embodiment, the amplitude level of the voltage signal Sv is larger than the amplitude level of the current signal Si.

[0034] The current signal Si is a second signal indicating the magnitude of a current flowing through a measurement object. The current signal Si of the first embodiment is a current detection signal output from a current sensor that detects the current flowing through a wire in a state where the wire is clamped. As the current sensor, for example, a current sensor that detects the current flowing through the wire in a non-contact manner in a state where the wire is clamped is used.

[0035] The voltage terminal 1A of the voltage channel input section 10 is a first input terminal for inputting the voltage signal Sv, and the current terminal 1B of the current channel input section 20 is a second input terminal for inputting the current signal Si.

[0036] The voltage signal Sv having a frequency of, for example, 1 [Hz] to several [MHz] is input to the voltage terminal 1A. Further, the magnitude of the voltage signal Sv of the first embodiment is a high voltage of several hundred [V] to several [kV].

[0037] The voltage channel input section 10 outputs voltage measurement data obtained by converting the analog voltage signal Sv into a digital voltage value by inputting the voltage signal Sv. The voltage channel input section 10 of the first embodiment has an input circuit 11, an LPF (Low Pass Filter) circuit 12, and an AD converter (Analog To Digital Converter) 13.

[0038] The input circuit 11 is a first input circuit having a voltage terminal 1A to which the voltage signal Sv from the 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.

[0039] The input circuit 11 of the first embodiment functions as a voltage measurement circuit that measures the output voltage of the voltage sensor, and has the input resistor 111, the first resistor 112, and a buffer circuit 113.

[0040] The input resistor 111 is an electrical resistor through which the voltage signal Sv is input from the voltage terminal 1A, and a parasitic capacitor Cp parasitic to the input resistor 111 is attached to the input resistor 111.

[0041] Since the amplitude level of the voltage signal Sv is larger than the amplitude level of the current signal Si, the input resistor 111 attenuates the amplitude level of the voltage signal Sv in such a manner that the amplitude level of the voltage signal Sv converges to the input range of the buffer circuit 113. The resistance values of the input resistor 111 and the first resistor 112 of the first embodiment are determined to be as large as the signal level of the voltage signal Sv is attenuated to a level equivalent to the input level of the input circuit 21.

[0042] The input resistor 111 is constituted by one or a plurality of resistor elements, and is realized by, for example, a general resistor or a high-voltage resistor that can be used at a higher voltage than a general resistor. The input resistor 111 of the first embodiment is constituted by a high-voltage resistor having a resistance value in the range of several [kΩ] to several [MΩ].

[0043] In order to increase the resistance value, the high-voltage resistor described above is formed with a meandering resistance pattern having a plurality of return portions between electrodes to make the path of the resistance pattern long. As a result, a plurality of capacitive couplings are continuously distributed like a distributed constant circuit between the plurality of return portions of the resistance pattern and the reference potential G.

[0044] As such, in the high-voltage resistor, a plurality of electrostatic capacitance components are continuously parasitic between the electrodes, and thus a plurality of capacitive couplings are continuously distributed between the plurality of return portions of the resistance pattern and the reference potential G. Figure 1In the first embodiment, the resultant capacitance of the plurality of capacitances coupled in series is expressed as a parasitic capacitance Cp. The resultant value of the parasitic capacitance Cp of the first embodiment has a capacitance value of several [pF], for example.

[0045] Due to the presence of the parasitic capacitance Cp, the frequency characteristic of the input resistor 111 is impaired. Specifically, due to the frequency characteristic possessed by a filter (RC circuit) constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112, the flatness of the frequency characteristic of the voltage channel input section 10 deteriorates. For example, the frequency characteristic of the voltage channel input section 10 starts to decrease from several [kHz] or several [MHz] or so.

[0046] The frequency characteristic referred to here includes the frequency characteristics of the amplitude and the phase. Also, hereinafter, the filter constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 will also be referred to as a parasitic filter.

[0047] The first resistor 112 is an electrical resistor for dividing the voltage signal Sv. The resistance value of the first resistor 112 is designed in accordance with the resistance value of the input resistor 111 so as to become an attenuation amount of the voltage signal Sv determined in such a manner that the level of the voltage signal Sv attenuated by the input resistor 111 and the first resistor 112 converges to the input range of the buffer circuit 113. The resistance value of the first resistor 112 of the first embodiment is determined to be a size in the range of several [Ω] to several [kΩ], for example.

[0048] The buffer circuit 113 amplifies the voltage generated across the first resistor 112 as the attenuated voltage signal Sv at a prescribed gain for conversion from a detection value to a measurement value, and outputs the amplified voltage signal Sv as a voltage measurement signal to the LPF circuit 12.

[0049] Next, the connection configuration of the input circuit 11 will be described. In the input circuit 11, the voltage terminal 1A is connected to the input terminal that is one end of the input resistor 111, and the output terminals that are the other end of the input resistor 111 are connected to one end of the first resistor 112 and the input terminal of the buffer circuit 113, respectively. Also, the other end of the first resistor 112 is connected to the reference potential G.

[0050] The LPF circuit 12 is an analog circuit that functions as a first filter unit that performs low-pass filter processing on the output signal of the input circuit 11. The LPF circuit 12 is a filter circuit connected to the output terminal of the input circuit 11 and aimed at suppressing aliasing noise (anti-aliasing).

[0051] The LPF circuit 12 in the first embodiment is an anti-aliasing filter that suppresses the generation of aliasing noise in the AD converter 13. The LPF circuit 12 is, for example, constructed from a second-order low-pass filter circuit. In the first embodiment, the LPF circuit 12 is implemented using an active filter with active elements.

[0052] For example, LPF circuit 12 is constructed from a second-order VCVS (Voltage Controlled Voltage Source) filter. An example of the configuration of LPF circuit 12 will be referred to later. Figure 3 The LPF circuit 12 outputs the low-pass filtered voltage measurement signal to the AD converter 13.

[0053] The AD converter 13 converts the output signal of the LPF circuit 12 from an analog signal to a digital signal. Then, the AD converter 13 outputs the converted digital signal representing the measured value of the voltage signal Sv to the processing unit 30 as voltage measurement data.

[0054] Next, the configuration of the current channel input section 20 will be explained.

[0055] The current channel input unit 20 outputs current measurement data obtained by converting the analog current signal Si into a digital voltage value through input current signal Si. 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.

[0056] The input circuit 21 is a second input circuit having a current terminal 1B for receiving the current signal Si from the current sensor. The input circuit 21 of the first embodiment functions as a measuring circuit for measuring the output voltage of the current sensor and includes a buffer circuit 211.

[0057] The buffer circuit 211 amplifies the voltage generated across the first resistor 112 as a current signal Si with a specified gain for converting the detected value into a measured value, and outputs the amplified current signal Si as a current measurement signal to the compensation circuit 22.

[0058] As part of the connection configuration of the input circuit 21, the input terminal of the 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.

[0059] For the buffer circuit 211 of the first embodiment, the circuit constants are designed in such a manner that the frequency characteristic becomes identical to that of the buffer circuit 113. Note that the input circuit 21 can also be constituted by a shunt resistor instead of the buffer circuit 211. Further, a resistive element can also be connected between the input terminal of the buffer circuit 211 and the reference potential G.

[0060] The compensation circuit 22 functions as a compensation unit that compensates for the frequency characteristic of the parasitic filter constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 parasitic to the input resistor 111 of the input circuit 11, with respect to the output signal of the input circuit 21.

[0061] The compensation circuit 22 of the first embodiment is implemented by an analog LPF circuit. Ideally, the compensation circuit 22 is implemented by an active filter that performs a first-order low-pass filter process on the input signal to make the frequency characteristics of the output signals of the input circuits 11 and 21 deviate from each other due to the parasitic capacitance Cp smaller.

[0062] As a specific example, Figure 2 The compensation circuit 22 shown in the drawing includes a resistive element 221, a capacitor 222, and a buffer circuit 223.

[0063] The resistance value of the resistive element 221 and the capacitance value of the capacitor 222 are determined in such a manner that the frequency characteristic of the compensation circuit 22 coincides with that of the parasitic filter constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112.

[0064] For example, the resistance value of the resistive element 221 is determined to be in the range of several [kΩ] to several tens of [kΩ] to suppress the generation of thermal noise in the resistive element 221. On the other hand, the capacitance value of the capacitor 222 is determined to be, for example, several tens of [pF] depending on the resistance value of the resistive element 221 to make the frequency characteristic of the compensation circuit 22 identical to that of the parasitic filter.

[0065] As a specific example, in a case where the circuit constants are designed in such a manner that the cutoff frequency of the compensation circuit 22 is 720 [kHz], the resistance value of the resistive element 221 is determined to be 10 [kΩ], and the capacitance value of the capacitor 222 is determined to be 22 [pF].

[0066] As a connection configuration of the compensation circuit 22, one end of the resistive element 221 is connected to the output terminal of the buffer circuit 211 of the input circuit 21, and the other end of the resistive element 221 is connected to one end of the capacitor 222 and the input terminal of the buffer circuit 223. Further, the other end of the capacitor 222 is connected to the reference potential G.

[0067] The compensation circuit 22 performs first-order low-pass filter processing on the current measurement signal output from the input circuit 21. Then, the compensation circuit 22 outputs the processed current measurement signal to the LPF circuit 23.

[0068] The LPF circuit 23 is an analog circuit that performs low-pass filter processing on the output signal of the compensation circuit 22. The LPF circuit 23 functions as an anti-aliasing filter in the same manner as the LPF circuit 12.

[0069] The configuration of the LPF circuit 23 of the first embodiment is the same as that of the LPF circuit 12. The LPF circuit 23 outputs the current measurement signal on which low-pass filter processing has been performed to the AD converter 24.

[0070] The AD converter 24 converts the output signal of the LPF circuit 23 from an analog signal to a digital signal. Then, the AD converter 24 outputs the converted digital signal that represents the measured value of the current signal Si to the processing section 30 as current measurement data.

[0071] The processing section 30 functions as an arithmetic unit that calculates a physical quantity of a measurement target based on the output signals of the input circuit 11 and the input circuit 21.

[0072] The processing section 30 of the first embodiment calculates a physical quantity of a measurement target based on the voltage measurement data output from the voltage channel input section 10 and the current measurement data output from the current channel input section 20. Specifically, the processing section 30 calculates the magnitude of the transmission power of an electric wire that is a measurement target using the voltage value indicated by the voltage measurement data and the current value indicated by the current measurement data.

[0073] In addition, the processing section 30 can calculate the phase difference between the voltage signal Sv and the current signal Si using the voltage value indicated by the voltage measurement data and the current value indicated by the current measurement data.

[0074] For example, in the case where the measurement target is an electric storage device such as a secondary battery or a fuel cell, the processing section 30 can calculate the internal impedance of the electric storage device using the voltage measurement data and the current measurement data.

[0075] Note that the compensation circuit 22 of the first embodiment is configured by an RC circuit having a resistance element 221 and a capacitor 222, but can be configured by an RL circuit having a resistance and a coil, or can be configured by combining a resistance element, a capacitor, and a coil.

[0076] Next, the LPF circuit 12 and the LPF circuit 23 will be described with reference to Figure 3 The LPF circuit 12 and the LPF circuit 23 will be described. As described above, the circuit configuration of the LPF circuit 12 is the same as that of the LPF circuit 23, and thus the circuit configurations are shown in the same drawing.

[0077] Figure 3 is a circuit diagram showing the circuit configuration of the LPF circuits 12 and 23. The LPF circuits 12 and 23 each have a resistance element 121, a resistance element 122, a capacitor 123, a capacitor 124, and an operational amplifier 125.

[0078] First, with respect to the LPF circuit 12, one end of the resistance element 121 is connected to the output terminal of the buffer circuit 113, and the other end of the resistance element 121 is connected to one end of the resistance element 122 and one end of the capacitor 123, respectively. The other end of the resistance element 122 is connected to one end of the capacitor 124 and the non-inverting input terminal (+) of the operational amplifier 125, respectively, and the other end of the capacitor 124 is connected to the reference potential G.

[0079] Further, the other end of the capacitor 123 is connected to the inverting input terminal (-) and the output terminal of the operational amplifier 125, respectively, and the output terminal of the operational amplifier 125 is connected to the input terminal of the AD converter 13.

[0080] Next, with respect to the LPF circuit 23, the connection configuration is the same as that of the above-described LPF circuit 12, except that one end of the resistance 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.

[0081] In the first embodiment, the resistance values of the resistance elements 121 and 122 are each determined to be several [kΩ], and the capacitance values of the capacitors 123 and 124 are each determined to be several hundred [pF].

[0082] As a specific example, in a case where the circuit constants are designed in a manner such that the cutoff frequencies of the LPF circuits 12 and 23 are 1 [MHz] and the Q value is 0.70, the resistance values of the resistance elements 121 and 122 are determined to be 1 [kΩ], the capacitance value of the capacitor 123 is determined to be about 200 [pF], and the capacitance value of the capacitor 124 is determined to be about 100 [pF].

[0083] Note that, in the first embodiment, the LPF circuits 12 and 23 are provided in the voltage channel input section 10 and the current channel input section 20, respectively, in order to suppress the generation of aliasing noise, but they can be omitted. For example, if the circuit configuration does not cause aliasing, the LPF circuits 12 and 23 can be omitted.

[0084] Next, with reference to Figure 4 The frequency characteristics of the input circuit 11 obtained by the simulation analysis will be described.

[0085] Figure 4 is a graph showing the frequency characteristics of each output signal of the input circuit 11 and the compensation circuit 22.

[0086] The simulation conditions of the input circuit 11 are such that the capacitance values of the parasitic capacitances connected in parallel to each of the resistance elements and the parasitic capacitances generated between each of the resistance elements and the reference potential G are each set to 0.4 [pF], and the capacitance value of the parasitic capacitance connected in parallel to the first resistance 112 is set to 0.4 [pF], with respect to the input resistance 111 in which five resistance elements are connected in series.

[0087] Further, the simulation conditions of the compensation circuit 22 are such that the resistance value of the resistance element 221 is set to 10 [kΩ], and the capacitance value of the capacitor 222 is set to 22 [pF].

[0088] In Figure 4 , the frequency characteristics of the amplitude and the phase related to the output signal of the input circuit 11 are indicated by a thick broken line and a thin broken line, respectively, and the frequency characteristics of the amplitude and the phase related to the output signal of the compensation circuit 22 are indicated by a thick solid line and a thin solid line, respectively.

[0089] Further, as a comparative example, the frequency characteristics of the amplitude and the phase related to the output signal of the input circuit 21 before the compensation processing of the frequency characteristics caused by the parasitic capacitance Cp is implemented are indicated by a thick one-dot chain line and a thin one-dot chain line, respectively.

[0090] As Figure 4 indicated, the frequency characteristics of the output signal of the input circuit 11 indicated by a broken line attenuate in a high frequency band, as compared with the frequency characteristics of the output signal of the input circuit 21 indicated by one-dot chain lines as a comparative example, which is not implemented with the compensation processing.

[0091] As a measure thereof, the input signal of the input circuit 21 is implemented with the filter processing in the compensation circuit 22 which constitutes a low-pass filter of the first order, and thus the frequency characteristics of the input signal of the compensation circuit 22 indicated by a solid line are substantially identical to the frequency characteristics of the input signal of the input circuit 11.

[0092] The frequency characteristics of the output signal of the input circuit 11 correspond to the frequency characteristics of a parasitic filter constituted by the parasitic capacitance Cp, the input resistance 111, and the first resistance 112, and the frequency characteristics of the parasitic filter are approximated with high precision by constituting the compensation circuit 22 with a low-pass filter of the first order.

[0093] Therefore, the inventors have insight that the frequency characteristics of the parasitic filter in the input circuit 11 can be implemented with the frequency characteristics of at least a low-pass filter of the first order.

[0094] In this way, in the first embodiment, by the compensation circuit 22 being constituted by a first-order low-pass filter, the output signal of the input circuit 21 can be compensated for the frequency characteristics of the parasitic filter in a manner that the frequency characteristics of the parasitic filter are added to the input section 20 of the current channel.

[0095] Next, the operation of the measurement device 1 of the first embodiment will be described with reference to Figure 5 The operation of the measurement device 1 of the first embodiment will be described with reference to

[0096] Figure 5 is a flowchart showing an example of the processing procedure of the measurement method performed by the measurement device 1. Here, a voltage signal Sv representing the magnitude of the voltage generated at the measurement object is output from the voltage sensor, and a current signal Si representing the magnitude of the current flowing through the measurement object is output from the current sensor.

[0097] In step S1, the voltage signal Sv output from the voltage sensor is input to the voltage terminal 1A in the measurement device 1, which is connected to the input terminal of the input resistance 111 of the input circuit 11 having the input resistance 111 and the first resistance 112.

[0098] In step S2, the current signal Si output from the current sensor is input to the current terminal IB of the input circuit 21 in the measurement device 1.

[0099] In step S3, the measurement device 1 performs compensation processing for compensating for the frequency characteristics of the parasitic filter constituted by the parasitic capacitance Cp parasitic to the input resistance 111, the input resistance 111, and the first resistance 112 on the output signal of the input circuit 21. The measurement device 1 of the first embodiment performs first-order low-pass filter processing as the compensation processing on the output signal of the input circuit 21.

[0100] In step S4, the measurement device 1 calculates the physical quantity of the measurement object on the basis of the output signal of the input circuit 11 and the output signal of the input circuit 21 after the compensation processing performed in step S3.

[0101] In the first embodiment, the measurement device 1 performs low-pass filter processing on the output signal of the input circuit 11 by the LPF circuit 12, and generates voltage measurement data by converting the output signal after the low-pass filter processing into a digital signal by the AD converter 13.

[0102] Then, the measurement device 1 performs low-pass filter processing on the output signal of the input circuit 21 after the compensation processing by the LPF circuit 23, and generates current measurement data by converting the output signal after the low-pass filter processing into a digital signal by the AD converter 24. Also, the measurement device 1 calculates the magnitude of the power transmitted to the electric wire serving as the measurement object using the generated voltage measurement data and current measurement data.

[0103] When the process of step S4 is completed, the series of processes of the measurement method of the first embodiment ends.

[0104] Next, the effects achieved by the first embodiment will be described.

[0105] In the first embodiment, the measurement device 1 is provided with the input circuit 11, the input circuit 21, and the processing section 30. The input circuit 11 constitutes a first input circuit provided with a voltage terminal 1A, which corresponds to a first input terminal for inputting a voltage signal Sv as a first signal representing the magnitude of the potential generated at the measurement object; an input resistor 111, one end of which is connected to the voltage terminal 1A; and a first resistor 112, one end of which is connected to the other end of the input resistor 111, and the other end of which is connected to a reference potential G.

[0106] Further, the input circuit 21 constitutes a second input circuit provided with a current terminal 1B, which corresponds to a second input terminal for inputting a current signal Si as a second signal representing the magnitude of the current flowing through the measurement object. The processing section 30 functions as an operation unit that operates the physical quantity of the measurement object based on the output signals of the input circuit 11 and the input circuit 21.

[0107] Furthermore, the measurement device 1 is provided with a compensation circuit 22 that functions as a compensation unit that performs processing for compensating the frequency characteristics of a filter constituted by the parasitic capacitance Cp parasitic to the input resistor 111 and the input resistor 111 on the output signal of the input circuit 21.

[0108] In addition, in the first embodiment, the measurement method includes a first input step (S1) of inputting the voltage signal Sv as the first signal to the input end of the input resistor 111 of the input circuit 11 provided with the input resistor 111 and the first resistor 112, and a second input step (S2) of inputting the current signal Si as the second signal to the input circuit 21.

[0109] Further, the measurement method includes a compensation step (S3) of performing processing for compensating the frequency characteristics of a filter constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 on the output signal of the input circuit 21, and an operation step (S4) of operating 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 after the processing in the compensation step (S3) is performed.

[0110] Further, the computer of the measuring device 1 that executes the program in the first embodiment acquires the output signal of the input circuit 11 that inputs the voltage signal Sv as the first signal to the input terminal of the input resistor 111 and the output signal of the input circuit 21 that inputs the current signal Si as the second signal. The above program is a program for causing the computer of the measuring device 1 to execute the above compensation step (S3) and the above operation step (S4).

[0111] According to these configurations, by the compensation circuit 22 or the compensation step (S3), the frequency characteristic of the filter constituted by the input resistor 111, the first resistor 112, and the parasitic capacitance Cp of the input circuit 11 is added to the output signal of the input circuit 21. Thereby, the shift of the frequency characteristics between the input circuit 11 and the input circuit 21 can be reduced.

[0112] Therefore, the phase shift between the output signal of the input circuit 11 for the operation of the physical quantity and the output signal of the input circuit 21 is small, and thus the physical quantity of the measurement target can be measured with high accuracy. That is, the reduction of the measurement accuracy caused by the parasitic capacitance Cp of the input resistor 111 can be suppressed.

[0113] Further, the compensation circuit 22 of the first embodiment performs the first-order low-pass filter processing on the output signal of the input circuit 21.

[0114] The reason for configuring as such is briefly explained. In the input circuit 11, the frequency characteristic of the input resistor 111 is deteriorated due to the existence of the parasitic capacitance Cp, but as shown in FIG. 4, it can be approximated with high accuracy by the first-order low-pass filter. Figure 4

[0115] Therefore, as described above, by adopting the first-order low-pass filter as the compensation circuit 22, the degree of coincidence of the frequency characteristic of the output signal of the compensation circuit 22 and the frequency characteristic of the output signal of the input circuit 21 can be improved compared to the case where the first-order low-pass filter is not adopted. Therefore, the phase shift of the measurement amount of the voltage signal Sv and the measurement amount of the current signal Si can be suppressed.

[0116] Further, the resistance values of the input resistor 111 and the first resistor 112 of the first embodiment are determined to be the following sizes: by the voltage division by the input resistor 111 and the first resistor 112, the input level of the input circuit 11 (voltage signal Sv) is attenuated to the 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.

[0117] ​According to this configuration, it is not necessary to attenuate the input signal in the compensation circuit 22, and it is possible to make the element values of the LPF circuit 23 the same as those of the LPF circuit 12 of the voltage channel input section 10, or to use the same AD converter 24 as the AD converter 13 of the voltage channel input section 10. Thus, the circuit design of the compensation circuit 22, the LPF circuit 23, and the AD converter 24 becomes easy.

[0118] (Second embodiment) Next, the measurement device of the second embodiment will be described with reference to Figure 6 .

[0119] Figure 6 is a circuit diagram showing the circuit configuration of the measurement device 2 of the second embodiment. In the second embodiment, the point at which the function of the compensation circuit 22 of the first embodiment is integrated into the LPF circuit 23 is different from that of the first embodiment.

[0120] The measurement device 2 is provided with a current channel input section 20A instead of the current channel input section 20 shown in Figure 1 . Note that the same reference numerals are given to the same configurations as those of the measurement device 1 of the first embodiment, and the repeated description is omitted.

[0121] The current channel input section 20A is provided with a compensation LPF circuit 25 instead of the compensation circuit 22 and the LPF circuit 23 of the first embodiment, in addition to the input circuit 21 having the same configuration as that of the first embodiment.

[0122] The compensation LPF circuit 25 functions as a compensation unit that implements compensation of the frequency characteristics of the parasitic filter constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112, like the compensation circuit 22 of the first embodiment.

[0123] The compensation LPF circuit 25 of the second embodiment implements a low-pass filter process of an order (N+1) that is one order higher than the order N of the LPF circuit 12 as the first filter unit, to the output signal of the input circuit 21. Note that N indicating the order is a positive integer.

[0124] The compensation LPF circuit 25 is an active filter circuit having an operational amplifier as an active element, connected to the output terminal of the input circuit 21. Further, as shown in Figure 3 , the LPF circuit 12 of the second embodiment is constituted by a second-order low-pass filter circuit.

[0125] For example, the compensation LPF circuit 25 is constituted by a third-order Gefell-type low-pass filter circuit that is one order higher than the order of the LPF circuit 12. Referring to Figure 7An example of the configuration of the compensation LPF circuit 25 will be described.

[0126] Figure 7 Fig. 8 is a circuit diagram showing an example of the circuit configuration of the compensation LPF circuit 25.

[0127] As shown in Fig. 8, the compensation LPF circuit 25 has, in addition to the configuration of the LPF circuit 23 of the first embodiment shown in Fig. 6, a resistance element 251 and a capacitor 252. Figure 7 Figure 3 The circuit constants of the compensation LPF circuit 25 are designed based on the cutoff frequency of the primary transfer function representing the frequency characteristic of the compensation circuit 22 of the first embodiment shown in Fig. 7 and the cutoff frequency and the Q value of the secondary transfer function representing the frequency characteristic of the LPF circuit 12.

[0128] The circuit constants of the compensation LPF circuit 25 are designed based on the cutoff frequency of the primary transfer function representing the frequency characteristic of the compensation circuit 22 of the first embodiment shown in Fig. 7 and the cutoff frequency and the Q value of the secondary transfer function representing the frequency characteristic of the LPF circuit 12. Figure 1

[0129] Specifically, the cutoff frequency and the Q value of the tertiary transfer function are calculated using the cutoff frequency of the primary transfer function of the compensation circuit 22 and the cutoff frequency and the Q value of the secondary transfer function of the LPF circuit 12. Then, the circuit constants of the compensation LPF circuit 25 are determined using the cutoff frequency and the Q value of the tertiary transfer function.

[0130] For example, the resistance values of the resistance elements 121, 122, and 251 are each determined to be several [kΩ], the capacitance values of the capacitors 123 and 252 are each determined to be several hundred [pF], and the capacitance value of the capacitor 124 is determined to be several tens [pF].

[0131] As a specific example, assume that the circuit constants are designed in a manner such that the cutoff frequency of the primary characteristic of the compensation circuit 22 is 720 [kΩ], the cutoff frequency of the secondary characteristic of the LPF circuit 12 is 1 [MHz], and the Q value is 0.70. In this case, the resistance values of the resistance elements 121, 122, and 251 are each determined to be 1 [kΩ], the capacitance value of the capacitor 123 is determined to be about 350 [pF], the capacitance value of the capacitor 124 is determined to be about 60 [pF], and the capacitance value of the capacitor 252 is determined to be about 260 [pF].

[0132] Note that the compensation LPF circuit 25 of the second embodiment can be configured by a coil and a resistance element instead of the resistance element 251 and the capacitor 252, or can be configured by a circuit that combines a resistance element, a capacitor, and a coil.

[0133] Next, the effects achieved by the second embodiment will be described.

[0134] ​​The measurement device 2 of the second embodiment has the input circuit 11 and the input circuit 21 as in the first embodiment. Also, the measurement device 2 has the LPF circuit 12 and the compensation LPF circuit 25.

[0135] At this time, the LPF circuit 12 functions as a first filter unit that performs low-pass filter processing on the output signal of the input circuit 11. Also, the compensation LPF circuit 25 functions as a compensation unit that performs low-pass filter processing on the output signal of the input circuit 21 with a higher order than the order of the LPF circuit 12.

[0136] According to this configuration, the compensation LPF circuit 25 has an order one higher than the order of the LPF circuit 12, and thus can add the frequency characteristic of a one-order parasitic filter composed of the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 to the frequency characteristic of the LPF circuit 12.

[0137] Thus, the frequency characteristic of the parasitic filter can be added to the output signal of the input circuit 21, and the same low-pass filter processing as the LPF circuit 12 can be performed. Therefore, as in the first embodiment, the shift of the frequency characteristic of the output signal of the compensation LPF circuit 25 from the frequency characteristic of the output signal of the LPF circuit 12 is small, and thus the measurement accuracy can be improved.

[0138] Further, in the second embodiment, the LPF circuit 12 is a filter circuit connected to the input circuit 11 and suppressing generation of aliasing noise. Also, the compensation LPF circuit 25 is an active filter circuit connected to the input circuit 21 and having the operational amplifier 125 as an active element.

[0139] According to this configuration, generation of aliasing noise is suppressed by the LPF circuit 12, and the influence of the parasitic capacitance Cp is suppressed by the compensation LPF circuit 25, and thus the measurement accuracy can be improved.

[0140] In addition, by adopting an active filter circuit as the compensation LPF circuit 25, a complex frequency characteristic can be formed. Therefore, even if the LPF circuit 12 has a frequency characteristic of two or more orders, the frequency characteristic of the output signal of the LPF circuit 12 can be approximated with high precision. Thus, a decrease in measurement accuracy caused by the adjustment precision of the frequency characteristic of the compensation LPF circuit 25 can be suppressed.

[0141] More specifically, in the second embodiment, the LPF circuit 12 is composed of a two-order low-pass filter circuit, and the compensation LPF circuit 25 is composed of a three-order Sallen-Key low-pass filter circuit.

[0142] According to this configuration, as in the first embodiment, the frequency characteristic of the output signal of the compensation LPF circuit 25 can be approximated with high precision from the frequency characteristic of the output signal of the LPF circuit 12. Figure 7As shown, the compensation LPF circuit 25 can be implemented with only one operational amplifier 125 as an active element. In contrast, the compensation circuit 22 and the LPF circuit 23 (refer to Figure 2 ) of the first embodiment, which have both functions of the compensation LPF circuit 25, require two active elements, the buffer circuit 223 and the operational amplifier 125.

[0143] As such, by employing a third-order Sallen-Key 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, and thus the increase in offset and the mixing of noise within the circuit can be reduced. In addition, the number of active elements can be minimized, and thus the size of the measurement device 2 can be reduced, and the increase in manufacturing cost can be suppressed.

[0144] (Third embodiment) Next, the measurement device of the third embodiment will be described with reference to Figure 8 . In the third embodiment, the compensation circuit 22 and the LPF circuit 12 and the LPF circuit 23 of the first embodiment shown in FIG. 1 are omitted, and the processing section 30 has the function of the compensation circuit 22. Figure 1

[0145] Figure 8 is a diagram showing the configuration of the measurement device 3 of the third embodiment.

[0146] The measurement device 3 has the voltage channel input section 10A obtained by omitting the LPF circuit 12 of the first embodiment, the current channel input section 20B obtained by omitting the compensation circuit 22 and the LPF circuit 23 of the first embodiment, and the processing section 30A having the function of the compensation circuit 22. Hereinafter, in order to avoid redundant description, only the functional configuration of the processing section 30A will be described.

[0147] The processing section 30A is configured by one or more processors that perform digital processing. The processing section 30A of the third embodiment has the compensation section 31 and the measurement quantity calculation section 32.

[0148] The compensation section 31 functions as a compensation unit that performs processing for compensating the frequency characteristics of the parasitic filter composed of the parasitic capacitance Cp parasitic to the input resistance 111 of the input circuit 11, the input resistance 111, and the first resistance 112, on the output signal of the input circuit 21.

[0149] The compensation section 31 of the third embodiment, like the first embodiment, performs a first low-pass filter process on the current measurement data output from the current channel input section 20B. For example, the compensation section 31 performs a process similar to the process performed by the compensation circuit 22 of the first embodiment. Figure 1 ​The circuit configuration of the illustrated compensation circuit 22 performs processing equivalent to the compensation processing. The compensation section 31 outputs the current measurement data after the compensation processing to the measurement quantity operation section 32.

[0150] The measurement quantity operation section 32 functions as an operation unit that operates the physical quantity of the measurement target based on the output signals of the input circuit 11 and the input circuit 21.

[0151] In the third embodiment, the measurement quantity operation section 32 acquires the voltage measurement data from the voltage channel input section 10A and acquires the current measurement data after the compensation processing from the compensation section 31. Then, the measurement quantity operation section 32 operates the magnitude of the power transmitted to the electric wire that becomes the measurement target using the voltage value indicated by the voltage measurement data and the current value indicated by the current measurement data after the compensation processing.

[0152] Further, the measurement quantity operation section 32 can also calculate the phase difference between the voltage signal Sv and the current signal Si using the voltage value indicated by the voltage measurement data and the current value indicated by the current measurement data after the compensation processing. For example, in the case where the measurement target is the power storage device, the measurement quantity operation section 32 can also operate the internal impedance of the power storage device using the voltage measurement data and the current measurement data after the compensation processing.

[0153] Next, the effects achieved by the third embodiment will be described.

[0154] The measurement device 3 of the third embodiment is provided with the input circuit 11, the input circuit 21, and the processing section 30A having the compensation section 31 and the measurement quantity operation section 32. The measurement quantity operation section 32 functions as an operation unit that operates the physical quantity of the measurement target based on the output signals of the input circuit 11 and the input circuit 21. The compensation section 31 functions as a compensation unit that performs processing of compensating the frequency characteristics of the parasitic filter constituted by the parasitic capacitance Cp, the input resistance 111, and the first resistance 112 on the output signal of the input circuit 21 input to the measurement quantity operation section 32.

[0155] According to this configuration, as in the first embodiment, compared to the functional configuration in which the compensation processing is not performed by the compensation section 31, it is possible to suppress the reduction in the measurement accuracy caused by the parasitic capacitance Cp of the input resistance 111.

[0156] In addition to this, since the processing of the compensation circuit 22 is performed in the processing section 30A that performs digital processing, unlike the first embodiment, it is not necessary to provide the compensation circuit 22 itself. Therefore, it is possible to suppress the increase in the size and the manufacturing cost of the measurement device 3.

[0157] (Fourth embodiment) Next, the effects achieved by the third embodiment will be described. Figure 9The measurement device of the fourth embodiment will be described. In the fourth embodiment, a point different from the third embodiment is that a function configuration of performing low-pass filter processing on both the voltage measurement data and the current measurement data is additionally added to the functional configuration of the processing section 30A of the third embodiment.

[0158] Figure 9 is a view showing the configuration of the measurement device 4 of the fourth embodiment.

[0159] The measurement device 4 is provided with a processing section 30B instead of the processing section 30A of the measurement device 3 of the third embodiment shown in Figure 8 . The processing section 30B is provided with an LPF section 311 and a compensation LPF section 312 instead of the compensation section 31 of the processing section 30A. Note that the same reference numerals are attached to the same configurations in the measurement device 4 as those of the measurement device 3 of the third embodiment shown in Figure 8 , and the repeated description is omitted.

[0160] The LPF section 311 functions as a first filter unit that performs low-pass filter processing on the output signal of the input circuit 11. The LPF section 311 functions to remove high-frequency noise contained in the voltage measurement data.

[0161] The LPF section 311 of the fourth embodiment performs second-order low-pass filter processing on the voltage measurement data output from the voltage channel input section 10A. As a specific example, the LPF section 311 performs low-pass filter processing performed by the same circuit configuration as the LPF circuit 12 of the first embodiment on the voltage measurement data.

[0162] The compensation LPF section 312 functions as a compensation unit that performs processing of compensating for the frequency characteristics of the parasitic filter constituted by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 on the output signal of the input circuit 21.

[0163] For example, the compensation LPF section 312 performs low-pass filter processing of one order higher than the order of the LPF section 311 on the output signal of the input circuit 21. As a specific example, the compensation LPF section 312 performs low-pass filter processing performed by a third-order Bessel-type low-pass filter circuit.

[0164] Next, the effects achieved by the fourth embodiment will be described.

[0165] In the fourth embodiment, the LPF section 311 functions as a first filter unit that performs low-pass filter processing on the output signal of the input circuit 11. Also, the compensation LPF section 312 functions as a compensation unit that performs low-pass filter processing of one order higher than the order of the LPF section 311 on the output signal of the input circuit 21.

[0166] According to this configuration, high-frequency noise mixed into the output signal of the input circuit 11 from the surroundings of the electric wire that becomes the measurement target, or high-frequency noise generated in the input resistor 111 and the AD converter 24 can be removed by the LPF section 311. Therefore, compared to a configuration that does not have the function of the LPF section 311, the measurement accuracy can be improved.

[0167] In addition, by the compensation LPF section 312, as with the second embodiment, the output signal of the input circuit 21 is subjected to the same low-pass filter processing as the LPF section 311, and the frequency characteristic of the parasitic filter caused by the parasitic capacitance Cp of the input resistor 111 is added.

[0168] As a result, the high-frequency noise of the output signals of the input circuits 11 and 21 is removed, and the phase shift between the output data of the LPF section 311 and the compensation LPF section 312 is smaller compared to the phase shift of the output signals between the input circuits 11 and 21. Therefore, the measurement accuracy of the physical quantity that is calculated based on the output signals of the input circuits 11 and 21 can be improved.

[0169] The above describes each of the embodiments of the present application, but the above-described embodiments merely show a part of the application examples of the present application, and are not intended to limit the technical scope of the present application to the specific configurations of the above-described embodiments.

[0170] For example, in the above-described embodiments, the number of current channel input sections 20, 20A, or 20B is one, but a plurality of current channel input sections 20, 20A, or 20B can be provided. In this case, the phase shift with the voltage channel input section 10 or 10A is also suppressed in the plurality of current channel input sections 20, 20A, or 20B, or the processing sections 30A or 30B, and therefore the calculation of the measurement quantity can be performed with high accuracy.

[0171] Further, in the first and second embodiments, the compensation circuit 22 and the compensation LPF circuit 25 are configured by active filters, but are not limited thereto. For example, if the frequency characteristic of the compensation circuit 22 and the compensation LPF circuit 25 is made to approximate the frequency characteristic of the parasitic filter configured by the parasitic capacitance Cp, the input resistor 111, and the first resistor 112 using passive filters, passive filters can also be employed for the compensation circuit 22 and the compensation LPF circuit 25.

[0172] Further, in the first and second embodiments, the LPF circuit 12 is configured by a second-order low-pass filter, but is not limited thereto, and a third-order or higher low-pass filter can also be employed for the LPF circuit 12. In this case, the compensation LPF circuit 25 can be a fourth-order or higher low-pass filter, and a low-pass filter other than the Butterworth type can also be employed.

[0173] This application claims priority based on Japanese Patent Application No. 2023-122599 filed on July 27, 2023 with the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0174] Reference sign explanation 1-4: measurement device; 1A: voltage terminal (first input terminal); 1B: current terminal (second input terminal); 11: input circuit (first input circuit); 111: input resistor; 112: first resistor; Cp: parasitic capacitance (capacitance parasitic to input resistor); 12: LPF circuit (first filter unit, filter circuit, second-order low-pass filter circuit); 21: input circuit (second input circuit); 22: compensation circuit (compensation unit); 25: compensation LPF circuit (compensation unit, active filter circuit, third-order Sallen-Key low-pass filter circuit); 30, 30A, 30B: processing section (arithmetic unit); 31: compensation section (compensation unit); 32: measurement amount arithmetic section (arithmetic unit); 311: LPF section (first filter unit); 312: compensation LPF section (compensation unit); S1-S4: (first input step, second input step, compensation step, arithmetic step).

Claims

1. A measurement device comprising: a first input circuit provided with a first input terminal into which a first signal representing a magnitude of an electric potential generated at 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; a second input circuit provided with a second input terminal into which a second signal representing a magnitude of a current flowing through the measurement object is input; and an arithmetic unit that operates a physical quantity of the measurement object based on output signals of the first input circuit and the second input circuit, the measurement device is provided with a compensation unit that performs a process of compensating a frequency characteristic of a filter composed of a capacitance parasitic to the input resistor, the input resistor, and the first resistor on an output signal of the second input circuit.

2. The measurement device according to claim 1, wherein the compensation unit performs a first-order low-pass filter process on the output signal of the second input circuit.

3. The measurement device according to claim 1, wherein the measurement device includes a first filter unit that performs a low-pass filter process on an output signal of the first input circuit, the compensation unit performs a low-pass filter process of a number of orders one order greater than that of the first filter unit on the output signal of the second input circuit.

4. The measurement device according to claim 3, wherein the first filter unit is a filter circuit connected to the first input circuit that suppresses aliasing noise, the compensation unit is an active filter circuit connected to the second input circuit that has an active element.

5. The measurement device according to claim 4, wherein the filter circuit is a second-order low-pass filter circuit, the active filter circuit is a third-order Sallen-Key low-pass filter circuit.

6. The measurement device according to any one of claims 1 to 3, wherein the compensation unit is a processor that performs a low-pass filter process on the output signal of the second input circuit as a process of compensating the frequency characteristic of the filter.

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

8. A measurement method comprising: a first input step of inputting a first signal representing a magnitude of an electric potential generated at a measurement object to the other end of an input resistor of a first input circuit provided with the 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 of inputting a second signal representing a magnitude of a current flowing through the measurement object to a second input circuit; a compensation step of performing a process of compensating a frequency characteristic of a filter composed of a capacitance parasitic to the input resistor, the input resistor, and the first resistor on an output signal of the second input circuit; and a The operation step calculates the physical quantity of the measurement target based on the output signal of the first input circuit and the output signal of the second input circuit after the processing in the compensation step.

9. A program for causing a computer to execute a compensation step and an operation step, The computer acquires an output signal of a first input circuit and an output signal of a second input circuit, the first input circuit being a circuit having an input resistor, a first resistor connected at one end to one end of the input resistor and at the other end to a reference potential, and inputting a first signal representing the magnitude of an electric potential generated at a measurement target to the other end of the input resistor, the second input circuit being a circuit inputting a second signal representing the magnitude of a current flowing through the measurement target, In the compensation step, the output signal of the second input circuit is subjected to processing for compensating the frequency characteristics of a filter composed of a capacitance parasitic to the input resistor, the input resistor, and the first resistor, In the operation step, the physical quantity of the measurement target is calculated based on the output signal of the first input circuit and the output signal of the second input circuit after the processing in the compensation step.

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