阅读说明：本技术 阻抗测定装置及阻抗测定装置中的负反馈电路的调整方法 (Impedance measuring device and method for adjusting negative feedback circuit in impedance measuring device ) 是由 池田正和 竹迫知博 于 2019-06-20 设计创作，主要内容包括：本发明缩短将测定对象的另一个端子的电位设为接地电位所需的时间。处理部(15)执行：第1测定处理,其将第1正弦波信号(V1)施加到端子(92),将零伏特输出到放大器(24),并且以信号(V1)为基准信号,此时,获取矢量电压计(22)所测定的振幅比(RT1)和相位差(θ1)；第2测定处理,其将零伏特施加到端子(92),将第2正弦波信号(V2)输出到放大器(24),并且以信号(V2)为基准信号,此时,获取矢量电压计(22)所测定的振幅比(RT2)和相位差(θ2)；以及振幅相位计算处理,其将信号(V1)施加到端子(92),将信号(V2)输出到放大器(24),并且在将信号(V1)设为基准信号的状态下根据振幅比(RT1、RT2)和相位差(θ1、θ2)计算要对第2信号源(23)设定的振幅(A)和相位(θ)并设定于第2信号源(23),以使矢量电压计(22)所测定的振幅比(RT)变为零。(The invention shortens the time required for setting the potential of the other terminal of the object to be measured to the ground potential. The processing unit (15) executes: a1 st measurement process of applying a1 st sine wave signal (V1) to a terminal (92), outputting zero volts to an amplifier (24), and taking a signal (V1) as a reference signal, acquiring an amplitude ratio (RT1) and a phase difference (theta 1) measured by a vector voltmeter (22); a2 nd measurement process of applying zero volts to a terminal 92, outputting a2 nd sine wave signal V2 to an amplifier 24, and acquiring an amplitude ratio RT2 and a phase difference theta 2 measured by a vector voltmeter 22 with a signal V2 as a reference signal; and an amplitude-phase calculation process of applying a signal (V1) to the terminal (92), outputting a signal (V2) to the amplifier (24), calculating an amplitude (A) and a phase (theta) to be set for the 2 nd signal source (23) from the amplitude ratio (RT1, RT2) and the phase difference (theta 1, theta 2) in a state where the signal (V1) is set as a reference signal, and setting the amplitude (A) and the phase (theta) to the 2 nd signal source (23) so that the amplitude Ratio (RT) measured by the vector voltmeter (22) becomes zero.)

1. An impedance measuring apparatus comprising:

a1 st signal source for applying a1 st sine wave signal having a predetermined amplitude and a fixed frequency to one terminal of a measurement object; and

a negative feedback circuit that specifies the other terminal of the measurement object as a reference potential in a state where the 1 st sine wave signal is applied to the one terminal, wherein the impedance measurement device measures the impedance of the measurement object based on a voltage of the one terminal and a current flowing through the negative feedback circuit when the other terminal is specified as the reference potential by the negative feedback circuit, and wherein the negative feedback circuit includes:

a current-voltage converter connected to the other terminal, converting an inflow current from the other terminal into a voltage and outputting the voltage;

a vector voltmeter that measures an amplitude ratio and a phase difference with respect to a reference signal related to the voltage output from the current-voltage converter;

a2 nd signal source that outputs a2 nd sine wave signal having the same frequency as the 1 st sine wave signal and having a set amplitude, while being shifted by a set phase from the 1 st sine wave signal;

an amplifier for amplifying the 2 nd sine wave signal into an amplified sine wave signal and outputting the amplified sine wave signal from an output terminal to the other terminal of the measurement object;

a current measuring unit that is attached between the other terminal and the output terminal of the amplifier and measures a current flowing between the other terminal and the output terminal; and

a processing unit that executes a negative feedback control process of adjusting the amplitude and the phase set for the 2 nd signal source so that the amplitude ratio approaches zero based on the amplitude ratio and the phase difference measured by the vector voltmeter,

and the impedance measuring apparatus includes: a1 st switch which is disposed between the 1 st signal source and the one terminal and applies a selected one of the 1 st sine wave signal and the reference potential to the one terminal; and

a2 nd switch which is disposed between the 2 nd signal source and the amplifier and outputs a selected one of the 2 nd sine wave signal and the reference potential to the amplifier,

the processing section executes: a1 st measurement process of performing control of the 1 st switcher and applying the 1 st sine wave signal to the one terminal, performing control of the 2 nd switcher and outputting the reference potential to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a1 st amplitude ratio and a1 st phase difference, respectively, with the 1 st sine wave signal as the reference signal;

a2 nd measurement process of performing control of the 1 st switch and applying the reference potential to the one terminal, performing control of the 2 nd switch and outputting the 2 nd sine wave signal to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a2 nd amplitude ratio and a2 nd phase difference, respectively, using the 2 nd sine wave signal as the reference signal; and

and an amplitude-phase calculation process of executing control of the 1 st switch and applying the 1 st sine wave signal to the one terminal, executing control of the 2 nd switch and outputting the 2 nd sine wave signal to the amplifier, and calculating the amplitude and the phase to be set to the 2 nd signal source from the 1 st amplitude ratio, the 1 st phase difference, the 2 nd amplitude ratio, and the 2 nd phase difference in a state where the 1 st sine wave signal is set as the reference signal, and setting the amplitude and the phase to the 2 nd signal source so that the amplitude ratio measured by the vector voltmeter becomes zero.

2. A method of adjusting a negative feedback circuit in an impedance measuring apparatus, the impedance measuring apparatus comprising:

a1 st signal source for applying a1 st sine wave signal having a predetermined amplitude and a fixed frequency to one terminal of a measurement object; and

a negative feedback circuit that specifies the other terminal of the measurement object as a reference potential in a state where the 1 st sine wave signal is applied to the one terminal, wherein the impedance measurement device measures the impedance of the measurement object based on a voltage of the one terminal and a current flowing through the negative feedback circuit when the other terminal is specified as the reference potential by the negative feedback circuit, and wherein the negative feedback circuit includes:

a current-voltage converter connected to the other terminal, converting an inflow current from the other terminal into a voltage and outputting the voltage;

a vector voltmeter that measures an amplitude ratio and a phase difference with respect to a reference signal related to the voltage output from the current-voltage converter;

a2 nd signal source that outputs a2 nd sine wave signal having the same frequency as the 1 st sine wave signal and having a set amplitude, while being shifted by a set phase from the 1 st sine wave signal;

an amplifier for amplifying the 2 nd sine wave signal into an amplified sine wave signal and outputting the amplified sine wave signal from an output terminal to the other terminal of the measurement object;

a current measuring unit that is attached between the other terminal and the output terminal of the amplifier and measures a current flowing between the other terminal and the output terminal; and

a processing unit that executes a negative feedback control process of adjusting the amplitude and the phase set for the 2 nd signal source so that the amplitude ratio approaches zero, based on the amplitude ratio and the phase difference measured by the vector voltmeter, the method comprising:

a1 st measurement process of applying the 1 st sine wave signal to the one terminal, outputting the reference potential to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a1 st amplitude ratio and a1 st phase difference, respectively, using the 1 st sine wave signal as the reference signal;

a2 nd measurement process of applying the reference potential to the one terminal, outputting the 2 nd sine wave signal to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a2 nd amplitude ratio and a2 nd phase difference, respectively, using the 2 nd sine wave signal as the reference signal; and

and an amplitude-phase calculation process of applying the 1 st sine wave signal to the one terminal, outputting the 2 nd sine wave signal to the amplifier, calculating the amplitude and the phase to be set for the 2 nd signal source from the 1 st amplitude ratio, the 1 st phase difference, the 2 nd amplitude ratio, and the 2 nd phase difference in a state where the 1 st sine wave signal is set as the reference signal, and setting the amplitude and the phase to the 2 nd signal source so that the amplitude ratio measured by the vector voltmeter becomes zero.

Technical Field

The present invention relates to an impedance measuring apparatus and a method of adjusting a negative feedback circuit in the impedance measuring apparatus.

Background

For example, as a technique disclosed as a conventional technique in patent document 1 below, there is known an impedance measuring apparatus of this type and a method for stabilizing a feedback loop (a method for adjusting a negative feedback circuit) in the impedance measuring apparatus. In this feedback loop stabilization method, adjustment is performed for the null amplifier unit 51 constituting the feedback loop (null loop) of the impedance measuring apparatus 50 shown in fig. 6 so as to stabilize the feedback loop. First, the impedance measuring apparatus 50 will be described.

In the impedance measuring apparatus 50, a1 st sine wave signal V1 (an ac voltage signal having a fixed frequency and a fixed amplitude) output from a1 st signal source 10 is applied to a protection resistor 12 via a switch 11, whereby a measurement current I is supplied from the 1 st signal source 10 to one terminal 92 of a measurement object 91 via the switch 11, the protection resistor 12, a measurement cable 6, and an Hc measurement terminal 2. In the impedance measuring apparatus 50, in a state where the feedback loop (the feedback loop constituted by the measurement cable 8, the null amplifying unit 51, the current measuring unit 25, the measurement cable 9, and the other terminal 93 of the measurement object 91) is stabilized, the null amplifying unit 51 introduces the measurement current I from the other terminal 93 through the Lc measurement terminal 5, the measurement cable 9, and the current measuring unit 25 (specifically, the detection resistance 25a of the current measuring unit 25), thereby performing a negative feedback operation of virtually grounding (equivalently connecting to the internal ground G) the other terminal 93.

In this state, the voltmeter 25b constituting the current measuring unit 25 together with the detection resistor 25a measures the voltage between both ends of the detection resistor 25a, thereby measuring the measurement current I by the current measuring unit 25. The voltage at the one terminal 92 of the object 91 to be measured is measured by a voltage measuring unit (voltmeter) 13 from the Hp measurement terminal 3 through the measurement cable 7. As described above, since the other terminal 93 is connected to the internal ground G, the voltage measuring unit 13 measures the voltage applied to both ends of the object to be measured 91 (voltage between both ends). Therefore, the impedance measuring device 50 can obtain the measured value of the impedance of the measurement object 91 from the ratio of the measured value in the voltage measuring section 13 and the measured value in the current measuring section 25.

Next, the zero bit amplification unit 51 will be specifically described. The null amplification unit 51 includes an input amplifier 61, a narrow-band high-gain amplifier 62, and an output amplifier 63 connected in series as shown in fig. 6 and 7. Further, the null amplifying unit 51 is provided with a synchronization signal source 64, a switch 65, and a vector voltmeter 66. The synchronization signal source 64 outputs a2 nd sine wave signal V2 (synchronization signal) of a fixed amplitude having the same frequency and synchronization as the 1 st sine wave signal V1 output from the 1 st signal source 10. The switch 65 is installed in a stage preceding the output amplifier 63, switches between the ac signal Vac output from the narrow-band high-gain amplifier 62 and the 2 nd sine wave signal V2 output from the synchronization signal source 64, and outputs the signal to the output amplifier 63.

As an example, as shown in fig. 7, the input amplifier 61 is configured by using an operational amplifier having a non-inverting input terminal connected to the internal ground G as a current-voltage converter, and converts a current flowing from the Lp measurement terminal 4 to the null amplifying unit 51 via the measurement cable 8 into a voltage Vi and outputs the voltage Vi. In this case, when the current flowing into null-position amplification section 51 is zero amperes (i.e., when voltage Vi is zero volts) as described above, the voltage of Lp measurement terminal 4 becomes the potential of internal ground G (i.e., the other terminal 93 becomes a virtual ground state).

As shown in fig. 7, the narrow-band high-gain amplifier 62 includes detectors 71, 72, integrators 73, 74, modulators 75, 76, an adder 77, phase shifters 78, 79, and a variable phase shifter 80. In the narrow-band high-gain amplifier 62, the voltage Vi is input to the detectors 71 and 72, the 2 nd sine wave signal V2 is input to the detector 71, and the 2 nd sine wave signal V2 phase-shifted by 90 ° by the phase shifter 78 is input to the detector 72. According to this configuration, detectors 71 and 72 function as quadrature detectors that divide voltage Vi into 2 orthogonal components and perform synchronous detection, detector 71 outputs a1 st direct current signal, and detector 72 outputs a2 nd direct current signal, where the 1 st direct current signal represents a component (in-phase component) in phase with 2 nd sine wave signal V2 regarding voltage Vi, and the 2 nd direct current signal represents a component (quadrature component) orthogonal to 2 nd sine wave signal V2 regarding voltage Vi. The integrator 73 integrates the 1 st dc signal and outputs the integrated signal to the modulator 75 as a 3 rd dc signal, and the integrator 74 integrates the 2 nd dc signal and outputs the integrated signal to the modulator 76 as a 4 th dc signal.

In the narrow-band high-gain amplifier 62, the variable phase shifter 80 shifts the phase of the input 2 nd sine wave signal V2 by a predetermined phase amount, and outputs the signal as the carrier V2 a. The carrier V2a is directly input to one 75 of the modulators 75, 76 and is 90 ° phase shifted by the phase shifter 79 and input as carrier V2b to the other modulator 76. With this configuration, the modulators 75 and 76 constitute a quadrature modulator, the modulator 75 amplitude-modulates the carrier wave V2a with the 3 rd dc signal output from the integrator 73 and outputs it as the 1 st ac signal, and the modulator 76 amplitude-modulates the carrier wave V2b with the 4 th dc signal output from the integrator 74 and outputs it as the 2 nd ac signal. The adder 77 combines the 1 st and 2 nd ac signals output from the modulators 75 and 76, and outputs the resultant signal to the switch 65 as an ac signal Vac.

Thus, the narrow-band high-gain amplifier 62 performs quadrature synchronous detection on the voltage Vi, converts the voltage Vi into a dc signal, integrates the dc signal, performs quadrature modulation, and returns the ac signal Vac, and therefore can perform high-gain amplification in a narrow band. In the narrow-band high-gain amplifier 62, the phase of the quadrature detector constituted by the detectors 71 and 72 and the phase of the quadrature modulator constituted by the modulators 75 and 76 can be shifted (shifted) by the variable phase shifter 80, and therefore the narrow-band high-gain amplifier 62 can function as a narrow-band high-gain amplifier having an arbitrary phase difference.

The stable condition of the feedback loop in the impedance measuring device 50 is such that no phase of 0 ° exists in the gain band of one round of the feedback loop (null loop). The impedance measuring apparatus 50 incorporates a function of searching for a required phase shift amount (phase correction amount) to be set in the variable phase shifter 80 so as to satisfy the stability condition, for example, in order to flexibly cope with and stabilize the feedback loop even when the phase state of the feedback loop is changed as in the case where the measuring cables 8 and 9 are extended. A method of finding the required amount of phase shift using this function and a feedback loop stabilizing method (adjustment method of the zero position amplification unit 51) of stabilizing a feedback loop by setting the found amount of phase shift to the variable phase shifter 80 will be described below.

First, the switch 11 is switched to the ground side, and the 1 st signal source 10 is separated from the protective resistor 12. Further, the switch 65 is switched to the synchronous signal source 64 side, the feedback loop is cut off, and the 2 nd sine wave signal V2 is input to the output amplifier 63. In this state, the voltage Vi output from the input amplifier 61 is measured by the vector voltmeter 66. Thus, the phase difference of the voltage Vi measured by the vector voltmeter 66 with respect to the 2 nd sine wave signal V2 is the amount of displacement of one round of the feedback loop except for the narrow-band high-gain amplifier 62. From the phase shift amount, a phase shift amount is obtained such that the total phase shift amount of the feedback loop is 180 ° (the most margin state with respect to 0 °), and is set in the variable phase shifter 80. Thus, the step of finding the phase shift amount in the variable phase shifter 80 necessary to satisfy the above-described stable condition and setting the phase shift amount in the variable phase shifter 80 is completed, and therefore, the switch 11 is switched to the 1 st signal source 10 side and the switch 65 is switched to the narrow-band high-gain amplifier 62 side to prepare for the subsequent impedance measurement.

Thus, by performing a stable negative feedback operation on the null amplifying unit 51 including the narrow-band high-gain amplifier 62 having the variable phase shifter 80 with a set phase shift amount, and controlling the amplitude and phase of the alternating current signal Vac output from the narrow-band high-gain amplifier 62 (and further, the amplitude and phase of the alternating current signal output from the output amplifier 63), the amplitude and phase of the current drawn through the detection resistor 25a are controlled so that the potential of the other terminal 93 of the measurement object 91 becomes the ground potential (the voltage of the internal ground G: zero volts). Thus, the voltage measured by the voltage measuring unit 13 from the Hp measurement terminal 3 through the measurement cable 7 becomes a voltage applied between the terminals 92 and 93 of the measurement object 91 (voltage between both ends). By this control, the measurement current I flowing through the measurement object 91 does not flow from the Lp measurement terminal 5 to the measurement cable 8 side, but is all introduced into the null amplifier unit 51 (specifically, the output amplifier 63) via the Lc measurement terminal 5, the measurement cable 9, and the detection resistor 25 a. Therefore, the current measured by the current measuring unit 25 becomes the measured current I. Thus, the impedance measuring device 50 can accurately measure the impedance of the object 91 based on the voltage across the terminals measured by the voltage measuring unit 13 and the measurement current I measured by the current measuring unit 25.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3930586 (pages 4-5, FIG. 2, FIG. 3, FIG. 6)

Disclosure of Invention

Disclosure of Invention

Technical problem to be solved by the invention

However, the adjustment method for the narrow-band high-gain amplifier 62 (adjustment method for the negative feedback circuit) in the impedance measuring apparatus disclosed in patent document 1 has the following problems. Specifically, in this adjustment method, the step of obtaining the phase shift amount by which the null position amplification means 51 can stably perform the negative feedback operation and setting the phase shift amount to the variable phase shifter 80 is performed, but thereafter, the null position amplification means 51 performs the negative feedback operation to control the amplitude and the phase of the ac signal Vac so that the potential of the other terminal 93 of the measurement object 91 becomes the ground potential. In this case, the following structure is adopted: the 3 rd and 4 th dc signals that define the gains (gains for amplitude modulation) of the carriers V2a and V2b that are the sources of the ac signal Vac are output from the integrators 73 and 74. Therefore, the adjustment method has the following problems to be solved: the time until the target voltage value (the voltage value at which the potential of the other terminal 93 of the measurement object 91 can be set to the ground potential) is reached becomes long.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an impedance measuring apparatus and a method of adjusting a negative feedback circuit in the impedance measuring apparatus, which can shorten the time required for setting the potential of the other terminal to be measured to the ground potential.

Technical scheme for solving technical problem

In order to achieve the above object, an impedance measuring apparatus according to claim 1 includes: a1 st signal source for applying a1 st sine wave signal having a predetermined amplitude and a fixed frequency to one terminal of a measurement object; and a negative feedback circuit that specifies the other terminal of the measurement object as a reference potential in a state where the 1 st sine wave signal is applied to the one terminal, and measures an impedance of the measurement object based on a voltage of the one terminal and a current flowing through the negative feedback circuit when the other terminal is specified as the reference potential by the negative feedback circuit, the negative feedback circuit including: a current-voltage converter connected to the other terminal, converting an inflow current from the other terminal into a voltage and outputting the voltage; a vector voltmeter that measures an amplitude ratio and a phase difference with respect to a reference signal related to the voltage output from the current-voltage converter; a2 nd signal source that outputs a2 nd sine wave signal having the same frequency as the 1 st sine wave signal and having a set amplitude, while being shifted by a set phase from the 1 st sine wave signal; an amplifier for amplifying the 2 nd sine wave signal into an amplified sine wave signal and outputting the amplified sine wave signal from an output terminal to the other terminal of the measurement object; a current measuring unit that is attached between the other terminal and the output terminal of the amplifier and measures a current flowing between the other terminal and the output terminal; and a processing unit that executes a negative feedback control process of adjusting the amplitude and the phase set for the 2 nd signal source so that the amplitude ratio approaches zero, based on the amplitude ratio and the phase difference measured by the vector voltmeter, and the impedance measurement device includes: a1 st switch which is disposed between the 1 st signal source and the one terminal and applies a selected one of the 1 st sine wave signal and the reference potential to the one terminal; and a2 nd switch which is disposed between the 2 nd signal source and the amplifier and outputs a selected one of the 2 nd sine wave signal and the reference potential to the amplifier, wherein the processing unit executes: a1 st measurement process of performing control of the 1 st switcher and applying the 1 st sine wave signal to the one terminal, performing control of the 2 nd switcher and outputting the reference potential to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a1 st amplitude ratio and a1 st phase difference, respectively, with the 1 st sine wave signal as the reference signal; a2 nd measurement process of performing control of the 1 st switch and applying the reference potential to the one terminal, performing control of the 2 nd switch and outputting the 2 nd sine wave signal to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a2 nd amplitude ratio and a2 nd phase difference, respectively, using the 2 nd sine wave signal as the reference signal; and an amplitude-phase calculation process of executing control for the 1 st switch and applying the 1 st sine wave signal to the one terminal, executing control for the 2 nd switch and outputting the 2 nd sine wave signal to the amplifier, and calculating the amplitude and the phase to be set for the 2 nd signal source from the 1 st amplitude ratio, the 1 st phase difference, the 2 nd amplitude ratio, and the 2 nd phase difference in a state where the 1 st sine wave signal is set as the reference signal, and setting the amplitude and the phase to the 2 nd signal source so that the amplitude ratio measured by the vector voltmeter becomes zero.

Further, the method for adjusting a negative feedback circuit in an impedance measuring apparatus according to claim 2, wherein the impedance measuring apparatus comprises: a1 st signal source for applying a1 st sine wave signal having a predetermined amplitude and a fixed frequency to one terminal of a measurement object; and a negative feedback circuit that specifies the other terminal of the measurement object as a reference potential in a state where the 1 st sine wave signal is applied to the one terminal, and measures an impedance of the measurement object based on a voltage of the one terminal and a current flowing through the negative feedback circuit when the other terminal is specified as the reference potential by the negative feedback circuit, the negative feedback circuit including: a current-voltage converter connected to the other terminal, converting an inflow current from the other terminal into a voltage and outputting the voltage; a vector voltmeter that measures an amplitude ratio and a phase difference with respect to a reference signal related to the voltage output from the current-voltage converter; a2 nd signal source that outputs a2 nd sine wave signal having the same frequency as the 1 st sine wave signal and having a set amplitude, while being shifted by a set phase from the 1 st sine wave signal; an amplifier for amplifying the 2 nd sine wave signal into an amplified sine wave signal and outputting the amplified sine wave signal from an output terminal to the other terminal of the measurement object; a current measuring unit that is attached between the other terminal and the output terminal of the amplifier and measures a current flowing between the other terminal and the output terminal; and a processing unit that executes a negative feedback control process of adjusting the amplitude and the phase set for the 2 nd signal source so that the amplitude ratio approaches zero, based on the amplitude ratio and the phase difference measured by the vector voltmeter, wherein the method for adjusting a negative feedback circuit in an impedance measurement device executes: a1 st measurement process of applying the 1 st sine wave signal to the one terminal, outputting the reference potential to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a1 st amplitude ratio and a1 st phase difference, respectively, using the 1 st sine wave signal as the reference signal; a2 nd measurement process of applying the reference potential to the one terminal, outputting the 2 nd sine wave signal to the amplifier, and acquiring the amplitude ratio and the phase difference measured by the vector voltmeter as a2 nd amplitude ratio and a2 nd phase difference, respectively, using the 2 nd sine wave signal as the reference signal; and an amplitude-phase calculation process of applying the 1 st sine wave signal to the one terminal, outputting the 2 nd sine wave signal to the amplifier, calculating the amplitude and the phase to be set for the 2 nd signal source from the 1 st amplitude ratio, the 1 st phase difference, the 2 nd amplitude ratio, and the 2 nd phase difference in a state where the 1 st sine wave signal is set as the reference signal, and setting the amplitude and the phase to the 2 nd signal source so that the amplitude ratio measured by the vector voltmeter becomes zero.

Effects of the invention

According to the impedance measuring apparatus of claim 1 and the method of adjusting the negative feedback circuit in the impedance measuring apparatus of claim 2, the time required for the other terminal of the object to be measured to be equivalently connected to the reference potential (the potential of the other terminal of the object to be measured is set to the ground potential) can be significantly reduced without using an integrator, compared to the method of adjusting the negative feedback circuit in the impedance measuring apparatus and the impedance measuring apparatus that perform the method of adjusting the negative feedback circuit, in which the zero-position amplification means (negative feedback circuit) including the narrow-band high-gain amplifier performs the negative feedback operation and the dc signal output from the integrator incorporated in the narrow-band high-gain amplifier is shifted to the target voltage value (thereby shifting the potential of the other terminal of the object to be measured to the ground potential). Further, according to the impedance measuring apparatus, a narrow-band high-gain amplifier having a complicated circuit configuration can be omitted, and therefore, the apparatus cost can be sufficiently reduced.

Drawings

Fig. 1 is a configuration diagram showing the configuration of an impedance measuring apparatus 1.

Fig. 2 is a block diagram of the current-voltage converter 21 in fig. 1.

Fig. 3 is a circuit diagram of the impedance measuring apparatus 1 when the impedance of the entire region surrounded by the two-dot chain line in fig. 1 is Z1 and the impedance of the entire region surrounded by the one-dot chain line is Z2.

Fig. 4 is a circuit diagram of the 1 st signal source 10 of fig. 3 alone.

Fig. 5 is a circuit diagram of the 2 nd signal source 23 of fig. 3 alone.

Fig. 6 is a configuration diagram showing the configuration of a conventional impedance measuring apparatus 50.

Fig. 7 is a structural diagram of the zero-position amplification unit 51 in fig. 6.

Detailed Description

Next, an embodiment of an impedance measuring apparatus and a method of adjusting a negative feedback circuit in the impedance measuring apparatus will be described with reference to the drawings.

First, the configuration of the impedance measuring apparatus 1 as the impedance measuring apparatus will be described with reference to fig. 1 and 2.

The impedance measuring apparatus 1 includes an Hc measurement terminal 2, an Hp measurement terminal 3, an Lp measurement terminal 4, an Lc measurement terminal 5, measurement cables 6, 7, 8, and 9, a1 st signal source 10, a1 st switcher 11, a protective resistor 12, a voltage measurement unit 13, a negative feedback circuit 14, and a processing unit 15, and is configured to be capable of measuring the impedance of a measurement object 91.

The 1 st signal source 10 outputs a1 st sine wave signal V1 having a predetermined amplitude and a fixed frequency as a reference potential (potential of the internal ground G of the impedance measuring apparatus 1, zero volts) based on the reference potential. The 1 st sine wave signal V1 is applied to one terminal 92 of the measurement object 91 via the 1 st switch 11, the protection resistor 12, the measurement cable 6 (a core wire (not shown) of the measurement cable 6 composed of a coaxial cable and a shielded cable), and the Hc measurement terminal 2. In a state where the 1 st sine wave signal V1 is applied to the one terminal 92, the measurement current I1, which is a sine wave signal, flows from the 1 st signal source 10 to the measurement object 91. In this example, the 1 st signal source 10 is controlled by the processing unit 15, and the output operation of the 1 st sine wave signal V1 is performed. It is needless to say that the protection resistor 12 is not used.

As an example, the 1 st switcher 11 is configured to function as a single-pole double-throw type switcher using a relay or an analog switch. The 1 st switcher 11 is controlled by the processing unit 15 to apply one of the 1 st sine wave signal V1 output from the 1 st signal source 10 and the potential of the internal ground G to the one terminal 92 of the measurement object 91. For the sake of easy understanding of the present invention, the 1 st switch 11 functions as an ideal changeover switch having a contact resistance value of zero ohm at the contact.

One of a pair of measurement terminals (not shown) of the voltage measurement unit 13 is connected to the Hp measurement terminal 3 via a measurement cable 7 (a core wire (not shown) of the same type of cable as the measurement cable 6), and the other measurement terminal is connected to the internal ground G. With this configuration, the voltage measuring unit 13 measures the voltage generated at the Hp measurement terminal 3 with the internal ground G as a reference, measures the voltage (voltage between both terminals) between the terminals 92 and 93 of the object 91 to be measured in a state where the other terminal 93 of the object 91 to be measured is set to the potential of the internal ground G by the negative feedback circuit 14, as will be described later, and outputs the measured voltage to the processing unit 15.

The negative feedback circuit 14 includes, as an example, a current-voltage converter 21, a vector voltmeter 22, a2 nd signal source 23, a2 nd switcher 26, an amplifier 24, and a current measuring unit 25. Further, as will be described later, the processing unit 15 executes processes (the 1 st measurement process, the 2 nd measurement process, and the amplitude phase calculation process) for calculating the initial amplitude a0 and the initial phase θ 0 and setting them to the 2 nd signal source 23 based on the amplitude ratio RT and the phase difference θ (specifically, the 1 st amplitude ratio RT1 and the 1 st phase difference θ 1, the 2 nd amplitude ratio RT2, and the 2 nd phase difference θ 2) output from the vector voltmeter 22, and a negative feedback control process of finely adjusting the amplitude a and the phase Φ (the amplitude of the 2 nd sine wave signal V2, and further the amplitude of the amplified sine wave signal V3, and the phase of the 2 nd sine wave signal V2, and further the phase of the amplified sine wave signal V3 with respect to the 1 st sine wave signal V1) set with respect to the 2 nd signal source 23 based on the amplitude ratio RT and the phase difference θ output from the vector voltmeter 22, and thus constitutes a part of the negative feedback circuit 14. The negative feedback circuit 14 has an input terminal 14a connected to the Lp measurement terminal 4 via a measurement cable 8 (a core wire (not shown) of the same type of cable as the measurement cable 6), and an output terminal 14b connected to the Lc measurement terminal 5 via a measurement cable 9 (a core wire (not shown) of the same type of cable as the measurement cable 6).

As shown in fig. 1, the measurement cables 6, 7, 8, and 9 have external conductors (braided wires) connected to one end portion to which the corresponding measurement terminals 2, 3, 4, and 5 are connected via wirings L1, L2, and L3, and have external conductors (braided wires) connected to the internal ground G at the other end portion.

As an example, as shown in fig. 2, the current-voltage converter 21 includes: an operational amplifier 21a whose non-inverting input terminal is connected to an internal ground G; an input resistor 21b having one end connected to the input terminal 14a and the other end connected to the inverting input terminal of the operational amplifier 21; and a feedback resistor 21c having one end connected to the inverting input terminal of the operational amplifier 21a and the other end connected to the output terminal of the operational amplifier 21. With this configuration, when the current-voltage converter 21 is connected to the other terminal 93 of the measurement object 91 via the measurement cable 8 and the Lp measurement terminal 4, the current flowing from the other terminal 93 to the negative feedback circuit 14 is converted into a voltage Vi and output.

The vector voltmeter 22 measures and outputs an amplitude ratio RT and a phase difference θ with respect to the voltage Vi output from the current-voltage converter 21. In this case, the amplitude ratio RT is a value obtained by dividing the amplitude of the reference signal input to the vector voltmeter 22 by the amplitude of the voltage Vi, and the phase difference θ is a value indicating a phase deviation occurring in the voltage Vi with the phase of the reference signal as a reference. Further, one selected by the processing unit 15 of the 1 st sine wave signal V1 output from the 1 st signal source 10 and the 2 nd sine wave signal V2 output from the 2 nd signal source 23 is input to the vector voltmeter 22 as a reference signal.

The 2 nd signal source 23 outputs a2 nd sine wave signal V2 having the same frequency as the 1 st sine wave signal V1 and having the set amplitude a, while being shifted by the set phase Φ from the 1 st sine wave signal V1. As an example, the 2 nd switcher 26 is configured to function as a single-pole double-throw type switching switch using a relay or an analog switch. The 2 nd switch 26 is controlled by the processing unit 15 to output one of the 2 nd sine wave signal V2 output from the 2 nd signal source 23 and the potential of the internal ground G to the input terminal of the amplifier 24. For the sake of easy understanding of the present invention, the 2 nd switch 26 functions as an ideal switch having a contact resistance value of zero at the contact and no signal delay.

The amplifier 24 amplifies the 2 nd sine wave signal V2 into an amplified sine wave signal V3, and outputs the amplified sine wave signal V3 from an output terminal, not shown, to the output terminal 14b of the negative feedback circuit 14. In this example, the current measuring section 25 is installed between the output terminal of the amplifier 24 and the output terminal 14b of the negative feedback circuit 14. Therefore, the amplified sinusoidal signal V3 is output to the other terminal 93 of the object to be measured 91 via the current measuring section 25, the output terminal 14b, the measurement cable 9, and the Lp measurement terminal 4.

As an example, the current measuring unit 25 is configured to include a voltmeter 25b, and the voltmeter 25b measures a detection resistor 25a attached between the output terminal of the amplifier 24 and the output terminal 14b of the negative feedback circuit 14, and a voltage between both ends of the detection resistor 25a (a voltage that changes in proportion to the current I2 flowing through the detection resistor 25a), and outputs the voltage to the processing unit 15.

The processing unit 15 includes a signal switcher, a CPU, a memory (none of which is shown), and the like, and executes control processing for the 1 st signal source 10, the 1 st switcher 11, the 2 nd signal source 23, and the 2 nd switcher 26, signal selection processing for selecting one of the 1 st sine wave signal V1 and the 2 nd sine wave signal V2 as a reference signal by the signal switcher and outputting the selected signal to the vector voltmeter 22, 1 st measurement processing, 2 nd measurement processing, amplitude phase calculation processing, negative feedback control processing, and impedance measurement processing.

In this case, the processing unit 15 performs the 1 st measurement process, the 2 nd measurement process, and the amplitude-phase calculation process, thereby applying the principle of superposition to the impedance measuring apparatus 1 to which the measurement object 91 is connected, and calculates the initial amplitude a0 as the amplitude a to be set to the 2 nd signal source 23 and the initial phase Φ 0 as the phase Φ so that the amplitude ratio RT measured by the vector voltmeter 22 becomes zero. The following describes the 1 st measurement process, the 2 nd measurement process, and the amplitude and phase calculation process. In order to facilitate understanding of the invention, in the impedance measuring apparatus 1 to which the object to be measured 91 is connected, as shown in fig. 1, the impedance of the entire impedance member including a plurality of components (the protection resistor 12, the measurement cable 6, the Hc measurement terminal 2, the one terminal 92, the object to be measured 91, the other terminal 93, the Lp measurement terminal 4, the measurement cable 8, and the current-voltage converter 21) included in a region surrounded by a two-dot chain line is represented as Z1, and the impedance of the entire impedance member including a plurality of components (the amplifier 24, the current measurement section 25, the measurement cable 9, the Lc measurement terminal 5, the other terminal 93, the Lp measurement terminal 4, the measurement cable 8, and the current-voltage converter 21) included in a region surrounded by a one-dot chain line is represented as Z2. In this case, the main components related to the 1 st measurement process, the 2 nd measurement process, and the amplitude and phase calculation process in fig. 1 are shown in a circuit diagram shown in fig. 3.

The processing unit 15 executes the 1 st measurement process based on the circuit shown in the circuit diagram of fig. 4 (in the circuit shown in the circuit diagram of fig. 3, the circuit when the 1 st signal source 10 is present alone). In the 1 st measurement process, the processing unit 15 performs control of the 1 st switcher 11 and applies the 1 st sine wave signal V1 to the one terminal 92 of the measurement object 91, performs control of the 2 nd switcher 26 and outputs the potential of the internal ground G (reference potential) to the amplifier 24, and outputs the 1 st sine wave signal V1 as a reference signal to the vector voltmeter 22. In this state, processing unit 15 acquires and stores amplitude ratio RT and phase difference θ measured by vector voltmeter 22 as 1 st amplitude ratio RT1 and 1 st phase difference θ 1.

Specifically, when the 1 st sine wave signal V1 output from the 1 st signal source 10 is, for example, a1 × sin (ω t), when the sine wave signal applied to the vector voltmeter 22 is B1 × sin (ω t + θ 1), the vector voltmeter 22 outputs (B1/a1) as the amplitude ratio RT and θ 1 as the phase difference θ. Therefore, the processing unit 15 stores the 1 st amplitude ratio RT1(═ B1/a1) and the 1 st phase difference θ 1.

The processing unit 15 executes the 2 nd measurement processing based on the circuit shown in the circuit diagram of fig. 5 (in the circuit shown in the circuit diagram of fig. 3, the circuit when the 2 nd signal source 23 alone exists). In the 2 nd measurement process, the processing unit 15 controls the 1 st switching device 11 to connect one end of the protection resistor 12 to the potential (reference potential) of the internal ground G, controls the 2 nd switching device 26 to output the 2 nd sine wave signal V2 to the amplifier 24, and outputs the 2 nd sine wave signal V2 to the vector voltmeter 22 as a reference signal. In this state, the processing unit 15 acquires and stores the amplitude ratio RT and the phase difference θ measured by the vector voltmeter 22 as the 2 nd amplitude ratio RT2 and the 2 nd phase difference θ 2.

Specifically, when the 2 nd sine wave signal V2 output from the 2 nd signal source 23 is, for example, a2 × sin (ω t), and the sine wave signal applied to the vector voltmeter 22 is B2 × sin (ω t + θ 2), the vector voltmeter 22 outputs (B2/a2) as the amplitude ratio RT and θ 2 as the phase difference θ. Therefore, the processing unit 15 stores the 2 nd amplitude ratio RT2(═ B2/a2) and the 2 nd phase difference θ 2.

In the amplitude and phase calculation processing, the processing unit 15 calculates the amplitude a (initial amplitude a0) and the phase Φ (initial phase θ 0) to be set in the 2 nd signal source 23 and sets them in the 2 nd signal source 23 so that the amplitude ratio RT measured by the vector voltmeter 22 becomes zero, in a state where the 1 st sine wave signal V1 is applied to the one terminal 92, the 2 nd sine wave signal V2 is output to the input terminal of the amplifier 24, and the 1 st sine wave signal V1 is output to the vector voltmeter 22 as the reference signal, based on the 1 st amplitude ratio RT1, the 1 st phase difference θ 1, the 2 nd amplitude ratio RT2, and the 2 nd phase difference θ 2 acquired and stored in the 1 st measurement processing and the 2 nd measurement processing.

According to the principle of superposition, in the circuit shown in the circuit diagram shown in fig. 3, that is, in the circuit when the 1 st signal source 10 and the 2 nd signal source 23 coexist, the voltage applied to the vector voltmeter 22 becomes the sine wave signal: b1 × sin (ω t + θ 1), and the sine wave signal: b2 × sin (ω t + θ 2). Therefore, the condition that the amplitude of the synthesized signal is always zero volts (i.e., the condition that the amplitude ratio RT measured by the vector voltmeter 22 is zero) needs to be a sinusoidal signal measured in the 2 nd measurement process: b2 × sin (ω t + θ 2) with respect to the sine wave signal measured in the 1 st measurement process: b1 × sin (ω t + θ 1) is uniform in amplitude and shifted in phase by 180 °.

In this case, in order to make the sine wave signal: amplitude B2 of B2 × sin (ω t + θ 2) and sine wave signal: the amplitude B1 of B1 × sin (ω t + θ 1) is equal, that is, B1 is B2(a1 × RT1 is a2 × RT2), and the amplitude a2 of the 2 nd sine wave signal V2 output from the 2 nd signal source 23 needs to have a value represented by the following expression (1).

A2＝A1×RT1/RT2…(1)

Further, in order to make the sine wave signal: phase of B2 × sin (ω t + θ 2) with respect to the sine wave signal: b1 × sin (ω t + θ 1) is shifted by 180 °, and the phase of the 2 nd sine wave signal V2 output from the 2 nd signal source 23 needs to be shifted by the phase Φ shown in the following expression (2) with respect to the phase of the 1 st sine wave signal V1 output from the 1 st signal source 10.

φ＝θ1+π-θ2…(2)

That is, when the phase of the 1 st sine wave signal V1 is set to be shifted by the phase Φ with respect to the 2 nd signal source 23, the sine wave signal: b1 × sin (ω t + θ 1) is shifted in phase by the phase θ 1 from the 1 st sine wave signal V1, whereas the sine wave signal: the phase shift of B2 × sin (ω t + θ 2) with respect to the 1 st sine wave signal V1 corresponds to the sum of the phase Φ and the phase θ 2(Φ + θ 2). In this case, the total amount (Φ + θ 2) is larger by π than the phase θ 1. Therefore, the following equation holds.

θ1+π＝φ+θ2

Therefore, in the amplitude-phase calculation process, the processing unit 15 substitutes the 1 st amplitude ratio RT1, the 1 st phase difference θ 1, the 2 nd amplitude ratio RT2, and the 2 nd phase difference θ 2 into the above equations (1) and (2) to calculate the initial amplitude a0 (a 2) and the phase Φ (initial phase θ 0) as the amplitude a to be set in the 2 nd signal source 23, and sets the amplitude ratio RT to be zero in the 2 nd signal source 23, which is measured by the vector voltmeter 22.

In the negative feedback control process, after the initial amplitude a0(═ a2) and the phase Φ (initial phase θ 0) are set in the 2 nd signal source 23, the 1 st sine wave signal V1 is applied to the one terminal 92 of the object 91 to be measured, the 2 nd sine wave signal V2 is output to the input terminal of the amplifier 24, and the 1 st sine wave signal V1 is output to the vector voltmeter 22 as the reference signal, the processing unit 15 detects the amplitude ratio RT and the phase difference θ measured by the vector voltmeter 22, and finely adjusts the amplitude a and the phase Φ set in the 2 nd signal source 23 so that the amplitude ratio RT is maintained at zero. As a result, the voltage of the Lp measurement terminal 4 is maintained at the potential of the internal ground G, and the other terminal 93 of the measurement object 91 is equivalently connected to the internal ground G.

In this case, in each component (for example, the 1 st signal source 10, the 2 nd signal source 23, etc.) constituting the impedance measuring apparatus 1, in a state (ideal state) in which there is no change with time or temperature change, the amplitude ratio RT measured by the vector voltmeter 22 is maintained at zero (that is, a state in which the other terminal 93 of the measurement object 91 is equivalently connected to the internal ground G) only by setting the initial amplitude a0 and the initial phase θ 0 obtained as described above to the 2 nd signal source 23 without performing the negative feedback control process. However, in practice, since each component (for example, the 1 st signal source 10, the 2 nd signal source 23, and the like) constituting the impedance measuring apparatus 1 changes with time and with temperature, the processing unit 15 performs this negative feedback control process to maintain the amplitude ratio RT measured by the vector voltmeter 22 at zero (the phase difference θ is also zero).

In the impedance measurement process, the processing unit 15 calculates the impedance of the measurement object 91 based on the voltage between both terminals 92 and 93 of the measurement object 91 measured by the voltage measurement unit 13 and the current I2 measured by the current measurement unit 25 in a state where the other terminal 93 of the measurement object 91 is equivalently connected to the internal ground G, by setting the initial amplitude a0 and the initial phase θ 0 with respect to the 2 nd signal source 23 (in this example, by performing the negative feedback control process). In a state where the other terminal 93 of the object to be measured 91 is equivalently connected to the internal ground G, since the current flowing into the current-voltage converter 21, that is, the current flowing from the Lp measurement terminal 4 into the negative feedback circuit 14 via the measurement cable 8 is zero, all of the measurement current I1 flowing from the 1 st signal source 10 through the object to be measured 91 flows as the current I2 through the current measurement section 25. Therefore, the current measuring unit 25 measures the measured current I1 flowing through the object to be measured 91 as the current I2 and outputs the measured current to the processing unit 15. Thus, the processing unit 15 accurately measures (calculates) the impedance of the measurement target 91. In the impedance measurement process, the processing unit 15 outputs the measured impedance to an output unit (not shown) (for example, a display device such as an LCD).

Next, the operation of the impedance measuring apparatus 1 will be described together with the adjustment operation (adjustment method) of the negative feedback circuit 14 in the impedance measuring apparatus 1 with reference to the drawings. Further, the impedance measuring apparatus 1 is assumed to be normally connected to the object 91.

In this state, in the impedance measuring apparatus 1, the processing unit 15 first calculates (measures) the 1 st amplitude ratio RT1 and the 1 st phase difference θ 1, and the 2 nd amplitude ratio RT2 and the 2 nd phase difference θ 2 by sequentially executing the 1 st measurement process, the 2 nd measurement process, and the amplitude phase calculation process, and calculates the initial amplitude a0 and the initial phase θ 0 based on these results to set the 2 nd signal source 23. In addition, either the 1 st measurement process or the 2 nd measurement process may be executed first. Thus, in the impedance measuring apparatus 1, in the ideal state described above, the amplitude ratio RT and the phase difference θ measured by the vector voltmeter 22 are both zero, and the other terminal 93 of the object 91 to be measured is equivalently connected to the internal ground G.

In this example, the processing unit 15 executes a negative feedback control process, and thereby keeps the amplitude ratio RT measured by the vector voltmeter 22 at zero (the phase difference θ is also kept at zero), and finely adjusts the amplitude a and the phase Φ set in the 2 nd signal source 23 so that the other terminal 93 of the measurement object 91 is continuously connected to the internal ground G in an equivalent manner.

In this state, since the current flowing into the current-voltage converter 21, that is, the current flowing from the Lp measurement terminal 4 into the negative feedback circuit 14 via the measurement cable 8 is zero, all of the measurement current I1 flowing from the 1 st signal source 10 to the measurement object 91 flows as the current I2 to the current measurement unit 25. Therefore, the current measuring unit 25 measures the current I2, which is the measured current I1 flowing through the object 91, and outputs the measured current to the processing unit 15. Since the vector voltage value Vsc is maintained at zero volts, the other terminal 93 of the object to be measured 91 is equivalently connected to the internal ground G. Therefore, the voltage measuring unit 13 measures the voltage generated at the Hp measurement terminal 3 with reference to the internal ground G, measures the voltage (voltage between both terminals) between the terminals 92 and 93 of the measurement object 91, and outputs the measured voltage to the processing unit 15.

Next, the processing unit 15 executes the impedance measurement processing in this state, and accurately calculates the impedance of the measurement object 91 based on the two-terminal voltage between the two terminals 92 and 93 of the measurement object 91 measured by the voltage measuring unit 13 and the current I2 measured by the current measuring unit 25. The calculated impedance is output to an output unit.

Thus, in the impedance measuring apparatus 1, the processing unit 15 executes the 1 st measurement process, the 2 nd measurement process, and the amplitude-phase calculation process, and calculates and sets the initial amplitude a0, which is the amplitude a to be set for the 2 nd signal source 23, and the initial phase θ 0, which is the phase Φ, so that the amplitude ratio RT measured by the vector voltmeter 22 becomes zero (the phase difference θ is also zero).

Therefore, according to the impedance measuring apparatus 1 and the method for adjusting the negative feedback circuit 14 in the impedance measuring apparatus 1, the integrator is not used, as compared with the method for adjusting the negative feedback circuit in the impedance measuring apparatus in which the zero-position amplification means (negative feedback circuit) including the narrow-band high-gain amplifier performs the negative feedback operation and the dc signal output from the integrator built in the narrow-band high-gain amplifier is shifted to the target voltage value (thereby shifting the potential of the other terminal of the measurement object to the ground potential (the potential of the internal ground G in this example)), and the impedance measuring apparatus performing the method for adjusting the negative feedback circuit, therefore, the time required for the other terminal 93 of the object to be measured 91 to be equivalently connected to the internal ground G (the potential of the other terminal 93 of the object to be measured 91 is set to the potential of the internal ground G (ground potential)) can be significantly reduced. Further, according to the impedance measuring apparatus 1, a narrow-band high-gain amplifier having a complicated circuit configuration can be omitted, and therefore, the apparatus cost can be sufficiently reduced.

Industrial applicability of the invention

According to the present invention, since the integrator is not used in the negative feedback circuit that defines the other terminal of the measurement object as the reference potential (ground potential) in a state where the 1 st sine wave signal is applied from the 1 st signal source to the one terminal of the measurement object, the time required for the other terminal to be equivalently connected to the reference potential can be significantly shortened. Thus, the present invention can be widely applied to an impedance measuring apparatus and a method of adjusting a negative feedback circuit in the impedance measuring apparatus.

Description of the reference symbols

1 impedance measuring device

10 st 1 signal source

11 st 1 switching device

14 negative feedback circuit

15 treatment section

21 current-to-voltage converter

22 vector voltmeter

23 nd 2 signal source

24 amplifier

25 current measuring part

26 nd 2 switching device

91 object to be measured

92 one terminal

93 another terminal

Amplitude of A

G internal ground

I2 Current

RT amplitude ratio

V1 1 st sine wave signal

V2 No. 2 sine wave signal

V3 amplified sine wave signal

Vi voltage

Theta phase difference

Phase phi.