CN109765429B - Impedance measuring system and impedance measuring method - Google Patents
Impedance measuring system and impedance measuring method Download PDFInfo
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Abstract
The invention provides an impedance measuring system and an impedance measuring method, which can reduce the measuring error caused by the influence of induced voltage among impedance measuring instruments when a plurality of impedance measuring instruments are used for measuring a measuring sample; synchronizing constant current sources as measurement alternating current sources of a plurality of impedance measuring instruments and supplying the synchronized measurement alternating current to a measurement sample; alternatively, the phases of the measurement alternating currents generated by the adjacent impedance measuring instruments are controlled to be opposite to each other and supplied to the measurement sample, thereby performing measurement.
Description
Technical Field
The invention relates to an impedance measurement system and an impedance measurement method.
Background
As a method for measuring internal impedance of an element constituting a circuit, there is an ac impedance measurement method in which an ac signal is applied to a sample as a measurement target and an electrical response thereof is measured. With this method, the magnitude of the resistance component, capacitance component, and inductance component of the sample can be examined. Further, it is possible to determine what equivalent circuit the components constitute in the sample or a parameter of the equivalent circuit.
As the above impedance measurement method, there are the following methods: that is, an impedance measurement method using synchronous detection is a method in which a sample is supplied with a sinusoidal measurement ac power from a constant current source, and a voltage signal appearing in the sample is synchronously detected by a reference signal (or also referred to as a "reference signal") having the same frequency in synchronization with the supplied measurement ac power, thereby reducing the influence of a noise component appearing in the sample.
The following prior art documents exist for impedance measurement using synchronous detection.
Hereinafter, the impedance measurement by synchronous detection will be described with reference to the drawings.
Fig. 6 is a diagram showing a configuration of an impedance measuring instrument using synchronous detection.
The impedance measuring operation in the impedance measuring instrument of fig. 6 will be described.
I = Isin (ω) was added to the sample 13 from a constant current source 1 t) as alternating current for measurement. Internal resistance R to the battery was generated at both ends of sample 13 X The corresponding voltage, amplified by amplifier 15 and then scaled by v 1 ＝iR X Is output in the form of (1). Further, a current detection resistor R is output from the amplifier 16 S Corresponding v 2 = iRs, and synchronous detection is performed by the synchronous detector 20. Here, v 1 、v 2 Comprises the following steps:
v 1 ＝Vsin(ω 1 t)＝IR X sin(ω 1 t)
v 2 ＝iR S ＝IR S sin(ω 1 t)＝ksin(ω 1 t)。
where k is a constant (I and Rs are constant).
The synchronous detection output is:
v 1 ×v 2 ＝kIR X sin(ω 1 t)sin(ω 1 t)
＝1/2·kIR X [cos(0)－cos(2ω 1 t)]。
when the alternating current component is cut off with the low-pass filter, the input of the analog-to-digital converter 23 becomes:
V AD ＝1/2·kIR X cos(0)＝1/2·kIR X ，
thus, the resistance Rx of the sample is given by the following formula
R X ＝2/k·(V AD /I)
And can be obtained.
In this way, the voltage detection signals at both ends of the sample are synchronously detected by the reference signal in phase with the alternating current for measurement, and the alternating current component (cos (2 ω) is removed by the low-pass filter 1 t)), so that only the direct current component is extracted, it is possible to obtain a component other than pure resistance, such as a batteryThe effective impedance of the sample of the measurement object. Further, since the ac component occurring in the synchronous detection is removed by the low-pass filter, the influence of the noise as the ac can be removed, and a minute signal buried in the noise can be extracted.
[ Prior art documents ]
[ patent literature ] A
Patent document 1: japanese Kokai publication 2017-058176
When a plurality of the impedance measuring instruments are used to measure ac impedance of, for example, a battery, as a measurement target, there are cases where: that is, a measurement error occurs due to an induced voltage generated by mutual interference of magnetic fluxes generated by the alternating current for measurement supplied from the impedance measuring instrument, and further, a measurement error occurs due to an induced voltage caused by an eddy current generated in a metal adjacent to the impedance measuring instrument.
The phenomenon that measurement errors are caused by the induced voltage will be described.
A case where metal exists in the vicinity of the impedance measuring instrument is described as a model. When the impedance of a battery of a sample as a measurement object is to be measured on a production line, a metal such as a holder for housing the battery or a case of the battery exists in the vicinity of the measurement object. In this metal, an eddy current is generated due to electromagnetic induction caused by the alternating current for measurement generated by the impedance measuring instrument.
The effect when a metal plate (parallel to the loop antenna of the cable) is present in the vicinity of the impedance meter is illustrated in fig. 7.
When a measurement alternating current i = Isin (ω t) is applied to a sample (resistance) to be measured from a constant current source of an impedance measuring instrument, a magnetic flux of Φ ∞ Isin (ω t) is generated in a cable of a probe. By this magnetic flux, the following V is generated as shown in fig. 7 (a) M The induced voltage of (2).
[ equation 1]
On the other hand, as shown in fig. 7 (B), an eddy current expressed by the following equation is generated in the metal plate 4 existing in the vicinity of the impedance measuring instrument due to the magnetic flux generated in the cable.
[ formula 2]
Due to the presence of the eddy current, a magnetic flux is generated to cancel the eddy current, and an induced voltage Vu is generated in the cable of the probe of the impedance measuring instrument by the magnetic flux.
[ formula 3]
Although the induced voltage having a phase difference of 90 degrees from the measurement signal detected from the sample can be eliminated by the above-described synchronous detection, the induced voltage Vu generated by the eddy current generated by the metal plate 4 in the vicinity of the impedance measuring instrument is not perpendicular to the phase of the alternating current for measurement because the induced voltage Vu is rotated in phase, and therefore, it is difficult to eliminate the induced voltage Vu by the synchronous detection, and the induced voltage Vu causes noise due to phase shift, thereby causing a measurement error.
The above-described example of the induced voltage generated when a metal is present in the vicinity of the impedance measuring instrument is studied by taking a case where a metal plate is present in parallel to a cable of the impedance measuring instrument as an example, but the phase and amplitude of the induced voltage Vu affecting the impedance measuring instrument change depending on the position, direction, and the like of the metal.
However, since the phase shift of the constant current source and the voltage detection unit 12 due to the induced voltage generated when metal exists in the vicinity of the individual impedance measuring instrument is small, the measurement error is small, and the measurement error can be corrected by the zeroing function using the zero impedance measuring jig.
On the other hand, when there are a plurality of impedance meters, it becomes more complicated. Magnetic flux is generated by one impedance measuring device, and due to the magnetic flux, induced voltages are generated in the cables of the other impedance measuring devices to affect each other. In addition, when there is metal in the vicinity, eddy current is generated in the metal in the vicinity by electromagnetic induction of one impedance measuring instrument, and induced voltage is generated in the other impedance measuring instrument by magnetic flux generated to cancel the eddy current, and induced voltage is generated in the other impedance measuring instrument by eddy current generated by the other impedance measuring instrument, and thus, the generated magnetic fluxes mutually affect each other. The induced voltages generated by the mutual interference of the magnetic fluxes generated by the impedance measuring instruments do not match the phases of the respective alternating currents for measurement, and therefore, the induced voltages cause large noises and large measurement errors.
In this way, when there is noise due to induced voltage generated by the mutual influence of a plurality of impedance measuring instruments and further noise due to eddy current of metal in the vicinity, it is difficult to eliminate the noise. Since the phases of the alternating current for measurement naturally deviate from each other when a plurality of impedance measuring instruments measure simultaneously, and the phases of the induced voltages generated thereby are different, the deviation between the induced voltages generated by other impedance measuring instruments and the phases of the measurement signals cannot be uniquely determined. Further, since the phase of the induced voltage generated differs between the impedance measuring instruments regardless of whether the impedance measuring instruments are simultaneously measuring or one impedance measuring instrument is operating and the other impedance measuring instrument is not operating, the deviation between the induced voltage generated between the impedance measuring instruments and the phase of the measurement signal cannot be uniquely determined. Further, since the direction of the generated magnetic flux changes depending on the positional relationship between the impedance measuring instruments, it is difficult to eliminate the noise caused by the induced voltage generated by the mutual influence of the impedance measuring instruments, and it is difficult to eliminate the measurement error caused by the noise.
Disclosure of Invention
It is desirable to reduce the above-mentioned measurement errors due to the plurality of impedance meters interacting with each other. Further, when a plurality of impedance measuring instruments are used for measurement, and further, when metal exists in the vicinity, induced voltages are generated due to magnetic fluxes with each other, which cause noise and cause measurement errors, and therefore, it is desirable to reduce such measurement errors.
An object of the present invention is to provide an impedance measurement system and an impedance measurement method capable of reducing measurement errors due to induced voltages generated by a plurality of measurement instruments and nearby metal as described above, and thereby capable of performing stable measurement.
A first aspect of the present invention is an impedance measuring system including a plurality of impedance measuring instruments for supplying a sample to be measured with alternating current for measurement of a predetermined frequency, wherein phases of alternating current for measurement of the plurality of impedance measuring instruments are synchronized.
The impedance measuring system includes a phase synchronization signal generating unit, and is capable of supplying a phase synchronization signal output from the phase synchronization signal generating unit to a measurement ac source of each impedance measuring instrument.
Another aspect of the present invention is an impedance measuring system including a plurality of impedance measuring instruments that supply a measuring alternating current having a predetermined frequency to a sample to be measured, wherein phases of the measuring alternating currents supplied from adjacent impedance measuring instruments are opposite phases.
Further, the impedance measuring instrument may include: the measurement device includes a measurement AC source for supplying a measurement AC power, a reference signal generating unit for generating a reference signal synchronized with the measurement AC power, a synchronous detection unit for synchronously detecting a detection signal appearing in a sample with the reference signal, and a low-pass filter for passing the signal after synchronous detection.
Another aspect of the present invention is an impedance measuring method for supplying a measuring ac power of a predetermined frequency from a plurality of impedance measuring instruments to a sample to be measured, synchronously detecting a detection signal appearing in the sample with a reference signal synchronized with the measuring ac power, extracting a dc component of the signal after the synchronous detection, and measuring an ac impedance of the sample, the impedance measuring method being characterized in that the measuring ac powers generated by the plurality of impedance measuring instruments are synchronized in phase.
Another aspect of the present invention is an impedance measuring method for supplying a measuring ac power of a predetermined frequency from a plurality of impedance measuring instruments to a sample to be measured, synchronously detecting a detection signal appearing in the sample with a reference signal synchronized with the measuring ac power, extracting a dc component of the signal after the synchronous detection, and measuring an ac impedance of the sample, wherein phases of the measuring ac powers generated by adjacent impedance measuring instruments are inverted.
(effect of the invention)
Since the occurrence of noise caused by the mutual influence of the plurality of measuring instruments can be suppressed or reduced, the error of the impedance measurement can be reduced, and more accurate measurement can be performed. In addition, stable measurement can be performed, and the efficiency of the production process of the measurement object can be improved.
Drawings
Fig. 1 is a diagram showing a configuration for synchronizing phases of alternating current for measurement generated by a plurality of impedance measuring instruments in a first embodiment of the present invention.
Fig. 2 is a diagram showing an example of an impedance measurement system using a plurality of synchronous detection impedance meters according to the first embodiment.
Fig. 3 is a diagram showing induced magnetic fluxes generated by a plurality of impedance measuring instruments being formed in phase.
Fig. 4 is a diagram showing a configuration in which the phases of the alternating current for measurement of adjacent impedance measuring instruments are inverted in the second embodiment of the present invention.
Fig. 5 is a diagram showing that the induced magnetic flux generated by the impedance measuring instruments is reversed and eliminated.
Fig. 6 is a diagram showing a configuration of an impedance measuring instrument using a synchronous detection method.
Fig. 7 is a diagram illustrating induced voltage generated by induced magnetic flux generated by eddy current of metal in the vicinity of the impedance measuring instrument.
(symbol description)
1-1 to 1-n … impedance measuring instrument
2 … phase synchronous signal generator
3-1, 3-2 … samples to be measured
4 … metal plate
11-1 to 11-n … constant current source
12 … Voltage detection part
13. 13-1 to 13 n … sample (DUT)
14. 14-1 to 14-n … resistor (Rs) for current detection
15. 15-1 to 15-n, 16-1 to 16-n … amplifier
17. 17-1 ~ 17-n … Band Pass Filter (BPF)
20. Synchronous detector for 20-1 to 20-n, 21-1 to 21-n …
22. 22-1 to 22-n … Low Pass Filter (LPF)
23. 23-1 to 23-n … analog-to-digital converter
24. 24-1 to 24-n … treatment section
25. 25-1 to 25-n … output part
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing the configuration of an impedance measurement system according to a first embodiment of the present invention, and shows a configuration in which measurement alternating currents generated by a plurality of impedance measurement instruments are supplied to a sample to be measured in phase in synchronization with each other to perform impedance measurement.
The impedance measuring instruments 1-1 and 1-2 … … measure the impedance of the sample to be measured by supplying the samples 3-1 and 3-2 … … to be measured with the alternating current for measurement of a predetermined frequency from the constant current sources 11-1 and 11-2 … …, respectively, and detecting the voltage by the voltage detecting units 12-1 and 12-2 … …. The impedance measuring system is provided with a plurality of impedance measuring instruments 1-1 and 1-2 … …, wherein the impedance measuring instruments 1-1 and 1-2 … … are connected in communication, and are controlled in such a manner that alternating current for measurement is supplied to a sample to be measured in phase.
An example in which an impedance measuring apparatus using a synchronous detection method constitutes the impedance measuring system shown in fig. 1 will be described with reference to fig. 2.
The impedance measuring system is provided with a plurality of impedance measuring instruments 1-1, 1-2 … … -n and a phase synchronization signal generator 2 shared by the impedance measuring instruments 1-1, 1-2 … … 1-n, and each of the impedance measuring instruments 1-1, 1-2 … … -n is configured such that: the phase synchronization signal supplied from the phase synchronization signal generator 2 is used to control the phases of the measurement alternating currents generated by the respective constant current sources in a synchronized manner, thereby measuring the impedance of the samples 13-1 and 13-2 … … -n to be measured.
Each impedance measuring instrument includes: a constant current source for generating a measurement alternating current i of a predetermined frequency, a current detection resistor (Rs) 14, amplifiers 15 and 16, a Band Pass Filter (BPF) 17 for allowing the measurement frequency to pass, a synchronous detector 20, a Low Pass Filter (LPF) 22, an analog-to-digital converter (ADC) 23, a processing unit 24, and an output unit 25.
The operation of the impedance measuring instrument will be described.
A measurement alternating current i is supplied from a constant current source to a sample 13 (DUT: device under test, abbreviated as "device under test"). Here, sample 13 is a battery having internal resistance Rx. The resistor (Rs) 14 is a current detection resistor for detecting the current value of the alternating current i for measurement, and is inserted in series with the constant current source and the sample 13. Reference numeral 15 denotes an amplifier which amplifies a detection signal (voltage signal) appearing in the sample 13 based on the alternating current i for measurement. Similarly, reference numeral 16 denotes an amplifier which amplifies a voltage signal detected by the current detection resistor (Rs) 14. The voltage detection signal v amplified by the amplifier 15 1 And is input to the synchronous detector 20 through a band-pass filter (BPF) 17 that allows the measurement frequency to pass. Further, a reference signal v synchronized with the alternating current i for measurement 2 Amplified by the amplifier 16 and input to the synchronous detector 20. The synchronous detector 20 uses the reference signal v 2 For voltage detection signal v 1 Synchronous detection is performed, and the detection output thereof is input to a Low Pass Filter (LPF) 22 for removing an alternating current component to remove the alternating current component, and then input to an analog-to-digital converter (ADC) 23. The analog-to-digital converter 23 converts the synchronous detection output into a digital signal. The converted digital signal is input to a processing unit 24 provided with an arithmetic unit, the ac impedance value of the sample 13, the parameter of the equivalent circuit, and the like are calculated, and these values are displayed on a display unit of an output unit 25 or the like, or printed and outputAnd (6) discharging. The data is recorded in the storage device by the processing unit 24.
The voltage detector 12 shown in fig. 1 corresponds to a structure for detecting the voltage of the sample after the amplifier 15 and outputting the ac impedance value.
The effect of synchronizing the phases of the alternating currents for measurement in the plurality of impedance measuring instruments 1-1 and 1-2 will be described with reference to fig. 3.
Since the phases of the alternating currents for measurement output from the constant current sources 11-1 and 11-2 of the impedance measuring instruments 10-1 and 10-2 are synchronized, the phases of the eddy currents and the magnetic fluxes generated in the metal plate 4 are uniform. Therefore, the induced voltage generated by the eddy current may become twice as large, but its influence becomes a fixed deviation for the impedance measuring instruments 10-1, 10-2. Because of the fixed offset, it can be ignored by performing null adjustment (also referred to as "Zero Adjust"). The zero adjustment means that: for the sample to be measured, a resistance value occurring when measurement is performed using a jig for null adjustment, for example, a sample of 0 Ω is subtracted from a subsequent measurement value, and fixed error adjustment is performed.
As described above, by synchronizing the phases of the measurement alternating currents supplied from the plurality of impedance measuring instruments, the deviation of the fixed measurement value is detected, and by adjusting the deviation of the fixed measurement value, even if there is an influence of the induced voltages, it is possible to perform more accurate impedance measurement with a small error.
Next, a second embodiment of the present invention will be described with reference to fig. 4 and 5.
In the second embodiment of the present invention, as shown in fig. 4, the phases of the alternating current for measurement output from adjacent impedance measuring instruments are opposite.
At this time, since the directions of magnetic fluxes generated from the cables of the probes of the adjacent impedance measuring instruments are opposite to each other, the magnetic fluxes cancel each other as shown in fig. 5, and unlike the case of fig. 3, the induced voltage is reduced, and the noise is reduced. In addition, since eddy current is not generated in the surrounding metal, measurement error due to the influence of eddy current generated in the surrounding metal becomes small. In this case, since there is no case where a fixed deviation of the measured value occurs due to the induced voltage of the magnetic flux generated by the plurality of impedance measuring instruments as in the first embodiment, the null adjustment of the error due to the induced voltage, which is necessary in the first embodiment, is not necessary in this case.
In the case where the impedance measuring instruments are odd-numbered, the measurement alternating currents of the impedance measuring instruments adjacent to the central impedance measuring instrument may be in opposite phases, and therefore, the impedance measuring instruments are not only even-numbered but also odd-numbered.
In order to invert the phase of the alternating current for measurement, the alternating current for measurement generated by one of the adjacent impedance measuring instruments may be output by being inverted by a half wavelength in phase, based on the phase synchronization signal supplied to each impedance measuring instrument.
In the above embodiment, as a configuration for synchronizing the phases of the alternating currents for measurement of the impedance measuring instruments, the phase synchronization signal generator 2 is configured to supply the synchronization signal to each impedance measuring instrument in fig. 2, but the configuration may be such that: the phase synchronization signal generator 2 is provided to the first impedance measuring device 1-1 as a main impedance measuring device, the other impedance measuring devices 1-2 and … … are sub impedance measuring devices, and a synchronization signal is transmitted from the first impedance measuring device 1-1. Further, the following may be configured: the clock pulses of the oscillators serving as constant current sources of the alternating current for measurement of the impedance measuring instruments are synchronized by the synchronization signal. Alternatively, the following may be configured: one main impedance measuring instrument outputs a measuring alternating current of a predetermined frequency, and each impedance measuring instrument supplies the phase of the measuring alternating current to a sample to be measured while synchronizing or shifting the phase of the measuring alternating current by a half wavelength. Further, not only a wire but also a wireless may be used to transmit the synchronization signal to the impedance measuring instrument.
In the above-described embodiment, the example in which the sample is supplied with the ac constant current from the constant current source to measure the impedance was described, but the impedance measurement may be performed using the voltage. For example, an ac constant voltage may be supplied from a voltage source to the sample, and the impedance may be measured by synchronous detection. When the object to be measured is a battery, it is preferable to measure the impedance with a constant current, but for example, when a capacitor, which is incorporated in a circuit and may cause noise, is used, the impedance may be measured with a constant-voltage ac.
Claims (3)
1. An impedance measuring system comprising a plurality of impedance measuring instruments for supplying a measuring alternating current having a predetermined frequency to a sample to be measured,
the phase of the alternating current for measurement supplied by the adjacent impedance measuring instrument is opposite; and is
When the impedance measuring instruments are odd, the alternating current for measuring instruments adjacent to the central impedance measuring instrument, which outputs the alternating current for measuring at a predetermined frequency, is formed in an opposite phase, and the alternating current for measuring adjacent to the central impedance measuring instrument is supplied to the sample to be measured while shifting the alternating current for measuring by half a wavelength.
2. The impedance measurement system of claim 1,
the impedance measuring instrument is a synchronous detection impedance measuring instrument, and the synchronous detection impedance measuring instrument includes:
a measurement alternating current source for supplying the measurement alternating current,
a reference signal generating unit for generating a reference signal synchronized with the alternating current for measurement,
a synchronous detection section for synchronously detecting a detection signal appearing in the sample with the reference signal, and
and a low pass filter for passing the synchronously detected signal.
3. An impedance measuring method of supplying a measuring alternating current of a predetermined frequency from a plurality of impedance measuring instruments to a sample to be measured, synchronously detecting a detection signal appearing in the sample with a reference signal synchronized with the measuring alternating current, extracting a direct current component of the signal after the synchronous detection, and measuring an alternating current impedance of the sample,
the phase of the alternating current for measurement generated by the adjacent impedance measuring instruments is in the opposite phase; and is
When the impedance measuring instruments are odd numbers, the alternating current for measuring instruments adjacent to the central impedance measuring instrument is formed into an opposite phase, wherein the central impedance measuring instrument outputs the alternating current for measuring with a predetermined frequency, and the respective alternating currents for measuring are supplied to the sample to be measured with a shift of half wavelength.
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| JP7364434B2 (en) | 2019-11-14 | 2023-10-18 | 日置電機株式会社 | Zero adjustment correction method and impedance measurement method |
| JP7338600B2 (en) * | 2020-10-02 | 2023-09-05 | 株式会社デンソー | gas sensor |
| US11604229B2 (en) | 2020-12-28 | 2023-03-14 | Analog Devices International Unlimited Company | Techniques for determining energy storage device state of health |
| JP2022188935A (en) * | 2021-06-10 | 2022-12-22 | 株式会社デンソー | Battery measuring device and battery state measuring method |
| JP2023008978A (en) * | 2021-07-02 | 2023-01-19 | 日置電機株式会社 | Impedance measurement system |
| CN114190041B (en) * | 2021-11-08 | 2023-10-20 | 陕西千山航空电子有限责任公司 | Electromagnetic interference filtering structure of power supply module |
| JP2023107030A (en) * | 2022-01-21 | 2023-08-02 | 日置電機株式会社 | Impedance measuring device and method |
| CN117169755B (en) * | 2023-11-02 | 2024-01-12 | 青岛艾诺仪器有限公司 | AC impedance measuring system and measuring method |
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