Impedance measuring device and impedance measuring method

Abstract

The invention provides an impedance measuring device and an impedance measuring method capable of carrying out stable measurement. By using a plurality of measuring frequencies to carry out following measurements and acquiring measuring frequencies having low noises, the measurements comprise steps that synchronous detection of a measuring object in a state without being supplied with measuring signals, namely, the detection signals occurring in samples, is carried out by using two reference signals synchronized with the measuring signals and having orthogonal phases, namely synchronous signals, and the noise level of the samples is measured; the measuring signals having the frequencies of low noises are provided to the samples, and the reference signals are used for the synchronous detection of the detection signals to measure the impedance of the samples; or the samples used as the measuring objects are used to provide the measuring signals having the specific frequencies to generate the reference signals synchronized with the measuring signals, and by using the reference signals, the synchronous detection of the detection signals occurred in the samples is carried out; a plurality of low pass filters having different characteristics are used to let the signals after the synchronous detection pass, and any of the plurality of low pass filters is selected, and the selection is ended by the acquisition of the measuring values without the noise influences.

Description

technical field [0001] The present invention relates to an impedance measuring device and an impedance measuring method. Background technique [0002] As a method of measuring the internal impedance of elements constituting a circuit, there is an AC impedance measurement method of applying an AC signal to a sample to be measured and measuring its electrical response. With this method, the magnitudes of the resistance component, capacitance component, and inductance component of the sample can be checked. In addition, it is possible to obtain what kind of equivalent circuit the above-mentioned components constitute in the sample, or the parameters of the equivalent circuit. [0003] As this AC impedance measurement method, there is a method in which a measurement AC current in the form of a sine wave is supplied to the sample from a constant current source, and a reference signal of the same frequency as the supplied measurement AC current (or also called This is an impedan...

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Problems solved by technology

[0027] However, there are cases where the noise cannot be completely removed even by performing synchronous detection using a reference signal that is in phase with the measurement AC current and removing the AC component with a low-pass filter.

[0028] When noise of the same frequency as the measurement signal enters the detection signal, the noise is superimposed on the DC component of the synchronous detection output, so the noise cannot be removed by a low-pass filter

Also, when the noise is at a frequency close to the measurement frequency, it is difficult to remove all the noise due to the characteristics of the low-pass filter.

[0029] For example, when the measurement frequency is 1kHz and the noise frequency is 1.01kHz, as for the non-DC low AC component, even if it can be removed, only a small part can be removed, but not all can be removed.

In addition, even a bandpass filter cannot remove noise at frequencies near the center frequency, which is the measurement frequency, so it is difficult to remove noise near the measurement frequency

[0030] Additionally, the low-pass filter has features such as Figure 12 The frequency characteristics shown can completely remove high-frequency noise above X(Hz), but can hardly remove low-frequency noise below X(Hz)

[0031] Thus, when the noise is close to the measured frequency (such as at Figure 12 In the case of noise at a frequency of X (Hz)), it is difficult to remove all the noise with a low-pass filter having an attenuation characteristic of almost no attenuation relative to the frequency

[0032] Therefore, there are problems that measurement errors occur when noise enters the detection signal, and the measured impedance value also varies, so that the measured value is unstable.

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