KR100350062B1 - Apparatus for accurately measuring impedance and method used therein - Google Patents

Abstract

An apparatus for measuring impedance generates alternating current from a digital code representing a sinusoidal wave, and converts an ac voltage by alternating current flowing into the object 11 into a digital signal; The multiplier 5 successively multiplies the binary values of the digital signal by the binary values of the digital code representing the sine and cosine waves, the accumulator 6 successively sums the products, and the microcomputer 9 By calculating the impedance of the object 11 based on the sum of the enemies, the accuracy of the calculation result is improved.

Description

Apparatus for accurately measuring impedance and method used therein}

The present invention relates to impedance measurement, and more particularly, to an impedance measuring apparatus and method.

In the following description, the term 'impedance' means the absolute value of the impedance of the electric circuit, the value of the real part, the value of the imaginary part and the ratio between them. A typical example of measuring impedance is known from Japanese Patent Laid-Open No. 61-266965. 1 shows a conventional apparatus for impedance measurement. Although the reference symbols are different, Fig. 1 corresponds to Fig. 1 known from the Japanese Laid-Open Patent Publication.

The conventional apparatus measures the impedance of the target circuit 100. The target circuit 100 is assumed to be a capacitive element and has an admittance (Y) expressed as Y = G + jB, where G is conductance and B is susceptance. Conventional devices include an AC power supply 102, a current voltage converter 103, a phase discriminator 104, a phase shifter 105, a phase discriminator 106, a comparator 107, a switching unit 108, and an analog It includes a digital converter 110. The AC power supply 102 applies the voltage e to the target circuit, and the current ig flows from the target circuit 100 to the current voltage converter 103. The amount of current is represented by e (G + jB). The current voltage converter 103 converts the current ig into the output voltage e _y , and the output voltage ey is equal to −R × ig. The output voltage ey is applied to the phase discriminators 104 and 106.

The phase discriminator 104 multiplies the voltage e _{y by} the output voltage e of the AC power supply 102 to obtain a DC component. The phase discriminator 104 outputs _a dc voltage e _a proportional to the conductance G. On the other hand, the other phase discriminator 106 multiplies the voltage e _{y by} the output voltage of the phase shifter 105. The phase shifter 105 receives a voltage e of the AC power supply 102 to allow a phase delay of 90 degrees between the voltage e and the output voltage. For this reason, the phase discriminator 106 outputs a dc voltage e _b proportional to the susceptance B.

The switching unit 108 has two input terminals 109a and 109b. The dc voltage e _a is applied to the input terminal 109a, and the other dc voltage e _b is applied to the other input terminal 109b. The switching unit 108 selectively supplies the dc voltages e _a and e _b to the analog-to-digital converter 110, and the analog digital converter 110 converts the dc voltages e _a and e _b to a digital signal. .

The conventional measuring device further includes a microcomputer 111, an AC voltage DC converter (AC / DC converter) 112, an analog digital converter 113, and display units 114a and 114b. The output voltage e _y is applied to the ac voltage dc voltage converter 112, and the ac voltage dc voltage converter 112 converts the output voltage e _y into a dc voltage and outputs the converted voltage. This dc voltage is proportional to the absolute value of the admittance (Y). The dc voltage is applied to the analog digital converter 113 and converted into a digital signal.

The analog digital converters 110 and 113 are connected to the microcomputer 111. The microcomputer 111 calculates the conductance G and the susceptance B based on the digital signal applied from the analog-to-digital converter 110, and the display units 114a and 114b respectively conduct the conductance G and the susceptor. The turn B is displayed. The microcomputer calculates the absolute value of the admittance based on the digital signal applied from the analog-digital converter 113.

The operation of the comparator 107 will now be described. Compare the dc voltage (e _a ) with the dc voltage (e _b ). If the admittance (Y) is much greater than the conductance (G), i.e. if Y '' G, then the susceptance (B) is

It is expressed as

For this reason, the microcomputer 111 ignores the digital signal converted from the dc voltage e _b and calculates the susceptance B based on the digital signal applied from the analog digital converter 113.

On the other hand, if the admittance (Y) is much larger than the susceptance (B), that is, if Y > B, then the conductance (G) is

It is expressed as

For this reason, the microcomputer 111 disregards the digital signal converted from the dc voltage e _a and calculates the conductance G based on the digital signal applied from the analog digital converter 113. This is because the ac voltage dc voltage converter 112 is much better than the phase discriminators 104 and 106. In fact, the error by phase discriminators 104 and 106 is on the order of 0.1 to 0.2 percent. On the other hand, the error caused by the ac voltage dc voltage converter 112 is about 0.01 percent. Therefore, the microcomputer 111 gives priority to the digital signal supplied from the ac voltage dc voltage converter 112 through the analog to digital converter 113, thereby improving accuracy.

In the above Japanese Laid-Open Patent Publication, a device for measuring impedance of an inductive element is further disclosed. The resistance R, reactance X and impedance Z are measured in a similar manner to the method described above. The mitrocomputer gives priority to the digital signal converted from the dc voltage representing the impedance Z, and calculates the resistance R or the reactance X based on the digital signal under the conditions Z »X or Z» R.

However, even if the priority given to the ac voltage dc voltage converter 112 improves the accuracy of the measurement (measurement of conductance or susceptance under the conditions Y '' G or Y '' B), the measurement is still a dc voltage (e _b or e _a). Susceptance or conductance calculated based on the converted digital signal. If the admittance (Y) is not much larger than the conductance (G) and the susceptance (B), both the conductance (G) and the susceptance (B) are calculated based on the digital signals converted from the dc voltages (e _a , e _b ). It is done. Therefore, the conventional apparatus still has a problem in the accuracy of the measurement. This is the first inherent problem in conventional devices.

The second problem is the noise component caused by the dc offset voltages of the phase discriminators 104 and 106. Conventional devices are connected to several types of electrical circuits 105 and phase discriminators 104 and 106 require dc amplification for the dynamic range. The dc voltage (e _a , e _b ) includes a dc offset voltage, which is transmitted as a digital signal through the AD conversion. As a result, the digital signal contains noise components, which degrade the measurement. This is the second essential problem in conventional devices.

The third problem lies in the phase shifter 105. The phase shifter 105 is for delaying the phase by 90 degrees, but the phase shifter cannot always shift the output voltage e by 90 degrees. This means that analog multiplication is not accurate.

The same problem arises with conventional devices using inductive elements.

Therefore, it is an object of the present invention to provide an apparatus for accurately measuring impedance.

Another object of the present invention is to provide a method for accurately measuring impedance.

1 is a block diagram showing a circuit configuration of a conventional measuring apparatus disclosed in Japanese Patent Laid-Open No. 61-266965.

2 is a block diagram showing a circuit configuration of a measuring apparatus according to the present invention.

3 is a graph showing a relationship between an average angular frequency and a gain.

4 is a block diagram showing a circuit configuration of another measuring apparatus according to the present invention.

5 is a block diagram showing a circuit configuration of another measuring apparatus according to the present invention.

6 is a block diagram showing a circuit configuration of another measuring apparatus according to the present invention.

* Explanation of symbols for the main parts of the drawings.

1: read-only memory 2: digital analog converter

3: voltage and current converter 4: analog and digital converter

5: multiplier 6: accumulator

7, 8: register 9: microcomputer

10: controller 11: object

12: mixer 13: noise source

14 ~ 23: Register 24: Voltage flower

25 resistor element 26 op amp

The present invention for achieving this object proposes to digitize signal processing to determine impedance.

In order to achieve the first object of the present invention, an apparatus for measuring an impedance of an object includes a terminal connected to the object and a second analog signal connected to the terminal and changing periodically to generate a second analog signal. A periodic signal generator for supplying a first analog signal generated from a digital signal to an object through a terminal, a digital signal generator for generating a second digital signal from a second analog signal, and a periodic signal generator and a digital signal generator And a data processor for supplying a first digital signal and a second digital signal for determining impedance.

To achieve another object of the present invention, a method for measuring an impedance of an object includes the steps of a) generating a first analog signal from a first digital signal, and b) generating a second analog signal that varies with impedance. Supplying a first analog signal to an object for the purpose, c) converting the second analog signal to a second digital signal, and d) determining impedance through digital processing on the first digital signal and the second digital signal. It includes a step.

Hereinafter, with reference to the accompanying drawings will be more clearly understood by explaining the characteristics and advantages of the measuring device and method.

First embodiment

In Fig. 2, the measuring device embodying the present invention includes a read-only memory 1, a digital analog converter 2, a voltage current converter 3, an analog digital converter 4, a multiplier 5 and an accumulator 6 , Registers 7 and 8, microcomputer 9 and controller 10. The object 11 is connected between the measuring device and the ground, and the impedance of the object 11 is measured.

The read only memory 1 stores discrete values representing one quarter of a sine wave (sine wave), which are stored over time. The sine wave is the angular frequency ( 0). The discrete values are repeatedly read from the read-only memory 1 and supplied to the voltage current converter 3 through the digital analog converter 2. The alternating current is generated from the discrete values and flows into the object 11, the alternating current is converted into an ac voltage, and the analog-digital converter 4 digitizes the ac voltage. The microcomputer 9 uses angular frequencies (based on digital data signals representing ac voltages and discrete values). The impedance of the object 11 is calculated at 0).

The controller 10 controls the read-only memory 1, the multiplier 5, and the accumulator 6. In detail, the controller 10 reads the discrete values from the read-only memory 1. As described above, the discrete value represents a quarter of the sinusoidal wave, and the controller 10 sequentially addresses the location of the memory as follows. First, the controller 10 sequentially reads the discrete values in a regular order, and then reads the discrete values in reverse. Next, the controller 10 instructs the read-only memory 1 to change the polarity of the discrete values, and read the discrete values in a regular order. Finally, the controller 10 reads back the discrete values whose polarities are changed. Sinusoidal waves are then generated from the discrete values.

A cosine wave (cosine wave) is further generated from the discrete values. The controller 10 repeats generation of a sine wave and generation of a cosine wave in a time division manner. First, the controller 10 reads the discrete values back. The controller 10 instructs the read-only memory 1 to change the polarities of the discrete values, and read the discrete values whose polarities are changed in a regular order. Next, the controller 10 reversely reads discrete values whose polarities are changed. Finally, the controller 10 reads the discrete values in a regular order without changing polarity. The cosine wave is 90 degrees out of phase with the sinusoidal wave.

The digital analog converter 2 converts a series of discrete values representing sinusoidal or cosine waves into an analog signal. The analog signal is changed in voltage level and applied to the voltage current converter 3. The voltage current converter 3 generates an alternating current from the analog voltage signal, and supplies the alternating current to the object 11. The voltage current converter 3 may be implemented by the OP amplifier of FIG. 1.

When alternating current flows into the object 11, the alternating current is multiplied by the impedance of the object 11. The product is expressed in ac voltage. The ac voltage represents sinusoidal and cosine waves in a time division manner. The ac voltage is supplied to the analog digital converter 4 and converted into a digital signal. The digital signal is applied to the multiplier 5.

The multiplier 5 multiplies the digital signal by discrete values representing part of the sinusoidal wave. The multiplier 5 also multiplies the digital signal by a discrete value representing a portion of the cosine wave. Discrete values stored in the read-only memory 1 can Only one quarter of a sinusoid with 0) is shown. However, signal processing from digital analog conversion to analog to digital conversion causes quantization noise and external noise to flow into the digital signal. For this reason, the digital signal must In addition to several angular frequencies (0) Represents a cosine wave or a sine wave. However, the digital signal does not take into account the difference between direct current and alternating current. Under the assumption that sine and cosine waves of 0) are represented, explanation of the principle of measurement according to the present invention has been made first.

Sine wave 0t) represents an alternating current, the impedance of the object 11 affects the alternating current, and the response functions are sinusoidal (sin) by the real part of the impedance. 0t) and the cosine wave by the imaginary part of the impedance (cos 0t). As described above, the multiplier 5 has a sinusoidal sin at different times in the digital signal. 0t) and cosine wave (cos Multiply the discrete values representing 0t). The multiplier (5) is sinusoidal (sin Value of 0t and cosine wave (cos Sine wave to the value of 0t Multiplying the discrete values representing 0t), the real part of the impedance is sin ² 0t = 1/2 (1-cos2 Create a procduct containing 0t), and the imaginary part of the impedance is sin 0t × cos 0t = 1/2 sin2 Create an enemy containing 0t. AC component cos2 0t and sin2 0t is subtracted from the product so that the digital signal representing the difference has a value proportional to the real part of the impedance.

On the other hand, the multiplier 5 is sinusoidal (sin Values of 0t and cosine wave Cos to the values of 0t Multiplying the discrete values representing 0t), the real part of impedance is cos 0t × sin 0t = 1/2 sin2 Create an enemy containing 0 t and the imaginary part of the impedance is cos 0t × cos 0t = 1/2 (1 + cos2 Create an enemy containing 0t). After removal of the AC component, the digital signal is proportional to the imaginary part of the impedance.

The accumulator 6 removes the AC component from the digital signal representing the enemies. The accumulator 6 successively adds enemies for multiple periods. If the digital signal applied from the analog-digital converter 4 does not include quantization noise and external noise, the AC component is only sin2. 0t and cos2 Only 0t, the alternating current component is removed from the digital signal only through accumulation for one cycle. However, the digital signal supplied to the multiplier 5 inevitably includes quantization noise and external noise. In order to remove such noise and alternating current components from the enemies, the accumulator 6 accumulates the enemies in more than 100 cycles. As a result of accumulation, the sum of the enemies and the sum of the other enemies are applied to the registers 7 and 8, respectively, and stored there. Registers 7 and 8 are assigned to the sine and cosine terms respectively, as will be explained below.

Upon completion of accumulation, the microcomputer 9 retrieves digital values representing the sums of the enemies from the registers 7, 8. The microcomputer 9 adds each other by square the sums of the enemies. The microcomputer 9 finds the square root of its sum. The square root is proportional to the absolute value of the impedance. The microcomputer 9 has a ratio of the real part to the imaginary part, that is, the phase angle tan Determine the same agreement ratio as

The digital signal vi applied to the multiplier 5 is divided into Asin ( t + φ). The multiplier 5 performs the product of the digital values representing the part of the sinusoid and the digital values representing the part of the sinusoid for n periods, and the accumulator 6 performs the sinusoidal term Hs ( ) And the cosine term Hc ( ) Are stored in registers 7 and 8, respectively. Sine Port Hs ( ) And the cosine term Hc ( ) Is expressed as

First of all, the sinusoidal term Hs ( )silver

Is calculated as = If 0, the sine term Hs ( )silver

Is given by

On the other hand, if ≠ If 0, the sine term Hs ( )silver

Hs ( ) = (Ai / 2) [[sin {( - 0) t + } / ( - 0)] -

= (Ai / 2) [[sin {2n (( Of 0) -1) + }-sin ( )] / ( - 0) -

[sin {2n (( Of 0) +1) + }-sin ( )] / ( + 0)]

= (Ai / 2) {sin {2n ( Of 0) + }-sin ( )}{2 0/( ^2- 0 ² )}

= 2 Aicos {n ( Of 0) + } sin {n ( Of 0) } { 0/( ^2- 0 ² )}

Is given by

Cosine Port Hc ( )

Is calculated as = If 0, the cosine term Hc ( )silver

Is given by

On the other hand, if ≠ If 0, the cosine term Hs ( )silver

=-(Ai / 2) [[cos {2n (( Of 0) +1) + }-cos ( )] / ( + 0) +

[cos {2n (( Of 0) -1) + }-cos ( )] / ( - 0)]

=-(Ai / 2) {cos {2n ( Of 0) + }-cos ( )}[{One/( + 0)} +

{One/( - 0)}]

= 2 Aisin {n ( Of 0) + } sin {n ( Of 0) } { 0/( ^2- 0 ² )}

Is given by

if, = If 0, sum of squares H ( ) ² is

Is given by

On the other hand, if ≠ If 0, sum of squares H ( ) ² is

Is given by

In the present invention, assuming that n is 32, the sum of H ( ² ). Angular frequency ( ) Is the angular frequency ( Off, 0, the gain decreases.

In the first embodiment, the read-only memory 1, the controller 10, the digital analog converter 2 and the voltage current converter 3 constitute a periodic signal generator as a whole, and the analog-digital converter 4 is digital. It acts as a signal generator. The multiplier 5, the controller 10, the accumulator 6, the registers 7 and 8 and the microcomputer all constitute a data processor.

As can be seen from the above description, the measuring apparatus according to the present invention stores a part of the data information representing the sine wave in the form of a digital code, and converts the ac voltage into a digital signal. This means that the impedance is determined through digital signal processing. Only quantization noise is introduced into the digital signal applied from the analog digital converter 4 to the multiplier 5. The discrete values are stored in the form of digital code and fed directly to the multiplier 5. This means that the digital signal has no noise component due to the dc offset voltage. When accumulating the product of the sine wave for the accumulator (6) N cycles, the improvement of the resolution (resolution) is given by 1 / 2log ₂ N. If N is 256, the resolution is improved to 4 bits. Therefore, digital signal processing becomes more accurate than analog signal processing, and the measuring device achieves better resolution than conventional devices.

Moreover, the accumulator 6 extracts the dc component after the multiplication like the digital filter. This means that some low pass filter is needed to remove the AC components. The capacitor is incorporated in the low pass filter, which is not suitable for the integrated circuit (IC). No capacitor is integrated into the accumulator 6, and the manufacturer easily integrates the components 1 to 10 into the semiconductor chip.

Second embodiment

4 illustrates another apparatus embodying the present invention. The mixer 12, the noise source 13 and the registers 14 and 15 have been added to the measuring device implementing the first embodiment, and other components correspond to the components of the first embodiment. For this reason, other components are omitted from the detailed description and given the same reference numerals as in the first embodiment. Discrete values representing the sine wave are assigned to the register 14, and discrete values representing the cosine wave are assigned to the other register 15.

As described above, the noise components added between the digital analog conversion and the analog-digital conversion are obtained through the accumulation of enemies through the sinusoidal term Hs ( ) And the cosine term Hc ( ) Is removed. However, while the controller 10 regularly reads discrete values from the read-only memory 1, the quantization noise is also regularly mixed with the digital signal applied to the multiplier 5, which is sine through accumulation of enemies. Term Hs ( ) And the cosine term Hc ( Rarely removed from The noise source 13 irregularly generates noise components, and the mixer 12 adds irregular noise components to the digital signal. The irregular noise component breaks the regularity of the quantized noise component, and the accumulator 6 causes the sinusoidal term Hs ( ) And the cosine term Hc ( To remove the noise component.

The registers 14 and 15 temporarily store discrete values representing part of the sinusoidal wave and discrete values representing part of the cosine wave, and apply them to the multiplier 5. Registers 14 and 15 simplify the control of the product. Of course, the measuring device implementing the second embodiment also achieves the advantages described in connection with the first embodiment.

In the second embodiment, the read-only memory 1, the controller 10, the digital analog converter 2 and the voltage current converter 3 constitute a periodic signal generator as a whole, and the analog digital converter 4, noise The circle 13 and mixer 12 are combined to form a digital signal generator. The multiplier 5, the controller 10, the accumulator 6, the registers 7, 8, 14, 15 and the microcomputer 9 constitute a data processor as a whole.

Third embodiment

5 shows another measuring device embodying the present invention. Registers 7, 8, 14, and 15 are replaced by a plurality of registers 16 and 18, a plurality of registers 17 and 19, a plurality of registers 20 and 22, and a plurality of registers 21 and 23, respectively. . The other components correspond to the other components of the second embodiment and are given the same reference numerals without detailed description.

The read only memory 1 stores a plurality of discrete value sets representing different sinusoids. The plurality of registers 20 and 22 store discrete values representing sinusoids at angular frequency f1 and discrete values representing different sinusoids at angular frequency f2. Similarly, the plurality of registers 21 and 23 store discrete values representing the cosine wave at angular frequency f1 and discrete values representing another cosine wave at angular frequency f2. On the other hand, the plurality of registers 16 and 18 correspond to the sinusoidal term Hs of the angular frequency f1 ( ) And the sinusoidal term Hs of the angular frequency (f2) ), And the plurality of registers 17 and 19 correspond to the cosine term Hs of the angular frequency f1 ( ) And the cosine term Hc (of angular frequency (f2) Save). As such, the device implementing the third embodiment measures the impedance at different frequencies f1 and f2. Such a characteristic is preferable because the impedance value varies with each frequency. Using the measuring device embodying the third embodiment, the user measures impedance at different angular frequencies f1 and f2. The measuring device implementing the third embodiment achieves all the advantages described in connection with the first embodiment.

Fourth embodiment

6 shows another measuring device embodying the present invention. The voltage current converter 3 is replaced with a voltage flowr 24. Resistor 25 and ac amplifier 26 were added to the circuit configuration. The resistor 25 has a resistance value much smaller than the absolute value of the impedance of the object 11. The resistor 25 is connected between the object 11 and the ground, and two input terminals of the ac amplifier 26 are connected to both ends of the resistor 25, respectively. In the first, second and third embodiments, the alternating current is supplied from the voltage current converter 13 to the object 11 and converted into an ac voltage. However, the present invention is not limited to the case of ac current. In the fourth embodiment, the voltage flower 24 applies an ac voltage to the object 11. The resistor 25 generates a very small voltage drop, which is amplified by the ac amplifier 26. The other characteristics are similar to those of the first embodiment, and further description thereof is omitted below. The measuring device carrying out the fourth embodiment achieves all the advantages described in connection with the first embodiment.

In the fourth embodiment, the read-only memory 1, the controller 10, the digital analog converter 2 and the voltage flowr 24 constitute a periodic signal generator as a whole. The resistor 25, ac amplifier 26 and analog-to-digital converter 4 are combined with each other to form a digital signal generator. The multiplier 5, the controller 10, the accumulator 6, the registers 7 and 8 and the microcomputer 9 constitute a data processor as a whole.

Way

Hereinafter, the impedance measuring method of a measuring apparatus is demonstrated. A measuring method will be described with reference to FIG. 2. The read only memory 1 stores discrete values representing one quarter of a sine wave. Discrete values are stored in the form of digital codes and represent one quarter of a sine wave at predetermined time intervals. The controller 10 stores a part of control data indicating a predetermined time interval and another part of control data indicating a predetermined period for accumulation.

The object 11 is connected between the terminals T1 and T2 of the measuring device. The measuring device is energized. Next, the controller 10 reads the discrete values at predetermined time intervals, and the discrete values are supplied from the read-only memory 1 to the digital analog converter 2. The digital analog converter 2 applies an analog signal to the voltage current converter 3, and the voltage current converter 3 causes an alternating current to flow to the object 11. As a result, an ac voltage is generated at the terminal T1 and supplied to the analog-digital converter 4. The analog digital converter 4 supplies the digital signals to the multiplier 5. The digital signals are multiplied by discrete values representing part of the sinusoidal wave and added continuously in the accumulator 6 for a predetermined period of time. The sum is the sinusoidal term Hs ( Is stored in the register (7). In addition, the digital signals are multiplied by discrete values representing a portion of the cosine wave, and continuously added in the accumulator 6 for a predetermined period. The sum is the cosine term Hc ( ), Which is stored in the register 8.

Finally, the microcomputer 9 has a sinusoidal term Hs ( ) And the cosine term Hc ( The absolute value of the impedance, the value of the real part, the value of the imaginary part, and the ratio between the real part and the imaginary part are determined.

As mentioned above, the measuring device performs digital data processing to determine the value of the impedance, thereby improving the resolution of the measurement and the accuracy of the measured values.

While specific embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications can be made within the spirit and scope of the invention.

For example, the read-only memory may store discrete values representing a portion of the cosine wave. In this case, the controller 10 generates a sine wave together with the cosine wave.

Displays and indicators can be connected to the microcomputer to show impedance.

According to the present invention, as described above, an apparatus for measuring impedance generates alternating current from a digital code representing a sine wave, converts ac voltage due to alternating current flowing into an object into a digital signal, and a multiplier is a binary value of the digital signal. Multiplied by binary values of digital codes representing sinusoidal and cosine waves, the accumulator successively sums the products, and the microcomputer calculates the impedance of the object based on the sum of the products, thereby improving the accuracy of the calculation result. Has an excellent effect.

Claims (21)

In the measuring device for measuring the impedance of the object, A port connected to the object; A periodic signal generator coupled to the port for supplying a first analog signal periodically changed and generated from a first digital signal to the object through the terminal to generate a second analog signal that changes with the impedance; A digital signal generator for generating a second digital signal from the second analog signal; And A data processor coupled to the periodic signal generator and the digital signal generator and supplied with the first digital signal and the second digital signal for determining the impedance; And the first digital signal is a digital signal representing both sinusoidal and cosine waves. delete delete 2. The first digital signal of claim 1, wherein the first digital signal is a series of discrete values on a first periodic wave and another phase on a second periodic wave (cosine wave) having a phase difference of 90 degrees from the first periodic wave. Represent a series of discrete values, The periodic signal generator, A memory for storing digital codes representing a portion of the series of discrete values; A controller coupled to the memory for repeatedly reading the portion of the series of discrete values in a different order in a time division manner to generate the first digital signal; And And a digital analog converter connected to the memory and the port to generate an alternating current acting as the first analog signal. 5. The method of claim 4, wherein the portion of the series of discrete values is on one quarter of the first periodic wave, and the controller is configured to transfer the portion of the series of discrete values from one end to the other end and from the other end to the one end. And reading out from one end to the other end after the polarity conversion of the discrete values and from the other end to the one end under the polarity conversion. The method of claim 1, wherein the periodic signal generator, A memory for storing a digital code representing a portion of the series of discrete values; A controller, coupled to the memory, for repeatedly reading the portion of the series of discrete values in a different order in a time division manner to generate the first digital signal; A digital analog converter coupled to the memory for converting the first digital signal into an analog signal; And And a voltage flower connected between said digital analog converter and said terminal to generate an alternating voltage serving as a first analog signal from said analog signal. 7. The method of claim 6, wherein the portion of the series of discrete values is on one quarter of the first periodic wave, and the controller is configured to transfer the portion of the series of discrete values from one end to the other. And reading from one end to said one end, from said one end to said other end after said polarity conversion of said discrete values, and from said other end to said one end under said polarity conversion. 2. The impedance meter of claim 1, wherein the digital signal generator comprises an analog to digital converter coupled between the port and the data processor. The method of claim 8, wherein the digital signal generator, A noise source for generating a noise signal indicative of irregular noise; And And a mixer having a first input terminal connected to the port, a second input terminal connected to the noise source, and an output terminal connected to the analog digital converter for mixing the noise signal and the second analog signal. Impedance measuring device, characterized in that. The digital signal of claim 8, wherein the port has an output terminal connected to the object and an input terminal connected to the periodic signal generator to supply an AC voltage serving as the first analog signal to the object, and the digital signal The generator further includes a resistance element connected between the output terminal of the port and a constant voltage source to generate a voltage signal that varies between both ends of the resistance element, and an amplifier is provided at both ends of the voltage signal to increase the magnitude of the voltage signal. Impedance measuring device having an input terminal connected to each and an output terminal connected to the analog-to-digital converter. 2. The method of claim 1, wherein the first digital signal represents a series of discrete values on a first periodic wave and another series of discrete values on a second periodic wave having a phase difference of 90 degrees from the first periodic wave. And the digital signal represents a first series of binary values relating to the real part of the impedance and a second series of binary values relating to the imaginary part of the impedance. 12. The method of claim 11, wherein the data processor is coupled to the periodic signal generator and the digital signal generator, the first series of binary values and the second series of values being coupled to the series of discrete values and the other series of discrete values. A multiplier for multiplying a series of binary values to produce first and second products; An accumulator coupled to the multiplier, accumulating first and second products to generate a sum of first products and a sum of second products; A first data store for storing the sum of the first products and the sum of the second products; And And a computer coupled to the first data store to determine the impedance based on the sum of the first products and the sum of the second products. 13. The computer-readable medium of claim 12, wherein the computer causes the sum of the first products and the sum of the second products to be the first square and the second square, respectively, And calculating a sum and calculating a square root of the sum to determine the impedance. 13. The apparatus of claim 12, wherein the data processor further comprises a second data store for storing the series of discrete values and the other series of discrete values, respectively. 13. The impedance measuring apparatus of claim 12, wherein the accumulator repeats accumulation for a predetermined period of time to remove noise components from the sum of the first products and the sum of the second products. 13. The method of claim 12, wherein the series of discrete values each has a plurality of additional series of discrete values on the first periodic wave at different frequencies, wherein the other series of discrete values are on the second periodic wave phase at different frequencies. Impedance measuring apparatus characterized in that it has a plurality of incident series of discrete values of. 17. The apparatus of claim 16, wherein the computer determines a plurality of values of the impedance at the different frequencies. In the method of measuring the impedance of the object, a) generating a first analog signal from the first digital signal; b) supplying the first analog signal to an object to generate a second analog signal that varies with the impedance; c) converting the second analog signal into a second digital signal; And d) determining the impedance through digital processing on the first digital signal and the second digital signal, And said first digital signal is a digital signal representing both sinusoidal and cosine waves. The method of claim 18, wherein step b) b-1) a substep of supplying the first analog signal to the object to generate a preliminary analog signal that varies with the impedance; And b-2) a sub-step of generating a second analog signal by mixing a noise signal representing irregular noise with the preliminary analog signal. 19. The method of claim 18, wherein the first digital signal represents a series of discrete values on a first periodic wave that is a sinusoidal wave and another series of discrete values on a second periodic wave that is a cosine wave, wherein the second digital signal is a real number of the impedance. A first series of binary values associated with a negative and a second series of binary values associated with an imaginary part of the impedance; Step d), d-1) multiplying the series of discrete values and the other series of discrete values by the first series of binary values and the second series of binary values to generate a first product and a second product A sub-step; d-2) accumulating the first and second products to obtain a sum of first products and a sum of second products; d-3) a substep of making the sum of the first products and the sum of the second products into a first square and a second square; d-4) calculating a sum of the first square and the second square; And d-5) a substep of obtaining a square root of the sum representing an absolute value proportional to the impedance. 20. The method of claim 19, wherein the series of discrete values and the series of other discrete values are values on a plurality of periodic waves of different frequencies and other periodic waves having a phase difference of 90 degrees from the plurality of periodic waves, respectively, and the impedance Impedance measuring method characterized in that having different values respectively corresponding to different frequencies.