KR20040094953A - Measuring method of true RMS voltage mixed with ripple noise - Google Patents

Abstract

PURPOSE: A method for measuring an effective value of a voltage of a micro signal included in a noise riffle is provided to obtain a real value of an impedance voltage by excluding a noise signal such as a riffle voltage from the impedance voltage. CONSTITUTION: A frequency of a constant current applied to a target commercial frequency is determined as s times of a frequency of commercial power in order to determine a frequency of an impedance voltage generated by the constant current as s times of the frequency of commercial power. A noise removal circuit such as a narrow band pass filter is used for passing only noise riffle voltage signals similar to the frequency of the constant current. In a first block, the noise riffle voltage is obtained during a constant integral period in the absent state of the constant current. In a second block, the impedance voltage is induced by supplying the constant current to the target. An AC instantaneous voltage including the impedance voltage and the noise riffle voltage is obtained during the integral period. An accurate value of the impedance voltage is calculated by using an effective value extraction method.

Description

Measuring method of true RMS voltage mixed with ripple noise}

To determine the degree of deterioration of the measuring object with the internal impedance that increases with aging, such as the battery, input AC current I _S across the terminals of the measuring object such as the battery to measure the voltage drop V _IS component (hereinafter referred to as impedance voltage) due to the internal impedance. The method of measuring internal impedance by measuring and diagnosing its health is common.

As shown in FIG. 1, since the internal impedance described above is very small in size, in order to minimize effects such as lead resistance of the lead or contact resistance of the plug, an AC 4-terminal measuring method is used. AC constant current I _S is input between both terminals of the measurement object such as battery, and internal impedance voltage V _IS generated between both terminals is measured through Sense terminal.

As an example, the impedance voltage signal measured at the battery terminal is converted into a pure AC signal through an operational amplifier coupled with a capacitor, amplified, and input to an A / D converter. The magnitude of the AC constant current I _S is converted into a voltage signal through a shunt, amplified by an operational amplifier, and the two values are input to an input circuit of an A / D converter of a microprocessor to obtain an effective value. The CPU calculates the impedance value by determining the effective value and phase of the two values, and the internal impedance mΩ = It is calculated according to the principle of × 10 ² × cosθ × K _C.

Recently, a patent filed by the present applicant (Application No .: 2003-0025823) proposes a system for diagnosing and selecting a defective battery by measuring the internal impedance of the battery while operating the battery in a constant floating state without disconnecting the battery from the operating system. It is becoming. When the battery is operating in a floating charge state, a harmonic ripple voltage is generated in the battery terminal voltage by the harmonic ripple current component included in the charging current of the battery. In addition, the size of the internal impedance of the battery has a very small value of several milliohms (mΩ). In general, in the case of a large capacity battery, the voltage due to the internal impedance of the battery cell is represented by several mV or less. As described above, since the internal impedance is extremely small, the parasitic impedance of the measurement circuit to be measured cannot be ignored and a large measurement error is caused by the parasitic impedance of the measurement circuit. Therefore, when the voltage due to the internal impedance is to be measured, the internal impedance voltage measurement of the battery is severely affected by the harmonic ripple voltage due to the charging current and the noise voltage due to parasitic impedance such as the wiring voltage drop of the measurement circuit.

In order to measure the effective internal impedance voltage from the above effect, AC constant current (I _S ) is input to the battery cell at the source terminal of the constant current circuit, the voltage signal V _IS of the internal impedance generated from the battery is measured, and the lead wire is only used using the 4-terminal circuit. In order to reduce the voltage drop of the resistance and the contact resistance so that it is hardly affected by it, a method has been used.

However, since the impedance voltage (V _IS ) of the battery cell is a minute signal in the unit of mV, it is very small compared with the cell terminal voltage (V _DC ) (one thousandth of a thousand) and the electromagnetic noise is mixed from the surroundings. It is necessary to amplify and extract only the AC voltage V _IS by optimally designing and using a noise removing circuit such as a pass filter. Furthermore, as described above, since the harmonic ripple current flows into the battery during floating charging, the terminal voltage waveform of the battery contains a large amount of harmonic ripple voltage. These harmonic ripple voltages vary depending on the rectification method of the charging device, but include harmonic ripples of various orders. Most of the high frequency ripple voltages can be removed by a noise removing circuit such as the band pass filter, but the AC constant current (I The high frequency ripple voltage in the frequency region adjacent to the frequency of _S ) is not completely removed by the noise canceling circuit. As an example, when the frequency of the AC constant current (I _S ) is around 1 KHz, the harmonic ripple voltage of 900-1140 Hz, which is similar in frequency range to the internal impedance voltage (V _IS ) used for the measurement, is not filtered (attenuated) and the internal impedance voltage. As it is mixed with the (V _IS ) signal and passed simultaneously, it severely affects the internal impedance measurement of the battery.

The frequency component of harmonic ripple voltage generated while the battery is running in the state of floating charge varies depending on the rectifier method (constant) of the charger. However, in the case of single-phase rectification method, the ripple frequency component of the commercial power supply 60Hz is better than even. In the three-phase rectification method, it has an odd (odd) times ripple frequency component. As described above, most of the frequency components other than the bandwidth can be filtered (attenuated) by a noise removing circuit such as a band pass filter, but high frequency ripple in the bandwidth (B = fr / Q) region adjacent to the AC constant current (I _S ) source frequency. The voltage cannot be removed. Therefore, when the frequency of the AC constant current (I _S ) is around 1 KHz as in the above embodiment, 900 Hz, the 15th order of the commercial power supply 60 Hz, 1020 Hz of the 17th order, 1140 Hz of the 19th order (16th order 960Hz and 18th order 1080Hz) ) Will have a significant impact on most measurements. As shown in FIG. 2, in the measurement signal at the rear stage filtered (attenuated) by a noise removing circuit such as a band pass filter, the multiple-order harmonic ripple voltage V _RP of the commercial power supply (60 or 50 Hz) and the AC constant current I _The impedance alternating voltage (V _IS ) by _S ) is mixed and measured at the same time, and the measured signal (hereinafter, 'AC instantaneous voltage') voltage waveform (V _SM ) is a shape that vibrates at regular intervals and contains a plurality of harmonic ripple voltages ( V _RP ) also has another constant period (T _RP ).

In the patent introduced above, the impedance AC voltage V _IS by the AC current I _S supplied from the constant current source from the measured signal voltage waveform V _SM including such a harmonic ripple voltage V _RP in claim 9. It suggests ways to obtain effective measures of. That is, in the first section T ₁ , without measuring the constant current I _S , the instantaneous value of the harmonic ripple voltage V _RP generated by the charging current of the battery cell during floating charging is measured and stored. The period T _RP of the ripple voltage V _RP from the internal high speed timer / counter value at the moment when the stored instantaneous value reaches the highest point (T ₁ ) and the timer / counter value at the moment when the next highest point is reached (T ₂ ). Calculate The instantaneous value of the stored harmonic ripple voltage V _RP may be always updated with the latest data when a value measured during one cycle is stored in a memory (shift register) and shifted. After a certain time, the constant current source is operated so that the constant current I _S is supplied and increases to the value T _RP corresponding to the Nth cycle after the internal timer / counter value reaches the lowest point in the second section T ₂ . At the moment of reading the value of ripple voltage (V _RP ) already stored in memory and ac voltage instantaneous voltage (V _SM ) including ripple coming through D / A converter, and the difference between the two instantaneous values (V _SM -V _RP ) Can be used to obtain the impedance voltage (V _IS ) that is not affected by the harmonic ripple voltage.

In addition, a cycle harmonic ripple voltage (V _RP), the rms value and the ripple voltage is included AC instantaneous voltage (V _SM) difference thereof to calculate the rms value of each of the during of the harmonic ripple voltage (V _RP) - impedance as () Although the method of calculating the impedance by taking the effective value of the voltage (V _IS ) has been proposed, the two methods must be calculated for the period (T _RP ) of the ripple voltage (V _RP ), but the ripple voltage is shown in several orders as shown in FIG. Since the harmonics of the oscillating waveform are contained, the process of calculating the period (T _RP ) is very complicated and has a difficult disadvantage of allocating a large amount of memory during processing in the CPU.

As described above, the AC instantaneous voltage signal V _SM obtained from the rechargeable battery cell operated in the floating charging state includes the high frequency ripple voltage V _RP due to the charging current and the impedance voltage V _IS due to the AC constant current I _S. ) Is mixed. A method for obtaining only the impedance voltage V _IS required for the measurement among the AC instantaneous voltage signal V _SM mixed with the high frequency ripple voltage V _RP will be described in detail below.

1 is a conceptual diagram of internal impedance measurement for degradation diagnosis of a battery

2 shows the ripple voltage and impedance voltage waveform

3 is a conceptual diagram of each data acquisition process and measurement time of the present invention

The fundamental frequency of the power supply used for floating charging the battery is ω _S , and the frequency of the constant current (I _S ) supplied to the battery cell to measure the internal impedance is s times the fundamental wave frequency ω _S of the power supply. When it is determined to be the angular frequency, the impedance voltage V _IS is generated by the constant current I _S , so the frequency also becomes the s-order frequency and passes only a signal corresponding to the s-order frequency through a noise canceling circuit such as the bandpass filter. Design the cutoff frequency as much as possible. Noise-canceling circuits, such as ideal narrowband bandpass filters, pass only signals corresponding to the s-order frequency set exactly at the pass frequency, but in reality, these noise-canceling circuits are very difficult to implement, and such an implementation is a cost driver. That is, the general band pass filter circuit attenuates only about 30% of the frequency components adjacent to the low cutoff frequency f _L or the high cutoff frequency f _H , and thus cannot be completely filtered. In this description, the narrowband filter is designed so that the resonant frequency (fr) is equal to the s-order harmonic, the low cutoff frequency is almost equal to the (s-2) difference, and the highpass cutoff frequency is approximately equal to the (s + 2) order harmonic. It is assumed that the frequency range other than the above is almost filtered (attenuated). As described above, the battery harmonic ripple voltage (V _RP ) according to the floating charge of the battery usually has only a ripple frequency component corresponding to one of odd multiples and even multiples of a commercial power supply of 60 Hz. Therefore, the high frequency ripple voltage V _RP remains only after the odd or even harmonics of the order similar in frequency to the impedance voltage V _IS generated by the constant current I _S pass through the noise canceling circuit, and the other harmonics It is almost attenuated.

Therefore, if the harmonic ripple voltage (V _{RP, FLT} ) after passing through the noise canceling circuit is displayed,

(1) where Is, Is the magnitude of the X-order harmonic ripple voltage, and each harmonic is not less than the second order, so s is an integer greater than or equal to 4 and the magnitude of the impedance voltage (V _IS ) generated by the constant current (I _S ) having the s-order frequency is K.

It is expressed as (2)

In addition, the AC instantaneous voltage (V _SM ) in which the harmonic ripple voltage (V _{RP, FLT} ) and the impedance voltage (V _IS ) are mixed after passing through the noise canceling circuit is the sum of the equations (1) and (2),

It is indicated by (3).

Since the definition of the effective value (S) for a function X (t) with an arbitrary multiple of one period (T _syn ) (T _s = l · T _syn , where l is an integer) is equal to equation (4)

(4) If the effective values (V _{SM, RMS} ) of the AC instantaneous voltage (V _SM ) are derived from equations (3) and (4), the effective values (V _{SM, RMS} ) Defined as

(5)

(6)

(7)

As explained above And using a known trigonometric theorem such as equations (6) and (7), the product of the product of the terms of the equation (5)

And (8)

And (9)

(10)

In formula (8), formula (9), formula (10) , , , , Are even-order harmonics of 2 (s-1), 2nd, 2 (s + 1), 2s, and 4th order of the power fundamental frequency ω _S. In the case where the trigonometric function is an integral multiple of the fundamental frequency as shown in Equation (11), it is known that the integral is equal to zero when the integral is performed for one period corresponding to the fundamental frequency.

(11)

here, And m is an integer. Since equation (8), equation (9), (10) both are expressed as an integral multiple of about 2ω _S 60㎐ / 50㎐ frequency of the cycle (the normal commercial power supply corresponding to the 2ω _S 376.99 rad / sec of about If the integral is performed during 8.33 msec / 10.0 m sec), the integral value is zero. That is, equation (12) is a sufficient condition for making the above equations (8), (9), and (10) all zero.

Therefore, the effective value (V _{SM, RMS} ) of the AC instantaneous voltage (V _SM ) of Equation (5) is

(13)

here, It may be represented as.

On the other hand, when the effective values V _{RP and RMS} of the harmonic ripple voltages V _{RP and FLT} after passing through the noise removing circuit are expressed from equations (1) and (4),

(14)

Using the known trigonometric theorem such as equations (6) and (7), the multiplication term on the left side of equation (14)

And (15)

And, (16)

(17)

In the above formulas (15), (16) and (17) , , , , Are harmonics of 2 (s-1) times, 2 times, 2 (s + 1) times, 2s times, and 4 times the power fundamental frequency ω _S. Equations (15), (16), and (17) are expressed as integer multiples of 2ω _{S according to} the same principle as described above. When the integration is performed during the period corresponding to 2ω _S , the integral value is zero (0). The sufficient condition for this is as shown in Eq. (18).

(18)

Therefore, the effective value (V _{RP, RMS} ) of the harmonic ripple voltage (V _{RP, FLT} ) after passing through the noise canceling circuit represented by Equation (14) is

(19)

here, In Equation (13) and Eq. (19), T _SM and T _RF are the same period value, so it can be expressed as Equation (20).

20

On the other hand, the effective values (V _{IS, RMS} ) of the impedance voltage (V _IS ) generated by the constant current (I _S ) having the order frequency are expressed from equations (2) and (4),

It can be represented by (21). In this case, since T _IS may be defined as any integer multiple of one period as in Equation (4), it may be set as the same value as in Equation (20) and may be represented as in Equation (22).

(22)

Therefore, the effective values V _{IS and RMS} of the impedance voltage V _IS can be easily calculated from equations (13) and (19) as follows.

(23)

here,

That is, the harmonic ripple voltage after calculating the effective values (V _{SM, RMS} ) of the AC instantaneous voltage (V _SM ) using the half period of the fundamental wave frequency ω _S of the power supply as the integral period and passing the noise elimination circuit by the same integration period. Calculate the effective value (V _{RP, RMS} ) of (V _{RP, FLT} ), square each of these two effective values, find the difference between the squared effective values, and calculate the square root of the difference (-). It can be seen that the same result as the effective value (V _{IS, RMS} ) of V _IS ) is shown.

More specifically, equations (8), (9), (10) and equation (10) are calculated by calculating the effective values of V _{SM, RMS} and V _{RP, RMS} with the half period of the fundamental wave frequency ω _S of the power supply. 15), (16), and the equation (17) multiplied term all zero (0), such as, V _SM, the square of the _RMS to the arithmetic, by subtracting the result from the squared result of the operation of the V _{RP, RMS,} V _{SM RMS} included in the result of the square operation All terms except for are removed, and square root calculations are performed on the result to obtain an exact value (V _{IS, RMS} ) of the impedance voltage V _IS .

In the above, the frequency of the constant current (I _S ) supplied to the battery cell to be measured is selected as the frequency that is s times the frequency ω _S of the commercial power supply _, and the specific order of the harmonic ripple voltage (V _{RP, FLT} ) caused by the charging current of the battery is determined. The harmonic ripple voltage (V _{RP, FLT} ) is equal to the harmonic ripple voltage (V _{RP, FLT} ) and the frequency component of the commercial power supply has a frequency component corresponding to one of multiples of odd and even multiples of the frequency ω _S Although the method of easily taking the effective value of V _IS ) has been described, all the frequency components of odd and even times are included in the harmonic ripple voltage (V _RP ) or the frequency of the constant current (I _S ) is converted into the ripple current (V _{RP). The} case where it is selected so as not to match the harmonic order of _FLT) will be described below.

The frequency of the constant current (I _S ) supplied to the battery cell is determined to be the s-order angular frequency that is s times the fundamental wave frequency ω _S of the power supply _, and all odd and even multiples of the harmonic ripple voltage (V _{RP, FLT} ) Harmonic ripple voltage (V _RP) after passing the noise canceling circuit by the same idea as described above for the case where the frequency component is included but only the s-order harmonic component, which is the frequency of the constant current I _S , does not exist. _{, FLT} ) is

(24)

Therefore, the harmonic content of AC instantaneous voltage (V _SM ) , , , Such as those generated by harmonic currents It is composed of a component generated by the constant current (I _S ) supplied to the battery cell as shown. During the expansion process to calculate the effective value (V _{SM, RMS} ) of the AC instantaneous voltage (V _SM ), the integral term generated by multiplying each harmonic component as shown in Eq. (8), (9), and (10) can be obtained. have. Among these integral terms And

If there are terms such as, and apply them to equations (6) and (7), And

As shown in the figure, the integral period must be selected as the period of fundamental wave frequency ω _{S so} that the integral value becomes zero. In other words, the frequency matching of the harmonic ripple voltage (V _{RP, FLT)} to contain the harmonic components of all orders or harmonic ripple voltage, the constant current (I _S) to be supplied to the harmonic order and a battery cell of the (V _{RP, FLT),} such as the If it is not, since the superior and odd harmonics are included in the AC instantaneous voltage (V _SM ), the integral period of the effective value is 2 compared with the case of only the superior or odd frequency in the harmonic ripple voltage (V _{RP, FLT} ). It must be doubled, and the amount of data required for its calculation is also doubled and more computation time is required. Of course, all the frequency components of odd and even times are included in the harmonic ripple voltages V _{RP and FLT} , and the same result can be obtained when the harmonic ripple components of the s-th order multiple of the constant current (I _S ) frequency exist.

When the above calculation process is examined in detail _, the integral period used to obtain the effective values of the AC instantaneous voltage (V _SM ) and the harmonic ripple voltage (V _{RP, FLT} ) is determined by all the components constituting the AC instantaneous voltage (V _{SM, FLT} ). By adding and subtracting the frequencies of the harmonic components mutually, the first maximum common divisor between the results of the addition and subtraction operations is obtained, and the frequencies of all harmonic components constituting the harmonic ripple voltage (V _{RP, FLT} ) are mutually added and subtracted. A second maximum common divisor between the result of the addition and subtraction operations may be obtained, and a third maximum common divisor between the first maximum common divisor and the second maximum common divisor may be determined and determined as an integer multiple thereof. In consideration of the time for calculating the effective value of the impedance voltage, it is preferable to determine the third greatest common factor as the integral period. If the frequency of the constant current (I _S ) supplied to the battery cell is selected in the same order as the specific order of the ripple voltage (V _{RP, FLT} ) frequency, the integration period can be reduced to the minimum, and the ripple voltage (V _{RP, FLT} ) is configured. If the harmonic order is composed of only odd or even difference, select the frequency of constant current (I _S ) supplied to the battery cell to be equal to the specific frequency of the ripple voltage harmonics, and calculate the half period of the commercial frequency when calculating the effective value of the impedance voltage. Since it can be selected as the integral period, there is an advantage to reduce the computation time.

The effective value extraction process, which is a series of ideological concepts, may be applied as a program for driving a numerical operation device such as a microprocessor. The process of calculating the effective value of the AC instantaneous voltage (V _SM ) and the ripple voltage (V _{RP, FLT} ) and the effective value of the impedance voltage (V _IS ) is as follows. As shown in FIG. 3, first, in the first section P ₁ , harmonic ripples generated by the charging current ripple of the battery cell during floating charging without passing the constant current I _S are passed through the noise removing circuit. Acquire the voltage (V _{RP, FLT} ) at regular intervals, but in the case of the first acquisition point (T _{1, RP} ) _{, take} the square value after subtracting the reference value (V _O ) from the obtained instantaneous value (V _{RP, FLT} ) Is the result of the calculation Is input to the specific memory M ₁ allocated. Thereafter _{, the} instantaneous ripple voltage values V _{RP and FLT} are obtained at the second acquisition time point T _{2, RP} , and the reference value V _O is subtracted, and the square power operation is performed as described above. The result of the operation Is the ripple voltage squared already stored in memory (M ₁ ) And store the result in the memory (M ₁ ) again, the memory (M ₁ ) The value is stored. After repeating the above calculation process at the time of acquiring a constant cycle interval for half a period or one period of the commercial power frequency, as a result the specified memory (M1) The value is stored.

After a certain time, the constant current source is started and stabilized, and the stabilized constant current (I _S ) is supplied to the battery cell, and in the second section (P ₂ ), the harmonic ripple voltage (V _{RP, FLT} ) and the impedance voltage (V) after passing through the noise removing circuit. AC instantaneous voltage V _SM mixed with _IS ) is obtained. Acquiring the AC instantaneous voltage (V _SM ) by a similar method as described above, in the case of the first acquisition time (T _{1, SM} ), the reference value (V _O ) is obtained from the obtained AC instantaneous voltage (V _SM ) Subtracted and then squared again to The value is stored in the specified separate memory (M ₂ ). Acquiring the AC instantaneous voltage V _SM at the second acquisition point T _{2, RP} , subtracts the reference value V _O , and performs a square power operation as described above. The result of the operation Value is already stored in memory (M ₂ ) In addition to the value, this result is again stored in memory (M ₂ ). Therefore, in the memory M ₂ The value is stored. After repeating the above calculation process at the time of acquiring a constant cycle interval for half a period or one period of the commercial power frequency, as a result the specified memory (M1) The value is stored.

After the series of steps as described above, the memory M ₁ is the result of calculating the square of the harmonic ripple voltage (V _{RP, FLT} ) after passing through the noise canceling circuit and integrating for a period of time. Value is stored in the memory (M ₂ ), which is the result of integrating the AC instantaneous voltage (V _SM ) and integrating The value is stored. Subtracts the two values stored in the memory M ₁ and the memory M ₂ and divides the result of the operation with respect to a half cycle or one period of the commercial power frequency applied previously. ), The exact impedance voltage V _IS to be measured can be obtained.

As described above, in the present invention, even when the impedance voltage V _IS is obtained by mixing with a noise signal such as the ripple voltage V _RP , the impedance voltage V _IS input by effectively excluding an operation value caused by the noise signal. Only the true value of can be taken. Therefore, by using the present invention, it is possible to diagnose the deterioration state by accurately measuring the internal impedance of the battery and the DC electrolytic capacitor while operating in a floating charge state, and the edema part is mixed with noise from the surroundings even from the medical diagnosis. It is also possible to take only the measurement signal in the noise voltage.

Claims (4)

In the diagnostic apparatus for measuring the internal impedance voltage for diagnosing degradation (health condition) of the battery, electrolytic capacitor or edema part, The frequency of the commercial power supply used for the measurement is ω _S , and the harmonic configuration of the noise ripple voltage (V _RP ) consists of arbitrary orders of frequencies of the frequency ω _S of the commercial power supply. The frequency of the constant current I _S supplied is determined to be the s-order frequency that is s times the frequency ω _S of the commercial power supply, so that the frequency of the impedance voltage V _IS generated by the constant current I _S is also the power frequency ω _S. Noise ripple filtered by installing a noise canceling circuit such as a known narrowband bandpass filter that can pass only a portion of the noise ripple voltage (V _RP ) signal in a frequency band similar to the frequency of the constant current Is The voltage V _RP and the AC instantaneous voltage V _SM are configured to be obtained, and the noise ripple voltages V _{RP and FLT} are not applied in the first section P ₁ without applying the constant current I _S. Since information integration period T _D, and the predetermined time obtained during a second period (P ₂₎ doemeurosseo constant current source is supplied to the the start stabilized constant current (I _S) is the measured water in the impedance voltage (V _IS) and the organic the impedance voltage AC instantaneous voltages V _{SM and FLT} including V _IS and noise ripple voltages V _{RP and FLT} are obtained during the constant integration period T _D , and noise ripple obtained in the first interval P ₁ . The square value of the effective value (V _{RP, RMS} ) during the constant integration period T _D is calculated from the voltage (V _{RP, FLT} ) _, and the AC instantaneous voltage (V _{SM, FLT} ) obtained in the second section P ₂ is calculated. Calculate the square value of the effective value (V _{SM, RMS} ) during the constant integration period T _D from, subtract the two calculated values, calculate the square root of the subtracted result value, and extract the correct impedance voltage through the effective value extraction process. voltage chamber of the constant current signal, characterized in that for obtaining a _IS) value Value measurement. The method according to claim 1, The frequencies of all harmonic components constituting the AC instantaneous voltages V _{SM and FLT} are mutually added and subtracted to obtain a first maximum common divisor between the results of the addition and subtraction operations, and the harmonic ripple voltages V _{RP and FLT.} Add and subtract the frequencies of all harmonic components constituting a), and obtain a second greatest common divisor between the results of the addition and subtraction operations; and a third maximum common divisor between the first greatest common divisor and the second maximum common divisor. , And determine the constant integral period T _D as the third greatest common divisor or its integer multiple to calculate the multiplication of all harmonic components constituting the AC instantaneous voltage (V _{SM, FLT} ) and the harmonic ripple voltage (V _{RP, FLT} ). A method for measuring the voltage effective value of a constant current signal, wherein the period integral value is all zero to easily obtain an accurate impedance voltage (V _IS ) value. The method according to claim 1, The harmonic order of the noise ripple voltage (V _RP ) generated during the measurement is composed of only the ripple frequency corresponding to either the odd order or the even order of the fundamental frequency ω _S of the commercial power supply, and the constant current source Is The frequency is determined to be the same frequency as a specific order among the harmonic orders constituting the harmonic ripple voltage (V _RP ), and the constant integral period T _D is determined as a half period of the fundamental frequency ω _S of the power supply to reduce the effective time calculation of the impedance voltage. Method for measuring the voltage effective value of a constant current signal, characterized in that the advantage. The method according to claim 1 The filtered harmonic ripple voltage (V _{RP, FLT} ) is obtained during the integration period T _{D in} the first period P ₁ to apply an effective value extraction process to a program in a numerical operation device such as a microprocessor. In the second interval P ₂ after time, the AC harmonic ripple voltages V _{RP and FLT} and the AC instantaneous voltages V _{SM and FLT} mixed with the impedance voltage V _IS are obtained during the integration period T _D. In order to calculate the square of the effective value of the harmonic ripple voltage (V _{RP, FLT} ) in the first section (P ₁ ), the instantaneous value of the harmonic ripple voltage (V _{RP, FLT} ) is read at the _nth acquisition point (T _{n, RP} ). Subtract the reference value (V _O ), and perform the operation to square the subtracted value Value and the sum up to the (n-1) th acquisition point stored in the specified memory (M1). Value and above And store the operation value again in the designated memory M1, and the operation and storage process are repeated N times from the acquisition point T _{1, RP} to the acquisition point T _{N, RP} . The AC instantaneous voltages V _{SM and FLT} are read at the n th acquisition point T _{n, SM of the} second period P ₂ , the reference value V _O is subtracted, the subtracted value is squared, and the squared value is The calculated value up to the (n-1) th acquisition point T _{(n-1), SM} stored in the specified memory M2. Summed with the value, the operation value is stored in the designated memory M2 again, and the operation and storage process are read N times from the acquisition point T _{1, SM} to the acquisition point T _{N, SM} , and then When necessary, the first operation value stored in the memory M1 and the second operation value stored in the memory M2 are subtracted, and the division result is divided with respect to the integration period T _D. Square root of A method for measuring the voltage rms value of a constant current signal, wherein a small memory space is used by obtaining a valid value of the rms value of an impedance voltage by performing a calculation. .