PL230330B1 - Method for measuring the voltage period and the system for measuring the voltage period - Google Patents

Description

Description of the invention

The subject of the invention is a voltage period measuring system for testing the electrical properties of periodically alternating current circuits.

There is a solution for determining the signal period presented in the Zieliński TP textbook "Digital Signal Processing from Theory to Applications" by Wydawnictwa Komunikacji i Łączności, Warsaw 2005, 2009, based on the value of the own correlation function R _x (t) in the form of the formula:

+ «O Ą ( ^T ) ⁼ f

-OO where x (t) is the tested signal, and χ (Ζ-τ) is the tested signal shifted by the time τ. The autocorrelation function takes maximum values for time shifts τ equal to the multiple of the signal period x (t), hence the signal period is equal to the smallest distance between the maxima of the autocorrelation function. In the case of real measurement systems, only a limited number of samples is available and the autocorrelation function is replaced by the unbiased estimator R _x (k) in the form of the formula:

^{(4ί =} Τγ Σ where Λ / is the number of samples, -Λ / + 1 <k <0 is the shift value, and x (n) are samples of the signal for 0 <η <Λ / -1. For these systems, the period is determined in the same way as for the continuous signal and is approximately equal to the minimum distance between the maxima of the autocorrelation function.

The known solution is characterized above all by the fact that the resolution of the measurement result is equal to the sampling period, hence the measurement result error is strongly dependent on the synchronicity of the measured signal and the sampling period.

An additional disadvantage is that the autocorrelation function estimator adopts approximate maximum values that differ slightly from each other and are not normalized, i.e. they assume different values for different signals.

For example, devices and systems for measuring the period of signals based on autocorrelation functions have been disclosed in US4463425, US5584295, US6477476.

The essence of the voltage period measuring system according to the invention is that this system measures the instantaneous voltage values at equal time intervals called the sampling period T _s less than half the time of the measured voltage period T, and the time of the entire measurement covers at least two full periods T of the measured voltage, i.e. t _n > 2T, and then, on the basis of the values of the measurement results, it analytically estimates the value of the voltage period.

The circuit for measuring the period T of the voltage u (f) comprises an amplifier whose input terminals are connected to points of the electrical circuit between which the measured voltage u (f) is present and whose output is connected to the input of an analog-to-digital converter. _{A digital clock signal generated by a clock signal generator with period T s} <0.57, triggering sampling at times 6, / 2, t3, ... t is connected to the digital input that triggers the sampling of the converter (measurement of the instantaneous value of the voltage at the analog input of the converter). _n where f, = (/ —1) T _s and the time of the last measurement meet the condition t _n = (n-1) 7 _s > 27 The output of the analog-to-digital converter to which the result signals with ui = u values are sent for individual samples (h), u? = u (h), U3 = u (t3), ... u _n = u (t _n ), is connected to the measuring line controller which is controlled by the interface controller used for communication with the user via the interface. The measuring data memory block is connected to the measuring line controller. It is used for storing data read by the measuring track controller from the analog-to-digital converter. To the measurement data memory block there is connected the objective function evaluation system, whose task is to determine the value of the objective function f _c for the value of the argument of the objective function T _m and to store the value of the objective function f _c in the memory unit of the value of the objective function and the argument of the objective function T _m in the unit. the memory of the argument value of the objective function. Attached to the objective function value memory unit and the objective function argument value memory unit is the objective function minimum calculator, which determines the value of the objective function argument T _m , for which the objective function f _c takes the minimum value, and stores this value in the period memory unit. voltage. The system of determining the minimum of the objective function activates the system of calculating the value of the objective function to determine the value of the objective function f _c for subsequent functions

PL 230 330 Β1 values of the arguments of the objective function T _m ranging from T _m and _n to T _max with a resolution of Tstep, and the interface controller indicates as the measured value of the voltage period T u (f) read from the voltage period memory unit after performing the calculation for the search range frequencies from Tmndo T _max with resolution Tstep The system for determining the value of the objective function consists of the following systems: the time modification system, the sequence sorting system, the data averaging system, the interpolation function determination system and the final value determination system of the objective function.

The time modification system reads the sequence of measurement data pairs from the data block in the form of the measurement time and the instantaneous voltage value at a given measurement time according to the formula:

((., ^), ((., 11.), ((^), ... ((,,, 11 ,,) and modifies the measurement data sequence by modifying the values of measurement times according to the formula:

<= where L J is a rounding down operation, obtaining a sequence of the form:

u ₂ ), ((^.), ... (((,, ^ which writes to the modified data memory block which is attached to the string sort system.

The sequence sort system sorts the modified sequence of measurement data pairs read from the modified data memory block according to the modified measurement time t ', obtaining a sequence in the form:

with the property t <t _{( n,} which saves in a block of sorted data memory, which is connected to the data averaging circuit.

The data averaging system averages the modified measurement data with the same modified measurement time read from the sorted data memory block by replacing several pairs of measurement data with the same modified time with one pair of measurement data with the same modified time and the voltage value equal to the arithmetic mean of the averaged measurement data voltages, yielding element string m:

(ą, u.), ((., u ₂ ), (t ₃ , u ₃ ), ... (1 ,,,, u ",) in which m <n and which saves in the averaged data memory block, which it is connected to the system for determining interpolation functions.

The system for determining the interpolation functions reads m pairs of averaged measurement data from the averaged data memory block and on their basis performs the following operations:

- using the argument T _m, determines the first extracted data string, which contains the averaged measurement data with odd indexes and finally the added voltage data pair u, at the time T _m :

(ϋ, ΰ _} ), (( ₃ , ΰ ₂ ), (ί ₅ , ΰ,), ... (ϊ ,, ΰ,), (Τ _ηι , ΰ _} ) whose values are saved in the memory block of the first sequence,

- using the argument T _m , the second extracted data sequence is determined, which includes the voltage pair u., at time 0 then the averaged measurement data with even indexes and finally the added voltage pair ΐμ at time T _m :

(0, ί / ^ 4ζ, ζ7 ₂ ), (ζ, Μ ₄ ), ... ^ whose values are saved in the memory block of the second sequence,

PL 230 330 Β1

- for the first sequence of separated pairs of time and voltage measurement data, it determines the first interpolation function u / (t) in the form of a spline function of a linear function (broken line) that determines the time course of the voltage over the time segment [0, T _m ], the parameter values of which are written to the block memory of the first auxiliary voltage waveform,

- for the second sequence of separated pairs of time and voltage measurement data, it determines the second interpolation function uu (f) in the form of a spline function of a linear function (broken line) that determines the voltage waveform over the time segment [0, T _m ], the parameter values of which are saved to the memory block the second wave of auxiliary voltage,

- reads the parameter values of the first voltage waveform ui (f) from the memory block of the first auxiliary voltage waveform and the second voltage waveform uu (f) from the memory block of the second auxiliary voltage waveform and then, by dividing the time segments, redetermines m parameters for both of these voltage waveform interpolation functions so that the voltage waveforms do not change, and the ends of the interpolation segments are respectively at the same m + 1 time points 0, t _2l t _3l t _4l ... t _m , T _m and the obtained m values of the parameters of the first function voltage time interpolation ui (t) stores in the first voltage waveform memory block and stores m parameter values of the second voltage time interpolation function ui (f) in the second voltage waveform memory block.

Connected to the memory blocks of the first voltage waveform and the second voltage waveform is a terminator for the objective function.

The end evaluator of the objective function reads the m parameter values of the first voltage waveform ui (f) from the first voltage waveform memory block and the second voltage waveform uu (f) from the second voltage waveform memory block, and:

- for the first waveform of voltage ui (f) and for the second waveform of voltage Uu (f) determine the mean value of their difference Ui-n over the time interval [0, T _m ] according to the formula:

/ "I ih-n = - J (w, is 0 which is saved in the memory unit of the average value of the difference in voltage waveforms, - finally determines the final value of the objective function f _c according to the formula:

which it stores in the memory unit of the objective function values.

An advantage of the period measuring system according to the invention is that it has any period measuring resolution, since the voltage period argument T _{m of} the objective function f _c does not have to be a multiple of the sampling period T _s as is the case with the autocorrelation method. The possibility of determining the objective function for any value of the argument T _m satisfying the condition 2T _S <T _m <^ (n-1) T _S and determining the value of this function over the entire appropriately interpolated interval [0, T _m ] results in a smaller impact of sampling asynchrony on the measurement error compared to the method of the autocorrelation function estimator. Another advantage is the non-negative value of the objective function, belonging to the interval [0, + oo], which makes it easier to determine the minimum value close to 0.

An embodiment of the measurement system according to the invention will be shown in the drawing, in which Fig. 1 shows an overall measurement arrangement and Fig. 2 shows a diagram of a UWWFC target function value evaluation arrangement.

The measuring system is adapted to be operated by the user via the INT interface. Through the INT interface, the user can set the operating parameters of the measuring system, start the voltage period measurement or read the measurement result. The INT interface is connected by a bi-directional digital bus with the KI interface controller. The KI interface controller is adapted to work in two modes: in communication mode (with the user) and in standby mode. In the communication mode, the KI controller supports the INT interface - it sends data to be displayed, downloads the setting parameters and gets the command to start the measurement. Additionally, the KI controller saves the operating parameters of the system using digital buses in the appropriate memory units: sampling period T _s in the unit T _s ,

PL 230 330 Β1 number of samples n in the unit n, the lower range of the voltage period search Tmin in the unit Tmin, the upper range of the voltage period search T _max in the unit Tmax, and the measurement resolution (i.e. the step of the searched voltage periods) Tstep in the unit Tstep. In addition, the KI controller reads, using the digital bus, the determined period of the electric voltage T _u stored in the memory unit Tu.At the moment of receiving a measurement initiation command from the INT interface, the Ki interface controller checks the correctness of the measurement parameters settings using five conditions:

1.The lower limit of the measuring range must be smaller than the upper limit of the measuring range, i.e. Tmin <Tm _a x

2. The measurement resolution must not be less than 0.1 of the measurement range, i.e. 107s _te p <T _ma x- T _mn

3.the sampling period T _s must not be less than the minimum data processing period Tminp resulting from the device parameters, i.e. T _s > Tminp

4. the measurement time must cover at least two full periods of the measured voltage, i.e. (nV) T _s > 2T _max

5, the sampling period must be less than half the period of the measured electrical voltage, C yli 2Ts <Tmin

If the settings are incorrect, the KI controller sends the appropriate error information to the INT interface and proceeds to setting the data. If, however, the measurement settings are correct, the KI interface controller sends to the INT interface information about the start of the measurement and sends a digital signal to the KTP measurement line controller in order to start the measurement. Then the KI controller suspends its operation in the communication mode, switching to the waiting mode until the digital signal informing about the end of the measurement coming from the system for determining the minimum value of the target function UWMINFC appears. When the signal ending the measurement from the UWMINFC system appears, the KI interface controller downloads the result from the unit Here, it sends it to the INT interface and then returns to user communication mode.

The KTP measurement path controller reads the data from the measurement path and places the results in the BD measurement data memory block. The measuring path includes: the W amplifier, the ADC analog-digital converter and the CLK clock signal generator. The generator G, connected to the input terminals of the test circuit, symbolically represents the system generating the alternating voltage, the period of which is being tested. The terminals of the periodic voltage generator G are connected with the input of the linear amplifier W. The output of the amplifier W is connected with the analog-to-digital converter ADC. The task of the W amplifier is to condition the input voltage to the ADC range. This means that the voltage at the output of the amplifier in relation to the mass is directly proportional to the input voltage of the measuring system and the amplifier gain is selected in such a way that at a given measuring range, the voltage at its output does not exceed the operating range of the ADC converter. The measurement result of the ADC converter is transmitted via the digital bus to the KTP measurement track controller. The measurement in the ADC converter is excited by an external signal coming from the controlled clock CLK. The signal from the CLK clock is also fed to the digital input of the KTP controller in order to provide information about the performed measurement. The time between successive measurement excitation signals is set in the CLK clock by means of a digital signal from the KTP measuring line controller. The CLK clock settings are constant throughout the measurement and are set so that the ADC excitation level lasts for the entire transducer processing period, and then the clock output is set to the opposite and re-changed to the transducer excited state after T _s .

The KTP controller is connected to the memory units T _s , i, n and the BD memory block. The controller, by means of digital buses, reads the sampling period T _s from the memory unit T _s and the number of samples n from the memory unit n, writes the measurement data to the measurement data memory block BD and writes and reads the value of the variable number of the measurement / from the memory unit i. KTP controller system also takes the measurement initiation digital signal from the KI interface controller and sends the data processing initiation digital signal to the UWMINFC target function minimum calculator.

The measuring line controller KTP, after receiving the digital signal of the measurement initiation from the controller KI, sets the value of the measurement number / = 1 in the unit i and reads the sampling period T _s from the unit Ts and sets the clock CLK. Then the controller starts the measurement cycle and performs the following sequence of actions:

1.reads the data / from the i unit, on the basis of which it determines the measurement time t, according to the formula t, = (i - V) T _S 2. waits for a digital signal from the CLK clock of the ADC measurement excitation

PL 230 330 Β1

3. waits for a digital signal from the CLK clock with the opposite state, which informs that the transducer

The ADC has completed the measurement

4. Reads data from ADC

5. processes data from the ADC converter taking into account the amplification of the amplifier W and obtains the voltage value at the input of the measurement circuit

6.saves the measurement result in the form of a pair (u ,, ty in block BD, where ui = u (tt) is the voltage at the input of the measuring line at time t,

7.increases the value of the measurement number / in the i unit by one (i = i + 1)

8. compares the values in the units i and n, if i <n, it goes to the next measurement - the beginning of the cycle, and if i> n, the controller ends the measurement cycle.

When all measurements are made, the KTP measurement path controller stops the CLK clock, sends a digital signal of excitation of the system for determining the minimum value of the UWMINFC target function, and then waits for the next digital signal of measurement initiation from the KI interface controller. As a result of the KTP controller operation, the measurement data in the BD block are stored in the form of a sequence of pairs:

The system for determining the minimum of the objective function UWMINFC determines the value of the period of the measured voltage on the basis of the argument for which the value of the objective function takes the minimum value. Objective function values are determined in a separate UWWFC objective function value evaluation system. The UWMINFC circuit uses digital buses to read the values of the lower search range of the voltage period Tmin from the memory unit Tmin, the upper range of the voltage period search T _maz from the memory unit Tmax, the measurement resolution - the step of the searched voltage periods Tstep from the memory unit Tstep and the values of the objective function f _c z memory units f _c . Additionally, the UWMINFC chip reads and writes the argument values of the objective function T _m in the memory unit T m, the minimum value of the objective function f _m in the memory unit fm, and the voltage period value T _u for which the objective function takes the minimum value, in the memory unit T _u . At the same time, the UWMINFC system receives the digital signal of initiation of measurement data processing from the KTP measurement path controller, sends the digital signal of initiation of the determination of the value of the objective function to the UWWFC system for determining the value of the objective function, receives the digital signal of the completion of determining the value of the objective function from the UWWFC system and sends the digital signal of the end of the measurement to KI interface controller.

The circuit for determining the minimum of the objective function UWMINFC, after receiving the digital data processing initiation signal from the measurement path controller KTP, reads the lower voltage period search range Tmin from the memory unit Tmin and stores it, as an argument of the objective function T _m , in the memory unit Tm. Then the UWMINFC system starts the argument search cycle, for which the objective function takes the minimum value and performs the following sequence of actions:

1.sends the digital signal initiating the determination of the value of the objective function to the UWWFC system,

2.waits for the digital signal of the end of determining the value of the objective function from the UWWFC system,

3.reads the data: T _m from the Tm unit, Tmin from the Tmin unit, f _c from the f _c unit, / ™ from the f _m unit and if Tm = Tmin or simultaneously T _m > Tmin and fc <fm, it assigns the value f _{c to the} variable f _m writing it to the unit f _m and assigns the value T _{m to the} variable T _u writing it to the unit T _u

4.reads T _m data from the Tm unit and T _max from the Tmax unit and if T _m = T _max then assigns the T _m variable from the Tm unit to 0, and if the condition T _m = T _max is not satisfied, it reads the Tsfep value from the unit Tstep i assigns the variable T _m from the unit Tm a value according to the formula Tm = min (Tm + Tstep, T _has x), where the function min returns the minimum value of two variables Tm + Tstep 0Γ3Ζ Tm _a x

5. reads the value of T _m from the T m unit and if T _m = 0 it ends the argument search cycle for which the objective function takes the minimum value, and if the condition T _m = 0 is not satisfied, it goes to the beginning of the cycle.

At the moment of the end of the cycle of searching for the argument for which the objective function takes the minimum value, the UWMINFC system sends the digital signal of the end of the measurement to the controller of the KI interface, and then waits for the next digital signal of initiating data processing from the controller of the measurement path KTP to appear.

The objective function evaluation system UWWFC waits for the digital initiation signal of the objective function evaluation from the UWMINFC chip, and then reads the value of the argument T _{m of} the objective function f _c from the memory unit Tm, the number of samples n from the memory unit n via the digital bus, and

PL 230 330 Β1 measurement data values from the measurement data memory block BD and on their basis determines the value of the objective function f _c , which is stored in the memory unit f _c , and then sends the digital signal of the completion of determining the value of the objective function to the LJWMINFC chip and waits for the next signal digital initiation of the determination of the value of the objective function. A detailed structure diagram of the UWWFC target function value determination system together with digital signals and external buses, and the measurement data memory block BD and memory units Tm, n and f _c is shown in Fig. 2.

The time modification circuit UMC, after receiving the objective function evaluation initiation digital signal from the UWMINFC circuit, reads the number of samples n from the memory unit n and the argument T _m from the memory unit T m. Then the UMC system reads successively n measurement results in the form of pairs (u, t) from the BD measurement data memory block and performs the modification of the times according to the formula:

where L J is a rounding down operation and then writes the time-modified data obtained to a BDM-modified data memory block. As a result of modifying the times in the BDM block, the data is saved in the form of a sequence:

> ^U 1), (^ 2- ^W l) ' ^w 3)> - (Ci' ^W «) with the property ie = 0. After modifying all data, the UMC system sends an initial digital signal to the USC sequence sort system and waits for the next signal digital initialization of the determination of the value of the objective function from the UWMINFC chip.

The USC string sorter, after receiving the initial digital signal from the UMC, reads the number of samples n from memory unit n, and n data pairs from the BDM modified data memory block. Then it sorts the data pairs modified by time / 'to obtain the string:

where t "<and t = 0. The sorted string USC writes to a block of BDP sorted data memory. The USC then sends a digital initiation signal to the UUD data averaging circuit and waits for the next digital initiation signal from the UMC.

The UUD data averaging circuit, after receiving the initial digital signal from the USC, reads the number of samples n from memory unit n, and n data pairs from the BDP sorted data memory block. Then the UUD system averages the data pairs with the same time by replacing several data pairs with the same time with one data pair with the same time and a voltage value equal to the arithmetic mean of the averaged voltages of the data pairs, resulting in the element sequence m:

with properties m <n and = O. After determining the averaged data sequence, the UUD system saves the obtained sequence in the BDU averaged data memory block and writes the number m of sequence elements in the memory unit m. Then the UUD system sends an initial digital signal to the UWFI interpolation function determination system and waits for the next initial digital signal from the USC system.

The UWFI interpolation function determination system determines two voltage waveform interpolation functions, used directly to determine the final value of the objective function, which is determined in the UWWKFC objective function terminator. The UWFI chip uses digital buses to read the argument values of the objective function T _m from the memory unit T m, the number of averaged data pairs m from the memory unit m and the averaged data pairs from the BDU averaged data storage block. In addition, the UWFI chip, using digital buses, reads and writes the values of two strings to memory blocks BC1, BC2, and to memory units mi and m2 the number of elements mi and m2 of strings from blocks BC1 and BC2, respectively. In addition, the UWFI circuit writes and reads from memory blocks BP1 and BP2 the auxiliary values of the voltage waveform interpolation function coefficients determined on mutually different intervals, while the circuit writes the final values of the voltage waveform interpolation function coefficients on mutually equal intervals to the memory blocks BU1 and BU2. At the same time, the UWFI chip receives the digital signal to initiate data processing

PL 230 330 Β1 from the data averaging unit UUD and sends a digital initiation signal to the final value calculator of the objective function LJWWKFC.

The UWFI interpolation function calculator, after receiving the initial digital signal from the UUD, reads the argument of the objective function T _m from the memory unit T m, the number of samples m from the memory unit m, and m data pairs from the BDU averaged data memory block. Then, the string of data pairs from the BDU block into two strings. First, the first sequence that contains the odd-index data pairs and finally the fti pair added at time T _{m is} determined:

and saves the resulting string in the BC1 buffer and the number of elements of this string m ·. in the unit m-i. Thereafter UWFI determines a second sequence which starts with the voltage data pair fti at time 0, then the even-indexed samples, and finally an added voltage data pair fti at time Tm;

(O, Wj), (F ₂ , Z7 ₂ ), (7; ,, ^) and stores the resulting string in the BC2 buffer and the number of elements of this sequence mi in the unit m2. Then the system determines the interpolation function ui (/) for the sequence 1, which interpolates the voltage waveform on the time segment [0, Tm] defined by the points of the sequence 1 by means of the broken line segments.

The circuit writes the voltage waveform parameters ui (f) to block BP1 in the form m ·. - 1-element sequence of four numbers:

(O, t ₃ , a ,, b _{ ), (ζ, t ₅ , a ₂ , b ₂ ), ...

in general form:

determining the interpolation function of the voltage waveform ui (/) on the section te [t _p , t _k ] according to the formula:

^u i = ~ t _p ) + b

Then the UWFI system analogically determines the interpolation function un (f) for the sequence 2, and writes its parameters to the BP2 block in the form of the sequence m ₂ - 1 of the sequence of four numbers:

(Ο, ξ, ^^, ^, ζ, α ’, ^), ...

determining the interpolation function of the voltage waveform uu (f) on the segment te [t _p , t _k ] in the same way as in the case of the sequence of four numbers describing the voltage waveform function ui (f). Then, based on the parameters of the voltage time functions ui (/) and uu (/) stored in blocks BP1 and BP2, respectively, the UWFI system, by appropriately dividing the time segments, determines new four numbers describing both voltage waveforms so that these waveforms do not change while the ends of the interpolation segments were at the same points, respectively. As a result of this operation, two m element sequences of four numbers are obtained, respectively for the functions ui (f) and uu (/) in the form:

(0, (Ą.jj, ĄĄ) .....), (/ ,,, 77, <"* ;,)

The obtained sequences of quadruplets of the interpolation functions ui (f) and uu (f) are saved by the UWFI system in blocks BU1 and BU2, respectively.

After the computation is completed and the results are saved, the UWFI system sends the initial digital signal to the final value calculator UWWKFC and waits for the next digital initiation signal from the UUD data averaging system to appear.

PL 230 330 Β1

The last element of the UWWFC objective function evaluation system is the UWWKFC objective function terminator. The UWWKFC system, after receiving the initial digital signal from the UWFI interpolation function determination system, reads the value of the variable m from the memory unit m. On this basis, it reads successively m values of sequences of four numbers describing the interpolation functions of voltage waveforms ui (f) and uu (f), respectively, from memory blocks BU1 and BU2. Then it determines the mean values of the difference of both functions on the interval [0.7 _m ] according to the formula:

- 1 ^r f / / Λ z XX, and stores the obtained result of the mean value u ^ n in the memory unit of the mean value of the difference of voltage waveforms sru. Then, based on the time functions of the voltage waveform ui (f) and uu (f) and the average value of their difference, it calculates the final value of the objective function according to the formula:

T fc [ ^T _m )} («/ (0 - U (0 -) ² dt which it writes to the memory unit f _c . Then, UWWKFC sends the digital signal of completion of evaluating the objective function to UWMINFC and waits for another initial digital signal from UWFI chip.

The inventive measurement arrangement outlined above is to be considered as an exemplary arrangement. The individual elements of the circuit may be in the form of digital or analog circuits. It is obvious to a skilled person how to implement the individual blocks in order to fulfill their functionality. In one of the possible implementations, the measurement system may be implemented in the form of a processor controlled by a suitable software. In another embodiment, the measurement circuitry may be implemented as an FPGA circuit of programmable logic gates.

Claims (1)

Patent claim 1. A system for measuring the period T of voltage u (f), comprising an amplifier (W) whose input terminals are connected to points of the electrical circuit between which the measured voltage u (f) is present, and whose output is connected to the input of an analog-to-digital converter ( ADC), to which the sampling trigger input is connected a clock signal generated by a clock signal generator (CLK) with period T _s <0.57, triggering sampling at times / 1/2/3, ... t _n , where t, = (iV) T _s and t _n = (n-1) T _s > 27, while the output of the analog-to-digital converter (ADC), on which the result signals with the values 1/1 = ui = 1 / (/ 2), 1/3 = 1 / (/ 3), ... u _n = u (t _n ) is connected to the measuring line controller (KTP) controlled by the interface controller (KI) for communication with the user via the interface (INT) system, characterized in that it comprises: - measurement data memory block (BD) connected with the measuring track controller (KTP) for storing data read by the measuring track controller (KTP) from the analog-to-digital converter (ADC); - Objective function value evaluation circuit (UWWFC) connected to the measurement data memory (BD) block for determining and storing: objective function values f _c in memory unit objective function value / odometer value of objective function argument 7 _m in memory unit of objective function argument value T _m ; - objective function minimum determination circuit (UWMINFC) attached to the objective function value memory unit (f _c ) and to the objective function argument value memory unit Tm for determining and storing the objective function argument value T _m , for which the objective function f _c value takes the minimum value , in memory unit T _u ; - the interface controller (KI) indicates as the measured value of the period T of the voltage u (f) read from the memory unit T _u after performing the calculations for the frequency search range from T _m in to T _max with a resolution of T _s te _P ', PL 230 330 Β1 - where the objective function calculating system (UWWFC) is activated to determine the value of the objective function f _c for successive values of the arguments of the objective function T _m from the range Tmin to T _max with a resolution of T _s te _P and includes: o time modification system (UMC), which reads a sequence of measurement data pairs from the data block (BD) in the form of measurement time and instantaneous voltage value at a given measurement time according to the formula: (f |, W |),)> (^ 3> ^W 3) / ··· (ζ |! ^li _n ) and modifies the measurement data sequence by modifying the measurement time values according to the formula: / '= /.- -L τ t I rp m where L J is a rounding down operation, obtaining a sequence of the form: which writes to a modified data (BDM) memory block; o which is connected to the sequence sort system (USC), which sorts the modified sequence of measurement data pairs read from the modified data memory block (BDM) according to the modified measurement time t ', obtaining a sequence in the form: (.λ l .η n \ i jr n \ (.nn \ with property t "<t" ₊₁ , by which it writes in the sorted data memory block (BDP), which is connected to the data averaging system (UUD), which averages the modified measurement data with the same modified measurement time read from the sorted data memory block (BDP) by replacing several pairs of measurement data with the same modified time with one pair of measurement data with the same modified time and the voltage value equal to the arithmetic mean of the averaged measurement data voltages, giving element string m: (^ i> «1) '( ^l 2 * ^ι λ)>(h> ^ 3)) where m <n for which writes to the average data memory block (BDU); which is connected to the interpolation function determination system (UWFI), which reads m pairs of averaged measurement data from the average data memory block (BDU) and based on them: using the argument T _m determines the first extracted data string, which contains the averaged measurement data with odd indices and finally the added voltage data pair ίί-, at time T _m : (O, Wj)>(ζ> ^ ₃ ), (f ₅ , w ₅ )> ··· (/ *> u _k ),) the values of which are stored in the first sequence memory block BC1, using the argument T _m determines the second sequence Extracted data, which contains the voltage pair ίί-, at time 0 then the averaged measurement data with even indices and finally the added voltage pair i and ₁ at time T _m : (0, / 7,), (^), (^, ^, ... ^ whose values are stored in the second sequence memory block BC2, for the first sequence of separated time and voltage measurement data pairs determines the first interpolation function ui (f) in the form of a spline function of linear functions (broken line) that determines the time course of voltage on a time segment PL 230 330 Β1 [0, T _m ], the parameter values of which are written to the memory block of the first auxiliary voltage waveform BP1, for the second sequence of separated time and voltage measurement data pairs determines the second interpolation function uu (f) in the form of a spline linear function (line the voltage waveform over the time segment [0.7n], the parameter values of which are written to the memory block of the second auxiliary voltage waveform BP2, reads the parameter values of the first voltage waveform interpolation function ui (f) from the BP1 memory block and the second waveform interpolation function temporal voltage uu (f) from the BP2 memory block and then, by dividing the time segments, redefines m parameters for both functions so that these functions do not change, and the ends of the interpolation segments are at the same m + 1 time points, respectively 0 , (2, (3, (4, ... t _m , T _m and the obtained m values of the parameters of the first function saves ji of voltage waveform interpolation ui (f) in the memory block of the first voltage waveform BU1 and m the parameter values of the second voltage waveform interpolation function ui (f) in the memory block of the second voltage waveform BU2, o to the memory blocks (BU1, BU2 ), the objective function end calculator (UWWKFC) is connected, which reads the m parameter values of the first voltage waveform ui (f) and the second voltage waveform uu (f) and for the first voltage waveform ui (f) i for the second waveform voltage uu (f) determines the mean value of their difference Ui-n over the time interval [0.7 _m ] according to the formula: (0) ^ which it stores in the memory unit sru, and determines the final value of the objective function f _c according to the formula: which it stores in the memory unit the values of the objective function f _c .