RU2212677C2 - Device for measuring parameters of double-pole multicomponent circuits - Google Patents

Abstract

FIELD: electrical instrumentation engineering. SUBSTANCE: device depends for its operation on measuring parameters of double-pole multicomponent circuit using integral characteristics of transient component in measuring circuit when square pulse is applied from reference-voltage source. Device enables measurement of parameters in both RC- and RLC-type double-pole multicomponent circuits in which case it may be both aperiodic and decaying-wave transient process. Integration operation enables reducing impact of random error component and transient component makes it possible to eliminate effect of measuring-channel additive error on measurement results. More universal measuring instruments and transducers for measuring parameters of double-pole multicomponent circuits can be built around proposed invention. EFFECT: enlarged functional capabilities of device. 1 cl, 5 dwg, 1 tbl

Description

 The invention relates to a control and electrical measuring technique, in particular to measuring the parameters of multi-element bipolar.

 Known measuring transducer of parameters of multi-element bipolar, containing a driver of the reference voltage, the studied bipolar, DC amplifier, a reference element, the first and second storage device, the first and second differentiator, a logarithmic converter, voltage divider (AS 1511708, class G 01 R 27/02, B.I. 36, 1989).

 The disadvantage of this device is its low functionality. It allows you to determine the parameters of only RC or RL circuits.

 The closest in technical essence to the proposed one is a device for determining the parameters of multi-element bipolar circuits, containing a reference voltage source, an operational amplifier with terminals for connecting the reference element and the studied bipolar circuit at the input and in the negative feedback circuit, three sampling-storage blocks, two blocks voltage subtraction, an integrator, and the output of the reference voltage source is connected via input terminals to the input of the operational amplifier, the output of which is connected to the first input of the first voltage subtraction unit and the input of the first sample-storage unit, the output of which is connected to the second input of the first voltage subtraction unit, the output of the second sample-storage unit is connected to the first input of the second voltage subtraction unit, control unit, scaling converter, fourth, fifth and the sixth sample-storage unit, a computing unit, a key, wherein the input of the scaling converter is connected to the output of the reference voltage source, the output of the scaling converter is connected to the input m integrator, the output of which is connected to the third input of the first voltage subtraction unit, the output of which is connected to the inputs of the second, third, fourth, fifth and sixth sampling-storage units, the output of the third sample-storage unit is connected to the second input of the second voltage subtraction unit, the output of the last connected to the control input of the scaling converter, the outputs of the second, fourth and fifth sampling-storage blocks are connected to the first, second and third inputs of the computing block, the output of the sixth sampling-storage block connected to the fourth input of the computing unit, the control inputs of the reference voltage source, all sampling-storage units and the key are connected to the corresponding outputs of the control unit, the key outputs are connected to the corresponding outputs of the studied bipolar network.

 The disadvantage of this device is its low functionality. The device allows to determine the parameters of multi-element bipolar circuits only for individual particular cases, and the studied bipolar circuits can be either RC-type or RL-type.

 The technical result is the expansion of the functionality of the device. The proposed device allows to determine the parameters of multi-element bipolar circuits of both RC- and RL-type, and RLC-type, while the transient can be either aperiodic or damped oscillatory.

 The technical result is achieved by the fact that in the device for determining the parameters of multi-element bipolar circuits, containing a reference voltage source, an operational amplifier with terminals for connecting the reference element and the studied bipolar circuit at the input and in the negative feedback circuit, and the output of the reference voltage source is connected through input terminals with the input of the operational amplifier, a key whose terminals are connected to the corresponding terminals of the operational amplifier, clock, bl ok storage samples, an integrator, a scaling converter, the output of which is connected to the integrator input, an electronic computer (computer), the first output of which is connected to the control inputs of the reference voltage source and key, a timer, an analog-to-digital converter (ADC), a free allocation block are introduced component, the input of which is connected to the output of the operational amplifier, and the output with the input of the scaling converter, the control inputs of which are connected to the second outputs of the computer, the first output of which is connected control input of the timer, the control input of the integrator is connected to the third output of the computer, and the output is connected to the input of the sampling-storage unit, the output of which is connected to the input of the ADC, the outputs of which are connected to the inputs of the computer, the output of the clock generator is connected to the counting input of the timer, the information inputs of which are connected with fourth computer outputs, and the output is connected to the control inputs of the sampling-storage unit and ADC.

 The structural diagram of the proposed device differs from the known one in that it is additionally introduced with a free component allocation unit, a timer and an ADC, which are standard nodes of analog and digital computing equipment. However, despite the fact that the introduced blocks are standard units of digital computer technology, their introduction, as well as the emergence of new functional relationships between them and existing blocks, makes it possible to manifest a new property in the device. Namely: the device allows to determine the parameters of multi-element bipolar circuits of both RC- and RL-type, and RLC-type, while the transient can be both aperiodic and damped oscillatory, which extends the functionality of the device.

 The theoretical rationale for the operation of the device. The operation of the device is based on the analysis of the transient process that occurs in the bipolar circuit under study when a step effect is applied to it from a reference voltage source.

где A_i - постоянные интегрирования (амплитуды экспонент), которые определяются из начальных условий; p_i - корни (показатели экспонент) характеристического уравнения (Атабеков Г.И. Основы теории цепей. Учебник для вузов. - М.: Энергия, 1969, с.202). Причем амплитуды A_i и показатели p_i являются функциями элементов исследуемой двухполюсной электрической цепи. Очевидно, определив амплитуды А_i и показатели р_i, можно определить и значения всех элементов электрической цепи.As you know, the transition process in any electrical circuit when applying a stepwise action consists of a forced and free component. The free component for a linear bipolar electric circuit in the general case has the form

where A _i are the integration constants (exponential amplitudes), which are determined from the initial conditions; p _i - the roots (exponents) of the characteristic equation (Atabekov GI Fundamentals of the theory of chains. Textbook for universities. - M .: Energy, 1969, p.202). Moreover, the amplitudes A _i and indicators p _i are functions of the elements of the studied bipolar electric circuit. Obviously, having determined the amplitudes A _i and the indicators p _i , it is possible to determine the values of all elements of the electric circuit.

The most famous method for determining the parameters of exponentials in the transition process is the Prony method (Marpl.-ml. S.L. Digital spectral analysis and its applications: Transl. From English - M .: Mir, 1990, p. 365). In accordance with this method, 2n equally spaced samples are taken in the transition process, where n is the number of exponentials and from which the sought-for amplitudes A _i and exponents p _{i are} determined in three stages. However, this method is extremely sensitive to errors in the source data.

т. е. определенный интеграл от экспоненты в пределах от некоторого момента времени t_р до бесконечности с точностью до постоянной времени совпадает со значением экспоненты в момент времени t_р. Следовательно, в методе Прони вместо равноотстоящих значений переходного процесса можно использовать значения интегралов от равноотстоящих ординат переходного процесса до окончания переходного процесса. Учитывая фильтрующие свойства операции интегрирования, очевидно, это позволит повысить точность определения параметров экспонент и соответственно параметров элементов двухполюсной цепи.However, we note that

that is, a certain integral of the exponent in the range from a certain point in time t _p to infinity, up to a time constant, coincides with the value of the exponent at time t _p . Consequently, in the Prony method, instead of equally spaced values of the transient process, one can use the values of the integrals from equally spaced ordinates of the transient process to the end of the transient process. Given the filtering properties of the integration operation, obviously, this will improve the accuracy of determining the parameters of the exponentials and, accordingly, the parameters of the elements of the bipolar circuit.

 Consider the definition of the parameters of an electric circuit using a specific example.

где U_ОП - напряжение на выходе источника опорного напряжения; р - комплексная частота. После преобразований (учитывая, что на входе исследуемой двухполюсной цепи формируется ступенчатое воздействие и U_ОП(р)=U_ОП/р) получим

Переходя к оригиналу, получим для свободной составляющей выходного напряжения

(2)
где p₁, р₂ - корни знаменателя (1), причем

где

Поскольку в данном случае n= 2, произведем интегрирование свободной составляющей выходного напряжения на четырех участках 0-t_ОП, t_Р-t_ОП, 2t_P-t_ОП, 3t_Р-t_ОП (где t_ОП - момент времени окончания переходного процесса):

По аналогии с методом Прони, составим систему уравнений

Решая систему уравнений (4) относительно c₀, с₁, получим:

Далее, в соответствии с методом Прони составляем алгебраическое уравнение
c₀+c₁ξ+ξ² = 0, (6)
корни которого равны

Здесь возможны три случая.Let the bipolar circuit consists of series-connected resistor R, capacitor C and inductance L, and the circuit under study is connected to the input of the operational amplifier (Fig. 1). The voltage at the output of the operational amplifier in operator form will be equal to

where U _OP is the voltage at the output of the reference voltage source; p is the complex frequency. After the transformations (taking into account that a stepwise effect is formed at the input of the bipolar circuit under study and U _ОП (р) = U _ОП / р) we get

Passing to the original, we obtain for the free component of the output voltage

(2)
where p ₁ , p ₂ are the roots of the denominator (1), and

Where

Since in this case n = 2, we will integrate the free component of the output voltage in four sections of 0-t _OD , t _P -t _OD , 2t _P -t _OD , 3t _P -t _OD (where t _OD is the transition end time) :

By analogy with the Prony method, we compose a system of equations

Solving the system of equations (4) with respect to c ₀ , c ₁ , we obtain:

Further, in accordance with the Prony method, we compose an algebraic equation
c ₀ + c ₁ ξ + ξ ² = 0, (6)
whose roots are equal

Three cases are possible here.

Для определения амплитуд A₁ и А₂ запишем выражение для интеграла H₁

откуда, учитывая, что А₁=-A₂, получим

Из курса электротехники известно, что для апериодического процесса

Подставляя (9) в (10) получим

Учитывая (3), заметим, что

Откуда получаем

Случай 2. c₁ ²/4=c₀, т.е. корни

- действительные и равны между собой (ξ₁ = ξ₂ = ξ). Свободная составляющая выходного напряжения будет иметь вид

Показатель экспоненты будет равен

Определим значение интеграла H₁ для данного вида переходного процесса

Откуда получаем
A = H₁p². (15)
Учитывая (14), получим

Далее, используя равенство корней и соотношения (3), получим:
R = 2Lp, C = 4L/R².Case 1. c ₁ ^2/4> c _0, ie, the roots ξ _{1,2 /} -.. Valid. The exponents will be equal to:

To determine the amplitudes A ₁ and A _2, we write the expression for the integral H ₁

whence, given that A ₁ = -A ₂ , we get

From the course of electrical engineering it is known that for an aperiodic process

Substituting (9) into (10) we obtain

Given (3), we note that

Where do we get

Case 2. c ₁ ^2/4 = c _0; the roots

are real and equal to each other (ξ ₁ = ξ ₂ = ξ). The free component of the output voltage will have the form

Exponent will be equal

Define the value of the integral H ₁ for this type of transient

Where do we get
A = H ₁ p ² . (fifteen)
Given (14), we obtain

Further, using the equality of roots and relations (3), we obtain:
R = 2Lp, C = 4L / R ² .

В соответствии с методом Прони значения р и ω_{св =} могут быть вычислены по формулам:

Получим значение H₁ для этого вида переходного процесса

Откуда получаем

Из (17) и (18) получаем

Аналогично записываем выражения для R и С:
R = 2pL;

Формулы, используемые при определении параметров двухполюсной цепи, содержащей последовательно соединенные элементы R, L, С, сведены в таблицу.Case 3. c ₁ ^2/4 <c _0, ie, the roots _{ξ 1,2 = x ± jy -.} . The complex conjugate. The free component of the output voltage will have the form:

In accordance with the Proni method, the values of p and ω _{sb =} can be calculated by the formulas:

We get the value of H ₁ for this type of transient

Where do we get

From (17) and (18) we obtain

Similarly, we write the expressions for R and C:
R = 2pL;

The formulas used in determining the parameters of a bipolar circuit containing series-connected elements R, L, C are summarized in the table.

Т.к.

процесс будет затухающим и колебательным. Учитывая, что

выражение для свободной составляющей выходного напряжения будет иметь вид

Осцилограмма этого переходного процесса показана на фиг.2.A numerical example. The above calculations are confirmed by a concrete numerical example. Let U _OD = 1 V, R ₀ = 1000 Ohm, R = 200 Ohm, C = 0.01 μF, L = 1 mH. Using (3), we define δ and ω ₀ :

Because

the process will be damping and oscillatory. Given that

the expression for the free component of the output voltage will be

An oscillogram of this transient is shown in FIG.

Участки интегрирования показаны на фиг.2.As t _P we take the value t _P = 5 μs = 5 • 10 ^-6 s. Using formula (19) for the integral for this type of transient, we find certain integrals of the free component of the output voltage in four sections:

Integration sites are shown in FIG.

From (5) we find the coefficients c ₀ and c ₁ : c ₀ = 0.3678, c ₁ = 0.08580.

По формулам (18) вычисляем:

По формуле (20) вычисляем амплитуду

Далее, используя (21) и (22), определяем значения элементов двухполюсной цепи:

R = 2pL = 2•100000•0,001 = 200 Ом,

Таким образом, по интегральным значениям от свободной составляющей переходного процесса были получены искомые значения параметров двухполюсной цепи.The roots of equation (6) in this case are complex conjugate
ξ _{1,2 /} = x ± jy,
Where

By the formulas (18) we calculate:

By the formula (20) we calculate the amplitude

Further, using (21) and (22), we determine the values of the elements of the bipolar circuit:

R = 2pL = 2 • 100000 • 0.001 = 200 Ohms,

Thus, from the integral values of the free component of the transient process, the desired values of the parameters of the bipolar circuit were obtained.

 The block diagram of the device for determining the parameters of multi-element bipolar circuits is shown in figure 1, where 1 is the source of the reference voltage; 2 - investigated bipolar circuit; 3 - supporting element; 4 - operational amplifier; 5 - key; 6 - block allocation of the free component; 7 - scaling amplifier; 8 - integrator; 9 - block sampling-storage; 10 - clock generator; 11 - timer; 12 - ADC, 13 - computer.

The reference voltage source 1 is designed to create a stepwise effect at the input of the two-terminal 2 under study. The voltage U _OP appears at the output of the reference voltage source 1 when a logical unit level is applied to its control input from the first computer output 13.

 The operational amplifier 4 is designed to connect the studied bipolar circuit 2 and the support element 3. Moreover, depending on the type of the studied bipolar circuit 2, it is switched on either at the input of the operational amplifier 4 or in the feedback circuit.

 The key 5 is intended for shorting the feedback loop of the operational amplifier 4, when the parameters of the studied bipolar circuit are not determined. This must be done to discharge the capacitors included in the circuit under study, when it is included in the feedback circuit.

Block 6 is designed to highlight the free component of the transition process. The free component extraction function can be implemented by using a separation capacitor C _P connected to a load resistance R _N.

 The scaling amplifier 7 is designed to amplify or attenuate the input signal in order to provide optimal conditions for the operation of the integrator 8. The operation of the scaling amplifier 7 is controlled by the signals received at its control inputs from the output of the computer 13.

 The integrator 8 is designed to perform the integration operation of the analog signal supplied to its input. The integration operation is performed by applying the level of a logical unit to its control input. If there is a logic zero level at the control input of the integrator 8, it acts as a buffer amplifier with a unity gain (when the integrator is implemented on an operational amplifier in its feedback circuit, a resistor is switched on instead of a capacitor under the influence of a signal at the control input).

 Block sampling-storage 9 is designed to store the signal level at the output of the integrator 8 at specified points in time. Memorization is performed on the leading edge of the pulse received at the control input of the fetch-storage unit 9 from the output of the timer 11.

 The clock generator 10 is designed to synchronize the operation of the device and provide pulses to the input of the timer 11.

The timer 11 is designed to form time intervals t _P and to issue a corresponding pulse to the control inputs of the sample-storage unit 9 and ADC 12. As a timer 11, a programmable timer chip KR580VI53 can be used, designed to obtain program-controlled delays in computers (Microprocessors and microprocessors sets of integrated circuits: a Handbook of 2 volumes, edited by V.A. Shakhnov. - M.: Radio and Communications, 1988, vol. 1, p. 76). The time intervals through which pulses appear at the output of the timer are set by writing to the timer through its information inputs of the corresponding coefficient from the fourth outputs of the computer 13.

 The ADC 12 is designed to convert an analog signal at the output of the sample-storage unit 9 into a digital code intended for further processing in a computer. The conversion of the input signal begins on the negative edge of the pulse received at its control input from the output of timer 11.

 A computer 13 is designed to control the operation of the device and perform calculations according to the above formulas when determining the parameters of the elements of a bipolar circuit. In the prototype, these functions are performed by the control unit and the computing unit.

Before describing the operation of the device, it should be noted that the accuracy of determining the parameters of multi-element two-terminal devices depends to a large extent on the correct choice of time intervals t _P and t _OP (time of the end of the transient process) and the corresponding setting of the scaling transducer 7. In particular, as t _P when transient, it is advisable to use a point in time corresponding to the first maximum of the transition process (Fig.2B). Therefore, as a rule, before determining the parameters of a bipolar circuit, it is necessary to carry out a calibration operation to determine the optimal parameters of the measurement process.

 In calibration mode, the device operates as follows. On command from the computer 13 at the control input of the integrator 8 sets the logic zero level, and, thus, it works as a buffer amplifier with a unity gain. The timer 11 is configured in such a way as to ensure the minimum time between individual measurements of the transient process when applying a voltage drop to the input of the investigated circuit.

 At the first output of the computer 13, a logical unit level is established, which opens the key 5 in the feedback circuit of the operational amplifier 4, enables the timer 11 and turns on the reference voltage source 1. In the bipolar circuit under study, a transient begins, which generates the corresponding voltage at the output of the operational amplifier 4. Block 6 selects the free component of the transient process, which is then scaled by block 7 and through the integrator 8 (which performs the functions of a buffer amplifier in this mode) and the input is a sampling-storage unit 9. On the leading edge of the pulses received from the timer 11, the sampling-storage unit 9 stores the values of the transient response at discrete time instants, and on the trailing edge of the pulse - converts to a digital code using ADC 12. Thus, digitization of the transient response and entering it into the computer 13.

After a certain time (obviously exceeding the time of the transition process) at the first output of the computer 13, the logical zero level is set and the calibration process ends. The values of the transient response determines the optimal values of the time intervals t _P and t _OP , as well as the optimal mode of operation of the scaling transducer 7.

 In the mode of determining the parameters of the elements of the bipolar circuit, the device operates as follows.

On command from the computer 13, the timer 11 is configured so as to ensure the issuance of pulses at equal intervals of time equal to t _P. At the first output of the computer 13, the level of the logical unit is established, which opens the key 5 in the feedback circuit of the operational amplifier 4, enables the timer 11 and turns on the reference voltage source 1. The level of the logical unit is also set at the control input of the integrator 8, which puts it into integration mode .

 In the bipolar circuit under study, a transient begins, generating the corresponding voltage at the output of the operational amplifier 4. Block 6 isolates the free component of the transient, which is then scaled by block 7 and fed to the integrator 8, with the help of which the free component of the transient is integrated.

After the time t _P , the first pulse appears at the output of the timer 11. On the leading edge of this pulse, the value of the integral of the free component of the transient process in the time interval 0-t _{P is} written to the sample-storage unit 9. 2b, the integral corresponding to this integration region is denoted by H ₂₀ . On the trailing edge of the pulse from the output of the timer 11, which is fed to the control input of the ADC 12, the value of the integral H _{20 is} converted from analog to digital and the resulting value of H ₂₀ is stored in a computer memory.

Similarly, at time intervals 2t _P and 3t _P , the values of the integrals H ₃₀ and H _{40 are} determined (Fig. 2c, d). At the end of the transition process, the digital value of the integral H _{1 is} entered into the computer (Fig. 2a).

 After that, at the first output of the computer 13, a logical zero level is set and the integration process of the free component of the transition process ends.

At the next stage, using a computer 13, based on the obtained values of the integrals, the parameters of the elements of the bipolar circuit are calculated. First, the obtained values of H ₂₀ , H ₃₀ and H ₄₀ determine the values of the integrals H ₂ , H ₃ and H ₄ :
H ₂ = H ₁ -H ₂₀ ; H ₃ = H ₁ -H ₃₀ ; H ₄ = H ₁ -H ₄₀ ,
and then according to the above formulas (for a bipolar circuit, consisting of elements R, L, C connected in series, these formulas are given in the table), the parameters of the elements of the bipolar circuit under study are calculated.

 Thus, the proposed device allows to determine the parameters of multi-element two-terminal circuits of an arbitrary structure containing simultaneously R, L, C elements, i.e. The transient process at the output of the circuit under study may have an oscillatory (decaying) character. In this case, the parameters of the bipolar circuit are determined by the integral characteristics of the free component of the transient process, which reduces the influence of random noise on the measurement result. The use of the free component of the transition process allows, in addition, to exclude the influence on the measurement result of the additive errors of the blocks included in the measuring channel (in particular, the bias voltage of the operational amplifier 4 and the scaling transducer 7).

Claims (1)

 A device for determining the parameters of multi-element bipolar circuits, containing a reference voltage source, an operational amplifier with terminals for connecting the reference element and the studied bipolar circuit at the input or in the negative feedback circuit, and the output of the reference voltage source is connected through input terminals to the inverse input of the operational amplifier, the key intended for shorting the feedback loop of the operational amplifier when the parameters of the circuit under study are not determined, The first key output is connected to the inverse input, and the second to the output of the operational amplifier, a clock generator, a storage fetch unit, an integrator, a scaling converter, the output of which is connected to the integrator input, and an electronic computer (computer), the first output of which is connected to the control inputs a reference voltage source and a key, characterized in that a timer, an analog-to-digital converter (ADC), a free component extraction unit, the input of which is connected to the output of the operational amplifier, are introduced into it I, and the output is with the input of the scaling converter, the control inputs of which are connected to the second outputs of the computer, the first output of which is connected to the control input of the timer, the control input of the integrator is connected to the third output of the computer, and the output is connected to the input of the sampling-storage unit, the output of which is connected with the input of the ADC, the outputs of which are connected to the inputs of the computer, the output of the clock generator is connected to the counting input of the timer, the information inputs of which are connected to the fourth outputs of the computer, and the output is connected to the control inputs of the unit Sample storage and ADC, and in determining the parameters of multi-element bipolar circuits using the formulas shown in the table.

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