RU2300112C2 - Method for measurement of frequency and device for its realization - Google Patents

Abstract

FIELD: measuring equipment, applicable in automatic measurement systems, control and emergency protection systems, in which the source information subject to analysis is presented in the frequency form.

SUBSTANCE: the offered device for frequency measurement has a shaper of the pulse train under investigation, standard-frequency oscillator, not circuit, the first counter and register, the second counter and register, microprocessor system, trigger pulse shaper, OR element, synchronizing unit, control unit, count pulse shaper, and a multiplexer interconnected in a respective way. The given device realized the method for frequency measurement.

EFFECT: expanded band and enhanced accuracy of frequency measurement.

2 cl, 8 dwg

Description

The invention relates to measuring equipment and can be used in automatic measurement, regulation and emergency protection systems, in which the source information to be analyzed is presented in frequency form.

, причем границы образцовых интервалов устанавливаются по моментам прихода импульсов измеряемой частоты, положение этих границ определяется по числу эталонных меток времени от начала предельного интервала, выбираемого большим или равным периоду низшей измеряемой частоты до начала (N_H) и конца (N_K) образцового интервала, а длительность образцового интервала определяется как Т_об=Т_о·(N_K-N_H).A known method of measuring the frequency of pulses [1], based on the formation of reference time stamps with a period of T _about and sample time intervals T _about , as well as the number M of periods of the measured frequency in the sample interval, with subsequent calculation of the current frequency according to the formula

moreover, the boundaries of the model intervals are set according to the moments of arrival of the pulses of the measured frequency, the position of these boundaries is determined by the number of reference time stamps from the beginning of the limit interval, chosen greater than or equal to the period of the lowest measured frequency to the beginning (N _H ) and the end (N _K ) of the model interval, and the duration of the model interval is defined as T _about = T _about · (N _K -N _H ).

The first significant drawback of this method is its low reliability of frequency measurement, due to the possibility of measurement errors caused by the asynchrony (time sharing) of some processes of counting pulses and storing the information received, as well as the asynchrony of the processes of storing the numbers M, N _H , N obtained as a result of counting _K and reading these numbers by a microprocessor system (PC) to calculate the frequency value. Accidental coincidence in time of these asynchronous processes can lead to distortion of information and, thereby, to unacceptably large values of the measurement error, which is equivalent to a failure in the measurement.

In particular, asynchrony of the counting processes of the number Mj of pulses of the measured frequency F _x and the formation of minimum time intervals T _m , after which the information obtained as a result of this counting is carried out, can lead to such failures. In this case, when the next pulse of the measured frequency F _x arrives in the corresponding counter, the process of generating a specific number will begin and if a read pulse arrives at the same time, then the information from the counter will be invalid.

The second significant drawback of the considered method of measuring the frequency is the complexity of its hardware and software implementation, which is caused, first of all, by the presence of four reference time intervals and a multi-stage system for transmitting and storing the information obtained from the measurement. In addition, when measuring it may turn out that N _K <N _N , therefore, the algorithm for determining the frequency must include additional operations associated with determining the sign of the difference N _K -N _N and calculating the frequency using a more complex formula.

при этом формируются первые временные ворота длительностью Δt₁, которые заполняются n импульсами исследуемой последовательности F_x, число n которых определяется путем счета и фиксируется, одновременно формируются вторые временные ворота длительностью Δt₂, такие что их фронт соответствует импульсу исследуемой последовательности, появившемуся сразу после начала первых ворот, а срез - импульсу, возникающему сразу после окончания первых ворот. Вторые временные ворота заполняются счетными импульсами частоты F_сч, число N которых также определяется путем счета и фиксируется.A known method of measuring the frequency [2], adopted as a prototype, which consists in converting the studied signals of frequency F _x into the studied pulse sequence of the same frequency F _x (2, Fig. 4.21, figure 1), in the simultaneous calculation of n pulses of the studied sequence and N counting pulses of frequency F _cf , in determining the frequency value of the studied signals according to the formula

in this case, the first temporary gates of duration Δt _{1 are formed} , which are filled with n pulses of the studied sequence F _x , the number n of which is determined by counting and fixed, simultaneously the second temporary gates of duration Δt _{2 are formed} , such that their front corresponds to the pulse of the studied sequence that appeared immediately after the start the first gate, and the slice - to the impulse that occurs immediately after the end of the first gate. The second temporary gate is filled with counting pulses of frequency F _cf , the number N of which is also determined by counting and fixed.

The first significant drawback of this method of measuring frequency is a significant limitation of the frequency measurement range, due to the impossibility of measuring low frequencies, since the maximum value of the period T _{xmax of the} studied signals should be less than the duration Δt _{1 of the} first time gate, that is, T _xmax <Δt ₁ (Fig. 2 ) Considering that F _xmin = 1 / T _xmax , from the above inequality we obtain the dependence defining the lower limit of the frequency measurement: F _xmin ≥1 / Δt ₁ . For example, when Δt = 10 ms ₁ F _xmin ≥100 Hz.

The second significant disadvantage of the prototype method is its low reliability of frequency measurement, due to the possibility of failures in the measurement process. The reason for such failures is the asynchrony of the processes of formation of the first time window and pulses of the studied sequence F _x .

In order to simplify the description of the considered method of measuring the frequency in [2], it is considered that the duration τ _and pulses of the sequence under study has an infinitely small value (2, Fig. 4.21-b, Fig. 1). However, in practice, the duration of τ _and these pulses has a certain value, most often commensurate with their repetition period T _x .

Moreover, the duration of the second time gate will not always be equal to an integer n periods T _x pulses of the investigated sequence. So, for example, if the front of the first time gate arises during the pulse of the investigated sequence (Fig. 3-a), then part Y _{1 of the} period T _x1 will be outside the second time gate and will take random values ranging from 0 to τ _AND .

If, during the action of the pulse of the test sequence, a cut of the first time gate occurs (Fig. 3-b), then outside the second time gate there will be part U _{2 of the} period T _x3 , taking random values ranging from (T _x -τ _and ) to T _x

In the measurement of low frequency when at the second time gate includes a small number n of periods T _x investigated sequences nonmultiple duration Δt ₂ of the gate integral number of periods T _x leads to unacceptably large errors, which amounts to a failure of the frequency measurement.

The third significant disadvantage of the prototype method is that it provides only a single frequency measurement. The introduction of additional operations can provide multiple frequency measurements with a measurement cycle greater than the total duration of the first two time gates, that is, at T _c > 2 · Δt ₁ (Fig. 4). However, in this case, when measuring the frequency of signals whose period is slightly less than Δt ₁ (Fig. 4-a), or significantly less than Δt ₁ (Fig. 4-b), a new significant drawback of the method arises due to the presence of "dead" time τ _m during which the measurement is not performed, which significantly reduces the efficiency (reliability) of the frequency measurement.

The known device [3], selected as an analogue, contains two programmable pulse counters, a counting pulse generator, a register, a bi-directional transceiver, input and output registers, a control unit with corresponding connections.

The device sets the number n of periods of the studied pulse sequence, determines the number N of pulses of the counting frequency F _cf arriving at counter 2 over a time interval t _x equal to the sum of the durations of these n periods. Then, the resulting number N is read by an external microprocessor system in which the frequency is calculated by the formula

The first significant drawback of the analog device is that it has a very limited frequency measurement range. Moreover, the upper limit F _{xmax of} this range is determined

Dependence (1) is derived as follows. The measured time interval t _x stacked N periods T of the counting frequency F _{MF MF} or n periods T _x measured frequency F _x, i.e. _x t = N · T _MF = n · T _x. The error δ _d measurement resolution is determined by:

From the last equation we get N = 1 / δ _d . Substituting the value of N in the equation defining t _x , we have

F _x = n · δ _D · F _MF

When determining the lower limit of the frequency measurement F _xmin , we proceed from the fact that when the frequency F _{x is} lowered, the number of counting pulses F _cf arriving at the 16-bit counter 2 should not exceed the capacity of this counter C _st = 2 ¹⁶ -1 = 65535. From the latter, the condition follows: n · T _xmax ≤С _Art · T _cf , whence, after simple transformations, we obtain the formula for determining the lower limit of the frequency measurement F _xmin

Thus, the analog device measures the frequency within

For example, with n = 4, F _cf = 10 ⁶ Hz, δ _d = 0.1%, the device in question will measure the frequency in the range from 61 to 4000 Hz. Expanding this range requires reprogramming the counters, which entails unacceptably large pauses in the measurement of frequency.

The second significant drawback of the device in question is that it is not designed for multiple continuous measurement of frequency: a single change is made in it, consisting of a cycle of a rough estimate of the current frequency value F _x and a cycle of accurate measurement of this parameter.

The closest in technical essence and achievable positive effect to the claimed device — the prototype — is a digital frequency meter [4], which includes a pulse train of the studied pulse sequence (input signal receiving port), a reference frequency generator F _о , an element NOT, a microprocessor system (processing tool and indications), the first counter and register, the second counter and register, two synchronization schemes, a port for receiving the pulse of the measurement cycle and their connection.

In the device, by means of the first and second counters, continuous counts are made, respectively, of pulses n of the studied sequence F _x and N of counting pulses F _cf = F _о , the number of pulses Δn _c = n (i + 1) -n (i) and ΔN _c = N ( i + 1) -N (i), entering the counters during the measurement cycle T _q, and the frequency calculated by the formula:

The first significant disadvantage of the prototype device is the limited frequency measurement range.

Moreover, the upper limit F _{xmax of} this range is determined by the dependence F _xmax <0.5 · F _cc , which follows from the principle of operation of the synchronization circuits used in the device under consideration: for stable operation of the synchronization circuit when measuring the maximum value of F _xmax frequency, the converted signals F _x should represent is a meander and to fix the levels of this meander along the front of the counting pulses F _cc, it is necessary that during each pulse and each pause of the meander at least one counting pulse F _{cc enters the} signaling circuit. And this is equivalent to the requirement F _cf > 2 · F _xmax or F _xmax <0.5 · F _cf.

The lower limit F _{xmin of the} frequency measurement range of this device is determined by the following formula obtained by the method of deriving dependence (1):

For example, when F _cf = 10 ⁶ Hz, T _c = 0.01 s, δ _d = 0.1% we will have:

F _xmin ≥100 kHz, F _xmax <500 kHz

The second significant drawback of the device under consideration is its low reliability of frequency measurement, due to the asynchrony of the processes of writing numbers n and N, respectively, into the first and second registers and the process of reading the recorded information by the microprocessor system to calculate the frequency value: random coincidence in time of these processes can lead to distortion of the numbers n, N and, as a result, a malfunction in the measurement of frequency.

The third significant drawback of this device is the complexity of its software and hardware implementation, because, firstly, the continuous parallel counting of pulses n and N used in this device requires additional computational operations that restore the true value of numbers in case of overflow of counters. Secondly, to measure the frequency of pulses F _x in a somewhat extended range, the device in question must be equipped with additional functional units, including analog ones, which unnecessarily complicates this device.

In addition, such a sophisticated device also has a significant limitation of the frequency measurement range, since in this case, the minimum value of the measured frequency F _{x is} required to have at least two to three whole periods of the measured frequency F _x during the measurement cycle T _c , that is, in a complicated version of the prototype device, the lower limit of the frequency measurement range is determined by F _xmin > (2-3) / T _c .

At T _c = 0.01 s, we will have F _xmin > (200-300) Hz.

The objective of the proposed method for measuring frequency and a device for its implementation is to expand the range and increase the reliability of frequency measurement.

в отличие от прототипа создают последовательность импульсов образцовой частоты F₀, из которой формируют счетные импульсы с частотой F_сч, определяемой требованием по точности измерения, причем фронт каждого такого импульса формируют на срезе соответствующего импульса образцовой частоты, а также формируют первую последовательность импульсов с периодом следования Δt₁, определяемым требованием по быстродействию измерения, одновременно формируют вторую последовательность импульсов с периодом следования Δt₂, фронт каждого импульса которой соответствует фронту импульса исследуемой последовательности импульсов, появившегося сразу после фронта соответствующего импульса первой последовательности импульсов, после фронта каждого импульса второй последовательности импульсов и окончания действующего во время этого фронта импульса образцовой частоты или окончания возникшего после этого же фронта импульса образцовой частоты на фронте очередного импульса образцовой частоты начинают выполнять с тактом Ti, равным периоду Т₀ следования импульсов образцовой частоты, тактируемую последовательность операций, причем на первом такте Т1 запрещают счет n импульсов исследуемой последовательности импульсов и N счетных импульсов, на втором такте Т2 фиксируют значения чисел n и N, полученные в результате предыдущего счета соответственно импульсов исследуемой последовательности импульсов и счетных импульсов, на третьем такте Т3 формируют сигнал RDY готовности зафиксированных значений чисел n, N и осуществляют подготовку нового счета, обеспечивающую со следующего такта счет N импульсов исследуемой последовательности и n счетных импульсов, начиная со значения, равного 0, на четвертом такте Т4 начинают новый одновременный счет n импульсов исследуемой последовательности и N счетных импульсов, а определение частоты F_x исследуемых сигналов осуществляют по сигналу RDY готовности зафиксированных значений чисел n и N или в любое время в течение нового одновременного счета n импульсов исследуемой последовательности и N счетных импульсов, причем перед началом определения частоты F_x к зафиксированному значению числа N прибавляют число ΔN, равное числу периодов следования счетных импульсов, укладывающихся в интервале времени, определяемом суммой длительностей трех тактов, в течение которых действует запрет счета импульсов.The problem is achieved in that in the method of measuring the frequency, which consists in converting the studied signals of frequency F _x into the studied pulse sequence of the same frequency F _x , in the simultaneous counting of n pulses of the studied sequence of pulses and N counting pulses of frequency F _cf , in determining the frequency value the studied signals according to the formula

Unlike the prototype creates a sequence of pulses the reference frequency F _0, in which the form of counting pulses at a frequency F _MF, defines the requirements for measurement accuracy, the edge of each such pulse is formed on the exemplary frequency slice corresponding pulse, and form a first sequence of pulses with a repetition period Δt ₁ , determined by the requirement for speed of measurement, simultaneously form a second sequence of pulses with a repetition period of Δt ₂ , the front of each pulse is This corresponds to the pulse front of the studied pulse sequence, which appeared immediately after the front of the corresponding pulse of the first pulse sequence, after the front of each pulse of the second pulse sequence and the end of the reference frequency pulse acting during this front or the end of the reference frequency pulse arising after the same front at the front of the next reference pulse begin performing frequency with tact Ti, equal to the period T ₀ of the pulse repetition exemplary, tact the sequence of operations, moreover, on the first step T1, the count of n pulses of the studied sequence of pulses and N counting pulses is prohibited, on the second step T2, the values of the numbers n and N are obtained as a result of the previous count, respectively, of the pulses of the studied sequence of pulses and counting pulses, on the third step T3 generate a signal RDY of readiness for the fixed values of numbers n, N and prepare a new account, ensuring from the next clock step the count of N pulses of the investigated sequence n counting pulses, starting from a value equal to 0, at the fourth clock cycle T4 start new concurrent expense n pulses of the target sequence and N the count pulse, and determination of the frequency F _x of the signals carried by the signal RDY ready fixed values of the numbers n and N or anytime for the new account simultaneous pulses n and N candidate sequence count pulses, wherein before determining the frequency F _x to fix the value of N is added number ΔN, equal to the number of the next period anija counting pulses which fit in the time interval determined by the sum of the durations of the three cycles during which the pulse count is a prohibition.

This object is achieved by the fact that in the device for measuring the frequency containing the shaper of the studied pulse sequence, the reference frequency generator, the element NOT, the first counter and register, the second counter and register, as well as the microprocessor system, and the input of the shaper of the studied pulse sequence is connected to the signal input devices, the generator output of the reference frequency is connected to the input of the element NOT, the data output of the first counter is connected by a bus to the data input of the first register, the data output x of the second counter is connected by a bus to the data input of the second register, the clock input of which is connected to the clock input of the first register, in contrast to the prototype, a start pulse shaper, an OR element, a synchronization unit, a control unit, a counting pulse shaper and a multiplexer are introduced, the output of the studied sequence generator pulses are connected to the first input of the synchronization unit and to the clock input of the first counter, the output of the reference frequency generator is connected to the clock input of the pulse shaper at the start and the first input of the control unit, the output of the element is NOT connected to the second input of the control unit and the clock input of the counting pulse shaper, the initial setup bus of the start pulse shaper is connected to the data input of this shaper, and its output to the first input of the OR element, the second input of which connected to the input of the external start of the device, and the output of the OR element to the second input of the synchronization unit, the output of which is connected to the third input of the control unit, the first output of the control unit is connected to enable and inputs of the first and second counters, the second output - with the clock input of the first register, the third output - with the inputs of zeroing the first and second counters and with the interrupt input of the microprocessor system, the fourth output of the control unit is connected to the third input of the synchronization unit, the bus of the initial installation of the counter pulse shaper connected to the data input of this shaper, and its output is connected to the clock input of the second counter, the data outputs of the first and second registers are connected by buses to the first and second input, respectively E data multiplexer, the third input of which is connected to the output address bus of the microprocessor system, the read output of which is connected to a fourth input of the multiplexer, the multiplexer data output connected through a microprocessor system bus with the output of the data.

A comparative analysis of the claimed technical solution with the prototype of the method shows that it differs from the known one in that it:

- create a sequence of pulses of a reference frequency F ₀ , from which counting pulses are formed with a frequency F _cf , determined by the requirement for measurement accuracy, and the front of each such pulse is formed on a slice of the corresponding pulse of a reference frequency;

- form the first sequence of pulses with a repetition period Δt ₁ determined by the requirement for the speed of measurement;

- simultaneously form a second sequence of pulses with a repetition period of Δt ₂ , the front of each pulse of which corresponds to the front of the pulse of the studied pulse sequence, which appeared immediately after the front of the corresponding pulse of the first pulse sequence;

- after the front of each pulse of the second sequence of pulses and the end of the reference frequency pulse operating during this front or the end of the pulse of the reference frequency arising after the same front, at the front of the next pulse of the reference frequency they start to execute with a clock cycle Ti equal to the period T _{0 of} following the pulse of the reference frequency a sequence of operations, moreover, on the first step T1, the count of n pulses of the studied sequence of pulses and N counting pulses is prohibited; on the second step T2, fix the n and N numbers obtained as a result of the previous count of the pulses of the pulse sequence under study and the counting pulses, respectively, are generated at the third step T3, the readiness signal RDY of the fixed values of the numbers n, N is generated and a new count is prepared, which ensures the count of n pulses of the studied sequence from the next step and N counting pulses, starting from a value equal to 0, on the fourth step T4 begin a new simultaneous count of n pulses of the studied sequence and N counting pulses, and about frequency distribution F _{x of the} studied signals is determined by the readiness signal RDY of fixed values of numbers n and N or at any time during a new simultaneous count of n pulses of the sequence under investigation and N counting pulses, and before starting the determination of the frequency F _{x, the} number ΔN is added to the fixed value of N equal to the number of periods of counting pulses that fall within the time interval determined by the sum of the durations of three cycles, during which the pulse count prohibition applies.

A comparative analysis of the claimed technical solution with the prototype of the device shows that it differs from the known one in that it:

- Introduced trigger pulse shaper, OR element, synchronization block, control unit, pulse shaper and multiplexer;

- the output of the generator of the pulse sequence under study is connected to the first input of the synchronization unit and to the clock input of the first counter, the output of the reference frequency generator is connected to the clock input of the driver pulse generator and the first input of the control unit, the output of the element is NOT connected to the second input of the control unit and the clock input of the calculator pulses, the bus of the initial installation of the driver pulse shaper is connected to the data input of this driver, and its output to the first input of the OR element, second the first input of which is connected to the input of the external start of the device, and the output of the OR element is connected to the second input of the synchronization unit, the output of which is connected to the third input of the control unit, the first output of the control unit is connected to the enable inputs of the first and second counters, the second output is connected to the clock input of the first register, the third output is with the inputs of zeroing the first and second counters and with the interrupt input of the microprocessor system, the fourth output of the control unit is connected to the third input of the synchronization unit, the initial installation bus of the generator of the counting pulses is connected to the data input of this shaper, and its output is connected to the clock input of the second counter, the data outputs of the first and second registers are connected by buses to the first and second data inputs of the multiplexer, the third input of which is connected by the bus to the output of the microprocessor system address, the read output which is connected to the fourth input of the multiplexer, the data output of the multiplexer is connected via a microprocessor system to the data output of the device.

The listed differences of the proposed method for measuring the frequency and device for its implementation allow us to conclude that the claimed technical solutions meet the criterion of "novelty." Signs that collectively distinguish the claimed technical solutions from prototypes of the method and device are not identified in other technical solutions when studying this and related areas of technology. They provide a new quality and significant differences in the measurement of frequency: the ability to continuously measure frequency over a wide range with increased reliability.

The essence of the prototype method [2] and its disadvantages are explained in FIGS. 1-4, and the essence of the proposed method for measuring frequency and devices for its implementation are explained in FIGS. 5-8, in which:

- figure 5 is a timing chart explaining the proposed method of measuring frequency;

- 6 is a block diagram of the proposed device;

- Fig.7 is a timing chart explaining the operation of the proposed device;

- Fig. 8 is a variant of a counting pulse shaper circuit implemented on a counter and a multiplexer;

In the text of the description and figure 5-8 adopted the following notation and abbreviations:

F _x - the frequency of the studied signals, the frequency of the studied pulse sequence, in short - the frequency F _x ;

F _xmin , F _xmax - respectively, the lower and upper limits of the frequency measurement range - the limits of F _xmin , F _xmax ;

T _x - period of the frequency F _x , T _x = 1 / F _x - period T _x ;

T _xmin , T _xmax - periods T _x corresponding to the limits of the frequency measurement range: T _xmin = 1 / F _max , T _xmax = 1 / F _xmin - periods T _xmin , T _xmax ;

F _o - reference frequency - frequency F _o ;

T _o - period of the reference frequency, T _o = 1 / F _o - period T _o ;

F _sc - the frequency of the counting pulses - the frequency of F _sc ;

T _sc - the period of the counting pulses, T _sc = 1 / F _sc - the period of T _sc ;

D - frequency division coefficient F ₀ , D = F ₀ / F _cf - coefficient D;

Δt ₁ - the pulse repetition period of the first pulse sequence - the period Δt ₁ ;

Δt ₂ - the pulse repetition period of the second pulse sequence - the period Δt ₂ ;

Ti, where i = 1-4 - measures with which a clocked sequence of operations is performed;

n is the number of pulses of the studied sequence of pulses is the number n of pulses;

N is the number of counting pulses is the number N of pulses;

RDY - ready signal of fixed values of numbers n and N - ready signal RDY;

ΔN is the number equal to the number of periods of the counting pulses falling within the interval τ _p is the number ΔN;

τ _and - pulse duration of the investigated pulse sequence - pulse duration τ _and ;

T _c - the duration of the measurement cycle - the interval T _c ;

τ _p is the time interval for the implementation of the clocked sequence of operations, the time interval for the prohibition of pulse counting is the interval τ _p ;

τ _sc - the time interval for counting pulses n and N is the interval τ _sc ;

With _st - the capacity of the binary pulse counter, With _st = 2 ^p -1 - capacity C _st ;

P is the number of bits of the binary counter is the number of P;

δ _d - relative measurement discreteness error - error δ _d .

Designations of the type F _x (1), TR (20) or A (0) (28) are the output signal, respectively, of driver 1, trigger 20, bit A (0) of address bus 28;

nCT (9), NCT (11), nRG (10), NRG (12) —numbers available in counters 9, 11 and registers 10 and 12, respectively;

MDO (27) is the number on the data bus 27;

MF _x (17) is the frequency value calculated in the microprocessor system 17;

T _x <Δt ₁ , T _x > Δt ₁ - respectively, T _{x is} slightly less than Δt ₁ , T _{x is} slightly larger than Δt ₁ .

In the proposed method for measuring the frequency create a sequence of pulses of the reference frequency F _o (Fig.5-a), from which the counting pulses F _cf (Fig.5-b) are formed, and the front of each such pulse is formed on a slice of the corresponding pulse of the reference frequency. In addition, form the first sequence of pulses with a repetition period Δt ₁ (Fig.5-c). At the same time, a second pulse train is formed with a repetition period of Δt ₂ (Fig. 5-d), the front of each pulse of which corresponds to the pulse front of the studied pulse sequence F _x (Fig. 5-d), which appears immediately after the front of the corresponding pulse of the first pulse train.

After the front of each pulse of the second sequence of pulses and the end of the reference frequency pulse operating during this front or the end of the pulse of the reference frequency arising after the same front, they begin to execute at the front of the next pulse of the reference frequency (Fig. 5th) with a clock cycle Ti equal to the period Т _о following the impulses of the reference frequency, the clocked sequence of operations. In order to compactly and graphically present time diagrams, steps T1-T4, with which a clocked sequence of operations is performed, are shown in FIG. 5th on the same time axis on two alternating ordinate levels.

Frequency is measured continuously, cycle by cycle. Figure 5-g shows adjacent cycles T _c (i-1), T _c (1), T _c (i + 1) measurements at different alternating ordinate levels. Each cycle consists measurement T _i (5-h) of the time interval τ _p clocked sequence of operations and the time interval τ account _MF n and N pulses.

The interval τ _p is equal to the total duration of the first three T1-T3 cycles of the implementation of the clocked sequence of operations. During this interval, the counting of n and N pulses is prohibited, the values of the numbers n and N are fixed (at step T2, Fig. 5-k, m) and the preparation of the subsequent count of n and N pulses (at step T3, Fig. 5-i , l). In addition, in the interval τ _r at the front of the third clock cycle, a ready signal RDY is generated (Fig. 5-n).

During the interval τ _SCH , the numbers n (FIG. 5-i) and N (FIG. 5-l) of the pulses are counted, and the frequency F _{x of the} studied signals is determined (FIG. 5-o) by the ready signal RDY or at any time during the new interval τ _cf , and before starting the determination of the frequency F _{x, the} number ΔN is added to the fixed value of the number N.

The proposed method for measuring frequency provides for the separation in time of asynchronous processes, the random coincidence of which can lead to a failure in the measurement. In particular, the count of N pulses of frequency F _{sc is} carried out at the slice of pulses of frequency F ₀ , and the prohibition or resolution of this account is at the front of these pulses.

Prohibition pulse counting begins on the first clock cycle T1 is clocked sequence of operations, which is formed after the second sequence of wavefront acting closure and during this pulse edge frequency F ₀ or closure arisen after the front pulse frequency F ₀ at the front of the next pulse frequency F _0. Such a sequence of operations makes it possible to separate in time the processes of counting n pulses of frequency F _x and prohibiting this counting.

The formation of the RDY ready signal (at step T3) is carried out after fixing the numbers n and N (at step T2), which eliminates the coincidence in time of the processes of fixing the numbers n, N and determining the frequency F _x .

In the proposed method for measuring frequency, the front of each pulse of the second sequence Δt ₂ corresponds to the pulse front of the investigated sequence F _x . Therefore, in the period Δt ₂ , equal to an error of ± T _{0 of the} duration T _c of the measurement cycle, an integer number of periods T _x always fits, which eliminates the discreteness error of the count of n pulses.

When determining the upper limit F _{xmax of the} frequency measurement range by the proposed method, we proceed from the following. The pulse front of the second sequence corresponds to the pulse front of the sequence being studied F _x , and the next pulse F _x following this pulse, in order to be taken into account, must arrive after the end of the interval τ _p , during which there is a count prohibition and which is equal to the total duration of three periods reference frequency.

From the aforesaid there follows a condition determining the value of the upper limit F _{xmax of the} frequency measuring range: T _xmin > 3 · T _o .

Considering that F _xmax = 1 / T _xmin , from the last inequality we obtain the dependence for determining the upper limit of the frequency measurement:

When the values of the frequency F _{x of the} studied signals are lower than the frequency of the signals of the first sequence of pulses, that is, at T _x > Δt ₁ , in the proposed method, the measurement process does not stop, as is the case in the prototype method, but continues until the pulses frequencies F _mid will not fill the capacity of the corresponding counter.

In this case, the lower limit F _xmin of frequency measurement by the proposed method is determined from the following relationships:

From the last equality we obtain the formula for determining the lower limit of frequency measurement:

Thus, in accordance with (2) and (3), the proposed method allows to measure the frequency within:

For example, when F _o = 10 ⁶ Hz, D = 4, p = 16, the frequency measurement range is defined as follows:

3,8 Гц≤F_x<333,3 кГц

3.8 Hz≤F _x <333.3 kHz

The value of the duration of the pulse repetition period Δt ₁ of the first sequence is determined by the requirements for the measurement speed, which in turn depends on the dynamics of the processes of the objects under study or the cycle duration T _p of the multichannel measurement system, which may include devices implemented on the basis of the proposed frequency measurement method.

Therefore, the required value of the period Δt _{1 is} always determined by external factors that are independent of the method and device of frequency measurement, and for most measurement systems is in the range from 0.01 to 1 s.

The structure of the proposed device (Fig.6) includes a shaper 1 of the studied pulse sequence, a generator of 2 reference frequencies, an element 3 NOT, a shaper 4 of the start pulses, an element 5 OR, a synchronization unit 6, a control unit 7, a shaper 8 of the counting pulses, the first counter 9 and register 10, the second counter 11 and register 12, multiplexer 13, microprocessor system 14, and the input of the shaper 1 of the investigated pulse sequence is connected to the signal input 15 of the device, the output of the generator 2 of the reference frequency is connected to the input ohm of element 3 is NOT, the data output of the first counter 9 is connected by a bus to the data input of the first register 10, the data output of the second counter 11 is connected by a bus to the data input of the second register 12, the output of the pulse train of the investigated pulse sequence is connected to the first input of the synchronization unit 6 and to the clock input the first counter 9, the output of the reference frequency generator 2 is connected to the clock input of the driver 4 of the start pulses and the first input of the control unit 7, the output of the element 3 is NOT connected to the second input of the control unit 7 and the clock input m shaper 8 counting pulses, the bus 18 of the initial installation of the shaper 4 start pulses is connected to the data input of this shaper, and its output is connected to the first input of the OR element 5, the second input of which is connected to the input 16 of the external start of the device, and the output of the 5 OR element to the second input of the synchronization unit 6, the output of which is connected to the third input of the control unit 7, the first output of the control unit 7 is connected to the enable inputs of the first 9 and second 11 counters, the second output to the clock inputs of the first 10 and second 12 registers, third output - with the inputs of zeroing the first 9 and second 11 counters and with the interrupt input of the microprocessor system 14, the fourth output of the control unit 7 is connected to the third input of the synchronization unit 6, the bus 19 of the initial installation of the shaper 8 of the counting pulses is connected to the data input of this shaper, and its the output is connected to the clock input of the second counter 11, the data outputs of the first 10 and second 12 registers are connected by buses, respectively, to the first and second data inputs of multiplexer 13, the third input of which is connected by a bus to the output a the microprocessor system 14, the readout output of which is connected to the fourth input of the multiplexer 13, the data output of the multiplexer 13 is connected via a bus through the microprocessor system 14 to the data output 17 of the device.

The proposed device for measuring frequency operates as follows (Fig.7).

Shaper 1 of the studied signals supplied to the signal input 15 of the device, continuously generates the investigated sequence of F _x (1) pulses. The reference frequency generator 2 continuously generates pulses of frequency F _o (2), of which pulses with a repetition period Δt ₁ are also generated continuously by dividing 4 by dividing 4, and pulses of the counting frequency F _cf (8) by dividing or inverting are generated by dividing or inverting 8.

The pulses from the output of the shaper 4 are fed to the first input of the OR element 5. Similar pulses can be fed to the input 16 of the device from an external unit or microprocessor system 14, and from input 16 to the second input of OR element 5 (the external unit and communications of the microprocessor system 14 with input 16 are not shown in FIG. 6).

The inputs of the OR element 5 should receive only one pulse sequence: either from the output of the driver 4, or from the input 16 of the device (switching elements of the pulse sequences are not shown in Fig. 6). In both cases, the OR element 5 generates trigger pulses Δt ₁ (5), which are the first pulse train.

The synchronization unit 6 generates a second pulse sequence Δt ₂ (21.6), the front of each pulse of which corresponds to the edge of the pulse of the sequence F _x (1), which appeared immediately after the edge of the corresponding pulse Δt ₁ (5) of the first pulse sequence.

The control unit 7 generates at the front of the pulses F _{o the} control signals T1-T4 (23), according to which a clocked sequence of operations is performed and a ban is generated for counting n and N pulses for the time τ _{p of} performing these operations.

Cycle T _n devices, as the frequency measurement method proposed measurements (5-w, h), consists of the time interval τ _p implementation clocked sequence of operations and the time interval τ _MF pulse count n and N (Figure 7).

In the interval τ _{SCH, the} D-flip-flops 20, 21, 22, 24, 25 and the counter-decoder 23 are in the initial state. Moreover, at the direct outputs of the triggers 20, 24 and at the outputs T1-T4 of the counter-decoder 23 there is a logical “0” signal, and at the inverse outputs of the triggers 21, 22 and 25 - a logical “1” signal.

The pulses F _x (1) of the shaper 1 are fed to the clock inputs of the trigger 21 and counter 9. In this case, the trigger 21 does not change its initial state, since a logical “0” signal is supplied to its D-input. The inputs CE counters 9 and 11 are supplied with the inverse output of the trigger 25, the enable signal logic "1" and both counters concurrently perform count of pulses: the counter 9 considers nCT (9) pulses sequence F _x (1), and the counter 11 - NCT (11) counting pulses F _cf (8).

The pulses F _o (2) of the reference frequency generator 2 arriving at the clock input of the counter-decoder 23 and through the inverter 3 to the clock input of the trigger 22 do not change the initial state of these elements, since their R-inputs have a logic inhibit signal “1” .

Counting nCT (9) and NCT (11) pulses in the counters 9 and 11 continues throughout the interval τ _cf.

With the arrival of the trigger pulse Δt ₁ (5), the trigger 20 is turned on, at the direct input of which a logic signal “1” appears, which is fed to the D-input of the trigger 21. The first pulse of the sequence F _x (1) arriving after this to the clock input of the trigger 21 includes trigger 21 and at its inverse output appears a signal of logical "0".

, происходит включение триггера 22, на инверсном выходе которого появляется сигнал логического «0», разрешающий работу счетчика-дешифратора 23.At the front of the next inverted pulse of the reference frequency

, the trigger 22 is turned on, at the inverse output of which a logical “0” signal appears, allowing the operation of the counter-decoder 23.

On receipt of the clock input of the counter-decoder 23 of the next pulse of frequency F _o (2) ends interval τ _MF nCT counting time pulses (9), NCT (11) and starts the time interval τ _p implementation clocked sequence of operations.

Moreover, at the front of four successive pulses of frequency F _o (2), the counter-decoder 23 generates control pulses T1-T4 (23) at its outputs. Moreover, the first pulse T1 (23) includes a trigger 25 and the logic signal “0” from its inverse output is supplied to the CE inputs of the counters 9, 10 and prohibits the counting of pulses in these counters. The second pulse T2 (23) is fed to the clock inputs of the registers 10 and 12, into which the nCT (9) and NCT (11) numbers accumulated in the counters 9 and 11 are recorded by this pulse. The third pulse T3 (23) resets the counters 9 and 11, preparing these counters for a new count of n and N pulses. In addition, the pulse T3 (23) in the form of a ready signal RDY / T3 (23) is supplied to the input INT of the microprocessor system 14.

The fourth pulse T4 (23) sets the trigger 25 to its original state, and the logical 1 signal from its inverse output is applied as the enable signal to the CE inputs of the counters 9, 11, and they start counting n and N pulses. Thus begins a new interval of time τ _MF pulse counting.

происходит включение триггера 24 и на его прямом выходе появляется сигнал логической «1», который поступает на R-входы триггеров 20, 21 и устанавливает их в исходное состояние.At the same time, the fourth pulse T4 (23) is fed to the D-input of trigger 24. With the arrival of the next inverted pulse of the reference frequency to the clock input of this trigger

trigger 24 is turned on and a logical 1 signal appears on its direct output, which is fed to the R inputs of triggers 20, 21 and sets them to their initial state.

устанавливает этот триггер в исходное состояние, снимая при этом запрещающий сигнал логической «1» с R-входов триггеров 20 и 21.Logical signal "1" from the inverted output of trigger 21 sets the trigger 22 to its initial state, the output signal of which in turn sets the counter-decoder 23 to its initial state. At the same time, a logical "0" signal and another inverted pulse appear on the D-input of trigger 24 reference frequency

sets this trigger to its original state, while removing the inhibitory logic signal “1” from the R inputs of triggers 20 and 21.

With the arrival of a new triggering pulse Δt ₁ (5), the triggers 20, 21, 22 are sequentially turned on, and then a new measurement cycle T _c begins in the proposed device.

In the device to determine the frequency of the signals F _x may be performed by the signal RDY / T3 (23) recorded in readiness registers 10 and 12, the values of the numbers N and n, or at any time during the time interval τ _MF n new account and N pulses.

In this case, the microprocessor system 14, via the address bus 28, alternately outputs codes A (0-2) (28) to the multiplexer 13 of the addresses of the registers 10 and 12. The multiplexer 13, in accordance with the received address code, connects the output data bus of the first 10 or second 12 registers to the bus data 27 of the microprocessor system 14. After setting the address, the microprocessor system 14 provides a read pulse RD (14) to the multiplexer 13, according to which the MDO data (27) from the selected register is sent to the microprocessor system 14, where the number of counting pulses is first corrected N = NRG (12) + ΔN, and then calculates the frequency of the test signal according to the formula:

Based on the proposed method for measuring frequency and a device for its implementation, multi-channel frequency measuring systems can be built in which the microprocessor system 14 can be common, receiving and processing information from several pairs of registers. In particular, the microprocessor system of the device shown in Fig.6 has 8 addresses A (0-2), that is, it is designed to receive and process information about the four studied signals.

The proposed device for measuring frequency can be performed on commercially available integrated circuits. So, for example, shaper 1 can be implemented on a 521СAZ bKO.347.015TU2 comparator, generator 2 on a GK56-PAFTTP.433520.004TU quartz oscillator, shapers 4 and 8 on a 564IE15 bKO.347.064TU programmable counter or 564IE10P counter and 564K2P multiplexer 564К10 (Fig. 8), the counter-decoder 23 is on the counter 564IE9, the multiplexer 13 is on the multiplexer 564KP1 or 564KP2. As counters 9, 11 and registers 10, 12, 564IE10 counters and 564IR6 registers can be used, as microprocessor 26 - one of the microprocessors or microcomputers produced by the industry, for example, N1830BE51 AEYAP.431280.070TU. The implementation of the remaining elements of the flowchart of Fig.6 does not cause difficulties. If necessary, instead of 564 series microcircuits, similar elements of one of the higher frequency series can be used, for example, 1554 AEYAR.431200.093 TU.

Variants of the implementation of the proposed device for measuring the frequency on the chip of one of the basic matrix crystals, for example, for N1537XM1 bKO.347.715TU or for programmable logic integrated circuit (FPGA), for example, for FPGAs of the Spartan-II XC2S100 series from XILINX company and configuration constant memory device ХС1700 of the same company.

The proposed method for measuring frequency and a device for its implementation allow you to implement high-speed high-precision continuous measurement of the frequency of the signals in its wide range, while completely eliminating the possibility of accidental failures in the measurement process.

Devices made in this way in the form of modules can be included in the systems of measurement, control and emergency protection of various objects of high speed, such as, for example, gas turbine aircraft engines [5].

High reliability of the result of each measurement allows you to implement high-speed protection of the studied objects, which is especially important during the development of these objects. At the same time, timely detection of an “emergency” situation and the formation of control teams will help to protect the investigated objects and test benches from destruction, which will significantly reduce the cost of creating new equipment.

LITERATURE

1. Patent RU No. 2173857, IPC ⁷ G01R 23/00, publ. 09/20/2001.

2. G.Ya. Mirsky Electronic measurements, M., “Radio and communication”, 1986, p. 129, 130, fig. 4.21.

3. Patent RU No. 2018173, 5 G04F 10/04, G01R 23/00, publ. 08/15/1994.

4. Patent RU No. 2210785, IPC ⁷ G01R 23/10, publ. 08/20/2003.

5. N.N. Sevryugin, I.A. Potapov, A.N. Popov, A.M. Tsirikhov. Experience in automating the testing process of aircraft gas turbine engines || Devices and Systems. Management, control, diagnostics. 2001. No5.

Claims (2)

1. The method of measuring frequency, which consists in converting the studied signals of frequency F _x into the studied pulse sequence of the same frequency F _x , in the simultaneous counting of n pulses of the studied sequence of pulses and N counting pulses of frequency F _MF , in determining the frequency value of the studied signals according to the formula

characterized in that they create a sequence of pulses of a reference frequency F _o , from which counting pulses are formed with a frequency F _cf , determined by the requirement for measurement accuracy, and the front of each such pulse is formed on the slice of the corresponding pulse of a reference frequency, and also form a first pulse sequence with a repetition period Δt ₁ , determined by the requirement for speed of measurement, simultaneously form a second sequence of pulses with a repetition period of Δt ₂ , the front of each pulse the swarm corresponds to the pulse front of the studied pulse sequence, which appeared immediately after the front of the corresponding pulse of the first pulse sequence, after the front of each pulse of the second pulse sequence and the end of the reference frequency pulse acting during this front or the end of the reference frequency pulse arising after the same front at the front of the next reference pulse frequencies begin to execute with a tact Ti equal to the period T _of the pulse repetition of the reference frequency, tact the sequence of operations, moreover, on the first step T1, the count of n pulses of the studied sequence of pulses and N counting pulses is prohibited, on the second step T2, the values of the numbers n and N are obtained as a result of the previous count, respectively, of the pulses of the studied sequence of pulses and counting pulses, on the third step T3 generate a signal RDY of readiness for the fixed values of numbers n, N and prepare a new account, ensuring from the next clock step the count of n pulses of the sequence being studied and N counting pulses, starting with a value of 0, on the fourth step T4, a new simultaneous counting of n pulses of the sequence under study and N counting pulses starts, and the frequency F _{x of the} studied signals is determined by the readiness signal RDY of fixed values of n and N or at any time during a new simultaneous count of n pulses of the test sequence and N counting pulses, and before starting the determination of the frequency F _{x, the} number ΔN equal to the number of trace periods is added to the fixed value of N counting pulses that fall within the time interval determined by the sum of the durations of three cycles during which the pulse count prohibition is in effect. 2. A device for measuring frequency, comprising a shaper of the pulse sequence under study, a reference frequency generator, an element NOT, a first counter and register, a second counter and register, and a microprocessor system, the shaper of the pulse sequence being studied is connected to the signal input of the device, and the generator output is exemplary frequency is connected to the input of the element NOT, the data output of the first counter is connected by a bus to the data input of the first register, the data output of the second counter is connected by a bus to the input m of data of the second register, the clock input of which is connected to the clock input of the first register, characterized in that it includes a start pulse shaper, an OR element, a synchronization block, a control unit, a counting pulse shaper and a multiplexer, and the output of the pulse sequence under study is connected to the first the input of the synchronization unit and with the clock input of the first counter, the output of the reference frequency generator is connected to the clock input of the trigger pulse generator and the first input of the control unit Phenomenon, the output of the element is NOT connected to the second input of the control unit and the clock input of the counting pulse shaper, the initial setup bus of the start pulse shaper is connected to the data input of this shaper, and its output is connected to the first input of the OR element, the second input of which is connected to the external start input of the device and the output of the OR element is to the second input of the synchronization unit, the output of which is connected to the third input of the control unit, the first output of the control unit is connected to the enable inputs of the first and second counter s, the second output is with the clock input of the first register, the third output is with the inputs of zeroing the first and second counters and with the interrupt input of the microprocessor system, the fourth output of the control unit is connected to the third input of the synchronization unit, the initial setup bus of the counting pulse generator is connected to the data input of this shaper, and its output is connected to the clock input of the second counter, the data outputs of the first and second registers are connected by buses to the first and second data inputs of the multiplexer, respectively, the third input One of which is connected by a bus to the output address of the microprocessor system, the readout of which is connected to the fourth input of the multiplexer, the data output of the multiplexer is connected by a bus through the microprocessor system to the output of the device data.

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