SU1228029A1 - Method of measuring frequency - Google Patents

Abstract

The invention relates to the field of instrumentation technology. Can be used when measuring the frequency of periodic oscillations. The purpose of the invention, the reduction of the frequency measurement time, is achieved by speeding up the process of refining the relative position of the pulses of the compared pulse sequences. According to this method, in order to reduce the measurement time, the tots form a delayed sequence of pulses by means of a time delay of the pulses of the test sequence by a predetermined value and performing a series of measurement and conversion operations of time parameters. A device that implements cnoco6j contains: a pulse shaper 1, a divider by three 2, counters 3, 4 and 5, a decoder 6, keys 7-14, measurement blocks 15, 16 and 1 each of which consists of time - amplitude converter 18, ADC 19 , trigger 20 and key 21, com.- mutator 22, triggers 23, 24 and 25, shift registers 26 and 27, registers S Ы

Description

28, 29 and 30, multiplication unit 31, combination adders 32 and 33, elements OR 34, 35, delay lines 36, 37 and 38, comparison block codes 39, amplitude converter 40, ADC 41 and m identical channels 1

The invention relates to instrumentation technology and can be used to measure the frequency of periodic oscillations.

The purpose of the invention is to reduce the time of frequency measurement by speeding up the process of refining the relative position of the pulses of the compared pulse sequences.

FIG. 1 shows a diagram of a device for implementing the method; in fig. 2 - time diagram, explaining his work.

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The device contains a shaper 1 pulses, a divider 2 into three, counters 3-5, a decoder 6, keys 7-14, blocks 15-17 of measurements, each of which consists of time — an amplitude converter (VAL) 18 analog-to-digital converter ( ADC 19), trigger 20 and key 21, switch 22, triggers 23-25, shift registers 26 and 27, memory registers 28-30, multiplication unit 31, combination adders 32 and 33, (adder 33 operates in subtraction mode ), elements OR 34 and 35, lines 36 - 38 delays, block 39 comparison of codes, VAL 40, ADC 41 and m identical channels, each of which has an input the counter 42, the register 43, the decoder 44, the code comparison block 45 and the keys 46 and 47. the counter 2 is connected to the pulse inputs of the keys 7, 8, 9, 10 12 and 14, the second time-amplitude converter 40 input and the analog control input - digital converter 41, and the output with control inputs of the decoder 6 and switch 22. The first, second and third outputs of the decoder 6 are connected respectively to the control inputs of the keys 7-9. The second output of the decoder 6

These include a counter 42, a register 43, a decoder 44, a code comparison block 45, and keys 46 and 47. The method is illustrated by the example of operation of the device according to the time diagrams in the description of the invention. 2 or

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connected also to the installation input unit trigger 23. The output of the key 7 is connected to the first input of the block 15 and the second input of the block 17. The output of the key 8 is connected to the first input of the block 16 and the second input of the block 15, the output of the key 9 - to the first input of the block 17 and the second input block 16. Tre-. These inputs of the blocks 15 - 17 are connected to the output of the pulse shaper 1, the input of the delay line 37, the pulse input of the key 13 and the pulse inputs of the counters 42 of all channels. The input of shaper 1 is the input for sigN of the measured frequency, and the input of counter 3 is the input for the reference pulse sequence. The first outputs of blocks 15 - 17 are connected to the switched inputs of the switch 22, and the second outputs of blocks 15 - 17 are connected to the corresponding inputs of the SHSh 34 element. The first and second inputs of the adder 32 are connected respectively to the outputs of the switch 22 and the multiplication unit 31, and the output of the adder 32 is connected to the information input of the register 26. trigger code 23 is connected to the control input of the key 10, the output of which is connected to the input of the counter 3. The first and second inputs of the multiplication unit 31 are connected to the outputs of the registers 28 and 29, respectively. Istra 28 is connected to the output of the counter 3, and its control input is connected to the control input of the multiplication unit 31, the input of the delay line 36 and the output of the IPI 34 element. The first and second outputs of the register 26 are connected to the first and second inputs of the adder, respectively 33, the output of which is connected to the information input of the register 30 and the first input of the code comparison block 39. The output of the delay line 36 is connected to the control unit.

1CMI inputs of registers 26 and 30. The second input of block 39 of code comparison is connected to the output of register 30, and the output to the control input of Key 11, the pulse input of which is connected to the output of the delay line 37. The output of the OR element 35 is connected to the first input of the time-amplitude converter 40, the installation input of the trigger unit 24 and the counting input of the trigger 25, whose output is connected to the control inputs of the keys 13 and 14, the output of the time-amplitude converter 40 is connected to the information input analog-digital converter 41, the output of which is connected to the information input of the register 27. The control input of the key 12 is connected to the output of the trigger 24, and the output - to the counting input of the trigger 24 and through the delay line 38 with the control input of the register 27. You the keys 13 and 14 are connected respectively to the inputs of the counters 4 and 5. Within each channel, the control input of the register 43 is connected to the control input of the counter 42 and the pulse inputs of the keys 46 and 47. The output of the counter 42 is connected to the input of the decoder 44, the information input of the register 43 and the first input of the code comparison unit 45, the second input of which is connected to the output of the register 43. The output of the decoder 44 is connected to the control input of the key 46. The output of the code comparison unit 45 is connected to the control input of the key- 47. The pulse input of the key 46 of each channel,In addition to the first one, it is connected to the output of the key 47 of the previous channel, and the pulse input of the key 46 of the first channel is connected to the output of key 11. The outputs of the keys 46 of all channels and the output of the key 47 of the last channel are connected to the corresponding inputs of the OR element 35. Inside each of the blocks 15 - 17 measurement output trigger-. 20 is connected to the control input of the switch 21, the output of which is connected to the control input of the analog-digital converter 19 and the second input of the time-amplitude converter 18. The first input time-amplitude converter 18 is connected to the installation input of the trigger unit 20 First input of the blocks 15 -17 is the first input of the VAL 18, the second and the third inputs are respectively the input

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setting the zero trigger 20 and the pulse input key 21, the first and second outputs - the outputs, respectively, of the ADC 19 and the key 21.

5 The device operates as follows.

In the initial state, all the counters and triggers are reset to zero. The number 29 is entered in register 29, (where m is the number

10 binary bits A1Shch.19 and 41, the remaining registers are reset. Key 7 is open, and the remaining keys are closed. In the proposed device, the frequency f of the pulses of the reference sequence must be not less than the maximum of the measured frequencies f. FIG. 2a shows a reference sequence whose pulses are numbered. The pulse of the reference sequence No. 1 is taken as the start of measurements. Shaper 1 generates a test sequence with a pulse frequency fy from the signal of the measured frequency fx.

25 In FIG. 26 these pulses are numbered.

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A divider counter 2 by three counts the pulses of the reference sequence at its input. The state of counter 2 analyzes the decoder 6, with which the keys 7–9 are managed. Each of the three periodically set states of counter 2 corresponds to the open state of one of the keys 7–9. The first state of counter 2 (the counter is zero ) corresponds to the open key state 7, supported by the control 30

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the first output of the reference sequence passes through the public key 7 to the first input of the block 15 and the second input, block 17

(Fig. 2c). On the trailing edge of the first pulse of the reference sequence, the counter 2 is set to the second state. At the same time, the control voltage from the second output of the decoded 6 sets the trigger 23 to one state, and also opens the key 8. From this moment, the key 10 opens, and the key 7 closes. Through the public key to the counter 3 impulses of the reference sequence. Thus, counter 3 performs sequential counting of reference pulses sequential 5.

ty start with the second. With the opening of the key 8 to the first input of the block 16 and the second input of the block 15 the second pulse of the reference sequence arrives (FIG. 2d). Similarly, the back of the front of the second pulse of the reference sequence sets the counter 2 to the third state, in which the key 9 opens and transmits the third pulse of the reference sequence to the first input of the block 17 and the second input of the block 16 (Fig. 2e). the pulse of the reference sequence counter 2 is set to the first state (the counter is zero). The process of alternately passing the pulses of the reference sequence through the keys 7–9 to the corresponding 1 × 1 inputs of the blocks 15–17 is periodically repeated (Fig. 2c – e). The functioning of the blocks 15 - 17 measurements.

The first and second inputs of blocks 15–17 receive the pulses of the reference sequence passing through the corresponding keys 7–9, and the third inputs receive the pulses of the sequence under investigation. The pulse of the reference sequence, which enters the first input of any of the blocks, for example, 15, measurements (the input of the start of the VAL 18), starts the VAL 18, after which the initial voltage and „„ (in particular and, „, 0)

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its output begins to change linearly. The same impulse sets the trigger 20 to one state. The pulse of the reference sequence arriving at the second input of the block 15 sets the trigger 20 of this block to the zero state. Thus, in the interval between the pulses of the reference sequence, arriving at the first and second inputs of the block 15 controlled by the trigger 20, the key 21 of this block is open. If during this period the impulse of the studied sequence arrives at the third input of the block 15, it will pass through the open key 21 to the control input (start input) of the ADC 19 and the second input (input stop) of the VAL 18. From this moment the output voltage of the VAL 18 is fixed and the A / D converter 19 converts the recorded voltage value to a digital code. If during

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nor, while the key 21 is open, the pulse of the studied sequence does not arrive at the third input of the block 15, then the launch of the ADC 19 will be absent. VAP 18 of each of blocks 15-17 is implemented in such a way that it is automatically reset to the initial state (the initial reference voltage Id is set at its output) after a certain time has elapsed since its start. This time is chosen equal to two periods T, the reference sequence. In addition, the rate of voltage change at the output of the VAL 18 of the blocks 15-17 is set so that during the period T of the reference sequence the magnitude of the voltage change coincides with the dynamic range of the input voltages of the ADC 19.

At the first output of each of blocks 15, 16, 17, there is a code that corresponds to the measured (in measured units) time interval value, limited by the pulses of the reference sequence and studied, arriving at its first and third inputs, respectively. Moreover, this measurement is only in the case if the measured time interval does not exceed the period T of the reference sequence. The alternate operation of blocks 15-17 provides for the sequential measurement of time intervals TD, the end boundary of which is each of the next in order from the moment of the beginning of measurements of the pulses of the studied sequence with the number i, and the initial one - the pulse of the reference sequence nearest to it (Fig. 2). FIG. , 2 e-z are diagrams of voltage variation at the output of the VAL 18 of blocks 15-17, respectively.

Codes of measured values of time intervals {T; from the first outputs of blocks 15–17, the outputs of switch 22 and through the counter to the first input of the adder 32 are switched by the counter 2. The pulses of the studied sequence from the second outputs of blocks 15–17 arrive at the corresponding inputs of the OR 34 element, which each input pulse forms the corresponding output pulse. Formed by the element OR 34, the pulses arrive at the control inputs.

register 28 and about 31 multiplications. Each of these pulses writes to the register 28 the value of the number of pulses of the reference sequence counted up to that moment and starts block 31 of multiplications. In block 31, the contents of registers 28 and 29 are multiplied. At the output of block 31, there is a code that corresponds to the measured (in units of) time value T; between the start of measurement (the first pulse of the reference sequence) and the pulse of the reference sequence immediately preceding the start pulse of block 31 (Fig. 2).

Thus, the measurement of time intervals T |, the initial boundary of which is the pulse of the reference sequence selected for the beginning of the measurements, and the i-e pulses of the sequence under investigation, is carried out by separately measuring the time intervals T; j and T; , characterizing in units of period T of the reference sequence, respectively, the integer and fractional parts of the interval Tj. Moreover, each of the indicated parts of the interval T; measured up to a measuring unit (. Time interval codes IT {and (tL are added in adder 32. At the same time, at the output of adder 32, time interval codes T are formed in units of T T, / ". For each pulse coming from the output of delay line 36 To the control input of register 26, the next code tj is output from the output of adder 32. The required delay time is selected taking into account the time spent on time measurements. Codes corresponding to two successively measured time are stored in register 26 intervals. The adder 33 each time from the code subtracts the code entered into it. The codes obtained at the output of the adder 33, corresponding to the differences Atj t, -tj., the values of measured time intervals, are entered into the register 30 control pulses from the output of the delay line 36 . Code comparison block 39 compares the code of the calculated difference and t; with the code of the previous difference At;., Stored in register 30. When the code is calculated 0

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The difference is less (or more) than the code of the previous difference, the code comparison block 39 generates a control signal by which 5 key 11 is opened and transmits the pulse of the sequence under investigation, which arrives at its pulse input from the le-. NII 37 delay. A delay is needed — realizable by the delay line 37 — is set on the basis of the total time required for the time measurements, as well as the operation of the adders 32 and 33 and the code comparison block 39. At the same time, at the output of the key 11, a sequence of pulses is generated. In each channel, the counters 42 count the pulses of the studied sequence arriving at their pulse inputs between the moments of arrival of the pulses to the control inputs of the counters 42, registers 43 and the pulse inputs of keys 46 and 47. At the time of the arrival of the pulse to the control input of the counter 42 Ruets The code comparison unit 45 compares the counter code 42 and the register code 43. If at this moment the counter code 42 is less (or more) than the register code 43, then block 45 opens

key 47 and passes a pulse arriving at that time to its pulse input. At the same time, the decoder 44 analyzes the counter code 42 and, if it is

5 more than the specified value, the decoder 44 opens the key 46 and transmits a pulse arriving at the pulse input of this key. Upon termination of the pulses (for example, by their

0 to the falling edge) arriving at the control inputs of counter 42 and register 43, the contents of counter 42 are overwritten into register 43, and the counter itself is zeroed. After this, the process is repeated 5. .

Thus, in each channel, the initial sequence of pulses is converted to the control inputs of counter 42 and register 43, as well as to the pulse inputs of keys 46 and 47. At the output of key 47, a new sequence is formed, consisting of those pulses of the original sequence are

the initial (or final) boundaries of such intervals between the nearest pulses of this sequence, | whose duration is longer (or less than

above) the duration of previous similar intervals. The generated new pulse train enters the next channel. In this case, for the first channel of the original, a sequence of pulses is introduced, which enters it from the output of the key 11. In turn, the sequence of pulses formed in the first channel goes through the key 47 to the second channel and for it is the original and so on. d.

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Obviously, the time interval

between the pulses of each new sequence is greater than the interval between the pulses of the original sequence, from which a new one is formed. Therefore, in the part of the channels starting with TorOj for which the time intervals between the pulses of the original sequence are sufficiently large, the codes of the decoder 44 exceed the specified value. In these channels, in addition to the conversion, the source sequences are passed through the public keys 46 to the corresponding inputs of the OR 35 element. If the keys 46 are not open in any of the channels, then the pulses from the output of the key 47 of the last channel are sent to the OR 35 element. The trigger 25 opens the first impulse that arrives at its counting input from the output of the element OR 35, opens it, and the second closes the keys it controls, 13, 14. These impulses are the starting and ending limits of the measuring interval. In the formed measuring interval, the counter 4 counts the number NJ, of the pulses of the test sequence of the measured frequency passing through the key 13, and the counter 5 the number N of pulses of the reference sequence passing through the key 14. For each of the pulses that are initial and final the boundaries of the measuring interval are set to trigger 24: to the single state and to start BAD 40 (identical to the VAL 18), after which the initial voltage at its output begins to vary linearly. The voltage at the output of the SHAFT 40 is changed until the pulse of the reference sequence following the initial ωsh boundaries arrives at the second input of the SHAFT 40 (Stop input), the trigger input of the A / D converter 41 and the pulse input of the switch 12. From this moment on

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The output of the SHAFT 40 is fixed, and the A / D converter 41 (identical to A1x 19) converts the recorded voltage to a digital code. In addition, this pulse passes through the switch 12 controlled by the trigger 24 and is fed to the input of the delay line 38 and the counting input of the trigger 24. On the trailing edge of this pulse, the trigger 24 is transferred to the initial zero state. The t, t codes obtained at the output of the A / D converter 41 correspond to the measured (in units of T., / „) values of time intervals, the initial boundaries of which are the initial and the final boundaries of the measuring interval, and the final ones immediately following the corresponding pulses of the reference sequence . The codes t, t are entered in the register by 27 pulses delayed by a delay line 38 for the conversion time of the A / D converter 41.

I .. According to the data obtained, the frequency f is unknown. determined according to the calculated ratio

f fx:

X Ng / fg + t t Thus, during the operation of the device, the following operations are performed.

Two sequences of pulses are formed: a reference one with a pulse-following frequency fg and a period of 1, and also a test with an unknown pulse-following frequency f and a period. Form a delayed sequence of pulses by the time delay of the pulses of the sequence under investigation by a given value j. One of the pulses of the reference sequence is chosen as the measurement start. The time intervals of the studied sequence are measured, the initial boundary of which is the pulse of the reference sequence chosen for the beginning of the measurements, and the final intervals are all subsequent ones for the order of time, Qc of the pulses of the studied sequence. Measurements are carried out with an accuracy of the duration of the interval Tp taken as a measuring unit. Here, the interval T is chosen so that it is placed an integer number of times in the period T of the reference sequence, i.e. , „. Thus, each i-th pulse

the sequence under study corresponds to the measured value of t, the interval T; bounded by this pulse and the beginning of measurements (where i is the sequence number of the pulses of the sequence under investigation relative to the beginning of the measurements). Subtract from each measured value .t; the time interval T starting with the second, the preceding measured value t,., and get the corresponding difference At; , Thus, for each i-ro pulse of the studied sequence, starting with i-2, the corresponding difference Atj is obtained.

Each obtained difference At is compared; each time, the pulse of the delayed sequence is obtained by delaying by a predetermined value of the pulse of the sequence under study, for which the corresponding HocTfr ut is greater (or less) than the difference τ obtained for the preceding () - ro of the pulse of the sequence under investigation, From a series of pulses of the delayed sequence, a sequence of selected pulses is formed. Several cycles of pulse sequence formation from source sequences are conducted. In the first cycle, the sequence of pulses assigned to the initial cycle is taken, and the durations of all adjacent time intervals formed by the nearest pulses of this sequence are compared in pairs. There are those pulses of a sequence of selected pulses, which are the initial or: final boundaries of those comparison time intervals, the duration: six which are longer (or less) than the duration of the preceding time intervals. From the selected pulses form a new sequence of pulses. In the second cycle, the sequence of impulses formed in the first cycle is taken as the initial one, and the durations of all adjacent time intervals formed by the nearest impulses of this sequence are compared in pairs. The pulses from the sequence formed in the first cycle, which are the initial

or the final boundaries of those compared time intervals, the duration of which is longer (or less) the duration of the previous time intervals. From the selected pulses form a new sequence of pulses.

Similarly, in each subsequent. cycle, the pulse sequence formed in the previous cycle is taken as the initial one, and the durations of all adjacent time intervals formed by the nearest pulses of this

sequences. Those pulses from the source sequence that are the starting or ending bounds of those compared time intervals, the duration of which is longer (or less) than the duration of the previous time intervals, are selected. From the selected pulses form the next new sequence.

The process of forming a sequence of pulses from the source sequences is stopped on the cycle in which the time interval. between pulses exceeded, the specified value.

A measuring interval is formed, as the boundaries of which the pulses of the sequence formed in the last cycle are used. The time interval between the initial boundary of the measuring interval and the pulse of the reference sequence immediately following it is measured with an accuracy of a measuring unit T and the corresponding measured value of t is obtained. The time interval between the final boundary of the measuring interval and the next neg5 directly behind it the pulse of the reference sequence is measured with an accuracy of a measuring unit T and the corresponding measured value of t is obtained. Count the number of NJ, the pulses of the test and the number of Ng pulses of the reference sequence in the measured interval. According to the data obtained, an unknown frequency value fу is calculated.

Thus, since the measured interval required to achieve a given accuracy is significantly reduced, the proposed method is characterized by a higher frequency measurement speed.

Claims (1)

13 claims A method of measuring the frequency, which includes the formation of two pulse sequences: a reference with a known pulse frequency and studied with an unknown pulse frequency, the formation of a measuring interval by cycling the pulses from the original sequences, for which in each cycle the pulse sequence formed in the preceding cycle, and compare in pairs the duration of all adjacent time intervals formed by the nearest pulses of this pos The units will select those pulses of the original sequence that are the initial or final boundaries of those compared time intervals, the length of which is longer (or less) than the duration of the preceding time intervals, while the process of separating the pulses is stopped on that cycle in which the interval between the selected pulses exceeds set value, counting the number of pulses of the studied and reference sequences in the measuring interval, characterized in that, in order to reduce the time of measurement and the frequencies form a delayed sequence of pulses by means of a time delay of the pulses of the sequence under investigation, by a predetermined value, the time intervals of the sequence under investigation are measured, the initial Limit of which is one of the pulses of the reference sequence chosen for the beginning of the measurements, and the final ones are all following in order the pulses under study sequence, so that each pulse of the sequence being studied becomes 1228029 14 0 five 0 five 0 five the measured value of the time interval limited by it, the measurement being carried out with an accuracy of up to the duration of the interval taken as a unit, which is chosen to fit an integer number of times in the period of the reference sequence, is subtracted from each measured value of the time interval starting from the second previous measured value, thus each pulse of the sequence under study, the corresponding measured value of the time interval to is deductible when the difference is received, the resulting difference is compared, each difference is compared with the preceding difference, and each time a delayed sequence pulse is obtained by delaying the specified value of that pulse for the sequence being studied for which the corresponding difference is greater (or less) the difference obtained by the dp of the preceding pulse of the studied sequence, from the selected pulses of the delayed sequence form the The strength of the selected pulses, which is taken as the initial one in the first cycle of formation of the measuring interval, is measured to the dimensional unit, the time interval formed by the initial boundary of the measurement interval and the pulse of the reference sequence immediately following it, the time interval formed by the measuring unit accuracy the ultimate border. the measured interval and the pulse of the reference sequence immediately following it, and using the data obtained, the unknown frequency is calculated. fig.g