RU2018173C1 - Frequency meter - Google Patents

Abstract

FIELD: pulse technique. SUBSTANCE: device has programmable pulse counters 1, 2 included in microcircuits 3, clock pulse generator 4, register 5, bidirectional transceivers; input and output registers 7, 8, control unit 9 with corresponding connections, components 5, 6, 7, 8 being combined in microprocessor unit 10. EFFECT: enhanced accuracy. 3 dwg

Description

 The invention relates to electrical measurements and can be used in measuring and computing systems and information-measuring systems for converting into a digital code the repetition rate of pulse signals from sensors of forces, pressures and other physical parameters.

 A device for measuring the time-frequency parameters of electrical signals, with good metrological characteristics and wide functionality. The device contains a group of AND elements, the first and second pulse counters, a code comparison unit, a microprocessor, three triggers, an OR element, and also two additional OR elements, two triggers, three I. elements. However, the meter’s wide functionality is achieved by extremely complicating its design, and metrological characteristics are not optimal for the experimental conditions in terms of accuracy and speed [1].

A device is known that makes it possible to measure frequencies in a wide range with a small discreteness error, the maximum value of which remains constant over the entire measurement range. The device comprises an input unit, a pulse shaper, a time selector, a counter, a counter of pulse counters, a time selector, a counter, a microprocessor system, a formation and control unit, as well as logical elements AND ₁ , AND ₂ , NOT related to the formation and control unit, but depicted outside of it for illustrative purposes [2]. This device is taken as a prototype.

 However, in the known device, the frequency measurement takes place over a fixed time interval, albeit programmed by the microprocessor. Moreover, to increase the accuracy of frequency measurement, the first measured interval is set programmatically, and the second is formed by the control and formation unit exactly equal to an integer number of periods of the measured frequency. Counters count the number of periods of the measured and reference frequencies for a time equal to the second time interval and transmit the measurement result to the microprocessor. The formation of two time intervals complicates the design of the device, and the measurement of the frequency for a fixed measuring interval makes it impossible to measure it in a wide range with accuracy and speed that are optimal for the experimental conditions.

 The aim of the invention is to expand the range of measured frequencies at a given optimal accuracy.

 The goal is achieved in that in a frequency meter containing the first and second pulse counters, a clock pulse generator, a control unit, a microprocessor unit, the output of which is connected to the first input of the control unit, and the first group of information inputs is connected to the information outputs of the first and second pulse counters, containing also the input bus, the pulse counters are made programmatically controlled with the ability to select the address, select the microcircuit, preset the code and separately control the writing and reading, and the first The first group of information inputs of the microprocessor unit is bi-directional, moreover, the count resolution inputs of the first and second pulse counters are connected to the first output of the control unit, the second output of which is connected to the counting input of the first pulse counter, the transfer output of which is connected to the second input of the control unit and the input of the microprocessor unit , the first group of information inputs of which is connected to the information inputs of the first and second pulse counters, inputs for recording, reading, and These are addresses, the choice of microchips of which are connected to the second group of information outputs of the microprocessor unit, the input bus is connected to the third input of the control unit, and the clock generator is connected to the counting input of the second pulse counter.

 In FIG. 1 shows a diagram of the proposed frequency meter; figure 2 - diagram of the control unit 9; figure 3 is a block diagram of a program of a frequency meter.

 The frequency meter (Fig. 1) contains programmable counters 1.2, which are part of the microcircuit 3, a clock pulse generator 4, a control register 5, bi-directional transceivers 6, an input register 7 and an output register 8, made on standard elements, as well as a control unit 9 and the input bus. The control register, bidirectional transceivers, input and output registers, as well as an external processor are combined in a microprocessor unit 10.

The measured frequency t _x in the proposed device is fed to the third input BX1 of the control circuit via the input bus. The first output of the NS control unit (beginning of counting) is connected to inputs P1 and P2 (resolution of counting) of both counters. The second output of the IF control unit (measured frequency) is connected to the counting input TI2 (clock frequency) of the first counter. To the counting input of the second counter TI1 is connected the output OUT of the clock generator. The transfer output OUT1 of the first counter is connected to the second input of the control unit KS (end of the count), as well as to the GOT input (readiness) of the microprocessor unit. The first group of inputs of the microprocessor unit is bi-directional and connected to the information inputs D of the first and second pulse counters. The second group of information inputs of the microprocessor unit is connected to the inputs of the write (ZP), read (ЧТ), address (А ₀ , А ₁ ), microchip (ВМ) selection of the first and second counters.

Programmable counters of 2.1, exemplary f _o and measured f _x frequencies are made on the KR580VI53 chip, which represents a three-channel timer-counter (see Industry Standard Application Guide OST 11.348.917-82, p. 62, P.V. Nesterov, Microprocessors .: Higher school, 1986, v. 1, p. 206, A crystal oscillator 4 clock frequencies f ₀ = 8 MHz is made on a K155LAZ microcircuit according to the standard scheme (see Industry Standard. Application Guide OST 11.340.909-80, part I, p.272a). The control register 5 and the output register 8 are made on K589ir12 microcircuits. The transceiver 6 is on the top the discharges were performed on two K589AP16 microcircuits, the input sixteen-bit register 7 was made on the K155TM7 microcircuits (see the catalog of integrated circuits T2, Central Design Bureau 1986).

 The frequency meter operates as follows.

Using the control register 5, into which the corresponding code is written through the input register 7 and transceivers 6 from the external processor, the START command is sent to the control circuit 9. The control circuit 9 binds the start time of filling the counter 2 clock frequency to the front of the measured frequency f _x and generates "start counting" command. Both counters 1 and 2, programmed in accordance with the measurement cycle, simultaneously start counting and work on subtraction. At the end of the counting, the counter end signal is set at the output of counter 1, blocking through the control circuit 9 the arrival of the clock and measured frequencies to the corresponding counters. The signal “end of counting” is the GOT ready command, according to which the data of the measurement results from the counter 2 by the command “reading data” of the readout through transceivers 6 and the output register 8 are read into an external processor. Bringing the control circuit 9 to its initial state is carried out by the RESET command in each measurement cycle.

из соотношений
t_x=n_xT_x=n_oT_o; (1)
t_x=

T_o. (2)
Число импульсов n_o фиксируется в счетчике 2, а число импульсов n_x в счетчике 1. Относительная погрешность измерения периода Т_х, обусловленная погрешностью квантования, определяется соотношением
δT_x= ±

+

, (3) где δ_г - погрешность генератора образцовой частоты, которой можно пренебречь.The result of measuring the frequency f _x is averaged over a time t _x equal to the duration n _x pulses of the measured frequency. The measurement time t _x and the period of the measured frequency T _{x are} determined by the number of pulses measured n _x and clock n _{about the} frequency and the known value of the clock frequency f _o =

from the relations
t _x = n _x T _x = n _o T _o ; (1)
t _x =

T _o . (2)
The number of pulses n _o is fixed in the counter 2, and the number of pulses n _x in the counter 1. The relative measurement error of the period T _x due to the quantization error is determined by the ratio
δT _x = ±

+

, (3) where δ _g is the error of the generator of the reference frequency, which can be neglected.

Relations (1) and (3) show the fundamental possibility of optimizing the frequency meter for accuracy and speed by choosing the number of periods of the measured frequency. To ensure the required performance in a given frequency range, the measurement is performed in one cycle, and the number of periods n _x for which averaging is performed is selected from relation (1) and programmatically entered in counter 1. To ensure the required measurement accuracy in the given range of measurement frequencies, are performed in one cycle, and the number of periods n _x over which averaging is performed is selected from relation (3) and programmatically entered in counter 1. To optimize the meter for accuracy and speed and ensure of error and speed, close to fundamentally possible and constant in a wide range of frequencies, the frequency is measured in two cycles. In the first cycle of measurement, the minimum number of periods n _{x is} programmed to obtain a rough estimate of the current value of f _x , and in the second cycle, to obtain increased accuracy and speed, the optimal number of periods is determined, determined from relations (1) and (3) under the condition n _x T _x = const.

The programming process of the counters begins with the recording from the external processor of the control word data ZP.D, which determines the mode of operation of the counter. To do this, a code corresponding to the counter address is supplied to the address input of the microcircuit, a signal for selecting the microcircuit is fed to the input of the microcircuit, and an input signal for the control word is written to the input of the input chip. Similarly, the data word ZP.D is written to counter 1, which determines the number of periods of the measured frequency n _x and the data word, which determines the maximum possible subtraction account, is written to counter 2.

 This device provides frequency measurement in both a narrow and a wide range of frequencies at specified accuracy and speed that are optimal for the experimental conditions.

Claims (1)

 A FREQUENCY METER, comprising the first and second pulse counters, a clock pulse generator, a control unit, a microprocessor unit, the output of which is connected to the first input of the control unit, and the first group of information inputs is connected to the information outputs of the first and second pulse counters, also containing an input bus, different the fact that, in order to expand the range of the measured frequency at a given optimal accuracy, the pulse counters are made programmatically controlled with the ability to select an address, select m ICs for code presetting and separate writing and reading control, and the first group of information inputs of the microprocessor unit is bi-directional, and the resolution enable inputs of the first and second pulse counters are connected to the first output of the control unit, the second output of which is connected to the counting input of the first pulse counter, the transfer output of which connected to the second input of the control unit and the input of the microprocessor unit, the first group of information inputs of which are connected to information inputs the first and second pulse counters, inputs for writing, reading, address selection, chip selection are connected to the second group of information outputs of the microprocessor unit, the input bus is connected to the third input of the control unit, and the clock generator is connected to the counting input of the second pulse counter.

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