Dual-channel digital frequency meter

Abstract

The utility model provides a dual-channel digital frequency meter, and belongs to the technical field of digital frequency meters. Comprising a single-chip microcomputer, a display circuit and a power supply circuit used for supplying power, the system also comprises a first signal shaping circuit, a first relay switch K1, a first frequency divider circuit, a second relay switch K2, a second signal shaping circuit, a third relay switch K3, a second frequency divider circuit, a fourth relay switch K4, a multivibrator circuit used for outputting a preset gate signal, and a gate control circuit. According to the dual-channel digital frequency meter, dual-channel measurement can be achieved, two paths of signals can be measured and compared at the same time, and the requirement for simultaneous detection and analysis of different signals in more complex scenes is met.

Description

TECHNICAL FIELD

[0001] The utility model relates to a double -channel digital frequency meter belongs to digital frequency meter technical field. BACKGROUND

[0002] Digital frequency meter as a kind of frequency measurement most common measuring instrument with its measurement precision high, fast, easy operation, digital display etc. Widely used. With the continuous development of single-chip microcomputer technology, there is a single-chip microcomputer as the system core controller frequency meter, it has the advantages of high precision, fast response, low cost. The digital frequency meter for measuring signal frequency using single-chip microcomputer currently mainly has following 3 methods: timer counting method, input capture method and fast fourier transform method, wherein, timer counting method is to use the timer of STM32 to the pulse of input signal is counted, the number of pulses in a certain time is measured to calculate frequency. For example, the working mode and clock source of timer are configured, the counting is accurately controlled, and the counting value can be read in combination with interruption or DMA mode, so as to obtain the period or pulse width information of input signal, and then obtain the frequency value.

[0003] But at present the digital frequency meter for measuring signal frequency using single-chip microcomputer has the problems of single channel, narrow bandwidth. The current simple digital frequency meter usually has only one input channel for receiving measured signal, which means that it can only measure the frequency of one signal source at a time, and cannot measure and compare multiple signals simultaneously. For example, in the scene of needing to monitor multiple sensor signal frequencies or multi-channel communication signal frequencies, the single-channel frequency meter cannot meet the demand. In addition, the hardware circuit design of simple frequency meter is relatively simple, and the working frequency range of its counter or timer is limited. For example, the clock frequency of the counter is low, or the pre-division coefficient and other parameters of the timer cannot be flexibly adjusted, so that the high-frequency signal cannot be accurately counted, and the counting time cannot be effectively prolonged to measure low-frequency signal. The bandwidth of signal conditioning circuit is limited. If there is no suitable amplifier and filter to adapt to signals in different frequency ranges, the frequency bandwidth that the frequency meter can measure will be limited. For example, the bandwidth of the amplifier is not wide enough, and the high-frequency signal cannot be effectively amplified, or the cutoff frequency of the filter is not reasonably set, so that part of the frequency components is filtered out. UTILITY MODEL CONTENTS

[0004] The utility model aims at providing a kind of double -channel digital frequency meter to solve the problem of single channel existing in prior art.

[0005] The technical solution of the utility model is:

[0006] The utility model provides a double -channel digital frequency meter, including single -chip microcomputer, display circuit and power supply circuit for power supply, display circuit connects single -chip microcomputer, still include first signal shaping circuit, first relay switch K1, first frequency divider circuit, second relay switch K2, second signal shaping circuit, third relay switch K3, second frequency divider circuit, fourth relay switch K4, for output preset gate signal multivibrator circuit and gate control circuit, first measured signal input first signal shaping circuit, first signal shaping circuit connects the common terminal of first relay switch K1, the normally closed end of first relay switch K1 passes through first frequency divider circuit and connects the normally closed end of second relay switch K2, the normally open end of first relay switch K1 connects the normally open end of second relay switch K2, the moving end of second relay switch K2 is connected with the input of gate control circuit and the input of single -chip microcomputer respectively, second measured signal input second signal shaping circuit, second signal shaping circuit connects the common terminal of third relay switch K3, the normally closed end of third relay switch K3 passes through second frequency divider circuit and connects the normally closed end of fourth relay switch K4, the normally open end of third relay switch K3 connects the normally open end of fourth relay switch K4, preset gate signal passes through gate control circuit and connects the input of single -chip microcomputer, and the output of single -chip microcomputer is connected with first relay switch K1, second relay switch K2, third relay switch K3 and fourth relay switch K4 respectively.

[0007] Further, the single-chip microcomputer adopts an STM32F429IGT6 chip.

[0008] Further, the first signal shaping circuit and the second signal shaping circuit both adopt a comparison shaping circuit.

[0009] Further, the comparison shaping circuit comprises an adjustable resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a comparator TLV3501, the first measured signal or the second measured signal is input into the inverting input terminal of the comparator TLV3501, the non-inverting input terminal of the comparator TLV3501 is grounded through the resistor R4 and the adjustable resistor R1, the positive power input terminal of the comparator TLV3501 is connected with the power supply circuit and grounded through the capacitor C1, the two ends of the resistor R2 are connected with the adjustable resistor R1 and the capacitor C1 respectively, the negative power input terminal of the comparator TLV3501 is grounded, the non-inverting input terminal of the comparator TLV3501 is connected with the output terminal of the comparator TLV3501 through the resistor R3, and the output terminal of the comparator TLV3501 outputs the shaped measured signal.

[0010] Further, the first frequency divider circuit and the second frequency divider circuit adopt the same circuit.

[0011] Further, the first frequency divider circuit comprises a chip 74164 and an inverter 7404, the pin CLK of the chip 74164 is connected with the shaped measured signal, the pin QE of the chip 74164 is connected with the pin A of the chip 74164 through the inverter 7404, the pin B of the chip 74164 is connected with the pin CLR respectively, and the pin QE of the chip 74164 outputs the measured signal ten times frequency.

[0012] Further, the multi-resonance oscillator circuit comprises a chip LM555, the pin VCC and the pin RST of the chip LM555 are connected with the power supply circuit respectively, the pin DIS of the chip LM555 is connected with the power supply circuit through a resistor R1, the pin DIS of the chip LM555 is also connected with the pin TRI and the pin THR of the chip LM555 respectively through a resistor R2, the pin CON of the chip LM555 is connected with the ground through a capacitor C1, the pin TRI of the chip LM555 is connected with the ground through a capacitor C2, the pin GND of the chip LM555 is connected with the ground, and the pin OUT of the chip LM555 outputs the pre-preparation gate signal.

[0013] Further, the gate control circuit comprises a first double D flip-flop and a second double D flip-flop, the first double D flip-flop and the second double D flip-flop are both chip 74HC74N, the pre-preparation gate signal is input into the pin D of the first double D flip-flop and the pin D of the second double D flip-flop respectively, the shaped measured signal one is input into the pin CLK of the first double D flip-flop, the shaped measured signal two is input into the pin CLK of the second double D flip-flop, the pin Q of the first double D flip-flop outputs the actual gate signal one, and the pin Q of the second double D flip-flop outputs the actual gate signal two.

[0014] Further, the phase measurement circuit is further connected with the input end of the single-chip microcomputer.

[0015] The beneficial effects of the double-channel digital frequency meter are as follows: the double-channel digital frequency meter can realize double-channel measurement, can realize simultaneous measurement and comparison of two signals, and meets the demand of simultaneous detection and analysis of different signals in more complex scenes. In addition, by adopting the first signal shaping circuit, the second signal shaping circuit, the first frequency divider circuit and the second frequency divider circuit, the measurement frequency bandwidth can be widened, and the wide frequency band can be adapted, so that the double-channel digital frequency meter can be applied to a wider frequency range of signal measurement scenes. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a circuit schematic diagram of the double-channel digital frequency meter of the utility model embodiment;

[0017] Figure 2 is a circuit schematic diagram of the comparison shaping circuit in the embodiment;

[0018] Figure 3 This is a circuit diagram of the first frequency divider circuit in the embodiment;

[0019] Figure 4 This is a circuit diagram of the gate control circuit in the embodiment;

[0020] Figure 5 This is a waveform diagram of the equal-precision frequency measurement method used in the embodiment;

[0021] Figure 6 This is a waveform diagram of phase difference measurement in the embodiment. Detailed Implementation

[0022] The preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings.

[0023] An embodiment provides a dual-channel digital frequency meter, such as Figure 1 The system includes a microcontroller, a display circuit, and a power supply circuit for powering the microcontroller. The display circuit is connected to the microcontroller. It also includes a first signal shaping circuit, a first relay switch K1, a first frequency divider circuit, a second relay switch K2, a second signal shaping circuit, a third relay switch K3, a second frequency divider circuit, a fourth relay switch K4, a multivibrator circuit for outputting a preset gate signal, and a gate control circuit. The first measured signal is input to the first signal shaping circuit, which is connected to the common terminal of the first relay switch K1. The normally closed terminal of the first relay switch K1 is connected to the normally closed terminal of the second relay switch K2 through the first frequency divider circuit. The normally open terminal of the first relay switch K1 is connected to the first... The normally open terminal of the second relay switch K2 and the moving terminal of the second relay switch K2 are respectively connected to the input terminal of the gate control circuit and the input terminal of the microcontroller. The second measured signal is input to the second signal shaping circuit, which is connected to the common terminal of the third relay switch K3. The normally closed terminal of the third relay switch K3 is connected to the normally closed terminal of the fourth relay switch K4 through the second frequency divider circuit. The normally open terminal of the third relay switch K3 is connected to the normally open terminal of the fourth relay switch K4. The preset gate signal is connected to the input terminal of the microcontroller through the gate control circuit. The output terminal of the microcontroller is connected to the first relay switch K1, the second relay switch K2, the third relay switch K3 and the fourth relay switch K4 respectively.

[0024] This dual-channel digital frequency meter enables dual-channel measurement, allowing simultaneous measurement and comparison of multiple signals, thus meeting the needs of simultaneous detection and analysis of different signals in more complex scenarios. By employing a first signal shaping circuit, a second signal shaping circuit, a first frequency divider circuit, and a second frequency divider circuit, the measurement frequency bandwidth can be broadened, adapting to a wide frequency range and thus applicable to signal measurement scenarios across a wider frequency range.

[0025] The first signal shaping circuit and the second signal shaping circuit both adopt a comparison shaping circuit. As shown in Figure 2 , the comparison shaping circuit comprises an adjustable resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a comparator TLV3501. The first measured signal or the second measured signal is input to the inverting input terminal of the comparator TLV3501. The non-inverting input terminal of the comparator TLV3501 is connected to ground through the resistor R4 and the adjustable resistor R1. The positive power supply input terminal of the comparator TLV3501 is connected to the power supply circuit and is connected to ground through the capacitor C1. The two ends of the resistor R2 are connected to the adjustable resistor R1 and the capacitor C1, respectively. The negative power supply input terminal of the comparator TLV3501 is connected to ground. The non-inverting input terminal of the comparator TLV3501 is connected to the output terminal of the comparator TLV3501 through the resistor R3. The output terminal of the comparator TLV3501 outputs the shaped measured signal.

[0026] The first frequency divider circuit and the second frequency divider circuit adopt the same circuit. As shown in Figure 3 , the first frequency divider circuit comprises a chip 74164 and an inverter 7404. The shaped measured signal is input to the pin CLK of the chip 74164. The pin QE of the chip 74164 is connected to the pin A of the chip 74164 through the inverter 7404. The pin B of the chip 74164 and the pin CLR are connected to the power supply circuit, respectively. The pin QE of the chip 74164 outputs the measured signal frequency.

[0027] As shown in Figure 4 , the preset gate signal of the frequency meter is output by the multivibrator circuit designed by the chip LM555. The multivibrator circuit comprises a chip LM555. The pin VCC and the pin RST of the chip LM555 are connected to the power supply circuit, respectively. The pin DIS of the chip LM555 is connected to the power supply circuit through the resistor R1. The pin DIS of the chip LM555 is also connected to the pin TRI and the pin THR of the chip LM555 through the resistor R2, respectively. The pin CON of the chip LM555 is connected to ground through the capacitor C1. The pin TRI of the chip LM555 is connected to ground through the capacitor C2. The pin GND of the chip LM555 is connected to ground. The pin OUT of the chip LM555 outputs the preset gate signal.

[0028] As shown in Figure 4The gate control circuit includes a first double D flip-flop and a second double D flip-flop, both of which are 74HC74N chips, preset gate signals are input into the pin D of the first double D flip-flop and the pin D of the second double D flip-flop, the first shaped measured signal CH1 is input into the pin CLK of the first double D flip-flop, the second shaped measured signal CH2 is input into the pin CLK of the second double D flip-flop, the pin Q of the first double D flip-flop outputs the actual gate signal one to the single-chip microcomputer, and the pin Q of the second double D flip-flop outputs the actual gate signal two to the single-chip microcomputer. The gate control circuit ensures the synchronization of the actual gate signal one, the actual gate signal two, the first measured signal and the second measured signal when the gate is opened, thereby reducing the frequency measurement error.

[0029] The double-channel digital frequency meter further includes a phase measurement circuit, and the normally open end of the first relay switch K1 and the normally open end of the second relay switch K2 are connected to the input end of the single-chip microcomputer through the phase measurement circuit.

[0030] The double-channel digital frequency meter controls the first relay switch K1, the second relay switch K2, the third relay switch K3 and the fourth relay switch K4 through the single-chip microcomputer, and the first measured signal and the second measured signal are directly input into the single-chip microcomputer after shaping or are sent into the single-chip microcomputer after passing through the first frequency division circuit and the second frequency division circuit respectively for frequency measurement. The single-chip microcomputer adopts an STM32F429IGT6 chip. In a specific example, the actual gate signal 1 and the actual gate signal 2 output by the gate control circuit are connected to the pins PE2 and PE4 of the single-chip microcomputer respectively, the first relay switch K1 and the second relay switch K2 are connected to the pin PB0 of the single-chip microcomputer, the third relay switch K3 and the fourth relay switch K4 are connected to the pin PB1 of the single-chip microcomputer, the first measured signal is directly input into the single-chip microcomputer after shaping or is sent into the pin PA0 of the single-chip microcomputer after passing through the first frequency division circuit for frequency measurement, the first measured signal is directly input into the pin PE3 of the single-chip microcomputer for pulse width duty cycle measurement, the second measured signal is directly input into the single-chip microcomputer after shaping or is sent into the pin PI3 of the single-chip microcomputer after passing through the second frequency division circuit for frequency measurement, the second measured signal is directly input into the pin PE5 of the single-chip microcomputer for pulse width duty cycle measurement, and the phase measurement circuit is connected to the pin PE6 of the single-chip microcomputer for phase difference measurement.

[0031] The first measured signal and the second measured signal are directly input into the single-chip microcomputer after shaping or are sent into the single-chip microcomputer after passing through the first frequency division circuit and the second frequency division circuit respectively for frequency measurement.

[0032] Because the timer input capture function of STM32F429IGT6 chip can only detect the edge signal with frequency lower than 1MHz, in order to measure the signal with higher frequency, a frequency division circuit with frequency division ratio of 10 or 100 is set according to the range of the measured signal frequency, the frequency division circuit with frequency division ratio of 10 is shown in Figure 3 , and the frequency division circuit with frequency division ratio of 100 can be realized by cascading two frequency division circuits with frequency division ratio of 10. When the frequency of the first measured signal and the second measured signal is higher than the set frequency such as 500KHz, the first measured signal and the second measured signal are shaped and then sent to the single-chip microcomputer through the first frequency division circuit and the second frequency division circuit respectively to output the measurement results. When the frequency of the first measured signal and the second measured signal is not higher than the set frequency such as 500KHz, the first measured signal and the second measured signal are shaped and then directly sent to the single-chip microcomputer to measure and output the measurement results.

[0033] The double-channel digital frequency meter mainly comprises a power supply circuit, a signal shaping circuit, a preset gate, a gate control circuit, a frequency divider circuit, a phase measurement circuit, a single-chip microcomputer and a display circuit. The single-chip microcomputer is an STM32F429IGT6 single-chip microcomputer, which is a 32-bit single-chip microcomputer with enhanced performance, low power consumption and low cost based on Cortex-M4 core, and has a highest working frequency of 180MHz, 14 timers / counters and each GPIO port as an input port of external interrupt, and has very powerful external interrupt and timing counting functions.

[0034] The double-channel digital frequency meter adopts the existing equal-precision frequency measurement method to improve the precision of frequency measurement. Figure 5

[0035] In the actual gate time T = the falling edge time t2 - the rising edge time t1, it is assumed that the count value of the measured signal with frequency Fx is N x , and the count value of the standard signal with frequency Fs is Ns. Then,

[0036]

[0037] According to formula (2), the frequency measurement of the measured signal adopts the method of combining the external interrupt of the single-chip microcomputer with the external trigger input of the timer. The actual gate signal is connected to the external interrupt of the single-chip microcomputer, and the measured signal is connected to the external trigger input end of the timer of the single-chip microcomputer. The external interrupt of the single-chip microcomputer is set as double-edge trigger, and at the rising edge time t1, the external trigger counting function and the timer of the single-chip microcomputer are started at the same time, and the measured signal is counted by one every time the rising edge comes, and the timer of the single-chip microcomputer starts counting as the standard signal. At the falling edge time t2, the count value N x ​​and the count value Ns of the internal clock timing counter, and turn off the external trigger function counter and the internal clock timing counter, and pay attention to the count overflow processing of the two counters. The frequency Fs of the standard signal can be set by the single-chip microcomputer, in order to ensure high precision of measurement, the frequency Fs of the standard signal is set to 10MHz, and then the frequency Fx and the period Tx of the measured signal are as follows:

[0038] ,

[0039] The double-channel digital frequency meter realizes double-channel measurement, can measure two signal sources at the same time, expands the measurement channel, changes the limitation that the simple digital frequency meter can only measure the frequency of a single signal source, adopts a high-speed comparator and increases a frequency division circuit to improve the measurement frequency bandwidth. When the single-chip microcomputer is used to realize frequency measurement, the external interrupt and the external trigger input of the timing counter are combined, the related powerful functions of the STM32 single-chip microcomputer are used, the equal-precision measurement method is used, the precision of the measured frequency is improved to less than 0.001%, the high precision, the extremely low error and the effective improvement of the accuracy and reliability of the measurement result of the frequency measurement are ensured.

[0040] In addition, the measurement parameter expansion is expanded, in addition to the frequency and period measurement, the signal pulse width, the duty cycle and the phase difference of the same frequency signal are newly measured. The specific description is as follows:

[0041] The pulse width measurement adopts the method that the single-chip microcomputer is combined with the internal clock timing counter. The measured signal is connected to another external interrupt, the external interrupt is set to double-edge trigger, when the rising edge time t3 of the measured signal, the timing counter is started to count up, when the falling edge time t4 of the measured signal, the timing counter is turned off, and the current value of the counter is taken out. The frequency of the internal clock timing counter is set to 10MHz, the count value of the counter is CNT, and then the pulse width and the duty cycle of the measured signal are as follows:

[0042] ,

[0043] The phase difference measurement is as Figure 6 , the two measured signals after comparison and shaping are subjected to exclusive-OR operation by using a 74LVC1G86 chip to obtain a pulse wave. The pulse width △t of the pulse wave reflects the phase difference of the two measured signals, and the phase difference of the two measured signals is as follows:

[0044] ,

[0045] The double-channel digital frequency meter can realize double-channel measurement, facilitate processing of multiple signals, realize high-precision measurement by combining with an existing equal-precision measurement method, widen a measurement frequency bandwidth, realize more measurement parameters, enable a user to comprehensively understand signal characteristics, and provide more abundant data basis for subsequent analysis and application.

[0046] The above merely describes the embodiments of the present application and is not intended to limit the present application. The present application can be changed and modified in various ways by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims

1. A double-channel digital frequency meter, comprising a single-chip microcomputer, a display circuit and a power supply circuit for power supply, the display circuit being connected to the single-chip microcomputer, characterized in that: The first signal shaping circuit, the first relay switch K1, the first frequency divider circuit, the second relay switch K2, the second signal shaping circuit, the third relay switch K3, the second frequency divider circuit, the fourth relay switch K4, the multi-vibrator circuit for outputting the preset gate signal and the gate control circuit are further included, the first measured signal is input into the first signal shaping circuit, the first signal shaping circuit is connected to the common terminal of the first relay switch K1, the normally closed terminal of the first relay switch K1 is connected to the normally closed terminal of the second relay switch K2 through the first frequency divider circuit, the normally open terminal of the first relay switch K1 is connected to the normally open terminal of the second relay switch K2, the moving terminal of the second relay switch K2 is connected to the input terminal of the gate control circuit and the input terminal of the single-chip microcomputer respectively, the second measured signal is input into the second signal shaping circuit, the second signal shaping circuit is connected to the common terminal of the third relay switch K3, the normally closed terminal of the third relay switch K3 is connected to the normally closed terminal of the fourth relay switch K4 through the second frequency divider circuit, the normally open terminal of the third relay switch K3 is connected to the normally open terminal of the fourth relay switch K4, the preset gate signal is connected to the input terminal of the single-chip microcomputer through the gate control circuit, and the output terminal of the single-chip microcomputer is connected to the first relay switch K1, the second relay switch K2, the third relay switch K3 and the fourth relay switch K4 respectively.

2. The dual channel digital frequency meter of claim 1, wherein: The single-chip microcomputer adopts an STM32F429IGT6 chip.

3. The dual channel digital frequency meter of claim 1, wherein: Both the first signal shaping circuit and the second signal shaping circuit adopt a comparison shaping circuit.

4. The dual channel digital frequency meter of claim 3, wherein: The comparison shaping circuit includes an adjustable resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a comparator TLV3501, the first measured signal or the second measured signal is input into the inverting input terminal of the comparator TLV3501, the non-inverting input terminal of the comparator TLV3501 is grounded through the resistor R4 and the adjustable resistor R1, the positive power supply input terminal of the comparator TLV3501 is connected to the power supply circuit and grounded through the capacitor C1, the two ends of the resistor R2 are connected to the adjustable resistor R1 and the capacitor C1 respectively, the negative power supply input terminal of the comparator TLV3501 is grounded, the non-inverting input terminal of the comparator TLV3501 is connected to the output terminal of the comparator TLV3501 through the resistor R3, and the output terminal of the comparator TLV3501 outputs the shaped measured signal.

5. A dual channel digital frequency meter as claimed in any one of claims 1 to 4, characterized in that: The first frequency divider circuit and the second frequency divider circuit adopt the same circuit.

6. A dual channel digital frequency meter as claimed in any one of claims 1 to 4, characterized in that: The first frequency divider circuit includes a chip 74164 and an inverter 7404, the shaped measured signal is input into the pin CLK of the chip 74164, the pin QE of the chip 74164 is connected to the pin A of the chip 74164 through the inverter 7404, the pin B and the pin CLR of the chip 74164 are connected to the power supply circuit respectively, and the pin QE of the chip 74164 outputs the measured signal frequency.

7. A dual channel digital frequency meter as claimed in any one of claims 1 to 4, characterized in that: The multi-resonance oscillator circuit comprises a chip LM555, a pin VCC and a pin RST of the chip LM555 are connected to a power supply circuit respectively, a pin DIS of the chip LM555 is connected to the power supply circuit through a resistor R1, the pin DIS of the chip LM555 is also connected to a pin TRI and a pin THR of the chip LM555 through a resistor R2, a pin CON of the chip LM555 is grounded through a capacitor C1, a pin TRI of the chip LM555 is grounded through a capacitor C2, a pin GND of the chip LM555 is grounded, and a pin OUT of the chip LM555 outputs a pre-gate signal.

8. The dual channel digital frequency meter of any one of claims 1-4, wherein: The gate control circuit comprises a first double D flip-flop and a second double D flip-flop, both of which are chip 74HC74N, the pre-gate signal is input into a pin D of the first double D flip-flop and a pin D of the second double D flip-flop respectively, a shaped measured signal one is input into a pin CLK of the first double D flip-flop, a shaped measured signal two is input into a pin CLK of the second double D flip-flop, a pin Q of the first double D flip-flop outputs an actual gate signal one, and a pin Q of the second double D flip-flop outputs an actual gate signal two.

9. The dual-channel digital frequency meter of any one of claims 1-4, wherein: The phase measurement circuit is further comprised, and a normally open end of a first relay switch K1 and a normally open end of a second relay switch K2 are connected to an input end of the single-chip microcomputer through the phase measurement circuit.

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