CN204461598U - A kind of signal generator being exclusively used in acoustic velocity measutement test - Google Patents

Abstract

The utility model discloses a signal generator specially used for the sound velocity measurement test. The encoder input module includes a rotary encoder and a steering identification circuit, and the output end of the rotary encoder is respectively connected with the single-chip microcomputer control module and the input end of the steering identification circuit. , the output end of the steering recognition circuit is connected with the input end of the single-chip microcomputer control module; the output end of the single-chip microcomputer control module is respectively connected with the corresponding input ends of the storage module, the display module and the DDS sine wave generation module, and the output of the DDS sine wave generation module The terminal is connected with the input terminal of the low-pass filter module, and the output terminal of the low-pass filter module is connected with the input terminal of the operational amplification module. The utility model is specially used in the sound velocity measurement experiment, and only generates sine waves in the range of 36KHz-38KHz required by the experiment. Since the frequency range of the output sine wave is narrow, frequency waste is avoided, and the frequency adjustment is easy, with high precision and small error.

Description

A Signal Generator Specially Used in Sound Velocity Measurement Test

technical field

The utility model relates to a signal generator, in particular to a signal generator specially used for sound velocity measurement tests.

Background technique

The speed of sound measurement experiment is one of the most classic college physics experiments. This experiment can not only enable students to understand the general laws of the quantitative relationship between wave velocity, wavelength and frequency, and the conditions for forming standing waves, but also further understand the nature of sound propagation. . Although the ultrasonic signal generator used in the sound velocity measurement experiment can basically meet the experimental requirements at present, there are still two shortcomings: (1) the frequency generated by the existing ultrasonic signal generator is too wide, which is 20Hz～200KHz, but Ultrasonic sound velocity measurement experiments generally only need signals of specific frequencies (36KHz to 38Hz), so when using sound velocity measurement experiments, it is often necessary to perform mechanical frequency modulation by turning the knob, which will cause mechanical loss and shorten the life of the instrument. Mechanical frequency modulation is not easy to complete accurately, and errors are prone to occur, which is not conducive to students' experiments. (2) Existing signal generators generate a wide variety of waveforms, but the sound velocity measurement experiment only needs to use sine waves, so many functions of existing signal generators are wasted, resulting in oversupply and high power consumption. Therefore, it is necessary to develop a high-quality and cheap ultrasonic signal generator with narrow frequency modulation range, close to the required output frequency, and only output sine wave signal for the sound velocity measurement experiment.

In terms of signal input, most of the existing ultrasonic signal sources use potentiometers to adjust the value of the required frequency, and then generate the required sine wave, square wave, triangle wave, etc. Because the frequency modulation is adjusted by the potentiometer by turning the knob, the operation is difficult and errors are prone to occur. Frequent use of potentiometer frequency modulation will cause mechanical loss, shorten the life of the instrument, and cause stationary point drift, and potentiometer frequency modulation is not easy to complete accurately, which is not conducive to students' experiments.

Utility model content

The technical problem to be solved by the utility model is to provide a signal generator specially used for the sound velocity measurement test, which only outputs sine waves in the frequency range of 36KHz-38KHz, and the frequency adjustment is convenient and the precision is high.

In order to solve the problems of the technologies described above, the technical scheme adopted by the utility model is as follows:

A signal generator dedicated to sound velocity measurement tests, including a power supply module, an encoder input module, a single-chip control module, a storage module, a display module, a DDS sine wave generation module, a low-pass filter module and an operational amplification module; the power supply module Provide the required DC voltage for other modules; the encoder input module includes a rotary encoder and a steering recognition circuit, the output of the rotary encoder is connected to the input of the single-chip control module and the steering recognition circuit respectively, and the steering recognition circuit Output end is connected with the input end of single-chip microcomputer control module; The output end of described single-chip microcomputer control module is connected with the corresponding input end of storage module, display module and DDS sine wave generation module respectively, the output end of DDS sine wave generation module is connected with low The input terminal of the pass filter module is connected, and the output terminal of the low-pass filter module is connected with the input terminal of the operational amplifier module; The encoder sends the rotation value of the knob to the steering recognition circuit. The steering recognition circuit judges whether the user is turning the knob left or right and sends the discrimination signal to the single-chip control module. At the same time, the rotary encoder sends the rotation value of the knob and the number of times the button switch is pressed continuously to the single-chip microcomputer control module; the single-chip microcomputer control module selects the corresponding step value according to the number of times the button switch is pressed continuously, and combines the knob rotation value and the discrimination signal to generate a frequency value in the range of 36KHz ~ 38KHz. The frequency value and step value are sent to the display module for display. On the one hand, the frequency value is sent to the storage module for storage, and on the other hand, the frequency value is sent to the DDS sine wave generation module, and the frequency generated by the DDS sine wave generation module is equal to The sine wave of the frequency value and send the sine wave to the low-pass filter module for denoising processing, the low-pass filter module sends the smooth sine wave generated after denoising to the operational amplifier module for signal amplification, and the final output amplitude is passed through Conditioned sine wave signal with a frequency of 36KHz ~ 38KHz.

Wherein, the power supply module includes a transformer, a rectifier bridge and three voltage stabilizing chips 7812, 7912 and 7805 to realize the conversion of AC 220V to DC +12V, -12V and +5V.

Wherein, the single-chip microcomputer control module includes a single-chip microcomputer STC89c52.

Wherein, the display module includes a GXM 1602NSL liquid crystal screen; the 39-32 pins of the single-chip microcomputer STC89c52 are respectively connected to the 7-14 pins of the GXM 1602NSL liquid crystal screen; the 26-29 pins of the single-chip microcomputer STC89c52 are respectively connected to the 4-6 pins of the GXM 1602NSL liquid crystal screen.

Wherein, the steering recognition circuit is a NAND gate circuit 74HC00; the 5 pins of the rotary encoder are connected to the 23 pins of the single chip microcomputer STC89c52, and the 1 pin of the rotary encoder is simultaneously connected to the 1 pin of the NAND gate circuit 74HC00 and the single chip microcomputer STC89c52 The 21 pins of the rotary encoder, the 3 pins of the rotary encoder are connected to the 2 pins of the NAND gate circuit 74HC00 and the 22 pins of the single-chip STC89c52; the 11 pins of the NAND gate circuit 74HC00 are connected to the 12 pins of the single-chip STC89c52; the rotary encoder When the knob is turned to the right, the frequency increases, and when it is turned to the left, the frequency decreases, and the corresponding frequency range is 36KHz to 38KHz when the knob is turned left and right; the corresponding step values are 1Hz, 10Hz and 100Hz when the button switch of the rotary encoder is pressed continuously for one to three times.

Wherein, the storage module includes an EEPROM chip 24c08; pins 25 and 24 of the single-chip microcomputer STC89c52 are respectively connected to pins 5 and 6 of the chip 24c08.

Wherein, the DDS sine wave generation module includes an AD9850 chip; pins 1-4 of the single-chip microcomputer STC89c52 are respectively connected to pins 8, 12, 7, and 25 of the AD9850 chip.

Wherein, the low-pass filter module includes resistors R4, R5, capacitors C7-C7, and inductors L1-L3; the operational amplifier module includes an op-amp chip NE5532, resistors R1, R3, and potentiometer R2; 1 of the op-amp chip NE5532 The pin is the output terminal of the sine wave signal of 36KHz ~ 38KHz; the inductance L1 and the capacitor C2 are connected in parallel to form the first resonant circuit, the inductance L2 and the capacitor C4 are connected in parallel to form the second resonant circuit, the inductance L3 and the capacitor C6 are connected in parallel to form the third resonant circuit, the second The first to third resonant circuits and resistor R3 are connected in series between pin 21 of the AD9850 chip and pin 3 of the operational amplifier chip NE5532; resistor C4 and capacitor C1 are connected in parallel and connected between pin 21 of the AD9850 chip and ground, and the capacitor C3 is connected between the node of the first resonant circuit and the second resonant circuit and the ground, the capacitor C5 is connected between the node of the second resonant circuit and the third resonant circuit and the ground, the capacitor C7 is connected in parallel with the resistor R5 and then connected to the third Between the resonant circuit and the node of the resistor R3 and the ground; the resistor R1 and the potentiometer R2 are connected in series between the pin 1 of the operational amplifier chip NE5532 and the ground, and the arm of the potentiometer R2 is connected to the pin 1 of the operational amplifier chip NE5532. Connect pin 2 of the chip NE5532 to the node of resistor R1 and potentiometer R2.

The beneficial effects produced by adopting the above-mentioned technical scheme are:

The utility model is specially used in the sound velocity measurement experiment, and only generates sine waves in the range of 36KHz-38KHz required by the experiment. Since the frequency range of the output sine wave is narrow, frequency waste is avoided, and the frequency adjustment is easy, with high precision and small error.

(1) The utility model uses the rotary encoder to generate the frequency value of the required frequency, and realizes the frequency adjustment easily. It not only avoids the shortcomings of large mechanical errors, difficult operation, and short life, but also improves the accuracy and frequency selection speed. Limit the frequency within the range of 36KHz to 38KHz, and set 3 gears, and the frequency increases when the encoder rotates clockwise (to the right), and decreases when the encoder rotates counterclockwise (to the left). The frequency value can be adjusted within a small range, which facilitates operation and experimental accuracy. (2) The special device of the utility model is dedicated to use the AD9850 chip to only output sine waves, which reduces power consumption and saves costs, and optimizes electronic devices to reduce the error to within 0.4Hz. (3) The price of the existing signal generator is between 800 and 1200. The utility model is preferably an electronic device, which reduces the cost very well. The cost of the utility model can be reduced to below 150, which has considerable cost performance, and the signal output Higher accuracy. (4) The utility model greatly reduces the use of electronic devices on the basis of streamlining power consumption, and uses more patch devices without increasing costs and causing adverse effects, and without generating electromagnetic interference. The degree of integration is higher, so the volume is smaller, which is convenient for moving.

Description of drawings

Fig. 1 is a block diagram of the utility model;

Fig. 2 is the connection schematic diagram of the first part of the utility model;

Fig. 3 is the connection diagram of the second part of the utility model;

Fig. 4 is a schematic connection diagram of the third part of the present invention.

Detailed ways

As shown in Figure 1, the utility model discloses a signal generator specially used for sound velocity measurement test, including a power supply module, an encoder input module, a single-chip microcomputer control module, a storage module, a display module, a DDS sine wave generation module, a low-pass filter module and operational amplification module; the power supply module provides the required DC voltage for other modules; the encoder input module includes a rotary encoder and a steering recognition circuit, and the output of the rotary encoder is connected to the single-chip control module and the steering recognition circuit respectively The input end of the circuit is connected, and the output end of the steering identification circuit is connected with the input end of the single-chip microcomputer control module; the output end of the single-chip microcomputer control module is connected with the corresponding input end of the storage module, the display module and the DDS sine wave generation module respectively , the output end of the DDS sine wave generating module is connected to the input end of the low-pass filter module, and the output end of the low-pass filter module is connected to the input end of the operational amplification module. The user turns the knob of the rotary encoder left or right and presses the button switch of the rotary encoder continuously, the rotary encoder sends the rotation value of the knob to the steering recognition circuit, and the steering recognition circuit judges whether the user is turning the knob left or right and will judge The signal is sent to the single-chip microcomputer control module, and at the same time, the rotary encoder sends the knob rotation value and the number of times the button switch is pressed continuously to the single-chip control module; the single-chip control module selects the corresponding step value according to the number of times the switch is pressed continuously, and combined with the knob The rotation value and the discrimination signal generate a frequency value in the range of 36KHz to 38KHz. On the one hand, the single-chip control module sends the frequency value and step value to the display module for display. On the one hand, it sends the frequency value to the storage module for storage. On the one hand, the frequency value is sent to the DDS sine wave generation module, and the DDS sine wave generation module generates a sine wave with a frequency equal to the frequency value and sends the sine wave to the low-pass filter module for denoising processing, and the low-pass filter module will The smooth sine wave generated after denoising is sent to the operational amplifier module for signal amplification, and finally the sine wave signal with adjusted amplitude and frequency of 36KHz-38KHz is output.

As shown in Figure 2, the power module includes a transformer, a rectifier bridge and three voltage regulator chips 7812, 7912 and 7805 to realize the conversion of AC 220V to DC +12V, -12V and +5V. Single-chip microcomputer STC89c52, GXM 1602NSL LCD screen, AD9850 chip, etc. need +5V DC voltage, and op-amp chip NE5532 needs +12V, -12V power supply voltage.

As shown in Figure 3, the single-chip microcomputer control module includes a single-chip microcomputer STC89c52; the display module includes a GXM1602NSL LCD screen; the 39-32 pins of the single-chip microcomputer STC89c52 are respectively connected to the 7-14 pins of the GXM 1602NSL LCD screen; the 26-29 pins of the single-chip microcomputer STC89c52 are respectively connected to the GXM 1602NSL The 4-6 pins of the LCD screen; the storage module includes the EEPROM chip 24c08; the 25 and 24 pins of the single-chip microcomputer STC89c52 are respectively connected to the 5 and 6 pins of the chip 24c08. The steering recognition circuit is the NAND gate circuit 74HC00; the 5-pin of the rotary encoder J1 is connected to the 23-pin of the single-chip microcomputer STC89c52, and the 1-pin of the rotary encoder J1 is simultaneously connected to the 1-pin of the NAND gate circuit 74HC00 and the 21-pin of the single-chip STC89c52 Pin 3 of the rotary encoder J1 is connected to pin 2 of the NAND gate circuit 74HC00 and pin 22 of the single-chip microcomputer STC89c52; pin 11 of the NAND gate circuit 74HC00 is connected to pin 12 of the single-chip microcomputer STC89c52. According to the working principle of the rotary encoder combined with the NAND circuit 74HC00, the button switch of the rotary encoder is set to the step value of three gears and the value can be changed by turning the knob left and right. When the knob of the rotary encoder is turned right, the frequency increases, and when it is turned left, the frequency decreases, and the corresponding frequency range is 36KHz to 38KHz when the knob is turned left and right; the corresponding step values of pressing the button switch of the rotary encoder one to three times are respectively 1Hz, 10Hz and 100Hz; when the encoder rotates, the corresponding gear value is changed every time, and the frequency range is limited to 36KHz ~ 38KHz. When the frequency is equal to 36KHz, the frequency remains unchanged at 36KHz when it is turned clockwise against the trend; when the frequency is equal to 38KHz, the frequency remains unchanged at 38KHz when it is turned clockwise again. The utility model narrows the frequency adjustment range to around 36.8KHz required by the sound velocity measurement experiment, so that it can be used exclusively for special devices and saves resources.

The single-chip microcomputer STC89c52 generates a frequency value within the range of 36KHz to 38KHz according to the setting program, and sends the frequency value to the EEPROM chip (power-off protection), GXM 1602NSL liquid crystal module (real-time display) and AD9850 chip (generating sine wave). The EEPROM chip saves the data. When the system is powered off, the value generated by the rotary encoder disappears, but the data in the EEPROM chip will not be lost. After the system is powered on again, the single-chip microcomputer STC89c52 will call the data in the EEPROM chip and continue to send it to the AD9850 chip , thus outputting the desired sine wave. The GXM 1602NSL LCD screen displays the step value and frequency value on the screen.

As shown in Figure 4, the DDS sine wave generation module includes the AD9850 chip; the 1-4 pins of the single-chip microcomputer STC89c52 are respectively connected to the 8, 12, 7, and 25 pins of the AD9850 chip; the low-pass filter module includes resistors R4, R5, and capacitors C7-C7 and inductance L1-L3; the operational amplifier module includes op-amp chip NE5532, resistors R1, R3 and potentiometer R2; pin 1 of op-amp chip NE5532 is the output end of a sine wave signal of 36KHz～38KHz; inductance L1 and capacitor C2 The first resonant circuit is formed in parallel, the inductance L2 and the capacitor C4 are connected in parallel to form the second resonant circuit, the inductance L3 and the capacitor C6 are connected in parallel to form the third resonant circuit, and the first to third resonant circuits and the resistor R3 are connected in series to the 21 of the AD9850 chip. between pin 3 and pin 3 of the operational amplifier chip NE5532; resistor C4 and capacitor C1 are connected in parallel between pin 21 of the AD9850 chip and the ground; capacitor C3 is connected between the node of the first resonant circuit and the second resonant circuit and the ground , the capacitor C5 is connected between the node of the second resonant circuit and the third resonant circuit and the ground, the capacitor C7 is connected in parallel with the resistor R5 and then connected between the node of the third resonant circuit and the resistor R3 and the ground; the resistor R1 and the potentiometer R2 Connect in series between pin 1 of the operational amplifier chip NE5532 and the ground, the boom of the potentiometer R2 is connected to pin 1 of the operational amplifier chip NE5532, and pin 2 of the operational amplifier chip NE5532 is connected to the node of the resistor R1 and the potentiometer R2.

Single-chip STC89c52 and AD9850 chip adopt serial connection. The reference clock frequency of the AD9850 chip is generally much higher than the clock frequency of the single-chip microcomputer STC89c52, so the reset terminal of the AD9850 chip is directly connected with the reset terminal of the single-chip microcomputer STC89c52. Since the analog waveform output directly from the D/A conversion inside the AD9850 chip is not a smooth sine wave, it is smoothed by the low-pass filter module, and then the signal amplitude output by the low-pass filter module is conditioned by the operational amplifier chip NE5532, and the expected waveform.

Claims (8)

1. be exclusively used in a signal generator for acoustic velocity measutement test, it is characterized in that: comprise power module, scrambler load module, single chip control module, memory module, display module, DDS sinusoidal wave generation module, low-pass filtering module and operation amplifier module, described power module provides required DC voltage for other modules, described scrambler load module comprises rotary encoder and turns to identification circuit, the output terminal of rotary encoder respectively with single chip control module with turn to the input end of identification circuit and be connected, turn to the output terminal of identification circuit to be connected with the input end of single chip control module, the output terminal of described single chip control module is connected with the respective input of memory module, display module and DDS sine wave generation module respectively, the sinusoidal wave output terminal of generation module of DDS is connected with the input end of low-pass filtering module, and the output terminal of low-pass filtering module is connected with the input end of operation amplifier module, user turn left or right-hand rotation rotary encoder knob and press the pushbutton switch of rotary encoder continuously, knob value is sent to and turns to identification circuit by rotary encoder, user turns left or right-hand rotation knob judgment signal is sent to single chip control module to turn to identification circuit to differentiate, the number of times that knob value and pushbutton switch are pressed continuously is sent to single chip control module by rotary encoder simultaneously, single chip control module selectes corresponding step value according to the number of times that pushbutton switch is pressed continuously, and in conjunction with knob value and judgment signal, generate the frequency values within the scope of 36KHz ~ 38KHz, this frequency values and step value are sent to display module and show by single chip control module on the one hand, on the one hand this frequency values is sent to memory module to store, on the other hand this frequency values is sent to the sinusoidal wave generation module of DDS, produce frequency by the sinusoidal wave generation module of DDS equal the sine wave of this frequency values and this sine wave is sent to low-pass filtering module carries out denoising, sine wave level and smooth for the waveform generated after denoising is sent to operation amplifier module and carries out signal amplification by low-pass filtering module, last output amplitude is through conditioning and frequency is the sine wave signal of 36KHz ~ 38KHz.

2. the signal generator being exclusively used in acoustic velocity measutement test according to claim 1, it is characterized in that: described power module comprises transformer, rectifier bridge and three voltage stabilizing chips 7812,7912 and 7805, realizes the conversion of alternating current 220V to direct current+12V ,-12V and+5V.

3. the signal generator being exclusively used in acoustic velocity measutement test according to claim 1, is characterized in that: described single chip control module comprises single-chip microcomputer STC89c52.

4. the signal generator being exclusively used in acoustic velocity measutement test according to claim 3, is characterized in that: described display module comprises GXM 1602NSL liquid crystal display; The 39-32 pin of single-chip microcomputer STC89c52 connects the 7-14 pin of GXM 1602NSL liquid crystal display respectively; The 26-29 pin of single-chip microcomputer STC89c52 connects the 4-6 pin of GXM1602NSL liquid crystal display respectively.

5. according to claim 3 be exclusively used in acoustic velocity measutement test signal generator, it is characterized in that: described in turn to identification circuit to be NAND gate circuit 74HC00; 5 pin of rotary encoder are linked into 23 pin of single-chip microcomputer STC89c52,1 pin of rotary encoder is linked into 1 pin of NAND gate circuit 74HC00 and 21 pin of single-chip microcomputer STC89c52 simultaneously, and 3 pin of rotary encoder are linked into 2 pin of NAND gate circuit 74HC00 and 22 pin of single-chip microcomputer STC89c52 simultaneously; 11 pin of NAND gate circuit 74HC00 are linked into 12 pin of single-chip microcomputer STC89c52; When the knob of rotary encoder is turned right, frequency increases, frequency decrease during left-hand rotation, and frequency range corresponding during left rotation and right rotation is 36KHz ~ 38KHz; The step value pressing the pushbutton switch one to three time of rotary encoder continuously corresponding is respectively 1Hz, 10Hz and 100Hz.

6. the signal generator being exclusively used in acoustic velocity measutement test according to claim 3, is characterized in that: described memory module comprises eeprom chip 24c08; 25,24 pin of single-chip microcomputer STC89c52 connect 5,6 pin of chip 24c08 respectively.

7. the signal generator being exclusively used in acoustic velocity measutement test according to claim 3, is characterized in that: the sinusoidal wave generation module of described DDS comprises AD9850 chip; The 1-4 pin of single-chip microcomputer STC89c52 connects 8,12,7,25 pin of AD9850 chip respectively.

8. the signal generator being exclusively used in acoustic velocity measutement test according to claim 6, is characterized in that: described low-pass filtering module comprises resistance R4, R5, electric capacity C7-C7 and inductance L 1-L3; Described operation amplifier module comprises amplifier chip NE5532, resistance R1, R3 and potentiometer R2; 1 pin of amplifier chip NE5532 is the output terminal of the sine wave signal of 36KHz ~ 38KHz; Inductance L 1 and electric capacity C2 compose in parallel the first resonant circuit, inductance L 2 and electric capacity C4 compose in parallel the second resonant circuit, inductance L 3 and electric capacity C6 compose in parallel the 3rd resonant circuit, are connected between 21 pin of AD9850 chip and 3 pin of amplifier chip NE5532 after the first to the 3rd resonant circuit and resistance R3 connect successively; Be connected between 21 pin of AD9850 chip and ground after resistance C4 and electric capacity C1 parallel connection, between the node that electric capacity C3 is connected on the first resonant circuit and the second resonant circuit and ground, between the node that electric capacity C5 is connected on the second resonant circuit and the 3rd resonant circuit and ground, between the node being connected on the 3rd resonant circuit and resistance R3 after electric capacity C7 is in parallel with resistance R5 and ground; Between 1 pin that resistance R1 and potentiometer R2 is connected on amplifier chip NE5532 after connecting and ground, the swing arm of potentiometer R2 connects 1 pin of amplifier chip NE5532, the 2 pin connecting resistance R1 of amplifier chip NE5532 and the node of potentiometer R2.