CN108627570B - Digital harmonic excitation source and implementation method - Google Patents
Digital harmonic excitation source and implementation method Download PDFInfo
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- CN108627570B CN108627570B CN201810505869.XA CN201810505869A CN108627570B CN 108627570 B CN108627570 B CN 108627570B CN 201810505869 A CN201810505869 A CN 201810505869A CN 108627570 B CN108627570 B CN 108627570B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
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- H—ELECTRICITY
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- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
- H03B5/20—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator
Abstract
The invention discloses a digital harmonic excitation source and an implementation method thereof, belonging to the field of signal excitation sources and comprising the following steps: the device comprises a main control chip, a low-frequency signal generation module, a high-frequency signal generation module, a harmonic signal generation module, a signal connection jumper, an adjustable power amplification module, a load, a harmonic signal acquisition module, a liquid crystal display module and a frequency and voltage adjustment module. The preceding harmonic radio frequency module includes: the device comprises a main control chip, a low-frequency signal generation module, a high-frequency signal generation module, a harmonic signal generation module, a liquid crystal display module and a frequency and voltage adjustment module; the rear-stage power amplification module includes: the power amplifier comprises an adjustable power amplification module, a harmonic signal acquisition module and a load; the front-stage harmonic radio frequency module is connected with the rear-stage power amplification module through a signal connection jumper wire. The invention can realize the digital regulation output of the frequency and the voltage of the harmonic signal, has the function of displaying the frequency and the voltage in real time by the liquid crystal, and can accurately and stably output the power harmonic signal.
Description
Technical Field
The invention relates to the technical field of harmonic signal excitation sources, in particular to a digital harmonic excitation source and an implementation method thereof, which can apply harmonic excitation signals with specific frequency and power to a load, have the functions of digital frequency adjustment, output power adjustment and liquid crystal display, and can be applied to the technical fields of nondestructive testing of metal materials such as steel pipelines, rails, storage tanks and the like, the communication field, biomedical inspection and the like.
Background
The eddy current nondestructive testing technology has the advantages of non-contact type, no need of couplant, high testing speed, rich frequency spectrum information of received signals and the like, and is widely applied to the aspect of nondestructive testing of ferromagnetic materials. Eddy current inspection techniques include: the single-frequency eddy current detection technology, the multi-frequency eddy current detection technology, the far-field eddy current detection technology, the pulse eddy current detection technology and the like are applied to various nondestructive detection fields, and good effects are obtained. The advantages of the eddy current testing techniques described above determine the importance of the excitation source for eddy current testing.
At present, the traditional eddy current detection technology mostly adopts a single-frequency or multi-frequency high-frequency sinusoidal signal as an excitation source, and the full wall thickness detection of a tested piece cannot be realized due to the skin effect of the high-frequency signal; in addition, the traditional excitation source does not have the functions of digitally adjusting the frequency and the voltage value, has poor signal stability, high cost and larger power supply volume, does not have the functions of adjusting and displaying the frequency and the power in real time, and directly determines the use convenience of the excitation source by taking the functions of digitally adjusting and displaying as important functions in the design of the excitation source.
Disclosure of Invention
In order to solve the above problems, the present invention provides a digital harmonic excitation source and a realization method thereof, which aims to realize a harmonic excitation source using a low-frequency sinusoidal signal as a carrier and a high-frequency sinusoidal signal as a detection waveform; the harmonic excitation source can realize full wall thickness detection in steel pipelines and metal test pieces, and has the advantages of high detection sensitivity and strong penetration capability.
In order to achieve the purpose, the invention provides a digital harmonic excitation source, which comprises a front-stage harmonic radio frequency module (11) and a rear-stage power amplification module (12);
the front-stage harmonic radio frequency module (11) comprises a main control chip (1), a low-frequency signal generation module (2), a high-frequency signal generation module (3), a harmonic signal generation module (4) and a frequency and voltage adjustment module (10);
the main control chip (1) is respectively connected with the low-frequency signal generation module (2) and the high-frequency signal generation module (3), and the main control chip (1) is connected with two groups of frequency and voltage adjustment modules (10); one group of the frequency and voltage adjusting module (10) is used for adjusting the frequency and the amplitude of a low-frequency sinusoidal signal, and the other group of the frequency and voltage adjusting module (10) is used for adjusting the frequency and the amplitude of a high-frequency sinusoidal signal;
the low-frequency input end of the harmonic signal generation module (4) is connected with the output end of the low-frequency signal generation module (1), the high-frequency input end of the harmonic signal generation module is connected with the output end of the high-frequency signal generation module (2), and the harmonic signal generation module is used for performing harmonic processing on a low-frequency sinusoidal signal and a high-frequency sinusoidal signal through an addition summation circuit formed by an operational amplifier and outputting a harmonic signal source;
the rear-stage power amplification module (12) comprises an adjustable power amplification module (6) consisting of a power amplification chip and a peripheral circuit thereof, a load (7) and a harmonic signal acquisition module (8);
the input end of the adjustable power amplification module (6) is connected with the output end of the harmonic signal generation module (4) through a signal connection jumper (5), and the output end of the adjustable power amplification module is connected with the load (7); and the harmonic signal acquisition module (8) is respectively connected with the load (7) and the main control chip (1) and is used for acquiring voltage values of harmonic signals at two ends of the load (7) and transmitting the voltage values to the main control chip (1).
As a further improvement of the invention, the front-stage harmonic radio frequency module (11) also comprises a liquid crystal display module (9);
the liquid crystal display module (9) is connected with the main control chip (1) through a bus and used for displaying the low-frequency of the low-frequency sinusoidal signal, the high-frequency of the high-frequency sinusoidal signal and the harmonic voltage collected at two ends of the load (7).
As a further improvement of the invention, the main control chip (1) is an STM32 main control chip, the low-frequency signal generation module (2) and the high-frequency signal generation module (3) have the same structure, are direct digital frequency synthesis chips DDS of the same type and have the same parameters and functions.
As a further improvement of the invention, the low-frequency signal generating module (2) comprises a sinusoidal signal generator, a digital potentiometer, an operational amplifier IC3, resistors R5-R6 and a capacitor C2, the frequency and voltage adjusting module (10) comprises an external signal input device (15), and the external signal input device (15) is provided with a button S1 for increasing the frequency of the sinusoidal signal, a button S2 for reducing the frequency of the sinusoidal signal, a button S3 for increasing the voltage peak value of the sinusoidal signal and a button S4 for reducing the voltage peak value of the sinusoidal signal;
the external signal input device (15) is connected with a control pin of the main control chip (1), the main control chip (1) is respectively connected with control ends of a sine signal generator and a digital potentiometer, an OUT pin of the sine signal generator is connected with a PB end of the digital potentiometer, a PA end of the digital potentiometer is connected with a non-inverting input end of an operational amplifier IC3, an inverting input end of an operational amplifier IC3 is connected with an output end of an operational amplifier IC3 through a resistor R5, an inverting input end of the operational amplifier IC3 is connected with a GND end through R6, and a forward power supply end of the operational amplifier IC3 is connected with a GND end through a capacitor C2;
output voltage V of sine signal generatorDDSAnd operational amplifier IC3 output voltage Vout1The proportion relation is as follows:
as a further improvement of the invention, the harmonic signal generation module (4) comprises operational amplifiers IC 2A-IC 2B, resistors R1-R4 and a capacitor C1;
the low-frequency input end of the harmonic signal generation module (4) is connected with a resistor R1, the high-frequency input end of the harmonic signal generation module is connected with a resistor R2, and then the low-frequency input end and the high-frequency input end of the harmonic signal generation module are connected in parallel and input to the inverting input end of an operational amplifier IC2A, the output end of the operational amplifier IC2A is connected with the inverting input end through a resistor R4, and the non-inverting input end of the operational amplifier IC2A is connected with a GND end through a resistor R3; the output end of the operational amplifier IC2A is connected with the non-inverting input end of the operational amplifier IC2B through a capacitor C1, the output end of the operational amplifier IC2B is connected with the inverting input end, and the output end of the operational amplifier IC2B outputs a harmonic signal source.
As a further improvement of the invention, the signal connection jumper (5) is a parallel two-wire link, namely a positive electrode connection jumper and a negative electrode connection jumper; the front end is connected with the front-stage harmonic radio frequency module (11), and the rear end is connected with the rear-stage power amplification module (12).
As a further improvement of the present invention, the adjustable power amplification module (6) is composed of a signal amplification module (13) and a power amplification module (14), an input end of the signal amplification module (13) is connected to an output end of the harmonic signal generation module (4) through a signal connection jumper (5), an output end of the signal amplification module is connected to an input end of the power amplification module (14), and an output end of the power amplification module (14) is connected to the load (7);
the signal amplification module (13) is composed of a second-order voltage-controlled voltage source low-pass filter, and comprises operational amplifiers IC 4A-IC 4B, resistors R10-R14 and an adjustable resistor RPAnd capacitors C11-C12; adjustable resistor RPOne fixed end of the operational amplifier IC4 is connected with the input end of the signal amplification module (13), the other fixed end of the operational amplifier IC4 is connected with the GND end, the adjustable end of the operational amplifier IC4 is connected with the inverting input end of the operational amplifier IC4A after being connected with the resistor R10 in series, the inverting input end of the operational amplifier IC4A is connected with the output end through the resistor R14, and the non-inverting input end of the operational amplifier IC4A is connected with the GND end through the resistor R13; the output end of the operational amplifier IC4A is connected with the non-inverting input end of the operational amplifier IC4B through resistors R11 and R12 which are connected in series, the inverting input end of the operational amplifier IC4B is connected with the output end, the pin at the right end of the resistor R11 is connected with the output end of the operational amplifier IC4B through a capacitor C11, and the pin at the right end of the resistor R12 is connected with the GND end through a capacitor C12;
the power amplification module (14) comprises a power amplifier IC5, resistors R15-R21 and capacitors C3-C6, the output end of an operational amplifier IC4B is connected with the non-inverting input end of a power amplifier IC5 through the resistor R15, the non-inverting input end of the power amplifier IC5 is connected with the inverting input end through the capacitor C3, the inverting input end of the power amplifier IC5 is connected with the GND end through the resistor R16 and the resistor R17 which are connected in series, the inverting input end of the power amplifier IC5 is connected with the output end through the resistor R16 and the resistor R18 which are connected in series, the inverting input end of the power amplifier IC5 is connected with the output end through the resistor R16, the capacitor C4 and the resistor R19 which are connected in series, the output end of the power amplifier IC5 is connected with the GND end through the capacitor C5 and the resistor R20 which are connected in series, and the output end of the power amplifier IC5 is connected with the load (7) through the resistor R21 and the capacitor C6 which are connected in series.
As a further improvement of the invention, the values of the resistor R11, the capacitor C11, the resistor R12 and the capacitor C12 are as follows:
according to the cut-off frequency foβ is 1, and R11R 12R 10(2-4)And omega, determining the value range of the capacitor C11 according to the formula (1):
the capacitance C11 takes on the following values according to the existing capacitance:
according to the parameters
β 1, unity gain aF1, the capacitance C12 is obtained by the formula (2):
wherein the content of the first and second substances,
the resistance values of the resistors R11 and R12 are determined according to equation (3):
the power amplification of the power amplifier IC5 is:
by means of an adjustable resistor RPThe power adjustment knob of (2) adjusts for harmonic signal power variations.
As a further improvement of the invention, the harmonic signal acquisition module (8) comprises an ABS4 rectifier bridge and resistors R7-R9;
the input end of the harmonic signal acquisition module (8) is connected with resistors R7 and R8 which are connected in parallel and then connected with a GND end through a resistor R9, the alternating current positive input end of an ABS4 rectifier bridge is connected with the left end pin of a resistor R9, the alternating current negative input end and the direct current negative output end are connected with the GND end, and the direct current positive output end is connected with the main control chip (1);
analog input end input voltage VADCAnd harmonic voltage VOUTThe relationship of (1) is:
the invention also provides a method for realizing the digital harmonic excitation source, which comprises the following steps:
step 3, the harmonic signal source enters a rear-stage power amplification module (12) through a signal connection jumper (5) to amplify the power of the harmonic signal; the harmonic signal acquisition module (8) acquires and processes the voltage values of the harmonic signals at the two ends of the load (7), and the voltage values are displayed by the liquid crystal display module (9).
Compared with the prior art, the invention has the beneficial effects that:
in the aspect of designing a digital harmonic excitation source, the harmonic signal source is output based on the main control chip, the signal generation module and the harmonic signal generation module, and the harmonic excitation source has the advantages of high frequency resolution, small time delay and stable harmonic signal; meanwhile, the harmonic excitation source is added with a digital frequency adjusting module, a liquid crystal display module and an adjustable power amplifying module, so that the harmonic excitation source has the advantages of simplicity, convenience, stability and reliability in the aspects of frequency, signal amplitude and power adjustment; the whole machine is debugged through a program, so that the device has the advantages of simple structure and convenience in debugging;
in the aspect of nondestructive testing application, the harmonic excitation source can output harmonic signals which take low-frequency signals as carriers and high-frequency signals as detection waveforms, and the low skin effect of the low-frequency signals and the high-frequency detection signals with high detection sensitivity of the high-penetrability carriers are utilized to realize the full-wall thickness detection of the steel pipeline, so that the effective detection of the damaged part of the steel pipeline is realized.
Drawings
FIG. 1 is a schematic structural diagram of a digital harmonic excitation source according to an embodiment of the present invention;
FIG. 2 is a schematic circuit diagram of the main control chip, the low frequency signal generating module, the liquid crystal display module and the frequency and voltage adjusting module shown in FIG. 1;
FIG. 3 is a schematic circuit diagram of the harmonic signal generating module of FIG. 1;
FIG. 4 is a schematic diagram of a two-stage circuit of the adjustable power amplifier module of FIG. 1;
fig. 5 is a schematic circuit diagram of the harmonic signal acquisition module of fig. 1.
In the figure:
1. a main control chip; 2. a low frequency signal generation module; 3. a high-frequency signal generating module; 4. a harmonic signal generation module; 5. a signal connection jumper wire; 6. an adjustable power amplification module; 7. a load; 8. a harmonic signal acquisition module; 9. a liquid crystal display module; 10. a frequency and voltage adjustment module; 11. a preceding harmonic radio frequency module; 12. a rear-stage power amplification module; 13. a signal amplification module; 14. a power amplification module; 15. an external signal input device.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention is described in further detail below with reference to the attached drawing figures:
the invention provides a digital harmonic signal excitation source and an implementation method thereof, wherein the excitation source has the functions of digitally adjusting and displaying the output frequency and amplitude of a harmonic signal in real time, and can limit the volume of the whole machine within a very small range; meanwhile, the harmonic excitation source utilizes a low-frequency signal carrier wave with low skin effect to deeply detect a high-frequency signal with high sensitivity so as to realize the full-wall thickness detection of the steel pipeline.
As shown in fig. 1, the present invention provides a digital harmonic excitation source, which includes a front-stage harmonic rf module 11 and a rear-stage power amplifying module 12; the front-stage harmonic radio frequency module 11 is arranged in front of the rear-stage power amplification module 12, is divided into two groups of discrete modules and is connected through a signal connection jumper 5; wherein:
the pre-harmonic radio frequency module 11 comprises a main control chip 1, a low-frequency signal generation module 2, a high-frequency signal generation module 3, a harmonic signal generation module 4, a liquid crystal display module 9 and a frequency and voltage adjustment module 10; the main control chip 1 is respectively connected with the low-frequency signal generation module 2 and the high-frequency signal generation module 3, and the main control chip 1 is connected with two groups of frequency and voltage adjustment modules 10; one group of frequency and voltage adjusting modules 10 are used for adjusting the frequency and amplitude of the low-frequency sinusoidal signals, the other group of frequency and voltage adjusting modules 10 are used for adjusting the frequency and amplitude of the high-frequency sinusoidal signals, and the liquid crystal display module 9 is connected with the main control chip 1 through a bus; the harmonic signal generation module 4 is connected with the output end of the low-frequency signal generation module 1 at the low-frequency input end and connected with the output end of the high-frequency signal generation module 2 at the high-frequency input end, and is used for performing harmonic processing on the low-frequency sinusoidal signal and the high-frequency sinusoidal signal through an addition summation circuit formed by an operational amplifier and outputting a harmonic signal source;
the post-stage power amplification module 12 comprises an adjustable power amplification module 6, a load 7 and a harmonic signal acquisition module 8, wherein the adjustable power amplification module 6 consists of a power amplification chip and a peripheral circuit thereof; the input end of the adjustable power amplification module 6 is connected with the output end of the harmonic signal generation module 4 through a signal connection jumper 5, and the output end of the adjustable power amplification module is connected with a load 7; the harmonic signal acquisition module 8 is respectively connected with the load 7 and the main control chip 1, and is used for acquiring voltage values of harmonic signals at two ends of the load 7, transmitting the voltage values to the main control chip 1, and displaying the voltage values in the liquid crystal display module 9. Specifically, the method comprises the following steps:
as shown in FIG. 2, the main control chip 1 of the present invention is an STM32 chip, the main control chip 1 is connected with the low frequency signal generation module 2 and the high frequency signal generation module 3 through SPI interface, the low frequency signal generation module 2 is connected with the high frequency signal generation module 3The frequency synthesizer DDS and its peripheral circuits are composed of a low frequency signal generation module 2 and a high frequency signal generation module 3, which have the same structure and the same parameters and functions, and fig. 2 only illustrates the low frequency signal generation module 2 as an example. The low-frequency signal generation module 2 and the high-frequency signal generation module 3 are used for respectively generating a low-frequency sinusoidal signal and a high-frequency sinusoidal signal, the low-frequency signal generation module 2 comprises a sinusoidal signal generator, a digital potentiometer, an operational amplifier IC3, resistors R5-R6 and a capacitor C2, an SPI (serial peripheral interface) of a main control chip 1 is respectively connected with control ends of the sinusoidal signal generator and the digital potentiometer, an OUT pin of the sinusoidal signal generator is connected with a PB (lead-OUT) end of the digital potentiometer, a PA (power amplifier) end of the digital potentiometer is connected with a non-inverting input end of an operational amplifier IC3, an inverting input end of the operational amplifier IC3 is connected with an output end of the operational amplifier IC3 through the resistor R5, an inverting input end of the operational amplifier IC3 is connected with a GND (ground) end through the R6, a forward power supply end of the operational amplifier IC3 is connected with a GND end through the capacitor C2, and a power supply voltage of the operational amplifier IC3 is +/-5V; output voltage V of sine signal generatorDDSAnd operational amplifier IC3 output voltage Vout1The proportion relation is as follows:
as shown in fig. 2, the frequency and voltage adjusting module 10 of the present invention includes an external signal input device 15, wherein the external signal input device 15 is connected to a control pin of the main control chip 1 and provides a frequency and voltage adjusting control signal to the main control chip 1; the main control chip 1 adjusts the frequency of the output signal of the sine signal generator according to the frequency control signal, adjusts the resistance value of the digital potentiometer according to the voltage control signal and further controls the output voltage Vout1. Included in the external signal input device 15 are four buttons, which are a button S1 for increasing the frequency of the sinusoidal signal, a button S2 for decreasing the frequency of the sinusoidal signal, a button S3 for increasing the voltage peak-to-peak value of the sinusoidal signal, and a button S4 for decreasing the voltage peak-to-peak value of the sinusoidal signal, respectively. The frequency and voltage adjusting module 10 of the present invention is composed of two module sets with the same structure and parametersThen, the frequency and voltage of the low frequency signal generation module 2 and the high frequency signal generation module 3 are controlled respectively.
As shown in fig. 2, the liquid crystal display module 9 of the present invention is a liquid crystal display screen, and is connected to the main control chip 1 through a data bus and an address bus; meanwhile, the specific content displayed by the liquid crystal display module 9 is as follows: the low frequency of the low frequency sinusoidal signal, the high frequency of the high frequency sinusoidal signal and the collected harmonic voltage across the load 7.
As shown in fig. 3, the harmonic signal generation module 4 of the present invention includes operational amplifiers IC 2A-IC 2B, resistors R1-R4 and a capacitor C1, and the power supply voltages of the operational amplifiers IC 2A-IC 2B are ± 15V; the low-frequency input end of the harmonic signal generation module 4 is connected with a resistor R1, and the high-frequency input end is connected with a resistor R2, and then the low-frequency input end and the high-frequency input end are connected in parallel and input to the inverting input end of an operational amplifier IC2A, the output end of the operational amplifier IC2A is connected with the inverting input end through a resistor R4, and the non-inverting input end of the operational amplifier IC2A is connected with a GND end through a resistor R3; the output end of the operational amplifier IC2A is connected with the non-inverting input end of the operational amplifier IC2B through a capacitor C1, the output end of the operational amplifier IC2B is connected with the inverting input end, and the output end of the operational amplifier IC2B outputs a harmonic signal source; and the output end of the harmonic signal generation module 4 outputs a harmonic signal source with a voltage peak-to-peak value of 4V.
As shown in fig. 1, the signal connection jumper 5 of the present invention is a parallel two-wire link, which is a positive electrode connection jumper and a negative electrode connection jumper respectively; the front end is connected to the front harmonic rf module 11, and the rear end is connected to the rear power amplifier module 12.
As shown in fig. 4, the adjustable power amplification module 6 of the present invention is composed of a signal amplification module 13 and a power amplification module 14, wherein an input end of the signal amplification module 13 is connected to an output end of the harmonic signal generation module 4 through a signal connection jumper 5, an output end of the signal amplification module is connected to an input end of the power amplification module 14, and an output end of the power amplification module 14 is connected to a load 7; wherein:
the signal amplification module 13 includes operational amplifiers IC4A to IC4B (OPA2604AP) as an inverting proportional operational amplifier and a second-order voltage-controlled voltage source low-pass filter. It comprises operational amplifiers IC 4A-IC 4B, resistors R10-R14 and adjustable power supplyResistance RPAnd capacitors C11-C12, and the power supply voltage of operational amplifiers IC 4A-IC 4B is +/-15V; adjustable resistor RPOne fixed end of the operational amplifier is connected with the input end of the signal amplification module 13, the other fixed end of the operational amplifier is connected with the GND end, the adjustable end of the operational amplifier is connected with the inverting input end of the operational amplifier IC4A after being connected with the resistor R10 in series, the inverting input end of the operational amplifier IC4A is connected with the output end through the resistor R14, the non-inverting input end of the operational amplifier IC4A is connected with the GND end through the resistor R13, and the amplification factor of the inverse proportion operational amplifier is as follows:
the output end of the operational amplifier IC4A is connected with the non-inverting input end of the operational amplifier IC4B through resistors R11 and R12 which are connected in series, the inverting input end of the operational amplifier IC4B is connected with the output end, the right end pin of the resistor R11 is connected with the output end of the operational amplifier IC4B through a capacitor C11, the right end pin of the resistor R12 is connected with the GND end through a capacitor C12, a second-order RC filter is formed by the resistor R11, the capacitor C11, the resistor R12 and the capacitor C12, a voltage follower is formed by the IC4B, and the two groups of circuits form a second-order voltage-controlled voltage source low-pass filter.
The values of the resistor R11, the capacitor C11, the resistor R12 and the capacitor C12 in the second-order RC filter are as follows:
according to the cut-off frequency foβ is 1, and R11R 12R 10(2-4)And omega, determining the value range of the capacitor C11 according to the formula (1):
the capacitance C11 takes on about:
according to the parameters
β 1, unity gain aF1, the capacitance C12 is obtained by the formula (2):
wherein the content of the first and second substances,
the resistance values of the resistors R11 and R12 are determined according to equation (3):
the power amplification module 14 comprises a power amplifier IC5(LM3886TF), resistors R15-R21 and capacitors C3-C6, wherein the power supply voltage of the power amplifier IC5 is +/-36V; the output end of the operational amplifier IC4B is connected with the non-inverting input end of the power amplifier IC5 through a resistor R15, the non-inverting input end of the power amplifier IC5 is connected with the inverting input end through a capacitor C3, the inverting input end of the power amplifier IC5 is connected with the GND end through a resistor R16 and a resistor R17 which are connected in series, the inverting input end of the power amplifier IC5 is connected with the output end through a resistor R16 and a resistor R18 which are connected in series, the inverting input end of the power amplifier IC5 is connected with the output end through a resistor R16, a capacitor C4 and a resistor R19 which are connected in series, the output end of the power amplifier IC5 is connected with the GND end through a capacitor C5 and a resistor R20 which are connected in series, and the output end of the power amplifier IC5 is a harmonic signal output end through a resistor R21 and a capacitor C6 which are connected in series and is connected with a load 7; the power amplification of the power amplifier IC5 is:
by means of an adjustable resistor RPThe power adjustment knob of (2) adjusts for harmonic signal power variations.
As shown in FIG. 5, the harmonic signal acquisition module 8 of the present invention includes an ABS4 rectifier bridge and resistors R7-R9; the input end of the harmonic signal acquisition module 8 is connected with resistors R7 and R8 which are connected in parallel and then connected with the GND end through a resistor R9, the AC positive input end (AC +) of the ABS4 rectifier bridge is connected with the left end pin of the resistor R9, namely, the point A and the AC negative input end (AC-)The direct current negative output end (DC-) is connected with the GND end, and the direct current positive output end (DC +) is connected with an ADC module channel of the main control chip 1; the harmonic signal acquisition module 8 is connected in parallel with two ends of the load 7 and is used for performing precise voltage division, current limitation and alternating current-to-direct current operation on the harmonic signals. The resistors R7 and R8 in the harmonic signal acquisition module 8 are precision resistors; the parameters of the ABS4 rectifier bridge are as follows: inverted repetitive peak voltage (V)RRM) 400V, maximum voltage effective value (V)RMS) 280V, maximum DC blocking voltage (V)DC) At 400V, average current (I) in forward directionF) 1A, forward surge peak current (I)FSM) Is 30A. The harmonic signal acquisition module 8 obtains an analog voltage signal within the range of 0V-3V, and the analog-to-digital conversion module of the main control chip 1 converts the analog voltage signal into digital quantity, so that the digital display of the voltage value of the output harmonic signal is realized.
The invention also provides a method for realizing the digital harmonic excitation source, which comprises the following steps:
step 3, the harmonic signal source enters a rear-stage power amplification module 12 through a signal connection jumper 5 to amplify the power of the harmonic signal; the harmonic signal acquisition module 8 acquires and processes the voltage values of the harmonic signals at the two ends of the load 7, and the voltage values are displayed by the liquid crystal display module 9; wherein, the resistors R7, R8 and R9 in the harmonic signal acquisition module 8 are high-power resistors, and the input voltage V is input at the analog input endADCAnd harmonic voltage VOUTThe relationship of (1) is:
the invention has the beneficial effects that:
in the aspect of digital harmonic excitation source design, the harmonic signal source is output based on the main control chip STM32, the signal generation module (direct digital synthesis chip DDS) and the harmonic signal generation module, and the harmonic excitation source has the advantages of high frequency resolution, small time delay and stable harmonic signal; meanwhile, the harmonic excitation source is added with a digital frequency adjusting module, a liquid crystal display module and an adjustable power amplifying module, so that the harmonic excitation source has the advantages of simplicity, convenience, stability and reliability in the aspects of frequency, signal amplitude and power adjustment; the whole machine is debugged through a program, so that the device has the advantages of simple structure and convenience in debugging;
in the aspect of nondestructive testing application, the harmonic excitation source can output harmonic signals which take low-frequency signals as carriers and high-frequency signals as detection waveforms, and the low skin effect of the low-frequency signals and the high-frequency detection signals with high detection sensitivity of the high-penetrability carriers are utilized to realize the full-wall thickness detection of the steel pipeline, so that the effective detection of the damaged part of the steel pipeline is realized.
The present invention has been described in terms of the preferred embodiment, and it is not intended to be limited to the embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A digital harmonic excitation source is characterized by comprising a front-stage harmonic radio frequency module (11) and a rear-stage power amplification module (12);
the front-stage harmonic radio frequency module (11) comprises a main control chip (1), a low-frequency signal generation module (2), a high-frequency signal generation module (3), a harmonic signal generation module (4) and a frequency and voltage adjustment module (10);
the main control chip (1) is respectively connected with the low-frequency signal generation module (2) and the high-frequency signal generation module (3), and the main control chip (1) is connected with two groups of frequency and voltage adjustment modules (10); one group of the frequency and voltage adjusting module (10) is used for adjusting the frequency and the amplitude of a low-frequency sinusoidal signal, and the other group of the frequency and voltage adjusting module (10) is used for adjusting the frequency and the amplitude of a high-frequency sinusoidal signal;
the low-frequency input end of the harmonic signal generation module (4) is connected with the output end of the low-frequency signal generation module (2), the high-frequency input end of the harmonic signal generation module is connected with the output end of the high-frequency signal generation module (3), and the harmonic signal generation module is used for performing harmonic processing on a low-frequency sinusoidal signal and a high-frequency sinusoidal signal through an addition summation circuit formed by an operational amplifier and outputting a harmonic signal source;
the rear-stage power amplification module (12) comprises an adjustable power amplification module (6) consisting of a power amplification chip and a peripheral circuit thereof, a load (7) and a harmonic signal acquisition module (8);
the input end of the adjustable power amplification module (6) is connected with the output end of the harmonic signal generation module (4) through a signal connection jumper (5), and the output end of the adjustable power amplification module (6) is connected with the load (7); the harmonic signal acquisition module (8) is respectively connected with the load (7) and the main control chip (1) and is used for acquiring voltage values of harmonic signals at two ends of the load (7) and transmitting the voltage values to the main control chip (1);
the main control chip (1) is an STM32 main control chip, the low-frequency signal generation module (2) and the high-frequency signal generation module (3) have the same structure, are direct digital frequency synthesis chips DDS of the same type and have the same parameters and functions;
the output voltage amplitudes of the low-frequency signal generation module (2) and the high-frequency signal generation module (3) are equal;
the harmonic signal generation module (4) comprises operational amplifiers IC 2A-IC 2B, resistors R1-R4 and a capacitor C1;
the low-frequency input end of the harmonic signal generation module (4) is connected with a resistor R1, the high-frequency input end of the harmonic signal generation module is connected with a resistor R2, and then the harmonic signal is input to the inverting input end of an operational amplifier IC2A in parallel, the output end of the operational amplifier IC2A is connected with the inverting input end through a resistor R4, and the non-inverting input end of the operational amplifier IC2A is connected with a GND end through a resistor R3; the output end of the operational amplifier IC2A is connected with the non-inverting input end of the operational amplifier IC2B through a capacitor C1, the output end of the operational amplifier IC2B is connected with the inverting input end, and the output end of the operational amplifier IC2B outputs a harmonic signal source;
the digital harmonic excitation source is used for detecting the full wall thickness of the steel pipeline and the metal test piece.
2. The digital harmonic excitation source of claim 1 wherein the front harmonic rf module (11) further comprises a liquid crystal display module (9);
the liquid crystal display module (9) is connected with the main control chip (1) through a bus and used for displaying the low-frequency of the low-frequency sinusoidal signal, the high-frequency of the high-frequency sinusoidal signal and the harmonic voltage collected at two ends of the load (7).
3. The digital harmonic excitation source as claimed in claim 1, wherein the low frequency signal generation module (2) comprises a sinusoidal signal generator, a digital potentiometer, an operational amplifier IC3, resistors R5-R6 and a capacitor C2, the frequency and voltage adjustment module (10) comprises an external signal input device (15), the external signal input device (15) is provided with a button S1 for increasing the frequency of the sinusoidal signal, a button S2 for decreasing the frequency of the sinusoidal signal, a button S3 for increasing the voltage peak-to-peak value of the sinusoidal signal and a button S4 for decreasing the voltage peak-to-peak value of the sinusoidal signal;
the external signal input device (15) is connected with a control pin of the main control chip (1), the main control chip (1) is respectively connected with control ends of a sine signal generator and a digital potentiometer, an OUT pin of the sine signal generator is connected with a PB end of the digital potentiometer, a PA end of the digital potentiometer is connected with a non-inverting input end of an operational amplifier IC3, an inverting input end of an operational amplifier IC3 is connected with an output end of an operational amplifier IC3 through a resistor R5, an inverting input end of the operational amplifier IC3 is connected with a GND end through R6, and a forward power supply end of the operational amplifier IC3 is connected with a GND end through a capacitor C2;
output voltage V of sine signal generatorDDSAnd operational amplifier IC3 output voltage Vout1The proportion relation is as follows:
4. the digital harmonic excitation source according to claim 1, wherein the signal connection jumpers (5) are parallel two-wire links, positive and negative connection jumpers, respectively; the front end is connected with the front-stage harmonic radio frequency module (11), and the rear end is connected with the rear-stage power amplification module (12).
5. The digital harmonic excitation source according to claim 1, wherein the adjustable power amplification module (6) is composed of a signal amplification module (13) and a power amplification module (14), wherein an input end of the signal amplification module (13) is connected with an output end of the harmonic signal generation module (4) through a signal connection jumper (5), an output end of the signal amplification module is connected with an input end of the power amplification module (14), and an output end of the power amplification module (14) is connected with the load (7);
the signal amplification module (13) is composed of a second-order voltage-controlled voltage source low-pass filter and comprises operational amplifiers IC 4A-IC 4B, resistors R10-R14 and an adjustable resistor RPAnd capacitors C11-C12; adjustable resistor RPOne fixed end of the operational amplifier IC4 is connected with the input end of the signal amplification module (13), the other fixed end of the operational amplifier IC4 is connected with the GND end, the adjustable end of the operational amplifier IC4 is connected with the inverting input end of the operational amplifier IC4A after being connected with the resistor R10 in series, the inverting input end of the operational amplifier IC4A is connected with the output end through the resistor R14, and the non-inverting input end of the operational amplifier IC4A is connected with the GND end through the resistor R13; the output end of the operational amplifier IC4A is connected with the non-inverting input end of the operational amplifier IC4B through resistors R11 and R12 which are connected in series, the inverting input end of the operational amplifier IC4B is connected with the output end, the pin at the right end of the resistor R11 is connected with the output end of the operational amplifier IC4B through a capacitor C11, and the pin at the right end of the resistor R12 is connected with the GND end through a capacitor C12;
the power amplification module (14) comprises a power amplifier IC5, resistors R15-R21 and capacitors C3-C6, the output end of an operational amplifier IC4B is connected with the non-inverting input end of a power amplifier IC5 through the resistor R15, the non-inverting input end of the power amplifier IC5 is connected with the inverting input end through the capacitor C3, the inverting input end of the power amplifier IC5 is connected with the GND end through the resistor R16 and the resistor R17 which are connected in series, the inverting input end of the power amplifier IC5 is connected with the output end through the resistor R16 and the resistor R18 which are connected in series, the inverting input end of the power amplifier IC5 is connected with the output end through the resistor R16, the capacitor C4 and the resistor R19 which are connected in series, the output end of the power amplifier IC5 is connected with the GND end through the capacitor C5 and the resistor R20 which are connected in series, and the output end of the power amplifier IC5 is connected with the load (7) through the resistor R21 and the capacitor C6 which are connected in series.
6. The digital harmonic drive source of claim 5 wherein the resistors R11, C11, R12 and C12 are selected from the group consisting of:
according to the cut-off frequency foβ is 1, and R11R 12R 102-4And omega, determining the value range of the capacitor C11 according to the formula (1):
the capacitance C11 takes on the following values according to the existing capacitance:
according to the parameters
β 1, unity gain aF1, the capacitance C12 is obtained by the formula (2):
the resistance values of the resistors R11 and R12 are determined according to equation (3):
wherein the content of the first and second substances,
the power amplification of the power amplifier IC5 is:
by means of an adjustable resistor RPThe power adjustment knob of (2) adjusts for harmonic signal power variations.
7. The digital harmonic excitation source as claimed in claim 1, wherein the harmonic signal acquisition module (8) comprises an ABS4 rectifier bridge and resistors R7-R9;
the input end of the harmonic signal acquisition module (8) is connected with resistors R7 and R8 which are connected in parallel and then connected with a GND end through a resistor R9, the alternating current positive input end of an ABS4 rectifier bridge is connected with the left end pin of a resistor R9, the alternating current negative input end and the direct current negative output end are connected with the GND end, and the direct current positive output end is connected with the main control chip (1);
analog input end input voltage VADCAnd harmonic voltage VOUTThe relationship of (1) is:
8. a method for implementing a digital harmonic excitation source according to any one of claims 1 to 7, comprising:
step 1, a low-frequency signal generation module (2) and a high-frequency signal generation module (3) jointly output low-frequency sine wave signals and high-frequency sine wave signals with equal voltage amplitudes;
step 2, the harmonic signal generation module (4) realizes the output of a harmonic signal source from a high-frequency signal carrier to a low-frequency signal, and adjusts the frequency and voltage values of the low-frequency and high-frequency signals through the frequency and voltage adjustment module (10);
step 3, the harmonic signal source enters a rear-stage power amplification module (12) through a signal connection jumper (5) to amplify the power of the harmonic signal; the harmonic signal acquisition module (8) acquires and processes the voltage values of the harmonic signals at the two ends of the load (7), and the voltage values are displayed by the liquid crystal display module (9).
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| CN113411095B (en) * | 2021-06-30 | 2022-04-01 | 杭州电子科技大学 | Induction coil signal receiving circuit based on numerical control resonant frequency |
| CN113676180B (en) * | 2021-08-25 | 2023-08-29 | 温州大学激光与光电智能制造研究院 | DDS-based intelligent excitation circuit and vibration pickup signal amplification circuit of resonant micro-cantilever sensor |
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