CN113484932A - Anti-interference inductive proximity switch measuring system and method - Google Patents
Anti-interference inductive proximity switch measuring system and method Download PDFInfo
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- CN113484932A CN113484932A CN202110730477.5A CN202110730477A CN113484932A CN 113484932 A CN113484932 A CN 113484932A CN 202110730477 A CN202110730477 A CN 202110730477A CN 113484932 A CN113484932 A CN 113484932A
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- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V13/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
An anti-interference inductive proximity switch measuring system and method comprises a processor, a low-pass filter, an alternating current bridge, a metal target, a differential acquisition processing circuit, a frequency mixing module and an A/D conversion circuit; one path of the processor, the low-pass filter and the alternating current bridge are sequentially connected, and the metal target is arranged on the side face of the alternating current bridge; the alternating current bridge is provided with two paths of outputs which are connected to the differential acquisition processing circuit, the frequency mixing module and the A/D conversion circuit are sequentially connected, and the output end of the A/D conversion circuit is connected with the processor. The invention greatly improves the anti-interference capability of the proximity switch, solves the problem of mutual interference between the proximity switches while ensuring the measurement distance, greatly improves the output performance of the proximity switch, and realizes the application of the proximity switch in pairs or multiple uses at a short distance.
Description
Technical Field
The invention belongs to the technical field of proximity switch measurement, and particularly relates to an anti-interference inductive proximity switch measurement system and method.
Background
Inductive proximity switches detect conductive metals based on the principle of eddy currents. The inductive approach switch is composed of LC high-frequency oscillator and amplifying circuit, and can generate eddy current on the surface of metal object when it approaches the metal object by using oscillating induction head capable of generating electromagnetic field. This eddy current reacts against the proximity switch, damping the ability of the proximity switch to oscillate. The parameter of the internal circuit of the oscillating signal of the induction head changes, so that whether a metal object approaches is identified, and the on or off of the switch is controlled.
Proximity switch can not wear and tear and damage detected object, and reaction rate is fast, and long service life can adapt to abominable detection environment such as aquatic, oil simultaneously, but easily receives other proximity switch influences on every side.
Some proximity switches can also be used in pairs, but the measurement distance is generally not more than 4mm, because the probe itself does not radiate enough energy, so the detection distance is short, and the capability of other proximity switches is affected.
Therefore, the essence of solving the mutual influence between the proximity switches is to improve the anti-interference capability of the inductive proximity switches, and particularly resist the influence of other proximity switches in a paired use environment or a dual-redundancy use environment.
Disclosure of Invention
The present invention is directed to a system and method for measuring an inductance type proximity switch to prevent interference.
In order to achieve the purpose, the invention has the following technical effects:
an anti-interference inductive proximity switch measuring system comprises a processor, a low-pass filter, an alternating current bridge, a metal target, a differential acquisition processing circuit, a frequency mixing module and an A/D conversion circuit; one path of the processor, the low-pass filter and the alternating current bridge are sequentially connected, and the metal target is arranged on the side face of the alternating current bridge; the alternating current bridge is provided with two paths of outputs which are connected to the differential acquisition processing circuit, the frequency mixing module and the A/D conversion circuit are sequentially connected, and the output end of the A/D conversion circuit is connected with the processor.
Further, the alternating current bridge comprises a test bridge arm and a compensation bridge arm, the test bridge arm comprises a test capacitor, a test coil and a test resistor, and the test capacitor, the test coil and the test resistor are connected in sequence; the compensation bridge arm comprises a compensation capacitor, a compensation coil and a compensation resistor, wherein the compensation capacitor, the compensation coil and the compensation resistor are sequentially connected; the test bridge arm outputs a second acquisition signal, and the compensation bridge arm outputs a first acquisition signal.
Further, the metal target is located on the side of the test coil.
Furthermore, the impedance states of the test bridge arm and the compensation bridge arm are completely consistent on the premise of not adding the influence of a metal target; the second acquisition signal and the first acquisition signal are connected with a differential acquisition processing circuit.
Further, the processor outputs a TTL excitation signal, and the low pass filter limits the frequency to be less than a multiple of the frequency of the TTL excitation signal.
Furthermore, the differential acquisition processing circuit outputs a sinusoidal signal to be detected, the first acquisition signal, the second acquisition signal and the TTL excitation signal have the same frequency f, and the amplitude and the phase are different.
Furthermore, the other path of the processor is connected with the frequency mixing module; the filter circuit in the mixing module contains a limiting frequency f, the filter circuit and the multiplying circuit in the mixing module form a band-pass filter, and the limiting frequency of the band-pass filter is in a range of f-f, f + f; and multiplying the TTL excitation signal and the sine signal to be detected, and forming the analog quantity signal through a filter circuit in the frequency mixing module.
Furthermore, after the multiplication circuit and the filter circuit of the mixing module, the obtained analog quantity signal only retains the constant component after multiplication.
Further, the interference-proof inductive proximity switch measuring method comprises the following steps:
the processor generates a TTL excitation signal, a sinusoidal signal with the same frequency as the TTL excitation signal is formed after the TTL excitation signal passes through the low-pass filter, and the sinusoidal signal enters the alternating current bridge to form a test loop;
after a first acquisition signal and a second acquisition signal output by the alternating current bridge pass through the differential acquisition processing circuit, an output sine signal to be detected and a TTL excitation signal enter the frequency mixing module together to obtain an analog quantity signal;
the size of the analog quantity signal can generate corresponding change along with the change of the distance between the metal target and the proximity switch probe, after the analog quantity signal passes through the A/D conversion circuit, the digital quantity signal is sent into the processor, and the processor calculates the distance between the metal target and the proximity switch probe through the lumped circuit.
Compared with the prior art, the invention has the following technical effects:
the invention adopts the phase-locked amplification principle to process signals, so that the product is sensitive to frequency signals in a certain specific range and is insensitive to signals in other frequency ranges. Through setting up the sensitive interval of different frequencies of adjacent proximity switch, not only improved proximity switch's interference killing feature in the environment greatly, also improved proximity switch and resisted other proximity switch's around interference, solved the mutual interference's between the switch the condition.
The invention greatly improves the anti-interference capability of the proximity switch, solves the problem of mutual interference between the proximity switches while ensuring the measurement distance, greatly improves the output performance of the proximity switch, and realizes the application of the proximity switch in pairs or multiple uses at a short distance.
Drawings
Fig. 1 is a schematic diagram of the patent.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
referring to fig. 1, the present invention discloses an interference-proof inductive proximity switch measuring method, which includes a processor 10, a low pass filter 12, an ac bridge 14 and a metal target 15, which form a main functional circuit. The first acquisition signal 16 and the second acquisition signal 17 are processed by the differential acquisition processing circuit 18, the frequency mixing module 20 and the A/D conversion circuit 22, and then sent to the processor 10 to obtain the information of the distance between the metal target 15 and the probe. Wherein the signal fed to the processor 10 varies as the distance between the metal target 15 and the probe varies. The invention adopts the phase-locked amplification principle to process signals, so that the product is sensitive to frequency signals in a certain specific range and is insensitive to signals in other frequency ranges. Through setting up the sensitive interval of different frequencies of adjacent proximity switch, not only improved proximity switch's interference killing feature in the environment greatly, also improved proximity switch and resisted other proximity switch's around interference, solved the mutual interference's between the switch the condition.
The processor 10 generates a TTL excitation signal 11, and forms a sinusoidal signal 13 having the same frequency as the TTL excitation signal 11 after passing through the low pass filter 12, and the sinusoidal signal 13 enters the ac bridge 14 to form a test loop. After a first acquisition signal 16 and a second acquisition signal 17 output by the alternating current bridge pass through a differential acquisition processing circuit 18, an output sinusoidal signal 19 to be tested and a TTL excitation signal enter a frequency mixing module 20 together to obtain an analog quantity signal 21. The magnitude of the analog signal 21 will vary with the distance of the metal target 15 from the proximity switch probe. After the analog signal 21 passes through the a/D conversion circuit 22, the digital signal 23 is sent to the processor 10. The processor 10 can solve the distance of the metal target 15 from the proximity switch probe through the circuit theory of the lumped circuit.
The low-pass filter 12 has a limiting frequency which is less than 2 times the frequency of the TTL excitation signal 11.
The alternating current bridge 14 comprises a test bridge arm and a compensation bridge arm, wherein the test bridge arm consists of a test capacitor 31, a test coil 32 and a test resistor 33; the compensation bridge arm is composed of a compensation capacitor 34, a compensation coil 35 and a compensation resistor 36.
By adjusting the parameters in the test bridge arm and the compensation bridge arm, the impedance states of the two bridge arms are completely consistent on the premise that the two bridge arms are not influenced by the metal target 15.
The test coil 32 is arranged at the position of the product probe, and the size of the signal in the test coil 32 is changed along with the distance between the metal target 15 and the probe.
The first collected signal 16, the second collected signal 17, the sinusoidal signal 19 to be measured and the TTL excitation signal 11 have the same frequency f1, but different amplitudes and phases.
And the differential acquisition processing circuit 18 performs vector difference on the first acquisition signal 16 and the second acquisition signal 17 to form the sinusoidal signal 19 to be detected.
The amplitude and the phase of the sinusoidal signal 19 to be detected are related to the distance between the metal target 15 and the probe, and the magnitude of the distance affects the magnitude and the phase of the amplitude and the phase.
The frequency mixing module 20 multiplies the TTL excitation signal 11 by the sinusoidal signal 19 to be measured, and forms the analog quantity signal 21 through a filter circuit in the frequency mixing module 20.
The filter circuit in the frequency mixing module 20 contains a limiting frequency f2, the filter circuit and the multiplying circuit form a band-pass filter, the limiting frequency of the band-pass filter is in the range of [ f1-f2, f1+ f2], and the effect of resisting the interference of the surrounding environment and the interference of other surrounding proximity switches can be achieved by adjusting f1 and f 2.
After passing through the multiplication circuit and the filter circuit of the mixing module 20, the obtained analog quantity signal 21 only retains the constant component after multiplication.
The novel tamper-proof inductive proximity switch measurement method comprises a microprocessor 40, said microprocessor 40 being adapted to perform the method and steps of any one of claims 7 to 11 in accordance with the claims.
The microprocessor 40 may integrate the microprocessor 10, the differential acquisition processing circuit 18, the mixing module 20, and the analog-to-digital conversion circuit 22.
The problems solved by the present invention are as follows:
the inductive proximity switches are susceptible to other surrounding proximity switches, and when the inductive proximity switches are used in pairs or groups and are not far away from each other, the problem of mutual interference between the switches needs to be solved.
The patent technical scheme of the invention is as follows:
the invention adopts a processor to generate square waves, and generates TTL original excitation after the square waves pass through a low-pass filter. The original excitation enters an alternating current bridge, and the capacitance and the inductance in two bridge arms of the alternating current bridge are resonated by adjusting the parameters of the alternating current bridge.
And the inductors in the alternating current bridge arms are respectively positioned in the test probe and the proximity switch, and the inductors in the proximity switch are used for temperature compensation.
And carrying out differential acquisition on output signals of the alternating current bridge arm, wherein the output signals of the differential acquisition are sinusoidal signals in direct proportion to the target distance, and the frequency of the sinusoidal signals is consistent with the original excitation frequency.
The sinusoidal signal of difference collection output gets into the mixing module, and the mixing module possesses the frequency selection function, can obtain the amplitude and the phase information of a certain specific frequency. The selection frequency of the frequency mixing module in the circuit is set to be consistent with the original excitation frequency, so that the interference of other frequency signals to the proximity switch can be greatly eliminated.
The proximity switches used in pairs are needed, and the original excitation settings in the proximity switches are similar but different in frequency, so that the electromagnetic interference between two proximity switches close to each other is greatly eliminated, and each proximity switch can be ensured to work and use normally.
The diagram in fig. 1 includes a microprocessor 10, wherein the microprocessor 10 sends out a TTL original excitation signal 11, which is converted into an intra-frequency sinusoidal signal 13 after passing through a low pass filter 12.
The same-frequency sinusoidal signal 13 enters the ac bridge 14. The alternating current bridge comprises a test loop and a compensation loop, wherein the test loop is composed of a test capacitor 31, a test coil 32 and a test resistor 33, and the compensation loop is composed of a compensation capacitor 34, a compensation coil 35 and a compensation resistor 36.
And respectively adjusting the parameters of the test capacitor 31 and the test coil 32 of the test loop and the parameters of the compensation capacitor 34 and the compensation coil 35 of the compensation loop, so that the test loop and the compensation loop resonate, and the electrical parameters of the test loop and the compensation loop are kept consistent.
The compensation loop is used for carrying out temperature compensation on the proximity switch.
The test loop output signal 17 and the compensation loop output signal 16 enter the differential acquisition circuit 18, and the test loop output signal 17, the compensation loop output signal 16 and the differential output signal 19 of the differential acquisition circuit 18 are all sinusoidal signals with the same frequency as TTL original excitation.
The phase and amplitude of the differential output signal 19 are related to the inductance and equivalent resistance of the test coil, respectively.
The differential output signal 19 passes through a mixer circuit 20 and outputs an analog signal 21 comprising phase information between the differential output signal 19 and the TTL original stimulus signal 11 and amplitude information of the differential output signal 19 itself.
The analog signal 21 is converted into a digital signal 23 by an analog-to-digital conversion circuit 22 and sent to the microprocessor 10.
The magnitude of the differential output signal 19 depends on the magnitude of the test loop output signal 17 and the compensation loop output signal 16.
The magnitude of the test loop output signal 17 depends on the relative magnitude of the electrical parameter of the test coil 32 in the test loop.
The magnitude of the compensation loop output signal 16 depends on the relative magnitude of the compensation coil 35 electrical parameter in the compensation loop.
The magnitude of the electrical parameters of the test coil 32 are affected by the distance of the test target and the test probe, temperature, and other environmental influences.
The magnitude of the electrical parameter of the compensation coil 35 is affected by temperature and other environments, and is insensitive to the distance between the test target and the test probe.
The frequencies of the internal TTL original excitations 11 of the proximity switches, mounted in pairs or groups, are close to each other and are different from each other.
Similarly, the internal TTL original excitation 11 has a different frequency, which causes the frequency of the same-frequency sinusoidal signal 13, the test loop output signal 17, the compensation loop output signal 16, and the differential output signal 19 to be different from other proximity switches.
In the embodiment of fig. 1, the microprocessor 10, the differential acquisition processing circuit 18, the mixer circuit 20, and the analog-to-digital conversion circuit 22 may be implemented by separate hardware circuits, or may be integrated into the microprocessor 40.
Claims (9)
1. An anti-interference inductive proximity switch measuring system is characterized by comprising a processor (10), a low-pass filter (12), an alternating current bridge (14), a metal target (15), a differential acquisition processing circuit (18), a frequency mixing module (20) and an A/D conversion circuit (22); one path of the processor (10), the low-pass filter (12) and the alternating current bridge (14) are sequentially connected, and the metal target (15) is arranged on the side face of the alternating current bridge (14); the alternating current bridge (14) is provided with two paths of outputs which are connected to the differential acquisition processing circuit (18), the frequency mixing module (20) and the A/D conversion circuit (22) are sequentially connected, and the output end of the A/D conversion circuit (22) is connected with the processor (10).
2. The interference-proof inductive proximity switch measurement system according to claim 1, characterized in that the ac bridge (14) comprises a test leg and a compensation leg, the test leg comprises a test capacitor (31), a test coil (32) and a test resistor (33), the test capacitor (31), the test coil (32) and the test resistor (33) are connected in sequence; the compensation bridge arm comprises a compensation capacitor (34), a compensation coil (35) and a compensation resistor (36), wherein the compensation capacitor (34), the compensation coil (35) and the compensation resistor (36) are sequentially connected; the test bridge arm outputs a second acquisition signal (17) and the compensation bridge arm outputs a first acquisition signal (16).
3. A tamper-proof inductive proximity switch measuring system according to claim 2, characterized in that the metal target (15) is located at the side of the test coil (32).
4. The interference-proof inductive proximity switch measurement system according to claim 2, characterized in that the impedance states of the test arm and the compensation arm are completely identical without the influence of the metal target (15); the second acquisition signal (17) and the first acquisition signal (16) are connected with a differential acquisition processing circuit (18).
5. A tamper-proof inductive proximity switch measurement system according to claim 1, characterized in that the processor (10) outputs a TTL excitation signal (11), the low-pass filter (12) limiting the frequency to less than (2) times the frequency of said TTL excitation signal (11).
6. The interference-free inductive proximity switch measurement system according to claim 2, wherein the differential acquisition processing circuit (18) outputs a sinusoidal signal to be measured (19), and the sinusoidal signal to be measured (19), the first acquisition signal (16), the second acquisition signal (17) and the TTL excitation signal (11) have the same frequency f (1) and different amplitudes and phases.
7. A tamper-proof inductive proximity switch measurement system according to claim 6, characterized in that the other path of the processor (10) is connected to the mixing module (20); the filter circuit in the mixing module (20) contains a limiting frequency f (2), the filter circuit and a multiplying circuit in the mixing module (20) form a band-pass filter, and the limiting frequency of the band-pass filter is in a range of [ f (1) -f (2), f (1) + f (2) ]; and multiplying a TTL excitation signal (11) and a sine signal (19) to be measured, and forming the analog quantity signal (21) through a filter circuit in the frequency mixing module (20).
8. The interference-free inductive proximity switch measurement system of claim 7, wherein the analog signal (21) obtained after multiplication of the mixer module (20) by the multiplier circuit and the filter circuit retains only the constant component after multiplication.
9. A method of interference-free inductive proximity switch measurement, based on any of claims 1 to 8, comprising the steps of:
the processor (10) generates a TTL excitation signal (11), a sinusoidal signal (13) with the same frequency as the TTL excitation signal (11) is formed after the TTL excitation signal (11) passes through the low-pass filter (12), and the sinusoidal signal (13) enters the alternating current bridge (14) to form a test loop;
after a first acquisition signal (16) and a second acquisition signal (17) output by the alternating current bridge pass through a differential acquisition processing circuit (18), an output sine signal (19) to be tested and a TTL excitation signal enter a frequency mixing module (20) together to obtain an analog quantity signal (21);
the size of the analog quantity signal (21) can be changed correspondingly along with the change of the distance between the metal target (15) and the proximity switch probe, after the analog quantity signal (21) passes through the A/D conversion circuit (22), the digital quantity signal (23) is sent to the processor (10), and the processor (10) calculates the distance between the metal target (15) and the proximity switch probe through a lumped circuit.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113917325A (en) * | 2021-12-16 | 2022-01-11 | 山东天大清源信息科技有限公司 | Proximity switch detection device and detection method thereof |
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| DE3603950A1 (en) * | 1986-02-06 | 1987-08-13 | Siemens Ag | Inductive temperature-compensated position detector |
| CN86208757U (en) * | 1986-11-06 | 1987-11-11 | 交通部第四航务工程局科研所 | Resonant bridge sensor |
| US20020070729A1 (en) * | 2000-03-16 | 2002-06-13 | Jens Muller | Electronic proximity switch |
| US20160033563A1 (en) * | 2013-04-25 | 2016-02-04 | Minus174, Llc | Electronic arrangement and vector network analyzer characterized by reduced phase noise |
| CN108692650A (en) * | 2018-04-12 | 2018-10-23 | 电子科技大学 | A kind of electromagnetic induction thickness measuring system for composite material surface coating layer thickness |
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|---|---|---|---|---|
| GB769774A (en) * | 1954-05-24 | 1957-03-13 | Daimler Benz Ag | Improvements relating to electrical measuring apparatus using inductive responsive devices |
| DE3440538C1 (en) * | 1984-11-07 | 1986-05-15 | Werner Turck Gmbh & Co Kg, 5884 Halver | Proximity switch |
| DE3603950A1 (en) * | 1986-02-06 | 1987-08-13 | Siemens Ag | Inductive temperature-compensated position detector |
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| US20020070729A1 (en) * | 2000-03-16 | 2002-06-13 | Jens Muller | Electronic proximity switch |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113917325A (en) * | 2021-12-16 | 2022-01-11 | 山东天大清源信息科技有限公司 | Proximity switch detection device and detection method thereof |
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