CN111649662B - Coating thickness gauge and coating thickness detection method - Google Patents
Coating thickness gauge and coating thickness detection method Download PDFInfo
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- CN111649662B CN111649662B CN202010552100.0A CN202010552100A CN111649662B CN 111649662 B CN111649662 B CN 111649662B CN 202010552100 A CN202010552100 A CN 202010552100A CN 111649662 B CN111649662 B CN 111649662B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
- G01B7/10—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance
- G01B7/105—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance for measuring thickness of coating
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Abstract
A coating thickness gauge and a coating thickness detection method are provided, the coating thickness gauge comprises: the device comprises a shell, a detection head, an auxiliary circuit board, a display screen, a USB interface, a battery, a switch key, a main circuit board and a trigger switch. The invention provides a coating thickness gauge and a coating thickness detection method, which are different from a traditional analog oscillation circuit, and the excitation signal adopts a digital oscillation technology, and a high-speed ADC (analog-to-digital converter) is adopted to acquire a detection signal, so that the ultrahigh stability of the gauge is ensured; the ultra-high measurement precision and repeatability provide an effective means for measuring the thickness of a very thin coating, can be used for measuring non-magnetic coatings such as paint, varnish, enamel, chromium, zinc plating and the like on ferromagnetic metal substrates such as steel and the like, and is particularly suitable for measuring a thin coating with high precision requirement.
Description
Technical Field
The invention belongs to the technical field of thickness measurement, and particularly relates to a coating thickness gauge and a coating thickness detection method.
Background
The thickness measurement is one of important items for detecting the physical properties of the coating, and the coating thickness measurement principle includes a magnetic method, an eddy current method, an X-ray spectroscopy method, an ultrasonic thickness measurement and the like. Wherein the magnetic method can nondestructively measure the thickness of a nonmagnetic coating on a magnetic metal substrate such as steel, iron, alloy, hard magnetic steel, and the like, such as aluminized iron, chromed iron, plated iron with copper, enameled iron, rubber on iron, paint coatings, and the like.
The electromagnetic induction method for detecting the thickness of the surface coating of the non-ferromagnetic material of the ferromagnetic substrate is a nondestructive detection method for the thickness of the surface coating designed according to the obvious difference of the magnetic conductivity of the substrate and the coating by utilizing the difference of the magnetic properties of the substrate and the coating. Because the magnetic resistance of the base body is far smaller than that of the coating, if the thicknesses of the coatings are different, the distance between the probe and the surface of the base body is different, so that the magnetic fluxes generated by the exciting coil of the probe are different, the induced voltage in the detecting coil on the probe is different, and the information of the thickness of the coating can be obtained by measuring the difference of the induced voltage signals.
The stability of the oscillation signal of the probe exciting coil is a key parameter of measurement accuracy, at present, an oscillation circuit generally adopts an analog circuit design, namely an LC oscillation circuit generates a sine wave signal, the oscillation frequency and amplitude generated by the circuit can change along with the change of temperature, humidity or power supply voltage, and the performance index of an instrument is greatly influenced.
Disclosure of Invention
In order to solve the above problems, the present invention provides a coating thickness gauge, comprising:
a housing for mounting components; the shell is internally provided with an installation space;
the detection head is used for transmitting a detection signal to the coating and receiving a feedback signal reflected by the coating; the detection head is arranged on the shell;
the auxiliary circuit board is used for controlling the detection head to generate a detection signal and processing a feedback signal sent by the detection head; the auxiliary circuit board is arranged in the mounting space and is fixedly connected with the detection head;
the trigger switch is used for receiving the pressing of the detection head so as to start the detection head to detect the coating thickness; the trigger switch is fixedly connected with the auxiliary circuit board and is opposite to the trigger baffle on the inner wall of the shell;
a display screen for displaying the measured value; the display screen is arranged on the shell;
the USB interface is used for exchanging data with external equipment; the USB interface is arranged on the shell;
the battery is used for supplying power to all parts; the battery is arranged in the installation space;
the switch key is used for turning on or off the thickness gauge; the switch key is arranged on the shell;
the main circuit board is used for processing each signal; the main circuit board is arranged in the shell and is respectively connected with the auxiliary circuit board, the display screen, the USB interface, the battery and the switch key.
Preferably, the detection head comprises: detect first shell, exciting coil, detection coil and iron core, wherein, detect first shell first end with the secondary circuit board is connected and the second end stretches out the casing, the iron core set up in detect in the first shell, and first end with detect first shell first end parallel and level and the second end stretches out detect first shell, the iron core side has 4 to be used for exciting coil with the routing groove that detection coil walked the line usefulness, exciting coil with detection coil with set up in detect in the first shell and twine in on the iron core, exciting coil sets up and is being close to one side of routing groove, detection coil sets up and is keeping away from the opposite side of routing groove, and with exciting coil hugs closely together, exciting coil with the wire of detection coil passes the routing groove with the secondary circuit board electricity is connected.
Preferably, the sub circuit board includes: the device comprises a D/A converter U, an amplifier U, a high-speed A/D converter U, a single chip microcomputer U, a capacitor C, a first capacitor C, a resistor R, a first resistor R, a resistor R and a resistor R, wherein a Vdd pin of the D/A converter U is connected with a first positive potential, a REFO pin of the D/A converter U is respectively connected with a second positive potential and a first end of the capacitor C, a second end of the capacitor C is grounded, a VFB pin and a Vout pin of the D/A converter U are both connected with a first end of the resistor R, a SYNC pin of the D/A converter U is connected with a TX/PA pin of the single chip microcomputer U, and an SCLK pin of the D/A converter U is respectively connected with a CLK pin of the high-speed A/D converter U and a PA/SCK pin of the single chip microcomputer U A pin is connected, a DIN pin of the D/a converter U3 is connected to a pin MO/PB1 of the single chip microcomputer U6, a Gnd pin of the D/a converter U3 is grounded, two pins R1 of the amplifier U4 are respectively connected to two ends of the resistor R11, a negative Vin pin of the amplifier U4 is connected to a second end of a detection coil in the detection head, a positive Vin pin of the amplifier U4 is connected to a first end of the detection coil, a negative V pin of the amplifier U4 is grounded, a pin R2 of the amplifier U4 is respectively connected to a first end of the capacitor C10 and a first end of the resistor R10, second ends of the capacitor C10 and the resistor R10 are both connected to the second positive potential, a pin VO pin of the amplifier U4 is connected to a first end of the resistor R14, a positive V pin of the amplifier U4 is connected to the first positive potential, a first end of the capacitor C18 is grounded, and a second end of the amplifier U4 is connected to a positive V pin, the REF pin of the high-speed a/D converter U5 is connected to the first positive potential, the positive IN pin of the high-speed a/D converter U5 is connected to the second end of the resistor R14 and the first end of the first capacitor C17, the second end of the first capacitor C17 is grounded, the negative IN pin and the GND pin of the high-speed a/D converter U5 are grounded, the/CS pin of the high-speed a/D converter U5 is connected to the PA7/MO pin of the single chip microcomputer U6, the Dout pin of the high-speed a/D converter U5 is connected to the PA6/MI pin of the single chip microcomputer U6, the VDD pin of the high-speed a/D converter U5 is connected to the first positive potential and the first end of the first capacitor C16, the second end of the first capacitor C16 is grounded, the second end of the resistor R1 is connected to the first end of the capacitor C9 and the second end of the excitation coil IN the detection head, a second terminal of the capacitor C9 is grounded, a first terminal of the excitation coil is grounded, a first terminal of the resistor R6 is connected to the second positive potential and a second terminal is connected to the first terminal of the detection coil, a first end of the first resistor R7 is connected to a first end of the detection coil and a second end is connected to a second end of the detection coil, a first terminal of the first resistor R8 is connected to a second terminal of the detection coil and a second terminal is connected to the second positive potential, a VSS pin and a Boot0 pin of the singlechip U6 are both grounded, a VDD pin of the singlechip U6 is respectively connected with the first positive potential and the first end of the capacitor C13, the second end of the capacitor C13 is grounded, the VDDA pin of the singlechip U6 is respectively connected with the first positive potential and the first end of the capacitor C11, the second end of the capacitor C11 is grounded, the first end of the capacitor C12 is grounded, and the second end of the capacitor C12 is connected with the NRST pin of the singlechip U6.
Preferably, the main circuit board is provided with: display screen control circuit, USB interface control circuit, battery control circuit, switch button control circuit and main control circuit, wherein, main control circuit respectively with display screen control circuit USB interface control circuit battery control circuit with the switch button is connected, display screen control circuit with the display screen is connected, USB interface control circuit with USB interface connection, battery control circuit with the battery is connected, switch button control circuit with the switch button is connected.
Preferably, the display screen control circuit includes: the display screen control circuit comprises a second resistor R8, a capacitor C15 and a display screen control chip J2, wherein first ends of the second resistor R8 and the capacitor C15 are all grounded, second ends of the second resistor R8 and the capacitor C15 are respectively connected with a VComh pin and an IRdf pin of the display screen control chip J2, a Vpp pin of the display screen control chip J2 is connected with a first positive potential, a Vdd pin is connected with a third positive potential, and an IM1 pin and a Vss pin of the display screen control chip J2 are both grounded.
Preferably, the USB interface control circuit includes: the USB socket comprises a capacitor C3 and a USB socket USB1, wherein a GND pin of the USB socket USB1 is grounded, a VBUS pin of the USB socket USB1 is connected with a VBUS signal end, a negative electrode of the capacitor C3 is grounded, and a positive electrode of the capacitor C3 is connected with the VBUS pin of the USB socket USB 1.
Preferably, the battery control circuit includes: a diode D2, a diode D3, a resistor R2, a resistor R9, a capacitor C2, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C8, a capacitor C12, an inductor L1, a power control chip U1 and a power control chip U2, wherein an anode of the battery is connected to a cathode of the diode D2 and a cathode thereof is grounded, an anode of the diode D2 is connected to the resistor R2, the capacitor C6 and a first end of the inductor L1, a second end of the resistor R2 is connected to the first ends of the resistor R9 and the capacitor C8, second ends of the resistor R9, the capacitor C6 and the capacitor C8 are grounded, a second end of the inductor L1 is connected to an SW/Vin pin of the power control chip U2 and a cathode of the diode D3, a power pin Vout of the power control chip U2 is grounded and an anode of the diode D3 is connected to a first potential and a positive potential of the diode D3, respectively, The Vin pin of the power control chip U1, the first ends of the capacitor C2 and the capacitor C4, the second ends of the capacitor C2 and the capacitor C4 are all grounded, the GND pin of the power control chip U1 is grounded, the Vout pin is respectively connected to the third positive potential, the first ends of the capacitor C5 and the capacitor C12, and the second ends of the capacitor C5 and the capacitor C12 are both grounded.
Preferably, the switch key control circuit includes: a second resistor R7 and a key S1, wherein a first terminal of the second resistor R7 is connected to a third positive potential and a second terminal is connected to a first terminal of the key S1, and a second terminal of the key S1 is grounded.
Preferably, the main control circuit includes: a second monolithic computer U3, a capacitor C1, a second capacitor C16, a second capacitor C17, a capacitor C19, a capacitor C21, and a resistor R4, wherein a Vdd pin of the second monolithic computer U3 is connected to a first terminal and a third positive potential of the capacitor C1, a second terminal of the capacitor C1 is grounded, a first terminal of the resistor R4 is connected to a PA5/SCK1 pin of the second monolithic computer U3 and a second terminal thereof is connected to a VBUS pin, a VDDA pin of the second monolithic computer U3 is connected to the third positive potential and the first terminal of the second capacitor C16, a second terminal of the second capacitor C16 is grounded, a first terminal of the second capacitor C17 is grounded and a second terminal thereof is connected to an NRST pin of the second monolithic computer U3, a first terminal of the capacitor C19 is grounded and a second terminal thereof is connected to a Vdd pin of the second monolithic computer U3 and the third positive potential, and a second terminal of the capacitor C21 is connected to the second terminal of the second monolithic computer U3 and a second terminal thereof is grounded, The second singlechip U3 is respectively connected with the display screen control circuit, the USB interface control circuit, the battery control circuit and the switch key.
The invention also provides a coating thickness detection method, which adopts the coating thickness gauge to detect the coating thickness, and comprises the following steps:
pressing a switch key to start the instrument;
pressing a detection head on the coating to be detected;
a first singlechip on the auxiliary circuit board detects a trigger signal of a trigger switch and starts a coating thickness measuring function;
the display screen displays the coating thickness measurements.
The application provides a coating thickness gauge and coating thickness detection method has following beneficial effect:
(1) the invention provides a coating thickness gauge and a coating thickness detection method, which are different from a traditional analog oscillation circuit, wherein an excitation signal adopts a digital oscillation technology, and a sine oscillation signal is controlled by a digital signal of a singlechip, so that the digital signal has the advantage of difficult interference, the variation of the oscillation signal caused by factors such as temperature, humidity, power supply voltage fluctuation and the like is avoided, and the stability of a measurement circuit is greatly improved;
(2) the high-speed ADC is adopted to collect detection signals, the difference value between the wave crest and the wave trough of the waveform of the induced voltage can be measured in one oscillation period, the thickness of the covering layer can be calculated by searching a corresponding curve of the thickness and the difference value, and an effective means is provided for quickly measuring the thickness of the coating layer;
(3) detect head and vice PCB board fixed connection, detect the head and vice PCB board whole motion on the main casing during the measurement to detection signal acquisition and thickness calculation are accomplished on vice PCB, have avoided causing the interference to the detection signal because of detecting the relative motion of head and vice PCB board at the measurement process, further improve measurement stability. The ultra-high measurement precision and repeatability provide an effective means for measuring the thickness of a very thin coating, can be used for measuring non-magnetic coatings such as paint, varnish, enamel, chromium, galvanized steel and the like on ferromagnetic metal substrates such as steel and the like, and is particularly suitable for measuring a thin coating with high precision requirement.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic view of the overall structure of a coating thickness gauge provided by the present invention;
FIG. 2 is a schematic view of the internal structure of a coating thickness gauge provided by the present invention;
FIG. 3 is a schematic view of the internal structure of a coating thickness gauge provided by the present invention;
FIG. 4 is a schematic structural diagram of a detection head in a coating thickness gauge provided by the present invention;
FIG. 5 is a schematic diagram of a secondary circuit board in a coating thickness gauge provided by the present invention;
FIG. 6 is a schematic diagram of a display screen control circuit in a coating thickness gauge provided by the present invention;
FIG. 7 is a schematic diagram of a USB interface control circuit in a coating thickness gauge according to the present invention;
FIG. 8 is a schematic diagram of a battery control circuit in a coating thickness gauge provided by the present invention;
FIG. 9 is a schematic diagram of a switch button control circuit in a coating thickness gauge provided by the present invention;
FIG. 10 is a schematic diagram of a main control circuit in the coating thickness gauge provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
In an embodiment of the present application, as shown in fig. 1 to 4, the present invention provides a coating thickness gauge, including: the electronic device includes a housing 10, a detection head 20, a sub circuit board 30, a display 40, a USB interface 50, a battery (not shown), a switch button 60, a main circuit board 70, and a trigger switch 80, which will be described in detail below.
In an embodiment of the present application, as shown in fig. 1 to 4, the present invention provides a coating thickness gauge, including:
a housing 10 for mounting various parts; the housing 10 has an installation space therein;
a detection head 20 for emitting a detection signal to the coating and receiving a feedback signal reflected by the coating; the detection head 20 is arranged on the shell 10;
the auxiliary circuit board 30 is used for controlling the detection head 20 to generate detection signals and processing feedback signals sent by the detection head 20; the auxiliary circuit board 30 is disposed in the mounting space and is fixedly connected to the detection head 20;
a trigger switch 80 for receiving the pressing of the detection head 20 to start the detection head 20 to perform the coating thickness detection; the trigger switch 80 is fixedly connected with the secondary circuit board 30 and is opposite to the trigger baffle on the inner wall of the shell 10;
a display 40 for displaying the measured values; the display screen 40 is arranged on the shell 10;
a USB interface 50 for exchanging data with an external device; the USB interface 50 is disposed on the housing 10;
the battery is used for supplying power to all parts; the battery is arranged in the installation space;
a switch button 60 for turning on or off the thickness gauge; the switch button 60 is arranged on the housing 10;
a main circuit board 70 for processing each signal; the main circuit board 70 is disposed in the casing 10 and is respectively connected to the sub circuit board 30, the display screen 40, the USB interface 50, the battery, and the switch button 60.
As shown in fig. 1 to 4, in the embodiment of the present application, the detection head 20 includes: a detection head shell 21, an exciting coil 22, a detection coil 23 and an iron core 24, wherein the first end of the detection head shell 21 is connected with the auxiliary circuit board 30, the second end of the detection head shell extends out of the shell 10, the iron core 24 is arranged in the detection head shell 21, and the first end is flush with the first end of the test head housing 21 and the second end extends out of the test head housing 21, the side of the iron core 24 is provided with 4 wiring grooves for wiring the exciting coil 22 and the detecting coil 23, the exciting coil 22 and the detecting coil 23 are both arranged in the detecting head casing 21 and wound on the iron core 24, the excitation coil 22 is arranged on one side close to the wiring groove, the detection coil 23 is arranged on the other side far away from the wiring groove, and closely attached to the excitation coil 22, and the wires of the excitation coil 22 and the detection coil 23 pass through the wiring groove to be electrically connected to the sub circuit board 30.
A positioning groove is formed in the inner wall of the casing 10 corresponding to the auxiliary circuit board 30, and a positioning block is arranged in the positioning groove and moves along the positioning groove. The auxiliary circuit board 30 is fixedly connected with the positioning block, and the detection head 20 is fixedly connected with the auxiliary circuit board 30 and extends out of the through hole on the shell 10. The auxiliary circuit board 30 is fixedly connected to the trigger switch 80, and a trigger baffle is disposed on the inner wall of the casing 10 corresponding to the trigger switch 80 and opposite to the trigger switch 80. When the thickness of the coating is detected, the detection head 20 is pressed to the coating, the detection head 20 moves backwards and drives the auxiliary circuit board 30 and the trigger switch 80 to move towards the trigger baffle together until the trigger switch 80 contacts the trigger baffle to trigger the auxiliary circuit board 30 to detect the thickness of the coating.
The detection coil 23 and the excitation coil 22 are wound around the same iron core 24. When the core 24 is in contact with the coating, the sensing head 20 and the magnetic metal substrate form a closed magnetic circuit, and the magnetic resistance of the magnetic circuit is changed due to the presence of the non-magnetic coating, resulting in a change in magnetic flux. The detection coil 23 generates an induced voltage varying with the thickness of the coating, and as the thickness of the coating is thicker, the distance between the core 24 and the magnetic substrate is larger, the coupling efficiency is lower, and the amplitude of the induced voltage waveform is smaller. The thinner the coating, the smaller the distance of the core 24 from the magnetic substrate, the higher the coupling efficiency and the larger the amplitude of the induced voltage waveform.
As shown in fig. 5, in the embodiment of the present application, the sub circuit board includes: the device comprises a D/A converter U, an amplifier U, a high-speed A/D converter U, a single chip microcomputer U, a capacitor C, a first capacitor C, a resistor R, a first resistor R, a resistor R and a resistor R, wherein a Vdd pin of the D/A converter U is connected with a first positive potential, a REFO pin of the D/A converter U is respectively connected with a second positive potential and a first end of the capacitor C, a second end of the capacitor C is grounded, a VFB pin and a Vout pin of the D/A converter U are both connected with a first end of the resistor R, a SYNC pin of the D/A converter U is connected with a TX/PA pin of the single chip microcomputer U, and an SCLK pin of the D/A converter U is respectively connected with a CLK pin of the high-speed A/D converter U and a PA/SCK pin of the single chip microcomputer U A pin is connected, a DIN pin of the D/a converter U3 is connected to a pin MO/PB1 of the single chip microcomputer U6, a Gnd pin of the D/a converter U3 is grounded, two pins R1 of the amplifier U4 are respectively connected to two ends of the resistor R11, a negative Vin pin of the amplifier U4 is connected to a second end of a detection coil in the detection head, a positive Vin pin of the amplifier U4 is connected to a first end of the detection coil, a negative V pin of the amplifier U4 is grounded, a pin R2 of the amplifier U4 is respectively connected to a first end of the capacitor C10 and a first end of the resistor R10, second ends of the capacitor C10 and the resistor R10 are both connected to the second positive potential, a pin VO pin of the amplifier U4 is connected to a first end of the resistor R14, a positive V pin of the amplifier U4 is connected to the first positive potential, a first end of the capacitor C18 is grounded, and a second end of the amplifier U4 is connected to a positive V pin, the REF pin of the high-speed a/D converter U5 is connected to the first positive potential, the positive IN pin of the high-speed a/D converter U5 is connected to the second end of the resistor R14 and the first end of the first capacitor C17, the second end of the first capacitor C17 is grounded, the negative IN pin and the GND pin of the high-speed a/D converter U5 are grounded, the/CS pin of the high-speed a/D converter U5 is connected to the PA7/MO pin of the single chip microcomputer U6, the Dout pin of the high-speed a/D converter U5 is connected to the PA6/MI pin of the single chip microcomputer U6, the VDD pin of the high-speed a/D converter U5 is connected to the first positive potential and the first end of the first capacitor C16, the second end of the first capacitor C16 is grounded, the second end of the resistor R1 is connected to the first end of the capacitor C9 and the second end of the excitation coil IN the detection head, a second terminal of the capacitor C9 is grounded, a first terminal of the excitation coil is grounded, a first terminal of the resistor R6 is connected to the second positive potential and a second terminal is connected to the first terminal of the detection coil, a first end of the first resistor R7 is connected to a first end of the detection coil and a second end is connected to a second end of the detection coil, a first terminal of the first resistor R8 is connected to a second terminal of the detection coil and a second terminal is connected to the second positive potential, a VSS pin and a Boot0 pin of the singlechip U6 are both grounded, a VDD pin of the singlechip U6 is respectively connected with the first positive potential and the first end of the capacitor C13, the second end of the capacitor C13 is grounded, the VDDA pin of the singlechip U6 is respectively connected with the first positive potential and the first end of the capacitor C11, the second end of the capacitor C11 is grounded, the first end of the capacitor C12 is grounded, and the second end of the capacitor C12 is connected with the NRST pin of the single chip microcomputer U6.
When the coating thickness detector works, the detector head 20 is vertically pressed on the surface of a coating to be detected, the detector head 20 drives the secondary circuit board 30 and the trigger switch 80 to integrally move towards the direction of the trigger baffle, the trigger switch 80 is closed to generate a trigger signal, the singlechip U6 receives the trigger signal and then outputs a sinusoidal oscillation digital signal to the D/A converter U3, the D/A converter U3 converts the sinusoidal oscillation digital signal into sinusoidal oscillation voltage and outputs the sinusoidal oscillation voltage to the exciting coil 22, the exciting coil 22 generates an exciting magnetic field around the singlechip U6, the detection coil 23 generates weak induction voltage according to the exciting magnetic field, the amplifier U4 amplifies the induction voltage and then transmits the weak induction voltage to the high-speed A/D converter U5, the high-speed A/D converter U5 converts the amplified induction voltage into a digital signal and transmits the digital signal to the singlechip U6, and the singlechip U6 obtains induction voltage wave crests and wave waves according to the digital signal output by the high-speed A/D converter U5 And normalizing the difference A to obtain a normalized difference delta A between the peak and the trough of the induction voltage. When the instrument leaves the factory, a quantitative relation curve between the delta A and the coating thickness H is obtained by measuring the normalized difference delta A between the induction voltage wave crest and the wave trough of the detection coil 23 corresponding to a series of coatings with different thicknesses, and the quantitative relation curve is stored on the instrument. When the coating thickness is tested, the difference value between the wave crest and the wave trough of the induced voltage waveform of the detection coil 23 is measured and normalized, and the coating thickness can be calculated by inquiring the stored relation curve.
When the detection head 20 is in contact with the cover layer, the magnetic head of the detection head 20 and the magnetic metal substrate form a closed magnetic circuit, and the magnetic resistance of the magnetic circuit is changed due to the existence of the non-magnetic cover layer, so that the magnetic flux is changed. Generally, the thicker the cover layer thickness, the smaller the magnetic flux and the smaller the induced voltage. The thickness of the covering layer can be calculated by measuring the peak voltage change of the sine oscillation signal of the detection coil 23 and searching the corresponding curve of the thickness and the voltage. Because the sine type oscillation signal is controlled by the digital signal of the singlechip U6, the digital signal has the advantage of difficult interference, the change of the oscillation signal caused by factors such as temperature, humidity and power supply voltage fluctuation is avoided, and the stability of the measuring circuit is greatly improved.
As shown in fig. 6, in the embodiment of the present application, the display screen control circuit includes: the display screen control circuit comprises a second resistor R8, a capacitor C15 and a display screen control chip J2, wherein first ends of the second resistor R8 and the capacitor C15 are all grounded, second ends of the second resistor R8 and the capacitor C15 are respectively connected with a VComh pin and an IRdf pin of the display screen control chip J2, a Vpp pin of the display screen control chip J2 is connected with a first positive potential, a Vdd pin is connected with a third positive potential, and an IM1 pin and a Vss pin of the display screen control chip J2 are both grounded.
In the embodiment of the present application, the main circuit board 70 may send a corresponding signal to the display screen control circuit to control the display screen 40 to be turned on and off, and display a corresponding detection data value.
As shown in fig. 7, in the embodiment of the present application, the USB interface control circuit includes: the USB socket comprises a capacitor C3 and a USB socket USB1, wherein a GND pin of the USB socket USB1 is grounded, a VBUS pin of the USB socket USB1 is connected with a VBUS signal end, a negative electrode of the capacitor C3 is grounded, and a positive electrode of the capacitor C3 is connected with the VBUS pin of the USB socket USB 1.
In the embodiment of the present application, the USB interface control circuit may control the USB interface 50 to provide the USB interface 50 to transmit and exchange data with an external device.
As shown in fig. 8, in the embodiment of the present application, the battery control circuit includes: a diode D2, a diode D3, a resistor R2, a resistor R9, a capacitor C2, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C8, a capacitor C12, an inductor L1, a power control chip U1 and a power control chip U2, wherein an anode of the battery is connected to a cathode of the diode D2 and a cathode thereof is grounded, an anode of the diode D2 is respectively connected to the resistor R2, the capacitor C6 and a first end of the inductor L1, a second end of the resistor R2 is respectively connected to the resistor R9 and the first end of the capacitor C8, second ends of the resistor R9, the capacitor C6 and the capacitor C8 are all grounded, a second end of the inductor L1 is respectively connected to a SW/Vin pin of the power control chip U2 and a cathode of the diode D3, a Vout pin of the power control chip U2 is grounded and a positive potential of the first GND and a positive potential of the diode D3 are respectively connected to a positive potential, The Vin pin of the power control chip U1, the first ends of the capacitor C2 and the capacitor C4, the second ends of the capacitor C2 and the capacitor C4 are all grounded, the GND pin of the power control chip U1 is grounded, the Vout pin is respectively connected to the third positive potential, the first ends of the capacitor C5 and the capacitor C12, and the second ends of the capacitor C5 and the capacitor C12 are both grounded.
In the embodiment of the present application, the battery control circuit may control the battery to supply power to the main circuit board 70 and the sub circuit board 30, and is connected to an external power source through the USB interface control circuit, and charges the power source.
As shown in fig. 9, in the embodiment of the present application, the switch key control circuit includes: a second resistor R7 and a key S1, wherein a first terminal of the second resistor R7 is connected to a third positive potential and a second terminal is connected to a first terminal of the key S1, and a second terminal of the key S1 is grounded.
In the embodiment of the present application, the switch key control circuit may receive the pressing of the switch key 60, accordingly analyze the command thereof, and send a corresponding control command to the main circuit board 70, such as turning on or off the display screen 40, setting the instrument parameters, and the like.
As shown in fig. 10, in the embodiment of the present application, the main control circuit includes: a second monolithic computer U3, a capacitor C1, a second capacitor C16, a second capacitor C17, a capacitor C19, a capacitor C21, and a resistor R4, wherein a Vdd pin of the second monolithic computer U3 is connected to a first terminal and a third positive potential of the capacitor C1, a second terminal of the capacitor C1 is grounded, a first terminal of the resistor R4 is connected to a PA5/SCK1 pin of the second monolithic computer U3 and a second terminal thereof is connected to a VBUS pin, a VDDA pin of the second monolithic computer U3 is connected to the third positive potential and the first terminal of the second capacitor C16, a second terminal of the second capacitor C16 is grounded, a first terminal of the second capacitor C17 is grounded and a second terminal thereof is connected to an NRST pin of the second monolithic computer U3, a first terminal of the capacitor C19 is grounded and a second terminal thereof is connected to a Vdd pin of the second monolithic computer U3 and the third positive potential, and a second terminal of the capacitor C21 is connected to the second terminal of the second monolithic computer U3 and a second terminal thereof is grounded, The second singlechip U3 is respectively connected with the display screen control circuit, the USB interface control circuit, the battery control circuit and the switch key.
In the embodiment of the application, the main control circuit can control each circuit part to work according to corresponding instructions.
The invention also provides a coating thickness detection method, which adopts the coating thickness gauge shown in figures 1-10 to detect the coating thickness, and the detection method comprises the following steps:
pressing the switch button 60 turns on the instrument;
pressing the detection head 20 on the coating to be detected;
the first singlechip on the auxiliary circuit board 30 detects a trigger signal of the trigger switch 80 and starts the coating thickness measuring function;
the display 40 displays the coating thickness measurements.
Further, a quantitative relationship curve between the normalized difference Δ a between the peaks and the valleys of the induced voltage waveform and the coating thickness H, which is pre-stored on the coating thickness gauge, may be obtained by the following method.
When the coating thickness gauge works, the gauge detection head 20 vertically presses a test object, the trigger switch 80 is started, the single chip microcomputer U6 sends sine wave digital values to the D/A converter U3, and the D/A converter U3 outputs voltage of
Wherein, VREFOUTN is the number of bits of the D/A converter U3 and D is the binary coded decimal equivalent loaded into the DAC register for the reference voltage of the D/A converter U3.
In this embodiment, VREFOUT2.5V, N is 16 bits, and D takes values from 0 to 65535.
D value satisfies sinusoidal function
Theta is taken from 0 degrees at intervals of 2 degrees, namely 0,2,4,6 and 8 … …, and is substituted into the formula (3) to obtain a D value. The single chip microcomputer U6 sends a corresponding D value to the D/A converter U3 every 32 us. And (3) substituting an integer part of the D value into the formula (2) to obtain the sine-shaped oscillating voltage output by the D/A converter U3. The D/a converter U3 outputs an oscillation voltage with a period T of 32us 360/2 us 5760us, an oscillation frequency f of 1000000/5760 HZ 173.61HZ, and an amplitude a of 2.5V.
The oscillating voltage is filtered by R1 and C9 and then output to an exciting coil, the exciting coil generates an alternating magnetic field, and the detecting coil generates an alternating induction voltage according to the alternating magnetic field. The sending period of the D value of the singlechip U6 is 32us, so the acquisition period of the detection circuit is required to be completed within 32us, and the conversion frequency of the selected high-speed ADC is 100 KHZ.
The D/a converter U3 is output from a 2.5V reference voltage, and the 2.5V reference voltage is used as a reference voltage for the detection coil and amplifier U4 at the same time, i.e., the induced voltage fluctuates on the 2.5 reference. According to the electromagnetic induction principle, the induced electromotive force is the largest at the place where the magnetic flux change rate is the largest, namely the induced voltage and the excitation voltage are 90 degrees different in phase, the induced voltage and the excitation voltage are amplified by an amplifier U4, the amplification factor G is 2R 12/R11, and proper R12 and R11 can be selected according to the actual signal strength.
When the instrument leaves a factory, the difference A between the induction voltage wave crest and the wave trough of the detection coil corresponding to a series of coatings with different thicknesses is measured, then the difference A is normalized to obtain the normalized difference delta A between the induction voltage wave crest and the wave trough, a quantitative relation curve of the delta A and the thickness H of the covering layer is obtained, and the quantitative relation curve is stored on the instrument. When the coating thickness is tested, the difference value between the wave crest and the wave trough of the induced voltage waveform is measured and normalized, and the coating thickness can be calculated by inquiring the stored relation curve.
Formula (4) is a normalized calculation formula of the difference between the peak and the trough of the induced voltage, wherein A0umThe difference A, A between the wave crest and the wave trough of the induction voltage corresponding to the magnetic metal matrix without the covering layer pressed by the detecting head∞For detecting difference A between wave crest and wave trough of induced voltage pressed by head on nonmagnetic object
The calibration sample is operated by covering a thin film sheet on an iron substrate, the standard thickness of the thin film is calibrated by a Sanfeng ten-thousandth micrometer, the resolution of the ten-thousandth micrometer is 0.1um, and the error is +/-0.5 um. The sheet material selects 22 films with different thicknesses, and the film thickness is respectively 1.5um,2.5um,6.2um,12.3um,25.2um,42.9um,50.8um,65.1um,76.2um,99.8um,125.1um,149.5um,174.8um,200.3um,225.0um,250.5um,300.6um,349.1um,401um,451um,497um and 524um measured by a ten-thousandth ruler.
During calibration, the corresponding A of the uncovered layer iron substrate is measured0umThen 22 pieces of 1.5um and 2.5um … … 524um are respectively placed on the iron base material to measure corresponding A1.5um，A2.5um……A5.34umAnd finally measuring A of a nonmagnetic material∞。
The measured value is normalized according to the formula (4):
ΔA0＝A0um-A0um＝0
………
the normalized data becomes 0 to 1, and the data has a nonlinear relation with the coating thickness, a high-order polynomial fitting algorithm or a multi-section straight line fitting algorithm is commonly used at present, the high-order polynomial fitting algorithm has the defect of numerical value oscillation, the multi-section straight line fitting needs to compare linear detection signals, and the detection signals do not meet the linear requirement. The fitting method adopts multi-segment 2-degree polynomial fitting, so that the problem of numerical value oscillation of a high-degree polynomial is solved, and the problem of signal nonlinearity is also solved.
In this embodiment, the fitting is performed by dividing 5 segments in total, and the fitting is performed by dividing according to the normalized voltage value: 0-0.253124, 0.253124-0.392915, 0.392915-0.55674, 0.55674-0.71811 and 0.71811-1, and can be divided into more sections if higher-precision fitting is needed.
Second degree polynomial as follows
Hn＝an·ΔA2+bn·ΔA+cn
Fitting by using a least square method to obtain the a, b and c coefficients of each section of quadratic polynomial. The fitting result meets the requirement of the A-grade machine of the national verification regulation with the measurement error of +/-1 percent (H +0.5) mu m.
In the embodiment of the present application, the main circuit board is provided with: display screen control circuit, USB interface control circuit, battery control circuit, switch button control circuit and main control circuit, wherein, main control circuit respectively with display screen control circuit USB interface control circuit battery control circuit switch button and secondary circuit board are connected, display screen control circuit with the display screen is connected, USB interface control circuit with USB interface connection, battery control circuit with the battery is connected, switch button control circuit with switch button is connected.
The application provides a coating thickness gauge and coating thickness detection method has following beneficial effect:
(1) the invention provides a coating thickness gauge and a coating thickness detection method, which are different from a traditional analog oscillation circuit, wherein an excitation signal adopts a digital oscillation technology, and a sine oscillation signal is controlled by a digital signal of a singlechip, so that the digital signal has the advantage of difficult interference, the variation of the oscillation signal caused by factors such as temperature, humidity, power supply voltage fluctuation and the like is avoided, and the stability of a measurement circuit is greatly improved;
(2) the high-speed ADC is adopted to collect detection signals, the difference value between the wave crest and the wave trough of the waveform of the induced voltage can be measured in one oscillation period, the thickness of the covering layer can be calculated by searching a corresponding curve of the thickness and the difference value, and an effective means is provided for quickly measuring the thickness of the coating layer;
(3) detect head and vice PCB board fixed connection, detect the head and vice PCB board whole motion on the main casing during the measurement to detection signal acquisition and thickness calculation are accomplished on vice PCB, have avoided causing the interference to the detection signal because of detecting the relative motion of head and vice PCB board at the measurement process, further improve measurement stability. The ultra-high measurement precision and repeatability provide an effective means for measuring the thickness of a very thin coating, can be used for measuring non-magnetic coatings such as paint, varnish, enamel, chromium, zinc plating and the like on ferromagnetic metal substrates such as steel and the like, and is particularly suitable for measuring a thin coating with high precision requirement.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (7)
1. A coating thickness gauge, comprising:
a housing for mounting components; the shell is internally provided with an installation space;
the detection head is used for transmitting a detection signal to the coating and receiving a feedback signal reflected by the coating; the detection head is arranged on the shell;
the auxiliary circuit board is used for controlling the detection head to generate a detection signal and processing a feedback signal sent by the detection head; the auxiliary circuit board is arranged in the mounting space and is fixedly connected with the detection head;
the trigger switch is used for receiving the pressing of the detection head to start the detection head to detect the thickness of the coating; the trigger switch is fixedly connected with the auxiliary circuit board and is opposite to the trigger baffle on the inner wall of the shell;
a display screen for displaying the measured value; the display screen is arranged on the shell;
the USB interface is used for exchanging data with external equipment; the USB interface is arranged on the shell;
the battery is used for supplying power to all parts; the battery is arranged in the installation space;
the switch key is used for turning on or off the thickness gauge; the switch key is arranged on the shell;
the main circuit board is used for processing each signal; the main circuit board is arranged in the shell and is respectively connected with the auxiliary circuit board, the display screen, the USB interface, the battery and the switch key;
the detection head includes: the detection head comprises a detection head shell, an exciting coil, a detection coil and an iron core, wherein the first end of the detection head shell is connected with the secondary circuit board, the second end of the detection head shell extends out of the shell, the iron core is arranged in the detection head shell, the first end of the detection head shell is flush with the first end of the detection head shell, the second end of the detection head shell extends out of the detection head shell, 4 wiring grooves for wiring of the exciting coil and the detection coil are arranged on the side edge of the iron core, the exciting coil and the detection coil are arranged in the detection head shell and wound on the iron core, the exciting coil is arranged on one side close to the wiring grooves, the detection coil is arranged on the other side far away from the wiring grooves and is tightly attached to the exciting coil, and wires of the exciting coil and the detection coil penetrate through the wiring grooves to be electrically connected with the secondary circuit board;
the sub circuit board includes: the device comprises a D/A converter U, an amplifier U, a high-speed A/D converter U, a single chip microcomputer U, a capacitor C, a first capacitor C, a resistor R, a first resistor R, a resistor R and a resistor R, wherein a Vdd pin of the D/A converter U is connected with a first positive potential, a REFO pin of the D/A converter U is respectively connected with a second positive potential and a first end of the capacitor C, a second end of the capacitor C is grounded, a VFB pin and a Vout pin of the D/A converter U are both connected with a first end of the resistor R, a SYNC pin of the D/A converter U is connected with a TX/PA pin of the single chip microcomputer U, and an SCLK pin of the D/A converter U is respectively connected with a CLK pin of the high-speed A/D converter U and a PA/SCK pin of the single chip microcomputer U A pin is connected, a DIN pin of the D/a converter U3 is connected to a MO/PB1 pin of the single chip microcomputer U6, a Gnd pin of the D/a converter U3 is grounded, two R1 pins of the amplifier U4 are connected to two ends of the resistor R11 respectively, a negative Vin pin of the amplifier U4 is connected to a second end of the detection coil in the detection head, a positive Vin pin of the amplifier U4 is connected to a first end of the detection coil, a negative V pin of the amplifier U4 is grounded, a R2 pin of the amplifier U4 is connected to the capacitor C10 and a first end of the resistor R10 respectively, second ends of the capacitor C10 and the resistor R10 are both connected to the second positive potential, a VO pin of the amplifier U4 is connected to a first end of the resistor R14, a positive V pin of the amplifier U4 is connected to the first positive potential, a first end of the capacitor C18 is grounded, and a second end of the amplifier U4 is connected to a positive V pin of the amplifier U4, the REF pin of the high-speed a/D converter U5 is connected to the first positive potential, the positive IN pin of the high-speed a/D converter U5 is connected to the second end of the resistor R14 and the first end of the first capacitor C17, the second end of the first capacitor C17 is grounded, the negative IN pin and the GND pin of the high-speed a/D converter U5 are grounded, the/CS pin of the high-speed a/D converter U5 is connected to the PA7/MO pin of the single chip microcomputer U6, the Dout pin of the high-speed a/D converter U5 is connected to the PA6/MI pin of the single chip microcomputer U6, the VDD pin of the high-speed a/D converter U5 is connected to the first positive potential and the first end of the first capacitor C16, the second end of the first capacitor C16 is grounded, the second end of the resistor R1 is connected to the first end of the capacitor C9 and the second end of the excitation coil IN the detection head, a second terminal of the capacitor C9 is grounded, a first terminal of the excitation coil is grounded, a first terminal of the resistor R6 is connected to the second positive potential and a second terminal is connected to the first terminal of the detection coil, the first end of the first resistor R7 is connected with the first end of the detection coil and the second end is connected with the second end of the detection coil, a first end of the first resistor R8 is connected to a second end of the detection coil and a second end is connected to the second positive potential, a VSS pin and a Boot0 pin of the singlechip U6 are grounded, a VDD pin of the singlechip U6 is respectively connected with the first positive potential and the first end of the capacitor C13, the second end of the capacitor C13 is grounded, the VDDA pin of the singlechip U6 is respectively connected with the first positive potential and the first end of the capacitor C11, the second end of the capacitor C11 is grounded, the first end of the capacitor C12 is grounded, and the second end of the capacitor C12 is connected with an NRST pin of the singlechip U6;
the coating thickness detection is carried out according to a coating thickness gauge, and the detection method comprises the following steps:
pressing a switch key to start the instrument;
pressing a detection head on the coating to be detected;
a first singlechip on the auxiliary circuit board detects a trigger signal of a trigger switch, and starts a coating thickness measuring function;
the detection method comprises the following steps:
pressing the switch button 60 turns on the instrument;
pressing the detection head 20 on the coating to be detected;
the first singlechip on the auxiliary circuit board 30 detects a trigger signal of the trigger switch, and starts a coating thickness measuring function;
the display 40 displays the coating thickness measurement;
further, a quantitative relation curve between the normalized difference value Δ a between the peaks and the troughs of the induced voltage waveform and the coating thickness H, which is pre-stored on the coating thickness gauge, can be obtained by the following method:
when the coating thickness gauge works, the gauge detection head 20 vertically presses a test object, the trigger switch 80 is started, the single chip microcomputer U6 sends sine wave digital values to the D/A converter U3, and the D/A converter U3 outputs voltage of
Wherein, VREFOUTIs the reference voltage of the D/A converter U3, N is the number of bits of the D/A converter U3, D is the binary coded decimal equivalent loaded into the DAC registers,
in this embodiment, VREFOUT2.5V, N is 16 bits, D takes the value 0 to 65535,
d value satisfies sinusoidal function
Theta is taken from 0 DEG, the interval is 2 DEG, namely 0,2,4,6 and 8 … …, the D value is obtained by substituting the formula (3), the singlechip U6 sends a corresponding D value to the D/A converter U3 every 32us, the integer part of the D value is substituted into the formula (2), the sine type oscillation voltage output by the D/A converter U3 is obtained, the D/A converter U3 outputs the oscillation voltage, the period T is 32us 360/2 is 5760us, the oscillation frequency f is 1000000/5760 173.61HZ, the amplitude A is 2.5V,
the oscillation voltage is filtered by R1 and C9 and then output to an excitation coil, the excitation coil generates an alternating magnetic field, a detection coil generates an alternating induction voltage according to the alternating magnetic field, the D value sending period of a single chip microcomputer U6 is 32us, so the acquisition period of a detection circuit is required to be completed within 32us, the conversion frequency of a selected high-speed ADC is 100KHZ,
the D/A converter U3 outputs a 2.5V reference voltage, the 2.5V reference voltage is simultaneously used as a reference voltage of a detection coil and an amplifier U4, namely, an induced voltage fluctuates on a 2.5 reference, according to the electromagnetic induction principle, the induced electromotive force is the largest at the position with the largest magnetic flux change rate, namely, the induced voltage is 90 degrees different from the excitation voltage, the induced voltage is amplified by an amplifier U4, the amplification factor G is 2R 12/R11, and proper R12 and R11 can be selected according to the strength of an actual signal,
the difference A between the induction voltage wave crest and the wave trough of the detection coil corresponding to a series of coatings with different thicknesses is measured, then the difference A is normalized to obtain the normalized difference delta A between the induction voltage wave crest and the wave trough, a quantitative relation curve of the delta A and the thickness H of the covering layer is obtained and stored on an instrument, when the thickness of the coating is tested, the difference between the induction voltage wave crest and the wave trough is measured and normalized, the thickness of the coating can be calculated by inquiring the stored relation curve,
formula (4) is a normalized calculation formula of the difference between the peak and the trough of the induced voltage, wherein A0umThe difference A, A between the wave crest and the wave trough of the induced voltage corresponding to the magnetic metal matrix without the cover layer pressed by the detection head∞For detecting difference A between wave crest and wave trough of induced voltage pressed by head on nonmagnetic object
The calibration sample is operated by covering a thin film sheet on an iron substrate, the standard thickness of the thin film is calibrated by a Sanfeng ten thousandth ruler, the resolution of the ten thousandth ruler is 0.1um, the error is +/-0.5 um,22 thin films with different thicknesses are selected from the thin films, and the thin films are respectively 1.5um,2.5um,6.2um,12.3um,25.2um,42.9um,50.8um,65.1um,76.2um,99.8um,125.1um,149.5um,174.8um,200.3um,225.0um,250.5um,300.6um,349.1um,401um,451um,497um and 524um measured by the ten thousandth ruler,
during calibration, the corresponding A of the uncovered layer iron substrate is measured0umThen 22 pieces of 1.5um and 2.5um … … 524um are respectively placed on the iron base material to measure corresponding A1.5um，A2.5um……A524umAnd finally measuring A of a nonmagnetic material∞，
The measured value is normalized according to the formula (4):
ΔA0＝A0um-A0um＝0
………
the normalized data becomes 0 to 1, which has a nonlinear relation with the coating thickness, the prior high-order polynomial fitting algorithm or multi-segment straight line fitting algorithm is commonly used, the high-order polynomial fitting algorithm has the defect of numerical value oscillation, the multi-segment straight line fitting needs to compare linear detection signals, the detection signals can not meet the linear requirement, the fitting method adopts the multi-segment 2-order polynomial fitting, thereby overcoming the numerical value oscillation problem of the high-order polynomial and also meeting the nonlinear problem of the signals,
and (3) totally dividing into 5 sections for fitting, and segmenting according to the normalized voltage value: 0-0.253124, 0.253124-0.392915, 0.392915-0.55674, 0.55674-0.71811 and 0.71811-1, if higher precision fitting is needed, the method can be divided into more sections,
second degree polynomial as follows
Hn＝an.ΔA2+bn.ΔA+cn
Fitting by using a least square method to obtain the coefficients a, b and c of each section of quadratic polynomial, wherein the fitting result meets the requirement of a class A machine of the national verification regulation with the measurement error of +/-1 percent H +0.5 mu m;
the display screen displays the coating thickness measurements.
2. The coating thickness gauge of claim 1, wherein the main circuit board has disposed thereon: display screen control circuit, USB interface control circuit, battery control circuit, switch button control circuit and main control circuit, wherein, main control circuit respectively with display screen control circuit USB interface control circuit battery control circuit with the switch button is connected, display screen control circuit with the display screen is connected, USB interface control circuit with USB interface connection, battery control circuit with the battery is connected, switch button control circuit with the switch button is connected.
3. The coating thickness gauge of claim 1, wherein the display screen control circuit comprises: the display screen control circuit comprises a second resistor R8, a capacitor C15 and a display screen control chip J2, wherein first ends of the second resistor R8 and the capacitor C15 are all grounded, second ends of the second resistor R8 and the capacitor C15 are respectively connected with a VComh pin and an IRdf pin of the display screen control chip J2, a Vpp pin of the display screen control chip J2 is connected with a first positive potential, a Vdd pin is connected with a third positive potential, and an IM1 pin and a Vss pin of the display screen control chip J2 are both grounded.
4. The coating thickness gauge of claim 1, wherein the USB interface control circuit comprises: the USB socket comprises a capacitor C3 and a USB socket USB1, wherein a GND pin of the USB socket USB1 is grounded, a VBUS pin of the USB socket USB1 is connected with a VBUS signal end, a negative electrode of the capacitor C3 is grounded, and a positive electrode of the capacitor C3 is connected with the VBUS pin of the USB socket USB 1.
5. The coating thickness gauge of claim 1, wherein the battery control circuit comprises: a diode D2, a diode D3, a resistor R2, a resistor R9, a capacitor C2, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C8, a capacitor C12, an inductor L1, a power control chip U1 and a power control chip U2, wherein an anode of the battery is connected to a cathode of the diode D2 and a cathode thereof is grounded, an anode of the diode D2 is respectively connected to the resistor R2, the capacitor C6 and a first end of the inductor L1, a second end of the resistor R2 is respectively connected to the resistor R9 and the first end of the capacitor C8, second ends of the resistor R9, the capacitor C6 and the capacitor C8 are all grounded, a second end of the inductor L1 is respectively connected to a SW/Vin pin of the power control chip U2 and a cathode of the diode D3, a Vout pin of the power control chip U2 is grounded and a positive potential of the first GND and a positive potential of the diode D3 are respectively connected to a positive potential, The Vin pin of the power control chip U1, the first ends of the capacitor C2 and the capacitor C4, the second ends of the capacitor C2 and the capacitor C4 are all grounded, the GND pin of the power control chip U1 is grounded, the Vout pin is respectively connected to the third positive potential, the first ends of the capacitor C5 and the capacitor C12, and the second ends of the capacitor C5 and the capacitor C12 are both grounded.
6. The coating thickness gauge of claim 1, wherein the switch button control circuit comprises: a second resistor R7 and a key S1, wherein a first terminal of the second resistor R7 is connected to a third positive potential and a second terminal is connected to a first terminal of the key S1, and a second terminal of the key S1 is grounded.
7. The coating thickness gauge of claim 2, wherein the main control circuit comprises: a second monolithic computer U3, a capacitor C1, a second capacitor C16, a second capacitor C17, a capacitor C19, a capacitor C21, and a resistor R4, wherein a Vdd pin of the second monolithic computer U3 is connected to a first terminal and a third positive potential of the capacitor C1, a second terminal of the capacitor C1 is grounded, a first terminal of the resistor R4 is connected to a PA5/SCK1 pin of the second monolithic computer U3 and a second terminal thereof is connected to a VBUS pin, a VDDA pin of the second monolithic computer U3 is connected to the third positive potential and the first terminal of the second capacitor C16, a second terminal of the second capacitor C16 is grounded, a first terminal of the second capacitor C17 is grounded and a second terminal thereof is connected to an NRST pin of the second monolithic computer U3, a first terminal of the capacitor C19 is grounded and a second terminal thereof is connected to a Vdd pin of the second monolithic computer U3 and the third positive potential, and a second terminal of the capacitor C21 is connected to the second terminal of the second monolithic computer U3 and a second terminal thereof is grounded, The second singlechip U3 is respectively connected with the display screen control circuit, the USB interface control circuit, the battery control circuit and the switch key.
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