TWI794764B - Eddy current sensing system and method thereof - Google Patents

Abstract

An eddy current sensing method is provided, which is suitable for an eddy current sensing system selectively coupled to a non-magnetic metal. The eddy current sensing method comprises the following steps: a signal processing unit generates an excitation current to an excitation sensing unit; the excitation sensing unit receives the excitation current and generates an excitation magnetic field according to the excitation current, wherein the non-magnetic metal generates an eddy current in response to the induced excitation magnetic field and then generates an induced magnetic field; the excitation sensing unit in response to the sensed spatial magnetic field, and transforms it into a voltage signal; the signal processing unit receives and inverses the voltage signal into the spatial magnetic field, and performs a magnetic field separation operation on the spatial magnetic field to obtain the magnitude and phase of the induced magnetic field, and performs an estimation operation according to the magnitude and phase of the induced magnetic field to estimate the conductivity and thickness of the non-magnetic metal.

Description

Eddy current sensing system and method thereof

The present invention relates to an eddy current sensing system and its method, and in particular to a method for controlling the penetration depth of the eddy current by controlling the operating frequency of the excitation current, and simultaneously estimating the Conductivity and thickness of non-magnetic metal, and eddy current sensing system and method for compensating conductance or correcting estimated value of conductivity through estimated thickness value.

Generally, there are two coils in the probe of a commercial conductivity tester, one is an excitation coil and the other is an induction coil. In operation, the excitation coil in the probe is passed with a fixed high-frequency current, thereby generating a high-frequency magnetic field. Therefore, when the probe is close to the metal to be tested (that is, non-magnetic metal), the metal to be tested will induce a high-frequency magnetic field, thereby generating an eddy current, and then generating an AC magnetic field. At this time, the induction coil in the probe can sense the size and phase of the spatial magnetic field (ie high-frequency magnetic field and AC magnetic field) around the metal to be tested. Then, the conductivity testing instrument estimates the conductivity of the metal to be tested based on this value. However, the general commercial conductivity tester does not take into account many factors that will affect the measurement error, such as the magnitude and phase of the AC magnetic field, the thickness of the metal to be tested, the penetration depth of the eddy current, etc., resulting in a high measurement error Or the measured value is unstable.

Therefore, in order to solve the problem that general commercial conductivity testers do not take into account factors such as the magnitude and phase of the AC magnetic field, the thickness of the metal to be tested, and the penetration depth of the eddy current, etc., the measurement error is too high or the measurement error is too high. The problem of unstable numerical values. An embodiment of the present invention provides an eddy current sensing system suitable for non-magnetic metals, including: a signal processing unit for generating an excitation current, wherein the excitation current has a specific frequency; and an excitation sensing unit coupled to the signal processing unit , to receive the excitation current and generate an excitation magnetic field accordingly, wherein when the excitation sensing unit is close to the non-magnetic conductive metal, the non-magnetic conductive metal generates eddy current in response to the induced excitation magnetic field, and then generates an induced magnetic field, and when When the excitation sensing unit senses the spatial magnetic field, the excitation sensing unit converts the spatial magnetic field into a voltage signal corresponding to the spatial magnetic field, wherein the spatial magnetic field is the excitation magnetic field and the induced magnetic field; wherein the signal processing unit receives the voltage signal and converts the voltage signal The signal is converted into a space magnetic field, and the magnetic field separation operation is performed on the space magnetic field to separate the induced magnetic field, and then the magnitude and phase of the induced magnetic field are obtained, and the estimation operation is performed accordingly to estimate the conductivity of the non-magnetic metal. and thickness.

In an embodiment of the present invention, the signal processing unit includes: a signal generator for generating an excitation current; a signal receiver for receiving a voltage signal and converting the voltage signal into a digital signal; and a processor coupled to In the signal generator and the signal receiver, it is used to control the signal generator and the signal receiver, and to receive the digital signal; among them, the processor inverts the digital signal into a space magnetic field, and performs a magnetic field separation operation on the space magnetic field, so as to The induced magnetic field is separated, and then the magnitude and phase of the induced magnetic field are obtained, and an estimation operation is performed accordingly to generate the conductivity and thickness of the non-magnetic conductive metal.

In an embodiment of the present invention, the excitation sensing unit includes: an excitation coil coupled to a signal generator for receiving an excitation current and generating an excitation magnetic field accordingly; a magnetic field sensor coupled to the excitation coil, It is used to sense the space magnetic field and convert the space magnetic field into a voltage signal; and the voltage amplifier is coupled to the magnetic field sensor to receive and amplify the voltage signal.

An embodiment of the present invention further provides an eddy current sensing system suitable for non-magnetic metals, including: a signal processing unit for generating multiple excitation currents, wherein each excitation current has a specific frequency, and the multiple specific frequencies are different from each other. the same; and the excitation sensing unit, coupled to the signal processing unit, is used to receive multiple excitation currents, and accordingly generate multiple excitation magnetic fields corresponding to the multiple excitation currents, wherein when the excitation sensing unit is close to the non-magnetic conduction When it is metal, the non-magnetic metal generates multiple eddy currents in response to the multiple excitation magnetic fields sensed, and then generates multiple induced magnetic fields corresponding to the multiple eddy currents, and the excitation sensing unit a plurality of spatial magnetic fields, respectively converting the plurality of spatial magnetic fields into a plurality of voltage signals corresponding to the plurality of spatial magnetic fields, wherein the plurality of spatial magnetic fields are a plurality of excitation magnetic fields and a plurality of induction magnetic fields; wherein the signal processing unit receives a plurality of voltage signals , and reversely transform multiple voltage signals into multiple spatial magnetic fields, and respectively perform magnetic field separation operations on multiple spatial magnetic fields to separate multiple induced magnetic fields, and then obtain the magnitude and phase of multiple induced magnetic fields, and Based on this, the average operation is performed to calculate the average value of the magnitude of the multiple induced magnetic fields and the average value of the phases of the multiple induced magnetic fields, and an estimation operation is performed accordingly to estimate the conductivity and thickness of the non-magnetic metal. .

In an embodiment of the present invention, the signal processing unit includes: a signal generator for generating multiple excitation currents; a signal receiver for receiving multiple voltage signals and converting the multiple voltage signals into multiple Digital signals corresponding to multiple voltage signals; and a processor, coupled to the signal generator and the signal receiver, for controlling the signal generator and the signal receiver, and receiving multiple digital signals; A digital signal is inversely converted into multiple spatial magnetic fields, and the magnetic field separation operation is performed on the multiple spatial magnetic fields to separate the induced magnetic field, and then the magnitude and phase of the multiple induced magnetic fields are respectively obtained, and the average operation is performed accordingly to calculate The average value of the magnitudes of the multiple induced magnetic fields and the average value of the phases of the multiple induced magnetic fields are obtained, and an estimation operation is performed accordingly to estimate the conductivity and thickness of the non-magnetic conductive metal.

In an embodiment of the present invention, the excitation sensing unit includes: an excitation coil, coupled to a signal generator, for receiving a plurality of excitation currents, and accordingly generating a plurality of excitation magnetic fields corresponding to a plurality of excitation currents; A sensor, coupled to the excitation coil, is used to sense multiple spatial magnetic fields, and respectively converts multiple spatial magnetic fields into multiple voltage signals; and a voltage amplifier, coupled to the magnetic field sensor, is used to receive and amplify voltage signal.

An embodiment of the present invention provides an eddy current sensing method, which is suitable for an eddy current sensing system selectively coupled to a non-magnetic metal, wherein the eddy current sensing system includes a signal processing unit and an excitation coupled to the signal processing unit The sensing unit, the eddy current sensing method includes: the signal processing unit generates an excitation current to the excitation sensing unit, wherein the excitation current has a specific frequency; the excitation sensing unit receives the excitation current, and generates an excitation magnetic field accordingly, wherein when the excitation sensing When the unit is close to the non-magnetic metal, the non-magnetic metal generates eddy current in response to the induced excitation magnetic field, and then generates an induced magnetic field; the excitation sensing unit responds to the sensed spatial magnetic field and converts the spatial magnetic field into a corresponding The voltage signal of the spatial magnetic field, wherein the spatial magnetic field includes the excitation magnetic field and the induced magnetic field; and the signal processing unit receives the voltage signal, converts the voltage signal into a spatial magnetic field, and performs a magnetic field separation operation on the spatial magnetic field to separate the induced magnetic field, and then The magnitude and phase of the induced magnetic field are obtained, and an estimation operation is performed based on the magnitude and phase, so as to estimate the conductivity and thickness of the non-magnetic metal.

An embodiment of the present invention further provides an eddy current sensing method, which is suitable for an eddy current sensing system selectively coupled to a non-magnetic metal, wherein the eddy current sensing system includes a signal processing unit and a sensor coupled to the signal processing unit Exciting the sensing unit, the eddy current sensing method includes: the signal processing unit respectively generates multiple excitation currents to the excitation sensing unit, wherein each excitation current has a specific frequency, and the multiple specific frequencies are different from each other; the excitation sensing unit respectively Receive a plurality of excitation currents, and accordingly generate a plurality of excitation magnetic fields corresponding to the plurality of excitation currents, wherein when the excitation sensing unit is close to the non-magnetic conductive metal, the non-magnetic conductive metal responds to the induced multiple excitation magnetic fields A plurality of eddy currents are respectively generated, and then a plurality of induced magnetic fields corresponding to the plurality of eddy currents are respectively generated; the excitation sensing unit responds to the sensed plurality of spatial magnetic fields, and respectively converts the plurality of spatial magnetic fields into a plurality of corresponding to the plurality of magnetic fields. A voltage signal of a spatial magnetic field, wherein the multiple spatial magnetic fields are multiple excitation magnetic fields and multiple induced magnetic fields; the signal processing unit receives multiple voltage signals, and respectively inverts the multiple voltage signals into multiple spatial magnetic fields, and respectively Multiple spatial magnetic fields perform magnetic field separation operations to separate multiple induced magnetic fields, and then obtain the magnitudes and phases of multiple induced magnetic fields; and the signal processing unit performs average calculations on the magnitudes and phases of multiple induced magnetic fields to calculate multiple The average value of the magnitude of the induced magnetic field and the average value of the phases of the multiple induced magnetic fields are used to perform an estimation operation to estimate the conductivity and thickness of the non-magnetic metal.

The eddy current sensing system and method provided by the embodiments of the present invention control the operating frequency of the excitation current, and then control the penetration depth of the eddy current to obtain a specific skin depth; and obtain it by magnetic field separation calculation The magnitude and phase of the induced magnetic field are used to perform estimation calculations to simultaneously estimate the conductivity and thickness of the non-magnetic metal; and the estimated value of the thickness is used to compensate the conductance or correct the estimated value of the conductivity. Thereby, the estimation accuracy of the conductivity is greatly improved. In addition, different skin depths can also be obtained by generating multiple excitation currents with different frequencies; and the magnitude and phase of multiple induced magnetic fields can be obtained by magnetic field separation operations, and the average operation can be performed accordingly to calculate multiple The average value of the size of an induced magnetic field and the average value of the phases of multiple induced magnetic fields, and based on this, perform an estimation operation to estimate the conductivity and thickness of the non-magnetic metal; and by the estimated thickness value, to come up with Compensate Conductance or Correct Estimates of Conductivity. In this way, the accuracy of the conductivity estimation is avoided when the non-magnetic conductive metal is too thin, and the estimation accuracy of the conductivity is greatly improved.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , the following preferred embodiments are specifically cited below, and are described in detail as follows in conjunction with the accompanying drawings. In order to make the above and other objects, features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

The eddy current sensing system and method provided by the embodiments of the present invention can be applied to measure the conductivity and thickness of non-magnetic metals (such as copper, molybdenum, and zinc).

Please refer to Figure 1 and Figure 2 at the same time, Figure 1 is a schematic diagram of the system architecture of an eddy current sensing system for measuring non-magnetic metals according to an embodiment of the present invention, and Figure 2 is a schematic diagram of the system according to an embodiment of the present invention Schematic flow chart of the eddy current sensing method. The eddy current sensing system 1 executes the eddy current sensing method by loading and executing the eddy current sensing software, wherein the eddy current sensing system 1 includes a signal processing unit 10 and an excitation sensor coupled to the signal processing unit 10 Unit 20. The eddy current sensing method includes the following steps: First, as shown in step S110, the signal processing unit 10 generates an excitation current (ie, alternating current) with a specific frequency, and transmits it to the excitation sensing unit 20, for example, from a frequency range of 100 Hz From ~8000Hz, select a specific frequency as the working frequency of the excitation current.

Furthermore, the signal processing unit 10 includes a signal generator 110 and a processor 130 . The signal generator 110 is controlled by the processor 130 to generate an excitation current with a specific frequency and a specific amplitude. In an example of the present invention, the signal processing unit 10 may further include a power amplifier (not shown) coupled to the signal generator 110 for receiving and amplifying the excitation current output by the signal generator 110 . Certainly, the signal generator 110 and the power amplifier can be integrated into a module.

Next, as shown in step S120 , the excitation sensing unit 20 is used to receive the excitation current and generate an excitation magnetic field (ie, an AC magnetic field) accordingly. When the excitation current passes through the excitation sensing unit 20, an excitation magnetic field will be generated around it. When the excitation sensing unit 20 is close to the non-magnetic metal 2, the excitation magnetic field will be coupled to the non-magnetic metal 2, and the non-magnetic metal 2 will generate an eddy current (current opposite to the excitation current) in response to the induced excitation magnetic field. , which in turn generates an induced magnetic field (that is, another AC magnetic field, generated by eddy currents).

Then, as shown in step S130, when the excitation sensing unit 20 responds to the sensed spatial magnetic field (mainly including the excitation magnetic field and the induced magnetic field), it performs signal conversion on the spatial magnetic field, that is, converts the spatial magnetic field into a signal corresponding to the spatial magnetic field. voltage signal. In an embodiment of the present invention, the relationship between the spatial magnetic field and the voltage signal may be a positive correlation, that is, a conversion function (conversion function) may be generated according to the positive correlation, so that the processor 130 realizes the spatial Signal conversion of magnetic field and voltage signals, but not limited thereto.

Furthermore, the drive sensing unit 20 includes a drive coil 210 , a magnetic field sensor 220 coupled to the drive coil 210 , and a voltage amplifier 230 coupled to the magnetic field sensor 220 . The excitation coil 210 generates an excitation magnetic field with a specific magnetic flux density according to the excitation current flowing therein. In other words, the excitation coil 210 is driven by the excitation current to generate an excitation magnetic field of a specific magnitude around it. The magnetic field sensor 220 generally refers to various sensors for measuring the magnetic field, preferably an anisotropic magnetoresistance sensor (AMR, Anisotropic Magnetoresistance Sensor), which is used to sense the magnetic field in the space and sense the magnetic field. The magnetic field is converted into a corresponding voltage signal. The voltage amplifier 230 is used for receiving and amplifying the voltage signal. In an example of the present invention, the magnetic field sensor 220 and the voltage amplifier 230 can be integrated into a module, that is, a magnetic field sensor that amplifies the voltage.

Afterwards, as shown in step S140 , the signal processing unit 10 receives the voltage signal, and inversely converts the voltage signal into a spatial magnetic field, so as to obtain the magnitude and phase of the spatial magnetic field. Then, a magnetic field separation operation is performed on the spatial magnetic field to separate the induced magnetic field, and then the magnitude and phase of the induced magnetic field are obtained. Then, an estimation operation is performed according to the value of the magnitude and phase of the induced magnetic field, so as to estimate the conductivity and thickness of the non-magnetic conductive metal 2 . Regarding the inverse conversion, further speaking, the signal processing unit 10 further includes a signal receiver 120 controlled by the processor 130 to convert the received voltage signal into a digital signal, and then the processor 130 uses the inverse function (inverse function) ) Convert the digital signal into a spatial magnetic field to obtain the magnitude and phase of the spatial magnetic field. It should be understood that the inverse function can be generated according to the conversion function in step S130. Each specific voltage signal corresponds to a specific digital signal, and each specific digital signal corresponds to a specific size and phase of the spatial magnetic field, that is, each specific voltage signal corresponds to a specific size and phase of the spatial magnetic field. In the embodiment of the present invention, the signal receiver 120 is preferably an analog-to-digital converter (ADC). In addition, the magnetic field separation calculation and estimation calculation will be described in detail after another embodiment is described.

In the example of the present invention, the signal processing unit 10 further includes a storage unit (not shown) and a display unit (not shown). The storage unit is preferably a non-volatile memory for storing various data, parameters, software and programs, such as storing eddy current sensing software and relevant data or parameters of the estimated template. The display unit (such as a display) is used for displaying the result of the estimation operation. For example, the processor 13 controls the signal generator 110 to generate an excitation current of a specific frequency according to the instructions or steps of the eddy current sensing software, or performs average calculation, magnetic field separation calculation, and estimation calculation on the received digital signal. , to produce the result of the operation.

Next, another embodiment of the present invention (hereinafter referred to as the second embodiment) will be described. The second embodiment is similar to the previous embodiment of the present invention, the difference is that the second embodiment uses a plurality of excitation currents of different frequencies to scan the non-magnetic metal 2 to obtain a plurality of different skin Depth (skin depth), so that the excitation sensing unit 20 generates a plurality of excitation magnetic fields and can sense a plurality of different spatial magnetic fields (such as a plurality of spatial magnetic fields of different sizes and phases); A plurality of different induced magnetic fields (such as a plurality of induced magnetic fields with different sizes and phases), and then the signal processing unit 10 performs an average operation on the plurality of induced magnetic fields, and performs an estimation operation according to the result of the average operation, thereby estimating the nonconductive Conductivity and thickness of magnetic metal 2.

Because the second embodiment combines the excitation frequencies of multiple different frequency bands (preferably combining the frequency bands of low frequency, intermediate frequency and high frequency), it can avoid using only the excitation frequency of a single frequency band to measure the thinner non-magnetic metal 2 , the influence on the accuracy of the estimated conductivity. In addition, the steps or system architecture of the second embodiment are similar or identical to those of the foregoing embodiments, and since the foregoing embodiments have been described in detail, they will not be repeated here and only focus on an overview.

Please refer to FIG. 1 and FIG. 3 at the same time. FIG. 3 is a schematic flowchart of an eddy current sensing method according to another embodiment of the present invention. The eddy current sensing method includes the following steps: First, as shown in step S210. The signal processing unit 10 respectively generates a plurality of excitation currents with different frequencies to the excitation sensing unit 20 , wherein each excitation current has a specific frequency and a specific amplitude, and these specific frequencies are different from each other. Furthermore, the signal generator 110 can separately or sequentially generate a plurality of exciting currents with different frequencies, and transmit them to the exciting coil 210 separately or sequentially, so as to sweep the frequency of the non-magnetic conductive metal 2, thereby obtaining multiple excitation currents. different skin depths. For example, the signal generator 110 can separately or sequentially generate excitation currents of a plurality of specific frequencies, such as 100Hz, 125Hz, 160Hz, 200Hz, 250Hz, 315Hz, 400Hz, 500Hz, 630Hz, 795Hz, 1000Hz, 1260Hz, 1585Hz, 1995Hz, 2510Hz, 3160Hz, 3980Hz, 5010Hz, 6310Hz, 7945Hz.

Next, as shown in step S220 , the excitation sensing unit 20 respectively or sequentially receives a plurality of excitation currents with different frequencies, and accordingly generates a plurality of excitation magnetic fields respectively or sequentially. It should be understood that each excitation current with a specific frequency corresponds to an excitation magnetic field with a specific magnitude and phase. Furthermore, when the excitation sensing unit 20 is close to the non-magnetic conductive metal 2, the excitation sensing unit 20 respectively or sequentially couples a plurality of excitation magnetic fields to the non-magnetic conductive metal 2, and the non-magnetic conductive metal 2 responds to the induction Multiple eddy currents are respectively or sequentially generated by the received multiple exciting magnetic fields, and then multiple induced magnetic fields corresponding to the eddy currents are respectively or sequentially generated.

Then, as shown in step S230, the excitation sensing unit 20 responds to the sensed multiple spatial magnetic fields, and respectively or sequentially converts the multiple spatial magnetic fields into multiple voltage signals corresponding to these spatial magnetic fields, wherein the multiple The spatial magnetic field includes multiple exciting magnetic fields and multiple induced magnetic fields. It should be understood that each spatial magnetic field with a specific magnitude and phase corresponds to a specific voltage signal.

After that, as shown in step S240 , the signal processing unit 10 respectively or sequentially receives a plurality of voltage signals, and respectively or sequentially converts these voltage signals into a plurality of spatial magnetic fields, so as to obtain the magnitude and phase of the plurality of spatial magnetic fields. Then perform a magnetic field separation operation on the multiple spatial magnetic fields separately or sequentially to separate the multiple induced magnetic fields, and then obtain the magnitudes and phases of the multiple induced magnetic fields. Furthermore, the signal receiver 120 is used to convert the multiple received voltage signals into multiple digital signals respectively or sequentially, and then the processor 130 converts the multiple digital signals into multiple digital signals respectively or sequentially through an inverse function. is the space magnetic field, so as to obtain the magnitude and phase of a plurality of space magnetic fields.

Next, as shown in step S250, the signal processing unit 10 performs an average operation on the magnitudes and phases of the multiple induced magnetic fields, so as to calculate the average value of the magnitudes of the multiple induced magnetic fields and the average value of the phases of the multiple induced magnetic fields, and calculate the average value of the multiple induced magnetic fields according to An estimation operation is performed to estimate the conductivity and thickness of the non-magnetic metal 2 .

Regarding the magnetic field separation operation, for example, the eddy current sensing system 1 can obtain the value of the magnitude and phase of the excitation magnetic field by measuring the spatial magnetic field without any non-magnetic conductive metal 2 (that is, only the excitation magnetic field exists in the spatial magnetic field). (including the real part and the imaginary part) and the corresponding voltage signal, and store it in the storage unit. In other words, each exciting magnetic field with a specific magnitude and phase corresponds to a specific voltage signal. Therefore, when the eddy current sensing system 1 is performing the magnetic field separation operation, the magnitude and phase of the measured spatial magnetic field (that is, including the excitation magnetic field and the induced magnetic field) can be subtracted from the value of the excitation magnetic field to calculate The magnitude and phase of the induced magnetic field. Then, an estimation operation (preferably a two-dimensional linear mapping interpolation method) can be performed according to the magnitude and phase of the induced magnetic field, so as to simultaneously estimate the conductivity and thickness of the non-magnetic conductive metal 2 . Because the magnitude and phase of the excitation magnetic field are excluded, and only the magnitude and phase of the induced magnetic field generated by the non-magnetic conductive metal 2 are estimated, the accuracy of the conductivity is greatly improved.

As for the estimation operation, it should first be explained that before performing the estimation operation, an estimation template must be established first. For example, it is established by means of actual measurement. For example, firstly, under the condition of inputting excitation currents with different excitation frequencies, measure The magnitude and phase of the induced magnetic field generated by the non-magnetic metal plate. Then, according to the measurement results (that is, the magnitude and phase of the induced magnetic field) and the known measurement parameters (including the thickness (Ti) of the non-magnetic metal plate, the conductivity (C _i ) of the non-magnetic metal plate and the excitation frequency ) to establish an estimation template as a basis for estimating the properties of the unknown non-magnetic metal 2 .

In an example of the present invention, the estimation template can be established by means of simulation, for example, the harmonic response of the eddy current and the magnetic field of non-magnetic metals 2 with different thicknesses and different conductivity can be established through a distributed current source model, and An estimation template is established according to the magnitude and phase of the magnetic field simulated by the distributed current source model as a basis for estimating the properties of the unknown non-magnetic conductive metal 2 . In another example of the present invention, the results obtained by simulation are used to correct the actual measurement results, and an estimation template is established according to the corrected data.

。 Please refer to FIG. 4A and FIG. 4B at the same time. FIG. 4A is a schematic diagram of an estimation template according to an embodiment of the present invention. FIG. 4B is a schematic diagram illustrating the grid mapping of the estimated template to a square grid according to an embodiment of the present invention. Each grid Qi is based on the measurement results, that is, the magnitude (M _i ) and phase (P _i ) of the induced magnetic field, and the corresponding measurement parameters or measurement conditions, which include the conductivity of the non-magnetic metal plate ( C _i ), thickness (T _i ) and excitation frequency. However, in order to improve the accuracy of the estimation, each grid in Fig. 3A can be mapped to a square grid of the coordinate system (ξ, η) using the linear interpolation function (Equation 1), such as the jth grid Q _j is formed by four calibration points (M _i , P _i ; C _i , T _i , where i =1~4), which are linearly mapped to a square grid in the coordinate system (ξ, η) using Equation 1, where

.

The estimation operation can be roughly divided into three steps. First, the first step is to determine that the value of the induced magnetic field obtained by measuring the non-magnetic conductive metal 2 (that is, the magnitude of the induced magnetic field (M _t ) and the phase of the induced magnetic field (P _t )) is located in the estimation template that grid. Assume that the result of the determination is a point D(M _t , P _t ) located on the jth grid Q _j . Knowing (M _t , P _t ) in grid Q _j , the second step is to solve a pair of nonlinear equations (Equation 1) for the corresponding (ξ, η).

=

，其中

(公式1)。

=

,in

(Formula 1).

Since (M _i , P _i ) to (C _i , T _i ) are bijective, the third step solves a pair of nonlinear equations (Eq. Conductivity (C _t ) and thickness (T _t ) of the magnetically permeable metal 2 . In other words, while estimating the thickness (T _t ), the estimated value of the thickness (T _t ) is also used to compensate the conductance or correct the estimated value of the conductivity (C _t ), thereby improving the estimate of the conductivity (C _t ). measurement accuracy, that is, to reduce the error of conductivity (C _t ).

=

(公式2)。

=

(Formula 2).

×100%。 In order to compare the accuracy of the eddy current sensing system and method of the embodiment of the present invention with that of a general commercial conductivity meter (product model FD-102) in measuring the conductivity of non-magnetic metals. Use the same non-magnetic metal material (zinc and copper) to measure non-magnetic metal plates with different thicknesses to compare the accuracy of conductivity. See Figure 5. Fig. 5 is a measurement result diagram of the eddy current sensing system and its method according to an embodiment of the present invention and a general commercial conductivity meter, wherein the triangle (△) mark represents the eddy current sensing system and its method of the embodiment of the present invention The measurement result of the circle (○) represents the measurement result of a general commercial conductivity meter; the horizontal axis represents the thickness (T) of the non-magnetic metal plate, and the vertical axis represents the error (E) of the conductivity. The calculation method As follows: E =

×100%.

It can be seen from Figure 5 that when using a general commercial conductivity meter to measure copper metal with a thickness of 0.5 mm, the error (E) of the conductivity is close to 10%, while when measuring the thickness of zinc metal with a thickness of 0.5 mm, the error (E) of the conductivity ( E) close to 20%. Conversely, when measuring copper metal with a thickness of 1~2mm, the error (E) of conductivity is close to 0%, and when measuring zinc metal with a thickness of 2mm, the error (E) of conductivity is close to 0%. This means that when a general commercial conductivity meter is used to measure a thin non-magnetic metal plate, the error (E%) of the conductivity will increase or increase significantly as the thickness decreases. In other words, general commercial conductivity meters are not suitable for measuring thin non-magnetic metal plates, that is, the measurement range is small.

It can be seen from FIG. 5 that when the eddy current sensing system of the embodiment of the present invention is used to measure copper metal and zinc metal with a thickness of 0.5-2 mm, the error (E%) of the measured conductivity is close to 0%. This means that when using the eddy current sensing system of the embodiment of the present invention to measure a thin non-magnetic metal plate, the error (E%) of the conductivity will not increase as the thickness decreases, but remains close to 0% error. In other words, the eddy current sensing system of the embodiment of the present invention is suitable for measuring non-magnetic metal plates of various thicknesses, that is, the measuring range is relatively large.

To sum up, the eddy current sensing system and method provided by the embodiments of the present invention obtain a specific skin depth by controlling the operating frequency of the excitation current and then controlling the penetration depth of the eddy current; The magnetic field separation operation is used to obtain the magnitude and phase of the induced magnetic field, and the estimation operation is performed accordingly to estimate the conductivity and thickness of the non-magnetic metal at the same time; and the estimated thickness value is used to compensate the conductance or correct the estimation of the conductivity value. Thereby, the estimation accuracy of the conductivity is greatly improved. In addition, different skin depths can also be obtained by generating multiple excitation currents with different frequencies; and the magnitude and phase of multiple induced magnetic fields can be obtained by magnetic field separation operations, and the average operation can be performed accordingly to calculate multiple The average value of the size of an induced magnetic field and the average value of the phases of multiple induced magnetic fields, and based on this, perform an estimation operation to estimate the conductivity and thickness of the non-magnetic metal; and by the estimated thickness value, to come up with Compensate Conductance or Correct Estimates of Conductivity. In this way, the accuracy of the conductivity estimation is avoided when the non-magnetic conductive metal is too thin, and the estimation accuracy of the conductivity is greatly improved.

Although the present invention has been disclosed above with the embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent application.

1: Eddy current sensing system 2: Non-magnetic metal 10: Signal processing unit 20: Exciting sensing unit 110: Signal generator 120: Signal receiver 130: Processor 210: Exciting coil 220: Magnetic field sensor 230: Voltage amplifier C ₁ , C ₂ , C ₃ , C ₄ , C _i : Conductivity M ₁ , M ₂ , M ₃ , M ₄ , M _i : The size of the induced magnetic field P ₁ , P ₂ , P ₃ , P ₄ , P _i : phase of induced magnetic field Q ₁ , Q ₂ , Q _i , Q _j , Q _n : grid T ₁ , T ₂ , T ₃ , T ₄ , T _i : thickness ξ,, η: coordinate system S110～S140 , S210～S250: steps

FIG. 1 is a schematic diagram of the system architecture of an eddy current sensing system for measuring non-magnetic metals according to an embodiment of the present invention. FIG. 2 is a schematic flowchart of an eddy current sensing method according to an embodiment of the present invention. FIG. 3 is a schematic flowchart of an eddy current sensing method according to another embodiment of the present invention. FIG. 4A is a schematic diagram of an estimation template according to an embodiment of the present invention. FIG. 4B is a schematic diagram illustrating the grid mapping of the estimated template to a square grid according to an embodiment of the present invention. FIG. 5 is a measurement result diagram of the eddy current sensing system and its method according to an embodiment of the present invention and a general commercial conductivity meter.

S110~S140: steps

Claims (8)

An eddy current sensing system suitable for a non-magnetic metal, comprising: a signal processing unit for generating an excitation current, wherein the excitation current has a specific frequency; and an excitation sensing unit coupled to the signal a processing unit for receiving the excitation current and generating an excitation magnetic field accordingly, wherein when the excitation sensing unit is close to the non-magnetic conductive metal, the non-magnetic conductive metal generates an eddy current in response to the induced excitation magnetic field, and Then generate an induced magnetic field, and when the excitation sensing unit senses a spatial magnetic field, the excitation sensing unit converts the spatial magnetic field into a voltage signal corresponding to the spatial magnetic field, wherein the spatial magnetic field is the excitation magnetic field and the induced magnetic field; wherein, the signal processing unit receives the voltage signal, converts the voltage signal into the space magnetic field, and performs a magnetic field separation operation on the space magnetic field to separate the induced magnetic field, and then obtains the induced The magnitude and phase of the magnetic field, and an estimation operation is performed accordingly to estimate the conductivity and thickness of the non-magnetic conductive metal. The eddy current sensing system as described in claim 1, wherein the signal processing unit includes: a signal generator for generating the excitation current; a signal receiver for receiving the voltage signal and converting the voltage signal is a digital signal; and a processor, coupled to the signal generator and the signal receiver, for controlling the signal generator and the signal receiver, and receiving the digital signal; Wherein, the processor converts the digital signal back into the space magnetic field, and performs the magnetic field separation operation on the space magnetic field to separate the induced magnetic field, and then obtains the magnitude and phase of the induced magnetic field, and performs the estimation accordingly. Calculate and calculate the conductivity and thickness of the non-magnetic metal. The eddy current sensing system as described in claim 2, wherein the excitation sensing unit includes: an excitation coil coupled to the signal generator for receiving the excitation current and generating the excitation magnetic field accordingly; a magnetic field a sensor, coupled to the excitation coil, for sensing the spatial magnetic field, and converting the spatial magnetic field into the voltage signal; and a voltage amplifier, coupled to the magnetic field sensor, for receiving and amplifying the voltage signal. An eddy current sensing system suitable for a non-magnetic metal, comprising: a signal processing unit for generating a plurality of excitation currents, wherein each excitation current has a specific frequency, and the specific frequencies are different from each other; and an excitation sensing unit, coupled to the signal processing unit, to receive the excitation currents, and accordingly generate a plurality of excitation magnetic fields corresponding to the excitation currents, wherein when the excitation sensing unit is close to the nonconductive When the magnetic metal is used, the non-magnetic metal generates a plurality of eddy currents in response to the induced excitation magnetic fields, and then generates a plurality of induced magnetic fields corresponding to the eddy currents, and the excitation sensing unit senses multiple space magnetic field, converting the spatial magnetic fields into a plurality of voltage signals corresponding to the spatial magnetic fields, wherein the spatial magnetic fields are the excitation magnetic fields and the induced magnetic fields; wherein the signal processing unit receives the voltage signals, Reversely convert these voltage signals into these spatial magnetic fields, and respectively perform a magnetic field separation operation on these spatial magnetic fields, so as to separate these induced magnetic fields, and then respectively obtain the magnitude and phase of these induced magnetic fields, and Perform an average operation accordingly to calculate the average value of the magnitudes of the induced magnetic fields and the average value of the phases of the induced magnetic fields, and perform an estimation operation accordingly to estimate the conductivity of the non-magnetic conductive metal and thickness. The eddy current sensing system as described in claim 4, wherein the signal processing unit includes: a signal generator for generating the excitation currents; a signal receiver for receiving the voltage signals, and respectively These voltage signals are converted into a plurality of digital signals corresponding to these voltage signals; and a processor, coupled to the signal generator and the signal receiver, is used to control the signal generator and the signal receiver, and receive These digital signals; wherein, the processor converts these digital signals into these space magnetic fields respectively, and separately performs the magnetic field separation operation on these space magnetic fields, so as to separate the induced magnetic field, and then respectively obtain the induced magnetic fields. The magnitude and phase of the magnetic field, and based on this average operation, to calculate the magnitude of the induced magnetic field small average value and the average value of the phases of the induced magnetic fields, and perform the estimation operation accordingly, so as to estimate the conductivity and thickness of the non-magnetic conductive metal. The eddy current sensing system as described in claim 5, wherein the excitation sensing unit includes: an excitation coil, coupled to the signal generator, for receiving the excitation currents and generating a plurality of excitation currents accordingly the excitation magnetic field corresponding to the current; a magnetic field sensor coupled to the excitation coil for sensing the spatial magnetic fields and converting the spatial magnetic fields into the voltage signals; and a voltage amplifier coupled to the The magnetic field sensor is used to receive and amplify the voltage signal. An eddy current sensing method suitable for an eddy current sensing system selectively coupled to a non-magnetic conductive metal, wherein the eddy current sensing system includes a signal processing unit and a signal processing unit coupled to the signal processing unit The excitation sensing unit, the eddy current sensing method includes: the signal processing unit generates an excitation current to the excitation sensing unit, wherein the excitation current has a specific frequency; the excitation sensing unit receives the excitation current, and according to generating an excitation magnetic field, wherein when the excitation sensing unit is close to the non-magnetic conductive metal, the non-magnetic conductive metal generates an eddy current in response to the induced excitation magnetic field, and then generates an induced magnetic field; The excitation sensing unit converts the spatial magnetic field into a voltage signal corresponding to the spatial magnetic field in response to a sensed spatial magnetic field, wherein the spatial magnetic field includes the excitation magnetic field and the induced magnetic field; and the signal processing unit receives The voltage signal, and convert the voltage signal into the space magnetic field, and perform a magnetic field separation operation on the space magnetic field to separate the induced magnetic field, and then obtain the magnitude and phase of the induced magnetic field, and perform an estimation accordingly Measurement operation to estimate the conductivity and thickness of the non-magnetic metal. An eddy current sensing method suitable for an eddy current sensing system selectively coupled to a non-magnetic conductive metal, wherein the eddy current sensing system includes a signal processing unit and a signal processing unit coupled to the signal processing unit Exciting the sensing unit, the eddy current sensing method includes: the signal processing unit respectively generates a plurality of excitation currents to the excitation sensing unit, wherein each of the excitation currents has a specific frequency, and the specific frequencies are different from each other; The excitation sensing unit respectively receives the excitation currents, and accordingly generates a plurality of excitation magnetic fields corresponding to the excitation currents, wherein when the excitation sensing unit is close to the non-magnetic conductive metal, the non-magnetic conductive metal responds to the induction Generate a plurality of eddy currents respectively by the excitation magnetic fields received, and then generate a plurality of induced magnetic fields corresponding to the eddy currents; In response to the sensed multiple spatial magnetic fields, the excitation sensing unit converts these spatial magnetic fields into a plurality of voltage signals corresponding to the spatial magnetic fields, wherein the spatial magnetic fields are the excitation magnetic fields and the induction magnetic field; the signal processing unit respectively receives the voltage signals, and converts the voltage signals into the space magnetic fields respectively, and performs a magnetic field separation operation on the space magnetic fields to separate the induced magnetic fields, and then obtaining the magnitudes and phases of the induced magnetic fields respectively; and the signal processing unit performing an average operation on the magnitudes and phases of the induced magnetic fields to calculate the average value of the magnitudes of the induced magnetic fields and the ratio of the phases of the induced magnetic fields average value, and perform an estimation operation accordingly to estimate the conductivity and thickness of the non-magnetic metal.

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