TW201918707A - Hardness measurement apparatus and hardness measurement method - Google Patents

Abstract

A hardness measurement apparatus including a storage device, a processing device, and an electromagnetic sensing device is provided. The storage device stores a hardness classification model. The processing device generates a control signal. The processing device outputs the control signal to the electromagnetic sensing device to operate the electromagnetic sensing device to sense a metal object in a non-contact sensing manner at a specific frequency. The electromagnetic sensing device outputs an electromagnetic sensing result of the metal object to the processing device. The processing device analyzes the electromagnetic induction result to determine the impedance parameter of a sensing coil. The processing device determines a hardness of the metal object according to the impedance parameter the sensing coil and the hardness classification model. In addition, a hardness measurement method is also provided.

Description

Hardness measuring device and hardness measuring method

The present invention relates to a sorting technique, and more particularly to a hardness measuring apparatus and a hardness measuring method.

In the manufacturing process of a metal component, if a plurality of metal components having the same shape and appearance are respectively processed through different heat treatment processes, these metal components having the same shape and appearance may have different hardnesses, respectively. In this regard, the manufacturer needs to measure the hardness of these metal components one by one to classify them. However, the hardness measurement method of the conventional metal component is to measure the hardness by a destructive method, and the single variable data conversion can only be performed by a single database, resulting in low measurement accuracy and slow measurement speed. Therefore, the hardness measurement method of the conventional metal component cannot be effectively applied to the classification of the metal component. In view of this, the present invention will set forth the solutions of several embodiments below.

The invention provides a hardness measuring device and a hardness measuring method, which can quickly and effectively sense a metal object to obtain an impedance parameter of a sensing coil corresponding to a magnetic field change of the metal object, and is determined according to the impedance parameter of the sensing coil. The hardness of metal objects.

The hardness measuring device of the present invention includes a storage device, a processing device, and an electromagnetic sensing device. The storage device is used to store the hardness classification model. The processing device is coupled to the storage device. The processing device is operative to generate a control signal. The electromagnetic sensing device is coupled to the processing device. The processing device outputs a control signal to the electromagnetic sensing device to operate the electromagnetic sensing device to sense the metal object in a non-contact sensing manner according to a specific frequency. The electromagnetic sensing device outputs an electromagnetic sensing result of the metal object to the processing device. The processing device analyzes the electromagnetic sensing results to determine an impedance parameter of the sensing coil. The processing device determines the hardness of the metal object according to the impedance parameter of the sensing coil and the hardness classification model.

The hardness measuring method of the present invention is suitable for a hardness measuring device. The hardness measuring device includes an electromagnetic sensing device. The hardness measuring method comprises the steps of: establishing a hardness classification model; operating the electromagnetic sensing device to sense the metal object in a non-contact sensing manner according to a specific frequency, and generating an electromagnetic sensing result of the metal object by the electromagnetic sensing device; And analyzing the electromagnetic sensing result to determine the impedance parameter of the sensing coil, and determining the hardness of the metal object according to the impedance parameter of the sensing coil and the hardness classification model.

Based on the above, the hardness measuring device and the hardness measuring method of the present invention can sense the metal object by the non-contact sensing method to effectively and quickly obtain the impedance parameter of the sensing coil, and can be further established by further basis. The hardness classification model and the impedance parameters of the sensing coil are used to accurately determine the hardness of the metal object.

The above described features and advantages of the invention will be apparent from the following description.

In order to make the content of the present invention easier to understand, the following specific embodiments are examples of the invention that can be implemented. In addition, wherever possible, the same elements, components, and steps in the drawings and embodiments are used to represent the same or similar components.

1 is a schematic view of a hardness measuring apparatus according to an embodiment of the present invention. Referring to FIG. 1, the hardness measuring apparatus 100 includes a processing device 110, a storage device 120, and an electromagnetic sensing device 130, wherein the electromagnetic sensing device 130 includes a sensing coil. In the present embodiment, the storage device 120 and the electromagnetic sensing device 130 are coupled to the processing device 110. The storage device 120 is configured to store the hardness classification model 121. In the present embodiment, the hardness measuring device 100 senses the metal object 200 through the electromagnetic sensing device 130 in a non-contact sensing manner to obtain the electromagnetic sensing result of the metal object 200. The processing device 110 analyzes the electromagnetic sensing result of the metal object 200 to determine the impedance parameter of the sensing coil of the electromagnetic sensing device 130, and determines the hardness of the metal object 200 according to the impedance parameter of the sensing coil and the hardness classification model 121.

However, it should be noted that the hardness described in the various embodiments of the present invention refers to the surface hardness of the metal object 200, and the electromagnetic sensing device 130 senses the metal object 200 by an Eddy Current sensing technique. That is, since the surface hardness of the metal object 200 is related to the magnetic field change of the sensing coil of the electromagnetic sensing device 130 during the sensing process, the hardness measuring apparatus 100 of the present embodiment calculates the difference in the magnetic field variation of the sensing coil. The corresponding impedance parameter change is obtained to cause the hardness measuring device 100 to determine the hardness of the metal object 200 by determining the change in the impedance parameter of the sensing coil before and after sensing. Also, in one embodiment, the hardness measuring device 100 is further collocated with a material property database to establish an association between impedance parameters and hardness.

Further, the calculation method of the impedance parameter of the sensing coil of the present embodiment is, for example, an impedance derivation equation to which the eddy current sensing technique of the following formula (1) is applied, but the present invention is not limited thereto. ...Formula 1)

In the above formula (1), Z is the impedance of the sensing coil, d is the width of the coil, α is the coefficient, μ0 is the magnetic permeability of the air, and λ is the wavelength of the sensing signal, r1 is the inner diameter of the coil, and r2 is The outer diameter of the coil and n _c are the number of turns of the coil. In the present embodiment, regarding the calculation method of the impedance parameter, those skilled in the art can obtain sufficient teachings, suggestions, and implementation instructions according to the general knowledge of general electromagnetic law derivation and hardness conversion, and therefore, no further description is made here. .

In the present embodiment, the hardness measuring apparatus 100 previously establishes the hardness classification model 121. The hardness classification model 121 includes a plurality of hardness classifications, and these hardness classifications respectively correspond to different impedance parameters. Therefore, after the electromagnetic sensing device 130 measures the impedance parameter, the processing device 110 classifies the metal object 200 into one of the plurality of hardness classes according to the impedance parameter. That is, when the hardness measuring apparatus 100 is used to sense a plurality of metal articles having different hardnesses, the hardness measuring apparatus 100 can quickly sense the metal products having different hardnesses one by one in a non-contact sensing manner.

In this embodiment, the processing device 110 is, for example, a central processing unit (CPU), a system on chip (SOC), or other programmable general purpose or special purpose microprocessor (microprocessor). ), Digital Signal Processor (DSP), programmable controller, Application Specific Integrated Circuits (ASIC), Programmable Logic Device (PLD), and other similar processing A device or a combination of these devices.

In this embodiment, the storage device 120 is, for example, a dynamic random access memory (DRAM), a flash memory, or a non-volatile random access memory (Non-Volatile Random Access Memory). , NVRAM) and so on. In the present embodiment, the storage device 120 is configured to store the data and modules described in the embodiments of the present invention, and provides the processing device 110 to read and execute the hardware measurement device 100 to implement various embodiments of the present invention. The operations and methods described.

2 is a schematic diagram of an electromagnetic sensing device according to an embodiment of the invention. Referring to FIG. 2, the electromagnetic sensing device 330 includes a signal generator 331, a filter 332, a signal amplifier 333, a driving circuit 334, a sensing coil 335, a filter 336, and a signal processor 337. The signal generator 331 is coupled to the filter 332 and the signal processor 337. The filter 332 is coupled to the signal amplifier 333. The signal amplifier 333 is coupled to the driving circuit 334. The driving circuit 334 is coupled to the sensing coil 335. The sensing coil 335 is coupled to the filter 336. Filter 336 is coupled to signal processor 337. In the present embodiment, the electromagnetic sensing device 330 receives the control signal CS output by the processing device such as the above-described embodiment of FIG. 1 by the signal generator 331 and outputs the electromagnetic sensing result SR by the signal processor 337 to, for example. It is the processing apparatus of the above embodiment of Fig. 1.

In the present embodiment, the signal generator 331 generates the sine wave signal SW to the filter 332, the signal amplifier 333, and the drive circuit 334 according to the control signal CS, and generates the reference signal RS to the signal processor 337. In the present embodiment, the sine wave signal SW is the same as the reference signal RS. In the present embodiment, the filter 332 filters out noise in the sine wave signal SW, and the signal amplifier 333 increases the amplitude of the sine wave signal SW. Therefore, the drive circuit 334 generates the drive signal DS in accordance with the modulated sine wave signal SW. The driving circuit 334 drives the sensing coil 335 by the driving signal DS to sense the metal object. In the present embodiment, the sensing coil 335 is used to sense a metal object and generate a sensing signal SS. The sense coil 335 outputs the sense signal SS to the filter 336. The filter 336 filters out the noise in the sensing signal SS and provides the modulated sensing signal SS to the signal processor 337. Therefore, the signal processor 337 analyzes the sensing signal SS to output the electromagnetic sensing result SR.

3 is a schematic view of a toroidal coil and a metal object according to an embodiment of the invention. Referring to FIG. 2 and FIG. 3, the sensing coil 335 according to various embodiments of the present invention may be, for example, shown in FIG. For example, the metal article 400 is, for example, a metal screw and has a single metal material or a combination of a plurality of metal materials, and the invention is not limited thereto. In the present embodiment, the sensing coil 335 is a single or multiple turns of a metal-shaped toroidal coil, and the sensing coil 335 generates an alternating magnetic field. When the metal object 400 passes through the enclosed area of the sensing coil 335, the surface of the metal object 400 generates an eddy current, and the sensing coil 335 generates a magnetic field change corresponding to the eddy current of the surface of the metal object 400 to output the sensing signal SS to Signal processor 337.

It is worth noting that the impedance change of the sensing coil 335 corresponds to the electromagnetic property of the material of the metal article, and the material electromagnetic property of the metal article corresponds to the hardness of the metal article. That is, when the manufacturer manufactures a plurality of metal products having different hardnesses (for example, a plurality of metal screws), the manufacturer can pass the metal products having different hardness one by one through the sensing coil 335 to obtain corresponding hardnesses. The magnetic field of the sensing coil 335 of these metal products is changed, and the impedance change of the sensing coil 335 is obtained according to the magnetic field variation result of the sensing coil 335. Therefore, the manufacturer can determine the hardness of these metal products of different hardness according to the impedance change of the sensing coil 335, and classify the metal products of different hardness according to the hardness.

4 is a flow chart showing a method of measuring hardness according to an embodiment of the present invention. Referring to FIGS. 1 and 4, the hardness measuring method of the present embodiment can be applied at least to the hardness measuring apparatus 100 of FIG. The hardness measuring apparatus 100 may sequentially perform steps S410 to S460 to determine the hardness of the metal object 200. First, the hardness measuring apparatus 100 of the present embodiment determines in advance a specific frequency for sensing the metal object 200. Therefore, in step S410, the processing device 110 controls the electromagnetic sensing device 130 to sense the test object by a plurality of electromagnetic test signals of different frequencies. Moreover, in step S420, the processing device 110 selects one of the plurality of test results corresponding to the electromagnetic test signals having the highest signal to noise ratio (SNR) as the specific frequency. That is, the hardness measuring apparatus 100 of the present embodiment has a function of automatically selecting a frequency having a relatively high noise as a specific frequency according to the electromagnetic characteristics corresponding to the metal material of the metal object 200, so that the hardness measuring apparatus 100 according to this A specific frequency is used to generate a sensing signal. In the present embodiment, the specific frequency may be selected, for example, from a frequency range of 1 Hz to 900 MHz.

Next, in step S430, the electromagnetic sensing device 130 senses a plurality of metal samples in advance according to the specific frequency, wherein the metal samples may have different hardnesses, respectively. In step S440, the processing device 110 determines the position of at least one of the plurality of coordinate systems based on the plurality of sample sensing results of the metal samples and the plurality of property databases. That is, the hardness measuring apparatus 100 of the present embodiment previously establishes hardness partitions corresponding to various different hardnesses.

In detail, FIG. 5 is a schematic diagram of a hardness classification model according to an embodiment of the present invention. As illustrated in FIG. 5, in the present embodiment, the hardness classification model stored by the storage device 120 may include a plurality of coordinate system information as shown in FIG. 5, wherein the horizontal axis represents the real (Re) impedance, and the vertical axis represents the virtual Part (Im) impedance. In the present embodiment, the arithmetic logic of the hardness measuring apparatus 100 performs the real part impedance measurement first, and then performs the imaginary part impedance measurement, and then performs the operation conversion. In addition, in this embodiment, the storage device 120 may further store a plurality of characteristic databases, and the processing device 110 senses a plurality of metal samples in advance through the electromagnetic sensing device 130 to sense multiple samples according to the metal samples. The results and these property databases determine the locations of these partitions 501-504 in the complex coordinate system.

For example, in the present embodiment, the partitions 501 to 504 correspond to different hardnesses, respectively. As shown in FIG. 5, the partitions 501 to 504 correspond to, for example, 20 Rockwell hardness (HRC), 30HRC, 40HRC, and 50HRC, respectively, but the present invention is not limited thereto. When the electromagnetic sensing device 130 senses the metal object 200 to obtain the electromagnetic sensing result of the metal object 200, the processing device 110 analyzes the electromagnetic sensing result to determine the impedance parameter Z of the sensing coil of the electromagnetic sensing device 130. In this example, the impedance parameter Z of the sensing coil of the electromagnetic sensing device 130 is complex and is represented by R+jX in the form of a complex coordinate system, wherein the real part of the impedance is R, and the imaginary part of the impedance is X. The processing device 110 classifies the hardness of the metal object 200 belonging to the partition 502 according to the position of the complex coordinate (R, X) in the plurality of coordinate systems of the impedance parameter Z of the sensing coil of the electromagnetic sensing device 130, wherein the hardness of the partition 502 is 30HRC.

In this embodiment, the property database includes at least one of a material property database, an electromagnetic property database, a standard metal database, a mechanical property data, a heat treatment property database, and an accessory database. These property databases provide, for example, material property parameters, electromagnetic property parameters, or thermal property parameters of various metal objects 200, and the like, to enable the processing device 110 to establish a hardness classification based on the property database and the plurality of sample sensing results described above. model. Further, regarding the relationship between the impedance parameter and the hardness of the present embodiment, for example, the impedance parameter and the hardness derivation formula of the following formula (2) are applied to determine the position (partition) of the impedance parameter in the complex coordinate system, However, the invention is not limited to this. ...formula (2)

In the above formula (2), Z is the impedance of the sensing coil, A is the material permeability parameter formula set, and B is the material conductivity parameter formula set. In the present embodiment, regarding the impedance parameter and the manner of conversion of the hardness, those skilled in the art can obtain sufficient teaching, suggestion, and implementation instructions according to the general knowledge of general electromagnetic law derivation and hardness conversion, and therefore do not More details.

Then, in step S450, the electromagnetic sensing device 130 senses the metal object 200 in a non-contact sensing manner according to the specific frequency, and obtains the impedance parameter of the sensing coil of the electromagnetic sensing device 130. In step S460, the processing device 110 determines the hardness of the metal object according to the impedance parameter of the sensing coil of the electromagnetic sensing device 130 and the hardness classification model. Therefore, the hardness measuring method of the present embodiment can effectively and quickly judge the hardness of a metal object.

It should be noted that the partitions 501 to 504 shown in FIG. 5 are hardnesses respectively corresponding to different impedance ranges. In the present embodiment, the hardness measuring apparatus 100 corresponds a specific impedance range to a specific hardness parameter. Since the electromagnetic sensing device 130 senses that the electromagnetic sensing result of the metal object 200 may have an error, or the metal object 200 is synthesized from a plurality of materials, the present invention has a specific impedance range corresponding to a specific hardness parameter. That is, the hardness measuring apparatus 100 estimates or estimates the impedance range corresponding to one or more specific hardness parameters based on the plurality of sample sensing results and the plurality of characteristic databases to establish the hardness classification model 121. For another example, when a manufacturer wants to classify a plurality of metal objects having different hardnesses, the manufacturer can sense the metal objects of different hardnesses via the electromagnetic sensing device 130. Moreover, the hardness measuring apparatus 100 only needs to calculate the electromagnetic parameter of the sensing coil of the electromagnetic sensing device 130 corresponding to the eddy current generated on the surface of the metal object 200 to obtain the impedance parameter of the sensing coil. The hardness measuring apparatus 100 determines the hardness of the metal object 200 in accordance with the position of the impedance parameter of the sensing coil in the plurality of coordinate systems. That is to say, the hardness measuring apparatus 100 does not need to take time to perform a conversion operation between the impedance parameter of the sensing coil and the hardness of the metal object 200. Therefore, the hardness measuring apparatus 100 can effectively and quickly judge the hardness of these metal objects of different hardnesses, and can efficiently and quickly classify these metal objects of different hardnesses. Additionally, in an embodiment, the hardness measuring apparatus 100 further includes a display device. The display device is coupled to the processing device 110 and displays an image frame of the classification result, and the classification result includes a hardness classification model and hardness information of the metal object.

6 is a flow chart showing a method of measuring hardness according to another embodiment of the present invention. Referring to FIGS. 1 and 6, the hardness measuring method of the present embodiment can be applied at least to the hardness measuring apparatus 100 of FIG. In step S610, the hardness measuring apparatus 100 establishes the hardness classification model 121 in advance. In step S620, the hardness measuring apparatus 100 operates the electromagnetic sensing device 130 to sense the metal object 200 in a non-contact sensing manner according to a specific frequency, and generates an electromagnetic sensing result of the metal object 200. In step S630, the hardness measuring device 100 analyzes the electromagnetic sensing result to determine the impedance parameter of the sensing coil of the electromagnetic sensing device 130, and according to the impedance parameter of the sensing coil of the electromagnetic sensing device 130 and the hardness classification model 121 The hardness of the metal article 200 is determined. Therefore, the hardness measuring method of the present embodiment can effectively measure the impedance parameter of the metal object 200, and quickly determine the hardness of the metal object 200 according to the impedance parameter of the metal object 200 and the hardness classification model 121.

In addition, other device features and implementation details of the hardness measuring apparatus 100 described in this embodiment can be referred to the contents of the foregoing embodiments of FIG. 1 to FIG. 5, and sufficient teachings, suggestions, and implementation descriptions are obtained, and details are not described herein again.

In summary, the hardness measuring device and the hardness testing method of the present invention can efficiently and quickly sense a metal object by a non-contact sensing method, and can further sense a metal object according to the sensing coil. The magnetic field change result in the process is used to obtain the impedance parameter of the sensing coil, so that the hardness measuring device of the present invention can estimate the hardness of the metal object according to the impedance parameter of the sensing coil and the pre-established hardness classification module, without It is complicated to convert the impedance parameter of the sensing coil into the hardness of the corresponding metal object. Therefore, the hardness measuring apparatus and the hardness testing method of the present invention can provide an effective and rapid hardness measurement of a metal object for classifying metal objects.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧ hardness measuring device

110‧‧‧Processing device

120‧‧‧Storage device

121‧‧‧ hardness classification model

130, 330‧‧‧Electromagnetic sensing device

200, 400‧‧‧Metal objects

331‧‧‧Signal Generator

332, 336‧‧‧ filter

333‧‧‧Signal Amplifier

334‧‧‧ drive circuit

335‧‧‧Sense coil

337‧‧‧Signal Processor

501, 502, 503, 504‧‧‧ partition

S410, S420, S430, S440, S450, S460, S610, S620, S630‧‧ steps

CS‧‧‧Control signal

SW‧‧ sine wave signal

RS‧‧‧ reference signal

SS‧‧‧Sensor signal

DS‧‧‧ drive signal

SR‧‧‧Electromagnetic sensing results

1 is a schematic view of a hardness measuring apparatus according to an embodiment of the present invention. 2 is a schematic diagram of an electromagnetic sensing device according to an embodiment of the invention. 3 is a schematic view of a toroidal coil and a metal object according to an embodiment of the invention. 4 is a flow chart showing a method of measuring hardness according to an embodiment of the present invention. FIG. 5 is a schematic diagram showing a hardness classification model according to an embodiment of the present invention. 6 is a flow chart showing a method of measuring hardness according to another embodiment of the present invention.

Claims (20)

A hardness measuring device, comprising: a storage device for storing a hardness classification model; a processing device coupled to the storage device for generating a control signal; and an electromagnetic sensing device coupled to the processing device, wherein The processing device outputs the control signal to the electromagnetic sensing device to operate the electromagnetic sensing device to sense a metal object in a non-contact sensing manner according to a specific frequency, and the electromagnetic sensing device outputs the metal object An electromagnetic sensing result is sent to the processing device, wherein the processing device analyzes the electromagnetic sensing result to determine an impedance parameter of a sensing coil, and the processing device classifies the impedance parameter of the sensing coil according to the impedance parameter The model determines the hardness of the metal object. The hardness measuring device according to claim 1, wherein the electromagnetic sensing device senses a test object by a plurality of electromagnetic test signals of different frequencies, and the processing device selects the electromagnetic test signals corresponding to the electromagnetic test signals. One of the multiple test results has the highest noise ratio frequency as the particular frequency. The hardness measuring apparatus according to claim 1, wherein the hardness classification model includes a plurality of coordinate systems, and the impedance parameter includes a real part impedance value and an imaginary part impedance value. The hardness measuring apparatus according to claim 3, wherein the plurality of coordinates includes at least one partition, and the at least one partition respectively corresponds to different hardnesses. The hardness measuring device of claim 4, wherein the storage device further stores a plurality of characteristic databases, and the processing device senses a plurality of metal samples in advance through the electromagnetic sensing device to determine the metal according to the metal A plurality of sample sensing results of the sample and the library of properties determine a location of the at least one partition in the plurality of coordinate systems. The hardness measuring device according to claim 5, wherein the property database comprises a material property database, an electromagnetic property database, a standard metal database, a mechanical property data, a heat treatment property database, and At least one of a library of accessories. The hardness measuring device of claim 1, further comprising: a display device coupled to the processing device for displaying a classification result, and the classification result includes the hardness classification model and the hardness of the metal object . The hardness measuring device of claim 1, wherein the electromagnetic sensing device comprises: a signal generator coupled to the processing device for receiving the control signal, and the signal processor generates the control signal according to the control signal a driving signal coupled to the signal generator and the sensing coil for receiving the driving signal, and driving the sensing coil according to the driving signal to sense the metal object to The sensing coil outputs a sensing signal; and a signal processor coupled to the signal generator and the sensing coil for receiving the reference signal and the sensing signal, and the signal processor compares the reference signal And the sensing signal to output the electromagnetic sensing result to the processing device. The hardness measuring device according to claim 8, wherein the sensing coil generates an alternating magnetic field, so that the metal object generates an eddy current correspondingly, and the sensing coil senses the eddy current to output the feeling Measuring signal. The hardness measuring device according to claim 8, wherein the sensing coil is a loop coil, and the sensing coil generates the sensing signal when the metal object passes through a surrounding area of the sensing coil. A hardness measuring method is applicable to a hardness measuring device, and the hardness measuring device comprises an electromagnetic sensing device, wherein the hardness measuring method comprises: establishing a hardness classification model; operating the electromagnetic sensing device to be non-contact according to a specific frequency Sensing means for sensing a metal object and generating an electromagnetic sensing result of the metal object; and analyzing the electromagnetic sensing result to determine an impedance parameter of a sensing coil, and according to the sensing coil The impedance parameter and the hardness classification model determine a hardness of the metal object. The method for measuring hardness according to claim 11, further comprising: sensing, by the electromagnetic sensing device, a test object by using a plurality of electromagnetic test signals of different frequencies, and selecting and corresponding to the electromagnetic tests One of the plurality of test results of the signal has the highest noise ratio frequency as the particular frequency. The hardness measuring method according to claim 11, wherein the hardness classification model includes a complex coordinate system, and the impedance parameter includes a real part impedance value and an imaginary part impedance value. The method of measuring hardness according to claim 13, wherein the plurality of coordinates includes at least one partition, and the at least one partition each corresponds to a different hardness. The method of measuring hardness according to claim 14, wherein the step of establishing the hardness classification model comprises: sensing a plurality of metal samples through the electromagnetic sensing device in advance, according to the plurality of metal samples; The sample sensing results and a plurality of property databases determine the location of the at least one partition in the hierarchy. The method for measuring hardness according to claim 15, wherein the property database comprises a material property database, an electromagnetic property database, a standard metal database, a mechanical property data, a heat treatment property database, and At least one of a library of accessories. The method for measuring hardness according to claim 11, further comprising: displaying a classification result by a display device, and the classification result includes the hardness classification model and the hardness of the metal object. The method of measuring hardness according to claim 11, wherein the electromagnetic sensing device comprises: a signal generator coupled to the processing device for receiving the control signal, and the signal processor generates the control signal according to the control signal a driving signal coupled to the signal generator and the sensing coil for receiving the driving signal, and driving the sensing coil according to the driving signal to sense the metal object to The sensing coil outputs a sensing signal; and a signal processor coupled to the signal generator and the sensing coil for receiving the reference signal and the sensing signal, and the signal processor compares the reference signal And the sensing signal to output the electromagnetic sensing result to the processing device. The method of measuring hardness according to claim 18, wherein the sensing coil generates an alternating magnetic field, so that the metal object correspondingly generates an eddy current, and the sensing coil senses the eddy current to output the feeling Measuring signal. The method of measuring hardness according to claim 18, wherein the sensing coil is a loop coil, and the sensing coil generates the sensing signal when the metal object passes through a surrounding area of the sensing coil.