CN211084978U

CN211084978U - Digital tape and coding device for digital tape

Info

Publication number: CN211084978U
Application number: CN201921304501.3U
Authority: CN
Inventors: 胡文亮; 彭圣
Original assignee: Zhuhai Yixun Technology Co ltd
Current assignee: Zhuhai Yixun Technology Co ltd
Priority date: 2019-08-12
Filing date: 2019-08-12
Publication date: 2020-07-24
Anticipated expiration: 2029-08-12

Abstract

The utility model discloses an encoder for digital tape measure, include: the center of the roller is provided with a rotating shaft matched with the central through hole; a metal elastic member fixed to the roller; a plurality of groups of metal contact elements protruding out of the side surface are arranged on one side surface of the coded disc in a radial direction along the one side surface in a staggered manner, and the plurality of groups of metal contact elements do not completely cover the one side surface of the coded disc; each of the plurality of sets of metal contacts includes one or more metal contacts; the metal spring members are distributed within the 1/4 circle of the roller and include one or more protruding strip-like metal spring contacts that mate with the metal contacts in the same number as the number of sets of the plurality of sets of metal contacts and that are spaced apart from each other.

Description

Digital tape and coding device for digital tape

Technical Field

The utility model relates to a digital measurement field, in particular to digit tape and be used for coding device of digit tape.

Background

Tape measures are a commonly used length measuring tool in everyday life, because they are flexible and can be unrolled, and thus also become tape measures. In order to facilitate measurement and reading, a digital tape measure has been developed in recent years, in which the rotation of a code wheel is converted into the length of an object to be measured by a certain digital method and displayed on a liquid crystal display. However, some existing digital tape measures have the problem that the measurement accuracy is not high enough although the reading is convenient, and such tape measures are not suitable for the application occasions with higher measurement accuracy requirements. Therefore, it is necessary to design a digital tape measure which is convenient for reading and can improve the measurement accuracy, so as to meet the use requirement of high measurement accuracy.

The Chinese patent application No. 201611240444.8 entitled "Intelligent tape measure and measuring method thereof" discloses an intelligent tape measure and measuring method thereof, wherein a counting roller is arranged at an outlet of the tape measure, the roller rotates when the tape measure is pulled out, the scale of the tape measure can be calculated by the number of turns of the roller and the circumference of the roller and displayed on a display screen, meanwhile, the counting roller is also arranged at the lower part of a tape measure box, the length of a concave surface can be conveniently measured, the data is automatically uploaded to a mobile terminal through a wireless network after being determined, and the data is automatically uploaded to a cloud end for storage after being processed on the mobile terminal. However, it needs two counting rollers, and the structure is complicated.

SUMMERY OF THE UTILITY MODEL

In order to solve the problem that the digital tape measure existing in the prior art is complex in measuring structure, the utility model provides a digital tape measure, be used for the coding device and the corresponding measuring method of digital tape measure.

First, the utility model provides an encoder for digital tape measure, include:

the coded disc is circular and is provided with a central through hole;

the roller wheel is matched with the code wheel, and the center of the roller wheel is provided with a rotating shaft matched with the central through hole, so that the roller wheel can be fixed above the code wheel, is in contact with the code wheel and rotates relative to the code wheel; and

a metal elastic member fixed to the roller;

a plurality of groups of metal contact pieces protruding out of one side face of the coded disc are arranged on the side face of the coded disc in a radial direction along the one side face in a staggered mode, and the plurality of groups of metal contact pieces do not completely cover the one side face of the coded disc; wherein each of the plurality of sets of metal contacts comprises one or more metal contacts;

the metal elastic members are distributed in 1/4 circles of the roller wheel and comprise one or more strip-shaped metal elastic contact bodies which are matched with the metal contact bodies and are mutually separated and have the same number as that of the groups of the multiple groups of metal contact bodies, so that when the roller wheel rotates relative to the code wheel, the metal elastic members can be contacted with only one metal contact body in the same group of the multiple groups of metal contact bodies at the same time, and the contact relation between the metal elastic contact bodies in the metal elastic members and the multiple groups of metal contact bodies is unique at different times in the same period.

Further, in the above-mentioned coding device provided by the utility model, among the multiunit metal contact, the center that belongs to each among the same group metal contact arrives the radial distance of code wheel centre of a circle equals to, the center that belongs to two arbitrary metal contacts of different groups arrives each other the radial distance inequality in code wheel centre of a circle.

Further, in the above-mentioned coding device of the utility model provides, each among the metal contact is the ring segment that has certain radial width, and it upwards has first cambered surface and second cambered surface in footpath, wherein, first cambered surface arrives the distance in the centre of a circle of code wheel is less than the distance in second cambered surface to the centre of a circle.

Further, in the above-mentioned coding device of the present invention, among the plurality of sets of metal contacts, each of the metal contacts belonging to the same set is uniformly distributed in the circumferential direction of the circle formed with the same radial distance, so that the centers of the two adjacent contacts belonging to the same set are equal to the central angle formed by the center of the code wheel.

Further, in the above-mentioned coding device provided by the present invention, the number of the groups of the plurality of groups of metal contacts is 4.

Further, in the above coding device provided by the present invention, a central through hole closest to the code wheel in the first group of metal contacts, and a central angle formed by the first arc surface of the first group of metal contacts and the center of the code wheel is 26 °; the second group of metal contact pieces are close to the first group of metal contact pieces and are further away from the center of the coded disc than the first group of metal contact pieces, and a central angle formed by a first cambered surface of the first group of metal contact pieces and the center of the coded disc is 30 degrees; the third group of metal contact pieces are close to the second group of metal contact pieces and are further away from the center of the coded disc than the second group of metal contact pieces, and the central angle formed by the first cambered surface of the first group of metal contact pieces and the center of the coded disc is 13 degrees; and a fourth group of metal contact pieces are close to the third group of metal contact pieces and are farther away from the center of the coded disc than the third group of metal contact pieces, and a central angle formed by a first cambered surface of each fourth group of metal contact pieces and the center of the coded disc is 6 degrees.

Further, in the above coding device provided by the present invention, the diameters of the code wheel and the roller are both phi 41, and the diameter of the central through hole of the code wheel is phi 10; the diameter of the rotating shaft of the roller is phi 10.6.

Further, in the above-mentioned encoder device provided by the present invention, copper is laid on the surface of the metal contact of the code wheel.

Further, in the above coding device provided by the present invention, the metal elastic member is a spring piece.

Secondly, the utility model provides a digital tape measure comprising the coding device, further comprising a processor, a decoding device, a communication device and a display device; wherein,

the processor is connected with the encoding device, the decoding device, the communication device and the display device of the digital tape measure and is used for sending a control command to the devices and calculating the displacement;

the decoding device is connected with the processor and the encoding device and is used for decoding the codes generated by the encoding device;

the communication device is connected with the processor and used for sending the displacement calculated by the processor;

the display device is connected with the processor and used for displaying the displacement calculated by the processor.

The utility model discloses a beneficial achievement is: a simple encoding device can be provided and the accuracy can be provided in deciles in centimeters, i.e. 0.1 centimeters.

Drawings

The invention is further described with reference to the following figures and examples. In the accompanying drawings, like reference numerals refer to like parts throughout.

FIG. 1 shows a code wheel of a digital tape measure according to the present invention;

fig. 2 shows a roller of a digital tape measure according to the present invention;

FIG. 3 is a schematic view showing the combination of a code wheel and a roller of a digital tape measure according to the present invention;

fig. 4 is a system frame diagram of a digital tape measure according to the present invention;

fig. 5 is a schematic view of a digital tape measure according to the present invention;

fig. 6 is a flow chart of a measuring method of a digital tape according to the present invention.

Detailed Description

The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below with reference to the embodiments and the accompanying drawings, so as to fully understand the objects, aspects, and effects of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The same reference numbers will be used throughout the drawings to refer to the same or like parts.

It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature or indirectly fixed or connected to the other feature. Furthermore, the descriptions of upper, lower, left, right, etc. used in this application are only relative to the positional relationship of the various elements of the application with respect to one another in the drawings. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The exemplary embodiments described herein and depicted in the drawings should not be considered limiting. Various mechanical, compositional, structural, electrical, and operational changes, including equivalents, may be made without departing from the scope of this disclosure and the claims. In some instances, well-known structures and techniques have not been shown or described in detail to avoid obscuring the disclosure. The same reference numbers in two or more drawings identify the same or similar elements. Moreover, elements and their associated features, which are described in detail with reference to one embodiment, may be included in other embodiments, where they are not specifically shown or described, where practicable. For example, if an element is described in detail with reference to one embodiment and not described with reference to the second embodiment, it may also be claimed to be included in the second embodiment.

Furthermore, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any combination of one or more of the associated listed items.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element of the same type from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "at … …" depending on the context.

In an embodiment of the invention, the method steps may be performed in another order. The present invention is not limited to the order in which the method steps are performed.

Refer to fig. 1 showing a code wheel of a digital tape according to the present invention, and fig. 2 shows a roller of a digital tape according to the present invention. In an embodiment of the present invention, the utility model provides a coding device of digital tape measure, include:

the coded disc is circular and is provided with a central through hole; the roller wheel is matched with the code wheel, and the center of the roller wheel is provided with a rotating shaft matched with the central through hole, so that the roller wheel can be fixed above the code wheel, is in contact with the code wheel and rotates relative to the code wheel; and a metal elastic member fixed on the roller; a plurality of groups of metal contact pieces protruding out of one side face of the coded disc are arranged on the side face of the coded disc in a radial direction along the one side face in a staggered mode, and the plurality of groups of metal contact pieces do not completely cover the one side face of the coded disc; wherein each of the plurality of sets of metal contacts comprises one or more metal contacts; the metal elastic members are distributed in 1/4 circles of the roller wheel and comprise one or more strip-shaped metal elastic contact bodies which are matched with the metal contact bodies and are mutually separated and have the same number as that of the groups of the multiple groups of metal contact bodies, so that when the roller wheel rotates relative to the code wheel, the metal elastic members can be contacted with only one metal contact body in the same group of the multiple groups of metal contact bodies at the same time, and the contact relation between the metal elastic contact bodies in the metal elastic members and the multiple groups of metal contact bodies is unique at different times in the same period. Specifically, in an embodiment of the present invention, the period is a rotation period, that is, a process of rotating the roller for one circle relative to the code wheel.

Preferably, in an embodiment of the present invention, the metal elastic member is a leaf spring, as shown in fig. 2.

Specifically, referring to the schematic diagram of the code wheel and the roller of a digital tape measure according to the present invention shown in fig. 3, it is schematically shown how the code wheel and the roller are engaged with each other. The structure that code wheel and gyro wheel spring leaf are constituteed is used for the level to detect, and when the metal covering contact of spring leaf and code wheel, signal detection foot is unanimous with the level of signal trigger foot, so can produce periodic level signal after the gyro wheel rotates a week, can judge the displacement volume according to periodic signal change.

Further, in an embodiment of the present invention, in the plurality of sets of metal contact elements, the radial distance from the center of each of the metal contact elements belonging to the same set to the center of the circle of the code wheel is equal, and the radial distances from the centers of any two metal contact elements belonging to different sets to the center of the circle of the code wheel are unequal. That is, the metal contacts with equal distance to the center of the code wheel belong to the same group.

Further, in an embodiment of the present invention, each of the metal contacts is a circular ring segment having a certain radial width, and the circular ring segment has a first arc surface and a second arc surface in a radial direction, wherein a distance from the first arc surface to a center of the code wheel is smaller than a distance from the second arc surface to the center of the code wheel. That is, just because the ring segment has a certain width in the radial direction, the ring segment defines two arc surfaces in the radial direction, and the first arc surface is closer to the center of the circle of the code wheel than the second arc surface, and the second arc surface is farther from the center of the circle of the code wheel than the first arc surface. It should be understood that the above-mentioned first and second expressions are only used for distinguishing different curved surfaces, and are not intended to limit the sequence, and the first curved surface or the second curved surface can be closer to the center of the circle of the code wheel without violating the spirit of the present invention.

Further, in an embodiment of the present invention, in the plurality of sets of metal contacts, each of the metal contacts belonging to the same set is uniformly distributed in a circumferential direction of a circle formed at the same radial distance, so that centers of two adjacent contacts belonging to the same set are equal to a central angle formed by a center of the code wheel. It should be understood that the above-mentioned arrangement is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and the centers of two adjacent contact elements belonging to the same group may not be equal to the central angle formed by the center of the code wheel without departing from the spirit of the present invention.

Preferably, in an embodiment of the invention, the number of sets of the plurality of sets of metal contacts is 4 sets, as is the case in fig. 1. It is understood that the provision of 4 sets of metal contacts is only a preferred embodiment of the present invention, and that more or fewer sets of metal contacts may be provided without violating the spirit of the present invention, depending on the choice of precision and ease of processing.

Preferably, in an embodiment of the present invention, a central angle formed by a first arc surface of the first set of metal contact elements and a center of the code wheel is 26 °; the second group of metal contact pieces are close to the first group of metal contact pieces and are further away from the center of the coded disc than the first group of metal contact pieces, and a central angle formed by a first cambered surface of the first group of metal contact pieces and the center of the coded disc is 30 degrees; the third group of metal contact pieces are close to the second group of metal contact pieces and are further away from the center of the coded disc than the second group of metal contact pieces, and the central angle formed by the first cambered surface of the first group of metal contact pieces and the center of the coded disc is 13 degrees; and a fourth group of metal contact pieces are close to the third group of metal contact pieces and are farther away from the center of the coded disc than the third group of metal contact pieces, and a central angle formed by a first cambered surface of each fourth group of metal contact pieces and the center of the coded disc is 6 degrees. It should be understood that such an arrangement is only a preferred embodiment of the present invention, and the central angle formed by the first arc surface of each group and the center of the code wheel can be set according to actual needs without violating the spirit of the present invention.

Preferably, in an embodiment of the present invention, the diameters of the code wheel and the roller are both phi 41, and the diameter of the central through hole of the code wheel is phi 10; the diameter of the rotating shaft of the roller is phi 10.6, and it should be understood that such a setting mode is only a preferred embodiment of the present invention, and other diameter sizes can be set without violating the spirit of the present invention, which depends on the size and the measuring range of the tape.

Further, referring to the system framework diagram of a digital tape measure according to the present invention shown in fig. 4, in an embodiment of the present invention, the digital tape measure further includes a processor, a decoding device, a communication device, and a display device; the processor is connected with the encoding device, the decoding device, the communication device and the display device of the digital tape, and is used for sending a control command to the devices and calculating the displacement; the decoding device is connected with the processor and the encoding device and is used for decoding the codes generated by the encoding device; the communication device is connected with the processor and used for sending the displacement calculated by the processor; the display device is connected with the processor and used for displaying the displacement calculated by the processor.

Preferably, in an embodiment of the present invention, the structure of the code wheel device mainly includes a rotation level detection sensor composed of a code wheel circuit board, a roller and a spring leaf fixed on the roller, a signal generating source and a signal detecting pin are provided on the code wheel circuit board in advance, when the tape measure is pulled to drive the roller to rotate, the spring leaf on the roller will sweep over the copper-laying plane of the code wheel. The signal detection pin corresponding to the place where the spring piece passes through is in short connection with the signal generation source, so that the signal transmitted back to the main control CPU by the detection pin can generate the same signal with the signal generation source. According to the principle, when the spring piece sweeps across the copper-paved surface of the code disc at the same time, different signals are generated and transmitted back to the main control CPU when the four signal detection pins are staggered. After the roller rotates for one circle, the spring sheet can leave a circle of regular string codes on the code disc, and the main control CPU calculates the repeated times of the string codes to judge the number of the circles of the roller which rotates and the current string codes to judge the final rotating angular displacement of the roller. The dimensions that can be obtained with very high accuracy according to the above principle. According to the regular copper-paved surface on the code disc, the reading precision of the tape measure is up to a ten-minute numerical value with centimeter as a unit, namely 0.1 centimeter, and the error value caused by converting the size by utilizing the rotation number and the perimeter of the roller can be solved. The accuracy of the numerical value read by the main control MCU depends on the spacing accuracy of the copper-exposed planes on the code disc.

Preferably, referring to fig. 5, the operation diagram of a digital tape measure according to the present invention shows the situation when the spring plate sweeps across the code disc at a detecting time, each circle on the code disc represents a signal detecting pin, the spring plate fixed on the roller is driven to rotate when the roller rotates, 4 electrical signals generated at the place where the spring plate sweeps across will be transmitted to the processor at the same time, and at a certain time, when the spring plate contacts a certain metal contact of the code disc, the code is represented by "1", and when the spring plate does not contact a certain metal contact of the code disc, the code is represented by "0", so that, as shown in fig. 5, at a certain time, the spring plate contacts 4 metal contacts at the same time, respectively, and a 4-bit code signal is generated, such as 1001 and 1110 in the figure. The processor converts the received electrical signals into corresponding displacement amount information. Therefore, the physical quantity measured by the coding device is converted into an electric signal according to the four pins, and the electric signal is converted into the digital quantity of the current tape after being calculated and processed by the processor and is displayed or sent out through the communication device. The signal generating source pins and the signal testing pins of PA1, PA2, PA3 and PA4 are shown in the figure, wherein the signal testing pins of PA1, PA2, PA3 and PA4 correspond to a group of metal contacts respectively, and as shown in the figure, PA1 is at the outermost circle and PA4 is at the innermost circle; the single chip microcomputer presets that PA0 always outputs square wave signals, PA1, PA2, PA3 and PA4 serve as signal input capture pins, when the spring piece sweeps across the code wheel, if the spring piece is in contact with one of the metal contact pieces, for example, PA1 is in contact with the metal contact piece, the PA0 pin and the PA1 pin are in short circuit, so that a contact signal is generated, and if the spring piece is not in contact with any metal contact piece, the short circuit is not generated, and the contact signal is not generated.

Before the tape is rotated, the spring plate is positioned to leave four level signals (such as 1001) on the four test pins on the code disc, and the tape is pulled from 0 size to 3 meters. Then, a series of string codes from 1001 to 1110 can be measured from the four signal pins, and then the obtained string codes after the tape is pulled from 1001 to 1110 are calculated, namely, the cyclic string codes are repeated for a total of times from 1001 to 1110. Since after all, the spring plate must return to 1001 again when it makes one more revolution, and then it cycles through the last string number again. 3000 serial codes are obtained according to the rule, and 50 circles are repeated in total. I.e. a ring of 60 strings. According to the rule, namely, the preset signal string codes can be measured on the four pins when the tape is pulled out for 1 cm, namely, the one-to-one corresponding values are obtained in a table look-up mode, and according to the rule, the size of the tape which is pulled out by the tape can be judged. The tabular form diagram is as follows:

tape measure size (cm)	Code wheel corresponding code (code wheel out value)	Number of turns of code wheel (processor for calculation)
			0.0	1001	0
1.0	1001	1
			2.0	1001	2
0.5	1100	0
			1.5	1100	1
2.5	1100	2

Further, according to the foregoing discussion, in an embodiment of the present invention, it is also possible to be right according to the required precision the present invention provides a tape measure that is purposefully designed, for example, if the required precision is centimeter, then the present invention only needs a changed signal string code corresponding to the tape measure when the tape measure is pulled out of 1 centimeter. Therefore, the child can find the position of the tape after being pulled out through a table look-up mode. For example, the total length of the tape pull is 3 meters, corresponding to 50 rotations of the tape, 60 signal strings are required on the code disc (namely, the four signal pins simultaneously signal from 1001 to 1110), therefore, 60 signal groups need to be designed correspondingly on the code disc, and the code disc with 60 signal groups or the code disc specifications of 70 signal groups and the like can be designed according to the signal group.

Further, referring to fig. 6, the flow chart of the measuring method of the digital tape measure according to the present invention includes the following steps: A. the metal elastic contact bodies are generated on each detection time point, and respectively form an encoding group by the metal contact pieces and the generated contact or the non-generated contact; B. obtaining the corresponding relation of angular displacement corresponding to two adjacent codes in the code group according to the size of the code disc, the arrangement mode of the metal contact pieces and the detection time interval; C. and determining the displacement according to the corresponding relation and the number of the codes in the received code group. In an embodiment of the present invention, the step C may also calculate the displacement according to the periodic rule as discussed above.

Finally, in an embodiment of the invention, a computer-readable storage medium is proposed, on which a computer program is stored, characterized in that the computer program realizes the above-mentioned method steps when executed by a processor.

It should be recognized that embodiments of the present invention can be realized and implemented by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer readable memory. The methods may be implemented in a computer program using standard programming techniques, including a non-transitory computer-readable storage medium configured with the computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner, according to the methods and figures described in the detailed description. Each program may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Furthermore, the program can be run on a programmed application specific integrated circuit for this purpose.

Further, the method may be implemented in any type of computing platform operatively connected to a suitable interface, including but not limited to a personal computer, mini computer, mainframe, workstation, networked or distributed computing environment, separate or integrated computer platform, or in communication with a charged particle tool or other imaging device, and the like. Aspects of the invention may be embodied in machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, optically read and/or write storage medium, RAM, ROM, or the like, such that it may be read by a programmable computer, which when read by the computer may be used to configure and operate the computer to perform the procedures described herein. Further, the machine-readable code, or portions thereof, may be transmitted over a wired or wireless network. The utility model described herein includes these and other different types of non-transitory computer-readable storage media when such media include instructions or programs that implement the steps described above in conjunction with a microprocessor or other data processor. When programmed according to the methods and techniques of the present invention, the present invention also includes the computer itself.

Embodiments of this disclosure are described herein, including the best mode known to the applicant for carrying out the invention. Variations of those described embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The applicant expects skilled artisans to employ such variations as appropriate, and the applicant intends for the embodiments of the disclosure to be practiced otherwise than as specifically described herein. Accordingly, the scope of the present disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, the scope of the present disclosure encompasses any combination of the above-described elements in all possible variations thereof unless otherwise indicated herein or otherwise clearly contradicted by context.

While the present invention has been described in considerable detail and with particular reference to several illustrated embodiments thereof, it is not intended to be limited to any such details or embodiments or any particular embodiments, but rather it is to be construed as effectively covering the intended scope of the invention by providing a broad, potential interpretation of the claims in view of the prior art with reference to the appended claims. Further, the foregoing description of the present invention has been provided in terms of embodiments foreseen by the applicant for the purpose of providing a useful description, wherein insubstantial modifications of the present invention, not presently foreseen, may nonetheless represent equivalent modifications thereto.

The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. However, it will be apparent that: various modifications and changes may be made thereto without departing from the broader spirit and scope of the application as set forth in the claims.

Other variations are within the spirit of the present application. Accordingly, while the disclosed technology is susceptible to various modifications and alternative constructions, certain embodiments thereof have been shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the application to the specific form or forms disclosed; on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the application, as defined in the appended claims.

Claims

1. An encoding device for a digital tape, comprising:

the coded disc is circular and is provided with a central through hole;

a metal elastic member fixed to the roller; it is characterized in that the preparation method is characterized in that,

2. The encoding device according to claim 1, wherein, in the plurality of sets of metal contact pieces, the radial distance from the center of each metal contact piece belonging to the same set to the center of the code wheel is equal, and the radial distance from the center of any two metal contact pieces belonging to different sets to the center of the code wheel is unequal.

3. The encoding device of claim 1, wherein each of the metal contacts is a circular ring segment having a radial width and having a first arc surface and a second arc surface in a radial direction, wherein a distance from the first arc surface to a center of the code wheel is smaller than a distance from the second arc surface to the center of the code wheel.

4. The encoding device according to claim 3, wherein each of the plurality of sets of metal contacts belonging to the same set is uniformly distributed in a circumferential direction of a circle formed at the same radial distance, so that a center angle formed by centers of two adjacent contacts belonging to the same set and a center of the code wheel is equal.

5. The encoding device of claim 4, wherein the number of sets of the plurality of sets of metal contacts is 4 sets.

6. The encoding device of claim 5, wherein a center through hole of a first set of metal contacts closest to a code wheel and a center angle of a first arc surface of the first set of metal contacts and a center of the code wheel is 26 °; the second group of metal contact pieces are close to the first group of metal contact pieces and are further away from the center of the coded disc than the first group of metal contact pieces, and a central angle formed by a first cambered surface of the first group of metal contact pieces and the center of the coded disc is 30 degrees; the third group of metal contact pieces are close to the second group of metal contact pieces and are further away from the center of the coded disc than the second group of metal contact pieces, and the central angle formed by the first cambered surface of the first group of metal contact pieces and the center of the coded disc is 13 degrees; and a fourth group of metal contact pieces are close to the third group of metal contact pieces and are farther away from the center of the coded disc than the third group of metal contact pieces, and a central angle formed by a first cambered surface of each fourth group of metal contact pieces and the center of the coded disc is 6 degrees.

7. The encoding device as claimed in claim 1, wherein the diameters of the code wheel and the roller are both phi 41, and the diameter of the central through hole of the code wheel is phi 10; the diameter of the rotating shaft of the roller is phi 10.6.

8. The encoding device of claim 1, wherein a surface of the metal contact of the code wheel is copper plated.

9. The encoding device of claim 1, wherein the metal elastic member is a leaf spring.

10. A digital tape measure comprising the encoding device of any one of claims 1-9, further comprising a processor, a decoding device, a communication device, a display device; wherein,