TW201629428A - Length measurement system, method and electronic tape - Google Patents

Abstract

The invention relates to the measurement field, especially relates to a kind of length measurement system, method and electronic tape. The system includes an information acquisition module, a calculation module and a display control module. The information acquisition module is used to acquire bar code information detected by a sensor from the tape and store the acquired bar code information in the storage unit. The calculation module is used to count the value of a cumulative variable S according to the bar code information acquired in the information acquisition module. The calculation module is also used to control to stop counting the cumulative variable S in a response to a use's operation and determine a current value of the cumulative variable S. The control calculation module counts the length value L based on the determined value of the cumulative variable S and a formula L=S*W. The display control module is used to display the length value of L on a display unit. The present invention is easy to realize and is beneficial to improve the precision of length measuring.

Description

Length measuring system, method and electronic tape measure

The present invention relates to the field of measurement, and in particular to a length measuring system, method and electronic tape measure.

In the prior art, the tape measure is usually engraved with a scale and is marked with a corresponding value for length measurement. However, the numerical value not only increases the width of the tape measure, but also increases the volume of the tape measure, and the accuracy is not high.

In view of the above, it is necessary to provide a length measuring system, method and electronic tape measure to solve the above problems.

An electronic tape measure comprising a tape measure tape and a tape measure body, the tape measure comprising a display unit, a processing unit, a storage unit and a sensor, wherein the tape measure tape is provided with a first code column and a second code column for indicating bar code information, The first code column and the second code column each include a first color bar code and a second color bar code of equal width, and the sensor is at the exit of the tape measure tape of the tape body for detecting at a fixed frequency The bar code information on the tape measure tape protruding from the body of the tape measure, the processing unit includes:

The information acquisition module is configured to obtain barcode information on the tape measure detected by the sensor and store the barcode information in the storage unit;

The calculation module is configured to count the value of the accumulated variable S according to the bar code information of the tape measure acquired by the information acquisition module, and control the stop of counting the accumulated variable S to determine the value of the current accumulated variable S in response to the user operation. And calculating the length value L according to the determined cumulative variable S and the formula: L=S*W, where W is the width of the first color barcode or the second color barcode;

The display control module is configured to display the length value calculated in the calculation module on the display unit for the user to view.

A length measuring system for use in an electronic tape measure, the system comprising:

The information acquisition module is configured to obtain barcode information on the tape measure detected by the sensor and store the barcode information in the storage unit;

The calculation module is configured to count the value of the accumulated variable S according to the bar code information of the tape measure acquired by the information acquisition module, and control the stop of counting the accumulated variable S to determine the value of the current accumulated variable S in response to the user operation. And calculating the length value L according to the determined cumulative variable S and the formula: L=S*W;

The display control module is configured to display the length value calculated in the calculation module on the display unit for the user to view.

A length measuring method for use in an electronic tape measure, the method comprising the steps of:

Obtaining bar code information on the tape measure detected by the sensor and storing the bar code information in the storage unit;

Counting the accumulated variable S according to the acquired bar code information, and in response to the user controlling the operation to stop counting the accumulated variable S, determining the current accumulated variable S, and calculating one according to the determined accumulated variable S and the formula: L=S*W Length value L; and

The calculated length value L control is displayed on the display unit for viewing by the user.

The invention determines the value of an accumulated variable S according to the detected bar code information of the tape measure of the protruding tape body and calculates a length value according to the determined accumulated variable S and the formula: L=S*W, which is simple and improves the length. measurement accuracy.

1 is a schematic view showing the appearance of an electronic tape measure in the present invention.

2 is a functional block diagram of an electronic tape measure in the present invention.

3 is a schematic view of a tape measure in an embodiment of the present invention.

4 is a functional block diagram of a length measuring system of the present invention.

FIG. 5 is a schematic diagram of the sensor detecting barcode information of a tape measure according to an embodiment of the present invention.

FIG. 6 is a table of bar code information change according to an embodiment of the present invention.

Figure 7 is a schematic view of a tape measure in accordance with another embodiment of the present invention.

FIG. 8 is a schematic diagram of the sensor detecting barcode information of a tape measure according to another embodiment of the present invention.

FIG. 9 is a table of bar code information change according to another embodiment of the present invention.

Figure 10 is a flow chart of the length measuring method of the present invention.

The length measuring system, method and electronic tape provided by the present invention are further described in detail below with reference to the accompanying drawings and embodiments.

Please refer to FIG. 1 , which is a schematic diagram showing the appearance of the electronic tape measure 100 . The electronic tape measure 100 includes a tape measure body 60 and a tape measure 10. The tape measure 10 can extend from the tape measure body 60 to measure the length of the object and can be received in the tape measure body 60. Referring to FIG. 2 together, the electronic tape measure 100 further includes a display unit 20, a processing unit 30, a storage unit 40, and a sensor 50 disposed on the tape measure body 60.

Referring to FIG. 3 together, a schematic view of the tape measure 10 in accordance with an embodiment of the present invention is shown. The tape strip 10 is provided with a first bar code column 11 and a second bar code column 12, and the first bar code column 11 and the second bar code column 12 each include a first color bar code 101 and a second color bar code 102. The width of the first color bar code 101 and the second color bar code 102 are the same, and the width value can be set according to the accuracy requirement of the measurement. For example, when the measurement accuracy of the electronic tape measure 100 is required to be 1 μm, the first color bar code can be used. The width of the 101 and second color bar code 102 is set to 1 μm. The first code column 11 is periodically alternately arranged from the beginning end of the tape measure 10 with a first color bar code 101, a second color bar code 102, and a second color bar code 102; the second bar code column 12 is from the tape tape 10 The beginning is periodically alternately arranged with the second color bar code 102, the second color bar code 102, and the first color bar code 101. In the present embodiment, the first color bar code 101 is a black bar code, and the second color bar code 102 is a white bar code. In other embodiments, the first color barcode 101 and the second color barcode 102 can be any two different colors, such as red and green, black and yellow, white, and black, respectively.

The sensor 50 is facing the exit 66 of the tape measure 10 of the tape measure body 60 for detecting bar code information on the tape measure 10 extending from the tape measure body 60 at a fixed frequency. In the present embodiment, the inductor 50 is a barcode scanner such as a laser or a CCD (Charge-Coupled Device). Specifically, the sensing area of the sensor 50 is a linear sensing area, and the linear sensing area covers the first barcode column 11 and the second barcode array 12, so that the sensor 50 senses the tape measure each time. The bar code information of 10 is combined information C1C2 including the first bar code bar code information C1 and the second bar code bar code information C2. In this embodiment, the first barcode column barcode information C1 and the second barcode column barcode information C2 are color information. For example, if the sensor 50 detects that the color of the first barcode column 11 is black, the second barcode is detected. The column 12 is white, and the sensor 50 determines that the barcode information of the detection is "black and white".

In the embodiment, the display unit 20 is an LCD display screen, an electronic paper display screen, an LED display screen, and the like. A length measurement system 200 (hereinafter referred to as system 200) is stored in the storage unit 40, and the system 200 can be invoked by the processing unit 30. In other embodiments, the system 200 is a program segment/firmware embedded in the processing unit 30. The processing unit 30 is configured to calculate a length value according to the barcode information detected by the sensor 50 and display the length value on the display unit 20 for the user to view.

Please refer to Figure 4. The system 200 includes an information acquisition module 210, a calculation module 220, and a display control module 230. The module referred to in the system 200 is a program segment that performs a specific function.

The information acquisition module 210 is configured to acquire barcode information on the tape measure 10 detected by the sensor 50, and store the barcode information of the detected tape measure 10 in the storage unit 40. For example, referring to FIG. 5, the bar code information on the tape measure 10 currently detected by the sensor 50 is C1C2, and the information acquisition module 210 acquires the bar code information C1C2 of the tape measure 10 and stores the information in the storage unit 40. When the bar code information on the tape measure 10 currently detected by the sensor 50 is C2C2, the information acquisition module 210 acquires the bar code information C2C2 of the tape measure 10 and stores the information in the storage unit 40; when the sensor 50 detects The bar code information on the current tape measure 10 is C2C1, and the information acquisition module 210 acquires the bar code information C2C1 of the tape measure 10 and stores the information in the storage unit 40.

Please refer to FIG. 6 , which is a schematic diagram of a barcode information change table T1 according to an embodiment of the present invention. The bar code information change table T1 defines the relationship between the bar code information change trend and the cumulative variable S increase and decrease. The calculation module 220 is configured to calculate the value of the accumulated variable S according to the barcode information of the tape measure 10 acquired by the information acquisition module 210. Specifically, the computing module 220 first determines, according to the barcode information of the obtained tape measure 10, whether the bar code information currently detected by the sensor 50 and the bar code information detected by the sensor 50 have changed before, if the tape measure 10 is determined before and after If the bar code information detected is changed, the trend of the change is further determined, and the accumulated variable S is incremented or decremented by 1 according to the bar code information change trend. If the calculation module 220 determines that the tape measure 10 is detected one after another. The bar code information does not change, and the value of the accumulated variable S does not change. In this embodiment, the sensor 50 detects the fixed frequency of the tape measure 10 to ensure that the tape measure 10 moves at least one time when the tape width 10 is moved. Obviously, the fixed frequency detected by the sensor 50 is greater than the tape width 10 The frequency of change of bar code information on the tape measure 10 when the tape measure body 60 is out. In the present embodiment, the barcode information detected by the inductor 50 on the tape measure 10 is only C1C2, C2C2, and C2C1. In other embodiments, the sensor 50 performs on-the-spot detection on the bar code information on the extended tape measure 10, and the calculation module 220 determines that the bar code information has not changed after a predetermined time. The bar code information detected before 50 is analyzed to determine the number of times and the trend of the change of the bar code information, and the accumulated variable S is further calculated.

Specifically, in the embodiment, the calculation module 220 calculates the accumulated variable S according to the relationship between the bar code information change trend and the accumulated variable S in the bar code information change table T1, including: 1) if the calculation module 220 determines the bar code When the information changes and the change trend is the first change trend, the calculation module 220 controls the accumulated variable S plus one. As shown in FIG. 6, the first change trend is C1C2->C2C2->C2C1->C1C2. If the bar code information on the previous tape measure 10 of the calculation module 220 is C1C2, and the bar code on the current tape measure 10 The information is C2C2, or the bar code information on the previous tape measure 10 is C2C2, and the bar code information on the current tape measure 10 is C2C1, or the bar code information on the previous tape measure 10 is C2C1, and the barcode on the current tape measure 10 is 10 The information is C1C2, and the calculation module 220 determines that the bar code information change trend is the first change trend control accumulation variable S plus 1. 2) If the calculation module 220 determines that the bar code information changes and the change trend is the second change trend, the calculation module 220 controls the accumulated variable S minus 1. Specifically, the second change trend is C1C2 -> C2C1 -> C2C2 -> C1C2. If the calculation module 220 determines that the bar code information on the previous tape measure 10 is C1C2, and the bar code information on the current tape measure 10 is C2C1, Or determining that the bar code information on the previous tape measure 10 is C2C1, and the bar code information on the current tape measure 10 is C2C2, or determining that the bar code information on the previous tape measure 10 is C2C2, and the bar code information on the current tape measure 10 is C1C2, the calculation module 220 controls the accumulated variable S minus 1.

Referring to FIG. 7, a schematic view of a tape measure 10 in accordance with another embodiment of the present invention is shown. The first bar code array 11 is periodically alternately arranged from the beginning end of the tape measure 10 with the first color bar code 101, the second color bar code 102, and the first color bar code 101; the second bar code column 12 is from the tape tape 10 The beginning is periodically alternately arranged with the first color bar code 101, the second color bar code 102, and the second color bar code 102. Please refer to FIG. 8 , which is a schematic diagram of the bar code information of the tape 50 detected by the sensor 50 according to another embodiment of the present invention. The barcode information detected by the sensor 50 on the tape 10 is only C1C1, C2C2, and C1C2. three situations. Referring to FIG. 9 together, the calculation module 220 calculates the accumulated variable S according to the relationship between the bar code information change trend and the accumulated variable S in the bar code information change table T2, including: 1) if the calculation module 220 determines the bar code information change When the change trend is the third change trend, the calculation module 220 controls the accumulated variable S plus one. As shown in FIG. 9, the third change trend is C1C1 -> C2C2 -> C1C2 -> C1C1. If the bar code information on the previous tape measure 10 of the calculation module 220 is C1C1, and the bar code on the current tape measure 10 The information is C2C2, or the bar code information on the previous tape measure 10 is C2C2, and the bar code information on the current tape measure 10 is C1C2, or the bar code information on the previous tape measure 10 is C1C2, and the barcode on the current tape measure 10 is 10 If the information is C1C1, the calculation module 220 determines that the bar code information change trend is the third change trend control accumulation variable S plus 1. 2) If the calculation module 220 determines that the bar code information changes and the change trend is the fourth change trend, the calculation module 220 controls the accumulated variable S minus 1. Specifically, the second change trend is C1C1 -> C1C2 -> C2C2 -> C1C1. If the calculation module 220 determines that the bar code information on the previous tape measure 10 is C1C1, and the bar code information on the current tape measure 10 is C1C2, Or determining that the bar code information on the previous tape measure 10 is C1C2, and the bar code information on the current tape measure 10 is C2C2, or determining that the bar code information on the previous tape measure 10 is C2C2, and the bar code information on the current tape measure 10 is C1C1, the calculation module 220 controls the accumulated variable S minus 1.

As shown in FIG. 1, the tape measure body 60 is further provided with a determination button 62 and a clear button 64.

The calculation module 220 further determines, in response to the user's pressing operation of the determination button 62, the counting of the accumulated variable S to determine the value of the current accumulated variable S and the value and formula according to the determined accumulated variable S: L=S* W calculates the length value L. Where W is the width of the first color bar code 101 or the second color bar code 102 on the first code column 11 / the second bar code column 12 . In other embodiments, the computing module 220 stops counting the accumulated variable S when the accumulated variable S has not changed for more than a predetermined time (for example, 2 seconds), and determines the current accumulated variable S, and according to the determined accumulated variable. S and the formula: L = S * W to calculate a length value L.

The display control module 230 is configured to display the calculated length value in the calculation module 220 on the display unit 20 for viewing by the user.

In the embodiment, the system 200 further includes a count clearing module 240 for responding to the user's pressing operation of the clear button 64 to control the accumulated variable S to be cleared so that the electronic tape measure 100 performs the next time. measuring. In other embodiments, the counting and clearing module 240 determines that the tape measure 10 has been completely accommodated in the tape measure body 60 when the sensor 50 does not detect the bar code information, and the control clears the accumulated variable S.

Please refer to FIG. 10, which is a flowchart of a method for measuring length in the present invention. The method is applied to the electronic tape measure 100 described above, the method comprising the steps of:

S301: The information acquisition module 210 acquires the bar code information on the tape measure 10 detected by the sensor 50, and stores the bar code information of the detected tape measure 10 in the storage unit 40.

S302: The calculation module 220 calculates the value of the accumulated variable S according to the barcode information of the tape measure 10 acquired by the information acquisition module 210. The calculation module 220 determines, according to the barcode information of the obtained tape measure 10, whether the bar code information currently detected by the sensor 50 and the bar code information detected by the sensor 50 have changed before, and if the tape measure 10 is determined to be detected before and after. If there is a change in the bar code information, the trend of the change is further judged, and the accumulated variable S is incremented or decremented by 1 according to the trend of the bar code information. If the calculation module 220 determines that the bar code information detected on the tape measure 10 has not changed, the value of the accumulated variable S does not change.

In the present embodiment: 1) If the calculation module 220 determines that the bar code information changes and the change trend is the first change trend, the calculation module 220 controls the accumulated variable S to increase by one. Wherein, as shown in FIG. 6, the first change trend is C1C2 (first color, second color) -> C2C2 (second color, second color) -> C2C1 (second color, first color) -> C1C2 (first color, second color), if the bar code information on the previous tape measure 10 of the calculation module 220 is C1C2, and the bar code information on the current tape measure 10 is C2C2, or the bar code information on the previous tape measure 10 For C2C2, the bar code information on the current tape measure 10 is C2C1, or the bar code information on the previous tape measure 10 is C2C1, and the bar code information on the current tape measure 10 is C1C2, the calculation module 220 determines the bar code information change trend. For the first change trend control, the accumulated variable S is incremented by 1. 2) If the calculation module 220 determines that the bar code information changes and the change trend is the second change trend, the calculation module 220 controls the accumulated variable S to decrease by one. Specifically, the second change trend is C1C2 (first color, second color) -> C2C1 (second color, first color) -> C2C2 (second color, second color) -> C1C2 (first color) The second color), if the calculation module 220 determines that the bar code information on the previous tape measure 10 is C1C2, and the bar code information on the current tape measure 10 is C2C1, or the bar code information on the previous tape measure 10 is C2C1, The bar code information on the current tape measure 10 is C2C2, or the bar code information on the previous tape measure 10 is C2C2, and the bar code information on the current tape measure 10 is C1C2, the calculation module 220 controls the accumulated variable S minus 1.

S303: The computing module 220 controls to stop counting the accumulated variable S in response to the user pressing the determining button 62 to determine the current accumulated variable S, and calculates according to the determined accumulated variable S and the formula: L=S*W A measured length value L is obtained.

S304: The display control module 230 displays the length value calculated in the calculation module 220 on the display unit 20 for the user to view.

The method further includes the step of: the counting and clearing module 240 is responsive to the pressing operation of the clearing button 64 by the user to control the accumulated variable S to be cleared.

The above embodiments are only intended to illustrate the technical solutions of the present invention and are not intended to be limiting, and the present invention will be described in detail with reference to the preferred embodiments. Without departing from the spirit and essence of the technical solutions of the present invention.

100‧‧‧Electronic tape measure

10‧‧‧ Tape measure tape

20‧‧‧ display unit

30‧‧‧Processing unit

40‧‧‧ storage unit

50‧‧‧ sensor

60‧‧‧Volume body

62‧‧‧OK button

64‧‧‧Clear button

66‧‧‧Exit

T1, T2‧‧‧ barcode information change table

11‧‧‧first code column

12‧‧‧Second code column

101‧‧‧First color bar code

102‧‧‧Second color barcode

200‧‧‧ Length measuring system

210‧‧‧Information acquisition module

220‧‧‧Computation Module

230‧‧‧Display Control Module

240‧‧‧Counting Clearing Module

S301~S304‧‧‧Steps

no

S301‧‧‧ obtains the bar code information on the tape measure detected by the sensor, and stores the bar code information of the detected tape tape in the storage unit

S302‧‧‧ Calculate the value of the accumulated variable S based on the bar code information of the tape measure acquired by the information acquisition module

S303‧‧‧ In response to the user pressing the determination button, the control stops counting the accumulated variable S to determine the current accumulated variable S, and calculates according to the determined accumulated variable S and the formula ‧‧‧L=S*W A measured length value L

S304‧‧‧ Display the calculated length value in the calculation module on the display unit for the user to view

Claims (10)

An electronic tape measure comprising a tape measure tape and a tape measure body, the improvement being:
The tape measure includes a display unit, a processing unit, a storage unit, and a sensor;
The tape strip is provided with a first code column and a second code column for indicating bar code information, and the first code column and the second code column respectively include a first color bar code and a second color bar code having the same width;
The sensor is being at the exit of the tape measure of the tape measure body for detecting bar code information on the tape measure tape extending from the tape measure body at a fixed frequency;
The processing unit includes:
The information acquisition module is configured to obtain barcode information on the tape measure detected by the sensor and store the barcode information in the storage unit;
The calculation module is configured to count the value of the accumulated variable S according to the bar code information of the tape measure acquired by the information acquisition module, and control the stop of counting the accumulated variable S to determine the value of the current accumulated variable S in response to the user operation. And calculating the length value L according to the determined cumulative variable S and the formula: L=S*W, wherein W is the width of the first color barcode or the second color barcode; and the display control module is used to control the calculation module The calculated length value is displayed on the display unit for the user to view. The electronic tape measure of claim 1, wherein the calculation module determines, according to the barcode information of the obtained tape measure, whether the bar code information currently detected by the sensor and the bar code information detected by the sensor have changed. If it is determined that the bar code information detected on the tape measure has changed, the bar code information change trend is further determined, and the accumulated variable S is added or subtracted according to the bar code information change trend, if the calculation module determines the tape measure tape If the bar code information detected before and after does not change, the value of the accumulated variable S does not change. The electronic tape measure of claim 2, wherein the first code sequence is periodically alternately arranged from a starting end of the tape measure with a first color bar code, a second color bar code, and a second color bar code. The two code sequences are periodically arranged alternately from the beginning end of the tape measure with the second color bar code, the second color bar code, and the first color bar code, and the calculation module calculates the accumulated variable S according to the bar code information change trend: When the calculation module determines that the bar code information changes and the change trend is the first change trend, the calculation module controls the accumulated variable S plus 1, wherein the first change trend is that the bar code information changes from the first color and the second color to the first a second color, a second color, or a change from the second color, the second color to the second color, the first color, or from the second color, the first color to the first color, the second color; When the bar code information changes and the change trend is the second change trend, the calculation module controls the accumulated variable S minus 1, wherein the second change trend is that the bar code information changes from the first color and the second color to the first Color, the first color or the second color, the first color change to a second color, the second color or the second color, the second color change to the first color, the second color. The electronic tape measure of claim 2, wherein the first code sequence is periodically alternately arranged from a starting end of the tape measure with a first color bar code, a second color bar code, and a first color bar code; The two code columns are alternately arranged from the beginning end of the tape measure with the first color bar code, the second color bar code, and the second color bar code. The calculation module calculates the accumulated variable S according to the bar code information change trend, including: When the bar code information is changed and the change trend is the third change trend, the calculation module controls the accumulated variable S plus 1, wherein the third change trend is that the bar code information changes from the first color, the first color to the second color, The second color, or changes from the second color, the second color to the first color, the second color, or from the first color, the second color to the first color, the first color; if the calculation module determines the bar code information change And when the change trend is the fourth change trend, the calculation module controls the accumulated variable S minus 1, wherein the fourth change trend is that the bar code information changes from the first color, the first color to the first color A second color, or from a first color, a second color change to a second color, the second color or the second color, the second color to the first color change, a first color. The electronic tape measure of claim 1, wherein the tape body is further provided with a clear button, and the processing unit further comprises a counting and clearing module, wherein the counting and clearing module is configured to respond to the user The pressing operation of the clear button controls the accumulated variable S to be cleared so that the electronic tape measure performs the next measurement. A length measuring system for use in an electronic tape measure, the improvement being that the system comprises:
The information acquisition module is configured to obtain barcode information on the tape measure detected by the sensor and store the barcode information in the storage unit;
The calculation module is configured to count the value of the accumulated variable S according to the bar code information of the tape measure acquired by the information acquisition module, and control the stop of counting the accumulated variable S to determine the value of the current accumulated variable S in response to the user operation. And according to the determined cumulative variable S and the formula: L=S*W calculates the length value L; and the display control module is configured to control the length value calculated in the calculation module to be displayed on the display unit for the user to view . The length measuring system of claim 6, wherein the calculating module determines, according to the barcode information of the obtained tape measure, whether the bar code information currently detected by the sensor and the bar code information detected by the sensor have changed before. If it is determined that the bar code information detected on the tape measure has changed, the bar code information change trend is further determined, and the accumulated variable S is added or subtracted according to the bar code information change trend, if the calculation module determines the tape measure band If the bar code information detected last time does not change, the value of the accumulated variable S does not change. The length measurement system of claim 7, wherein the calculating module calculates the accumulated variable S according to the bar code information change trend, comprising: if the calculation module determines that the bar code information changes and the change trend is the first change trend, The calculation module controls the accumulated variable S plus 1, wherein the first change trend is that the bar code information changes from the first color, the second color to the second color, the second color, or changes from the second color and the second color. To the second color, the first color, or from the second color, the first color to the first color, the second color; if the calculation module determines that the bar code information changes and the change trend is the second change trend, the calculation module controls The accumulated variable S is decremented by 1, wherein the second change trend is that the bar code information changes from the first color, the second color to the second color, the first color, or changes from the second color, the first color to the second color, The second color, or changes from the second color, the second color to the first color, the second color. A length measuring method for use in an electronic tape measure, the improvement comprising the steps of:
Obtaining bar code information on the tape measure detected by the sensor and storing the bar code information in the storage unit;
Counting the accumulated variable S according to the acquired bar code information, and in response to the user controlling the operation to stop counting the accumulated variable S, determining the current accumulated variable S, and calculating a length according to the determined accumulated variable S and the formula L=S*W The value L; and the calculated length value L control is displayed on the display unit for the user to view. The length measuring method according to claim 9, wherein in step "counting the accumulated variable S based on the acquired bar code information, and in response to the user controlling the operation to stop counting the accumulated variable S, determining the current accumulated variable S, and calculating a length value L according to the determined cumulative variable S and the formula L=S*W includes:
According to the bar code information of the obtained tape measure, it is judged whether the bar code information currently detected by the sensor and the bar code information detected by the sensor have changed. If it is determined that the bar code information detected on the tape measure has changed before and after, the further judgment is made. The bar code information changes trend, and according to the bar code information change trend, it is determined that the accumulated variable S is incremented or decremented by 1. If the calculation module determines that the bar code information detected before and after the tape measure does not change, the value of the accumulated variable S is not change.