TWI656321B - Length measuring device and control method thereof - Google Patents

Abstract

The present invention relates to a length measuring device having an automatic zero point adjustment function and a control method therefor. The length measuring device of the present invention comprises: a tape with a hook portion attached at one end; a casing having an outlet; and a rotating portion that rotates as the tape is taken out from the casing through the outlet or introduced into the casing; The rotation detecting unit detects the rotation of the rotating unit, and the control unit converts the amount of rotation of the rotating unit into a length measurement value, and when the length measuring device is in the first state, the converted length measured value is set by a preset value. reset.

Description

Length measuring device and control method thereof

The present invention relates to a length measuring device and a control method thereof, and more particularly to a length measuring device having an automatic zero point adjustment function (AUTOMATIC ZERO-POINT ADJUSTMENT FUNCTION) and a control method therefor.

Usually, the tape measure is formed in a tape form, and a scale for indicating the length is indicated on the surface for measuring the width of the predetermined space or the size, length or width of the object to be measured.

There is also an electronic tape measure that is displayed on the display unit by automatically calculating the lead length of the tape tape, unlike a conventional tape measure. However, in the conventional electronic tape measure, even if the tape tape to be drawn is all retracted, the measurement length is not accurately reduced to "0" as the tape is retracted. In order to solve such a problem, a manual zero point adjustment function for resetting the measurement length to "0" when the user presses the reset button has been proposed.

Therefore, the technical problem to be solved by the present invention is to provide a length measuring device and a control method thereof for automatically resetting the length measurement value when all of the extracted tapes are rewinded.

A length measuring device according to an embodiment of the present invention for solving the technical problem as described above includes: a tape having a hook portion attached to one end; a casing having an outlet; and a rotating portion passing through the tape An outlet is taken out from the outer casing or introduced into the outer casing to rotate; a rotation detecting portion for detecting rotation of the rotating portion; and a control portion for converting a rotation amount of the rotating portion into a length measurement value If the length measuring device is in the first state in which the tape is all retracted into the outer casing, the converted length measurement value is reset by a preset value.

The length measuring device may further include a ruler detecting portion for detecting the ruler hook portion.

When the ruler hook portion detects the ruler hook portion, the control portion can determine that the length measuring device is in the first state in which the tape is all retracted into the outer casing.

The ruler hook detecting portion may include a physical button, and the physical button is pressed by the ruler hook portion in a state where the ruler hook portion is caught in the outlet port.

The ruler hook detecting portion may include a magnetic sensor for detecting a magnetic field strength.

The ruler hook portion is formed of a material having magnetism or a magnet attached thereto.

When the intensity of the magnetic field detected by the magnetic sensor reaches the reference magnetic field strength or more, the control unit may determine that the length measuring device is in the first state.

If the intensity of the magnetic field detected by the magnetic sensor reaches the reference magnetic field strength and the converted length measurement value is below a predetermined reference, the control unit may determine that the length measuring device is in the a state.

The control unit may set the intensity of the magnetic field measured by the magnetic sensor to the reference magnetic field strength when the power of the length measuring device is turned on.

The control unit may determine that the length measuring device is in the first state if the rotating portion rotates in a direction in which the tape is introduced at a speed greater than a reference rotational speed.

The control unit may determine that the length measuring device is determined to be the length measuring device after the rotating portion maintains the stopped state for more than the reference time after the rotating portion rotates in a direction in which the tape is introduced at a speed greater than a reference rotational speed. In the first state.

The control unit may determine that the length measuring device is in the first stage, after the rotated length is rotated in a direction in which the tape is introduced, and the converted length measurement value is below a preset reference value. a state.

After the rotating portion rotates in a direction in which the tape is introduced at a speed greater than the reference rotational speed, the converted length measurement value is reached in a state where the rotating portion maintains the stopped state for a reference time or longer. Below the preset reference, the control unit may determine that the length measuring device is in the first state.

The length measuring device may further include an inertia sensing portion for detecting movement of the length measuring device.

The control unit if the movement of the length measuring device satisfies a preset condition It can be determined that the length measuring device is in the first state.

A control method of a length measuring device according to another embodiment of the present invention for solving the above-described technical problems includes: a step of detecting a rotation amount of a rotating portion; a step of converting a rotation amount of the rotating portion into a length measurement value; Whether the length measuring device is in the first state; and in the case where the length measuring device is in the first state, the step of resetting the converted length measurement value by a preset value.

According to the present invention, if all of the extracted tapes are rewinded, the length measurement value can be automatically reset.

The embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to illustrate the invention.

Fig. 1 is a schematic perspective view of a length measuring device according to the present invention; and Fig. 2 is a view showing electronic components of a length measuring device according to the present invention.

1 and 2, the length measuring device 100 of the present invention may include a housing 110, a tape 121, a hook portion 123, a rotation detecting portion 141, a ruler detecting portion 143, an inertial sensing portion 145, a storage portion 150, The power supply unit 160, the control unit 170, the input/output unit 180, the communication unit 190, and one or more rotating units (not shown).

The length measuring device 100 can remove some of the structural elements shown in FIGS. 1 and 2 or add other structural elements according to the embodiment. For example, the length measuring device 100 of the present invention may additionally include components related to long-distance measurement using laser, infrared, or ultrasonic waves. Further, the length measuring device 100 may further include a function related to a function of calculating a length measurement value based on a rotation amount of a rotating body that rotates in contact with the measurement object.

The casing 110 performs a function of protecting by accommodating the respective components of the length measuring device 100 therein. An outlet 110h that can lead the tape 121 to the outside can be formed in the outer casing 110. The form of the outer casing 110 may vary depending on the embodiment.

The tape 121 may have a shape such as a string, a tape, or the like. Moreover, the tape 121 can be formed from a variety of materials. For example, the tape 121 may be formed of a material such as steel, stainless steel, polyethylene fiber, or para-aramid synthetic fiber.

The ruler hook portion 123 is formed to be able to be caught in the outlet port 110h. For example, like "┐" or "┬", the ruler hook portion 123 may form a part of a vertically curved ring shape.

The ruler 121 can be withdrawn from the outer casing 110 or introduced into the outer casing 110 through the outlet 110h, thereby rotating one or more rotating portions.

When the user pulls the ruler hook portion 123 attached to one end of the tape 121, the rotation portion can be rotated in the direction in which the tape 121 is taken out (hereinafter referred to as "forward rotation"). On the contrary, if the tape 121 is introduced into the inside of the casing 110 through the outlet 110h, the rotating portion can be rotated in the direction in which the tape 121 is introduced (hereinafter referred to as "reverse rotation").

The rotation detecting portion 141 can employ a rotation detecting sensor such as a potentiometer sensor, a rotary encorder, a magnetic rotation detecting sensor, or the like. The rotation detecting unit 141 can detect the amount of rotation of the rotating portion.

Fig. 3 is a view showing the configuration of a rotating portion and a rotation detecting portion in the first embodiment of the present invention.

Referring to Fig. 3, the length measuring device 100 of the present invention may include a first rotating portion 131 that can wind and unwind the tape 121 a plurality of times. When the user pulls the tape 121, the first rotating portion 131 can be rotated in the direction in which the tape 121 is taken out (hereinafter referred to as "forward rotation"). Further, the first rotating portion 131 can have a restoring force for suppressing the tape 121 in the direction in which it is drawn by an elastic member (not shown) provided with a tension spring or a spring. Therefore, when the user finishes the length measurement and loosens the ruler hook portion 123, the first rotating portion 131 is rotated in the direction in which the tape 121 is introduced (hereinafter referred to as "reverse rotation"), so that the tape 121 can be re-received. Rewind.

In the embodiment shown in FIG. 3, the rotation detecting portion 141 can detect the amount of rotation, the number of rotations, the direction of rotation, and the like of the first rotating portion 131. To this end, the rotation detecting portion 141 may be provided on the rotation shaft of the first rotating portion 131.

Fig. 4 is a view showing the configuration of a rotating portion and a rotation detecting portion in a second embodiment of the present invention.

Referring to FIG. 4, the length measuring device 100 of the second embodiment of the present invention may include a first rotating portion 131, and may further include a second rotating portion 133.

As shown in FIG. 4, the tape 121 can be wound more than one turn in the second rotating portion 133. The first rotating portion 131 and the second rotating portion 133 can be simultaneously rotated by being introduced or taken out by the tape 121.

The first rotating portion 131 may have the same structure as that shown in FIG. 3 and operate in the same manner. The rotation detecting unit 141 can detect the amount of rotation, the number of rotations, the direction of rotation, and the like of the second rotating portion 133 by being provided on the rotating shaft of the second rotating portion 133.

Fig. 5 is a view showing the configuration of a rotating portion and a rotation detecting portion in a third embodiment of the present invention.

Referring to Fig. 5, the length measuring device 100 according to the third embodiment of the present invention is identical in structure and operation to the first rotating portion 131, the second rotating portion 133, and the rotation detecting portion 141 of the second embodiment.

The difference from the second embodiment is that, as shown in FIG. 5, the tape 121 is in contact only with a part of the circumference of the second rotating portion 133. Moreover, the length measuring device 100 may further include a tape guide portion 135.

The tape guide portion 135 performs a function of guiding the tape 121 so as to be in close contact with the second rotating portion 133. As shown in FIG. 5, the tape guide portion 135 is spaced apart from a portion of the circumference of the second rotating portion 133 along the circumferential direction, and the tape 121 is inserted between the tape guide portion 135 and the second rotating portion 133. The space shows the structure as described above, but is not limited thereto. The tape guide portion 135 may be formed into any structure as long as it can be guided in such a manner that the second rotating portion 133 is rotated by the frictional force generated when the tape 121 is introduced or taken out.

Referring back to FIGS. 1 and 2, the storage unit 150 performs a function of storing various programs or materials related to the operation of the length measuring device 100.

The power supply unit 160 performs a function of supplying a power source required for the operation of each component of the length measuring device 100, and a battery can be employed.

The input/output unit 180 can perform a function related to the operation of the length measuring device 100 input by the user or a function of displaying information related to the operation of the length measuring device 100 to the user.

According to an embodiment, the input/output unit 180 may include all or a part of the display unit 181, the button unit 183, the speaker unit 185, and the microphone unit 187.

The display unit 181 performs a function of visually displaying information related to the operation of the length measuring device 100, for example, a length measurement value, etc., for this purpose, it can pass through a light-emitting diode (LED), a liquid crystal display (LCD), and an organic light-emitting diode. Display modules such as polar bodies (OLEDs) are embodied.

The button portion 183 can perform a function of receiving various instructions related to the operation of the length measuring device 100 input by the user.

The speaker unit 185 can perform a function of outputting information related to the operation of the length measuring device 100 in an acoustic manner, such as a length measurement value or the like.

The microphone section 187 can perform a function of receiving various instructions or information related to the operation of the length measuring apparatus 100 in a voice manner.

The communication unit 190 can support the exchange of various information and materials between the length measuring device 100 and the external device by wired communication or wireless communication. The wired communication method may include a communication method using a universal serial bus (USB) cable, and the wireless communication method may include a wireless area network (Wi-Fi), a bluetooth, and a wireless network (zigbee). , Infrared communication (IrDA, Infrared Data Association), Ultra Wideband (UWB, Ultra Wideband) or Radio Frequency Identification (RFID), Near Field Communication (NFC), etc. Mobile communication methods such as mobile communication technology (3G, 3rd Generation), fourth generation mobile communication technology (4G, 4th Generation), and Long Term Evolution (LTE).

The control unit 170 is for controlling the overall operation of the length measuring device 100.

The control unit 170 can obtain a length measurement value corresponding to the degree of extraction of the tape 121. Therefore, the control unit 170 can convert the amount of rotation of the first rotating unit 131 or the second rotating unit 133 detected by the rotation detecting unit 143 into a length measurement value.

The control unit 170 can convert the amount of rotation detected by the rotation detecting unit 143 into a length measurement value according to a predetermined algorithm. Alternatively, the control unit 170 may convert the amount of rotation detected by the rotation detecting unit 143 into a length measurement value by using a table in which the rotation amount and the length measurement value are associated with each other.

When the length measuring device 100 is in a state in which the tape 121 is all rewinded, the control unit 170 can reset the length measurement value by a predetermined value, for example, reset to "0".

The control unit 170 can determine whether or not the tape 121 is all rewinded by using the ruler detecting unit 143.

If the tape 121 is completely rewinded, the ruler hook 123 will be caught in the outlet 110h. Therefore, when the ruler hook detecting unit 143 detects the ruler hook portion 123, the control unit 170 can determine that the tape measure 121 is all rewinded.

The ruler hook detecting portion 143 can be disposed around the outlet port 110h so that the ruler hook portion 123 can be detected to approach the outlet port 110h. The ruler hook detecting portion 143 can be embodied by a physical switch or a magnetic sensor.

Hereinafter, a case where the ruler hook detecting unit 143 is embodied by a physical switch will be described.

When the physical switch is pressed by the ruler hook portion 123, the control unit 170 can determine that the tape 121 is all rewinded. Further, the control unit 170 can automatically reset the length measurement value to "0". The physical switch may also be provided with an elastic member or a damper member for reducing impact at a portion in contact with the ruler hook portion 123.

Hereinafter, a case where the ruler hook detecting unit 143 is embodied by a magnetic sensor will be described.

The ruler hook portion 123 is formed of a material having magnetic properties or may be attached with a magnet in such a manner as to be detectable by the ruler hook detecting portion 143. The magnetic sensor can be embodied by a sensor that detects a magnetic field, such as a magnetoresistive sensor or a hall sensor. As the ruler hook portion 123 approaches the outlet port 110h, the intensity of the magnetic field detected by the magnetic sensor becomes large. Therefore, when the ruler detecting unit 143 detects a magnetic field equal to or higher than the reference magnetic field strength, the control unit 170 determines that the tape 121 is all rewinded. Further, the control unit 170 can automatically reset the length measurement value to "0". The reference magnetic field strength can be set to a value that can sufficiently judge the degree of the state in which the tape 121 is all rewinded.

According to the embodiment, the reference magnetic field strength can be reset every time based on the strength of the magnetic field measured by the ruler hook detecting portion 143 when the power of the length measuring device 100 is turned on. The magnetic field strength measured when the power is turned on can be directly set to the reference magnetic field strength or a value smaller than the measured magnetic field strength can be set as the reference magnetic field strength. Therefore, even if the intensity of the magnetic field generated in the ruler hook portion 123 becomes weak with time due to magnet heating or the like, the intensity of the magnetic field of the ruler hook portion 123 can be accurately detected to be within a predetermined range.

On the other hand, the physical switch can be pressed because it is not another factor of the hook portion 123. Further, when there are other magnets around the length measuring device 100, even if the hook portion 123 is not actually caught in the outlet 110h, a magnetic field equal to or higher than the reference magnetic field strength can be detected. In this case, there is a possibility that the control unit 170 resets the length measurement value even if the tape 121 is not actually rewinded.

Therefore, when the length measurement value is equal to or less than the predetermined reference value, if the physical switch is pressed or the magnetic field strength equal to or higher than the reference magnetic field strength is detected, the control unit 170 resets the length measurement value. .

On the other hand, according to the embodiment, whether or not the length measuring device 100 is in the tape 121 is all rewinded based on the rotation speed and the rotation direction of the first rotating portion 131 or the second rotating portion 133 detected by the rotation detecting portion 141. status.

If the user releases the ejected tape 121, the first rotating portion 131 rapidly rotates in the direction in which the tape 121 is introduced, and the tape 121 can be automatically rewinded. Further, if the tape 121 is all rewinded, the first rotating portion 131 stops rotating and stops. Therefore, whether or not the tape 121 is completely retracted can be determined by the rotation information of the number of rotations, the direction of rotation, and the like of the first rotating portion 131.

Since the rewinding speed when the user releases the ejected tape 121 is very fast, it is difficult to stop the first rotating portion 131 by re-engaging the tape 121 being rewinded. Therefore, if the first rotating portion 131 causes the tape to be introduced in a manner that the speed is greater than the preset speed (condition 1), it can be determined that the tape 121 is all rewinded. The preset speed is set to determine the extent to which the user automatically rewinds when the ruler 121 is released.

On the other hand, if the stop state is maintained above the reference time after the first rotating portion 131 is rotated at a speed greater than the preset speed in the direction in which the tape is introduced (condition 2), it can be determined that the tape 121 is all Rewind.

On the other hand, if the converted length measurement value reaches the preset reference or less after the first rotation portion 131 is rotated in the direction in which the tape 121 is introduced (condition 3), it can be determined that the tape 121 is all returned. volume.

If all of Condition 2 and Condition 3 are satisfied (Condition 4), it can be determined that the tape 121 is all rewinded.

Similarly, the rotation speed and the rotation direction of the second rotating portion 133 can be used to determine the state in which the tape 121 is all rewinded.

The inertial sensing portion 145 may include at least one of an acceleration sensor, a gyro sensor, and a geomagnetic sensor, and the movement or posture of the object may be measured. The inertia sensing unit 145 can perform a function of measuring the movement of the length measuring device 100, the posture, that is, the movement trajectory, and the like.

On the other hand, according to the embodiment, the control unit 170 can also reset the length measurement value by the movement of the length measuring device 100 detected by the inertia sensing unit 145. For example, when the user shakes the length measuring device 100 at a predetermined intensity or higher, the control unit 170 resets the length measurement value.

On the other hand, if the length measurement value is directly reset to "0" at the time when it is determined that the tape 121 is all rewinded, the user may feel unnatural. Therefore, the value displayed on the display unit 181 can be gradually reduced to "0" at the time point when the length measurement value is determined.

Fig. 6 is a flow chart for explaining a method of controlling the length measuring device of the present invention.

Referring to Fig. 6, first, the rotation detecting portion 141 can detect the amount of rotation of the first rotating portion 131 or the second rotating portion 133 that rotates as the tape 121 is introduced or taken out (step S610).

Next, the control unit 170 can convert the amount of rotation detected by the rotation detecting unit 141 into a length measurement value (step S620). The control unit 170 can display the length measurement value converted in step S620 on the display unit 181 (step S630).

When the control unit 170 determines in the process of repeating steps S610 to S630 that the length measuring device 100 is in the state in which the tape 121 is all rewinded (YES in step S640), the control unit 170 can set the preset value ( For example, “0”) resets the length measurement value converted based on the amount of rotation in step S620 (step S650).

Further, the control unit 170 can display the length measurement value reset in step S650 on the display unit 181 (step S660).

The embodiments of the present invention have been described above, but the scope of the present invention is not limited thereto, and the scope of the present invention includes those skilled in the art to which the present invention pertains. All changes and modifications within the scope of the equivalent technical solutions are considered.

100 Length measuring device 110 Housing 110h Opening port 121 Ruler tape 123-foot hook portion 131 First rotating portion 133 Second rotating portion 135 Tape guide portion 141 Rotation detecting portion 143 Ruler detecting portion 145 Inertia sensing portion 150 Storage portion 160 Power supply Unit 170 Control unit 180 Input/output unit 181 Display unit 183 Button unit 185 Speaker unit 187 Microphone unit 190 Communication unit S610 to S660 Procedure

1 is a schematic perspective view showing a length measuring device according to an embodiment of the present invention; FIG. 2 is a schematic view showing electronic components of the length measuring device of the present invention; and FIG. 3 is a view showing a rotating portion and rotation detecting of the first embodiment of the present invention. 4 is a schematic view showing the structure of a rotating portion and a rotation detecting portion according to a second embodiment of the present invention; and FIG. 5 is a schematic view showing a configuration of a rotating portion and a rotation detecting portion according to a third embodiment of the present invention; And Fig. 6 is a flowchart for explaining a control method of the length measuring device of the present invention.

Claims (9)

A length measuring device comprising: a one-foot belt with a hook portion attached at one end; a casing having an outlet; a rotating portion that is taken out from the casing through the outlet port or Introduced into the casing for rotation; a rotation detecting unit for detecting rotation of the rotating portion; and a control unit for converting a rotation amount of the rotating portion into a length measurement value, wherein the length measuring device is The tape is all retracted into a first state of the outer casing, and the converted length measurement value is reset by a preset value; and a one-foot hook detecting portion is configured to detect the ruler hook When the ruler hook detecting portion detects the ruler hook portion, the control portion determines that the length measuring device is in the first state; wherein the ruler hook detecting portion includes a magnetic field for detecting a magnetic sensor of the strength; and the hook portion is formed of a material having magnetic properties or a magnet is attached; and if the intensity of the magnetic field detected by the magnetic sensor reaches the reference magnetic field strength, the control unit determines For the stated Determination means in said first state; and when the power supply is turned on length measuring device, the control unit by the sensors measuring magnetic field intensity is set to the reference magnetic field strength. The length measuring device according to claim 1, wherein if the intensity of the magnetic field detected by the magnetic sensor is greater than or equal to the reference magnetic field strength and the converted length measurement value is below a predetermined reference, The control unit determines that the length measuring device is in the first state. A length measuring device comprising: a one-foot belt with a hook portion attached at one end; a casing having an outlet; a rotating portion that is taken out from the casing through the outlet port or Introduced into the casing for rotation; a rotation detecting unit for detecting rotation of the rotating portion; and a control unit for converting a rotation amount of the rotating portion into a length measurement value, if the length measuring device Setting a first state in which the tape is rewinded into the outer casing, the converted length measurement value is reset by a preset value; wherein if the rotating portion is greater than the reference rotational speed The speed is rotated in a direction in which the tape is introduced, and the control unit determines that the length measuring device is in the first state. A length measuring device comprising: a one-foot belt with a hook portion attached at one end; a casing having an outlet; a rotating portion that is taken out from the casing through the outlet port or Introduced into the casing for rotation; a rotation detecting unit for detecting rotation of the rotating portion; and a control unit for converting a rotation amount of the rotating portion into a length measurement value, if the length measuring device When the tape is all rewinded into the first state of the outer casing, the converted length measurement value is reset by a preset value; wherein, if the rotating portion is greater than the reference rotational speed After the rotation speed is maintained in the direction in which the tape is introduced, and the rotation portion is maintained in the stopped state for more than the reference time, the control unit determines that the length measuring device is in the first state. A length measuring device comprising: a one-foot belt with a hook portion attached at one end; a casing having an outlet; a rotating portion that is taken out from the casing through the outlet port or Introduced into the casing for rotation; a rotation detecting unit for detecting rotation of the rotating portion; and a control unit for converting a rotation amount of the rotating portion into a length measurement value, if the length measuring device In a first state in which the tape is all retracted into the outer casing, the converted length measurement value is reset by a preset value; wherein if the rotating portion is along the ruler After the rotated direction is rotated, and the converted length measurement value is equal to or less than a predetermined reference value, the control unit determines that the length measuring device is in the first state. A method of controlling a length measuring device, wherein the length measuring device includes a rotating portion that rotates as the tape is taken out from an outer casing through an outlet or introduced into the outer casing, the length measuring device The control method includes: a step of detecting an amount of rotation of the rotating portion; a step of converting a rotation amount of the rotating portion into a length measurement value; and determining whether the length measuring device is in a state in which the tape is all retracted a step of a first state of the outer casing; and a step of resetting the converted length measurement value by a predetermined value if the length measuring device is in the first state; wherein, if When the one-foot hook detecting portion detects a one-foot hook attached to one end of the tape, it is determined that the length measuring device is in the first state; if the strength of the magnetic field detected by the rule hook detecting portion reaches When the reference magnetic field strength is equal to or higher than the reference magnetic field strength, it is determined that the length measuring device is in the first state; and the intensity of the magnetic field detected by the ruled hook detecting portion is equal to or higher than the reference magnetic field strength Determining that the length measuring device is in the first state when the converted length measurement value is below a preset reference; and determining, by the ruler hook detecting portion when the power of the length measuring device is turned on The intensity of the magnetic field is set to the reference magnetic field strength. A method of controlling a length measuring device, wherein the length measuring device includes a rotating portion that rotates as the tape is taken out from an outer casing through an outlet or introduced into the outer casing, the length measuring device The control method includes: a step of detecting an amount of rotation of the rotating portion; a step of converting a rotation amount of the rotating portion into a length measurement value; and determining whether the length measuring device is in a state in which the tape is all retracted a step of a first state of the outer casing; and a step of resetting the converted length measurement value by a predetermined value if the length measuring device is in the first state; Wherein, if the rotating portion rotates in a direction in which the tape is introduced at a speed greater than a reference rotational speed, it is determined that the length measuring device is in the first state. A method of controlling a length measuring device, wherein the length measuring device includes a rotating portion that rotates as the tape is taken out from an outer casing through an outlet or introduced into the outer casing, the length measuring device The control method includes: a step of detecting an amount of rotation of the rotating portion; a step of converting a rotation amount of the rotating portion into a length measurement value; and determining whether the length measuring device is in a state in which the tape is all retracted a step of a first state of the outer casing; and a step of resetting the converted length measurement value with a predetermined value if the length measuring device is in the first state; wherein, if When the rotating portion rotates in a direction in which the tape is introduced at a speed greater than the reference rotational speed, and the rotating portion maintains the stopped state for a reference time or longer, it is determined that the length measuring device is in the first state. A method of controlling a length measuring device, wherein the length measuring device includes a rotating portion that rotates as the tape is taken out from an outer casing through an outlet or introduced into the outer casing, the length measuring device The control method includes: a step of detecting an amount of rotation of the rotating portion; a step of converting a rotation amount of the rotating portion into a length measurement value; and determining whether the length measuring device is in a state in which the tape is all retracted a step of a first state of the outer casing; and a step of resetting the converted length measurement value with a predetermined value if the length measuring device is in the first state; wherein, if After the rotation portion rotates in a direction in which the tape is introduced, and the converted length measurement value reaches a predetermined reference or less, it is determined that the length measuring device is in the first state.