WO2018134984A1 - Electronic balance - Google Patents

Electronic balance Download PDF

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Publication number
WO2018134984A1
WO2018134984A1 PCT/JP2017/002028 JP2017002028W WO2018134984A1 WO 2018134984 A1 WO2018134984 A1 WO 2018134984A1 JP 2017002028 W JP2017002028 W JP 2017002028W WO 2018134984 A1 WO2018134984 A1 WO 2018134984A1
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WIPO (PCT)
Prior art keywords
light
displacement
photodiode
unit
slit
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PCT/JP2017/002028
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French (fr)
Japanese (ja)
Inventor
耕介 藤田
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株式会社島津製作所
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Priority to PCT/JP2017/002028 priority Critical patent/WO2018134984A1/en
Priority to JP2018562839A priority patent/JPWO2018134984A1/en
Publication of WO2018134984A1 publication Critical patent/WO2018134984A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G7/00—Weighing apparatus wherein the balancing is effected by magnetic, electromagnetic, or electrostatic action, or by means not provided for in the preceding groups
    • G01G7/02—Weighing apparatus wherein the balancing is effected by magnetic, electromagnetic, or electrostatic action, or by means not provided for in the preceding groups by electromagnetic action
    • G01G7/04—Weighing apparatus wherein the balancing is effected by magnetic, electromagnetic, or electrostatic action, or by means not provided for in the preceding groups by electromagnetic action with means for regulating the current to solenoids

Definitions

  • the present invention relates to an electronic balance in which light from a light emitting diode is received by a photodiode and the mass of an object to be measured is calculated based on the amount of received light.
  • the electronic balance is placed on the opposite side of the weighing pan with the fulcrum between the weighing pan on which the measurement object is placed, and the displacement part that is displaced by the gravity of the measurement object and the displacement amount of the displacement part are detected. And a detecting unit for performing the operation.
  • an external force is applied so that the displacement of the displacement portion becomes zero, and the mass of the measurement object is calculated according to the value of the external force (for example, see Patent Document 1 below).
  • the electronic balance includes an electromagnetic force generator having a coil and a magnetic circuit, and a control unit.
  • the detection unit includes a light emitting diode and a photodiode that receives light from the light emitting diode.
  • the amount of light received by the photodiode changes according to the displacement of the displacement portion.
  • the electromagnetic force generator an electric current is passed through a coil to generate an electromagnetic force, and the electromagnetic force is applied to the displacement portion.
  • the control unit changes the value of the current passed through the coil based on the amount of light received by the photodiode so that the displacement of the displacement unit becomes zero.
  • the mass of the measurement object is calculated based on the current value.
  • the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic balance capable of improving measurement accuracy without causing structural problems.
  • the electronic balance according to the present invention includes a weighing pan, a displacement unit, an external force application unit, a detection unit, a control unit, and a calculation unit.
  • An object to be measured is placed on the weighing pan.
  • the displacement part is provided so as to be swingable with respect to a fulcrum, and is formed to swing in a certain direction due to the gravity of the measurement object placed on the weighing pan, and to form a slit extending in the certain direction.
  • the external force applying unit applies a force that swings the displacement unit in the reverse direction to the displacement unit that swings due to the gravity of the measurement target.
  • the detection unit includes a light emitting diode and a photodiode provided with the slit interposed therebetween.
  • the control unit controls the force applied by the external force applying unit to the displacement unit based on the amount of light received by the photodiode from the light emitting diode through the slit.
  • the calculation unit calculates a value corresponding to the force applied by the external force applying unit to the displacement unit as the mass of the measurement object.
  • the photodiode has two light receiving surfaces arranged with a gap in the fixed direction, and the gap is disposed in a region facing the light emitting diode in the optical axis direction.
  • the width of the slit in the certain direction is 0.4 mm or less.
  • light with high directivity is emitted from the light emitting diode.
  • the light from the light-emitting diode passes through a narrow slit having a width of 0.4 mm or less and is received by the photodiode.
  • the control unit controls the force applied by the external force applying unit to the displacement unit based on the amount of light received by the photodiode, and the calculation unit calculates a value corresponding to the force of the external force applying unit. Calculated as mass. Therefore, the influence of noise on the calculated mass can be reduced.
  • two light receiving surfaces with respect to a unit light reception amount of a photodiode are obtained by irradiating light with high directivity from the light emitting diode and passing the light through a narrow slit having a width of 0.4 mm or less.
  • the measurement accuracy can be improved by increasing the value of the difference between the received light amounts at the two light receiving surfaces with respect to the unit received light amount at the photodiode. As a result, it is possible to improve the measurement accuracy without causing structural problems.
  • FIG. 3 is a side sectional view taken along line AA in FIG. 2. It is the block diagram which showed the specific structure of the control part and its peripheral member. It is the graph which showed the relationship between the mechanical sensitivity in an electronic balance, and the slit width of a shutter.
  • the electronic balance 1 includes a beam 2, a fulcrum 3, a weighing pan 4, a displacement unit 5, a detection unit 6, and an external force application unit 7.
  • the beam 2 is formed in an elongated shape and extends in the horizontal direction.
  • the fulcrum 3 supports the central portion of the beam 2.
  • the beam 2 can swing around the fulcrum 3.
  • the weighing pan 4 is provided at one end of the beam 2.
  • a sample S that is a measurement object is placed on the weighing pan 4.
  • the displacement part 5 is provided at the other end of the beam 2.
  • the displacement part 5 swings integrally with the beam 2.
  • the detection unit 6 detects a displacement caused by the swinging of the displacement unit 5. The detailed configurations of the detection unit 6 and the displacement unit 5 will be described later.
  • the external force portion imparting portion 7 is provided in the vicinity of the other end portion of the beam 2.
  • the external force imparting portion 7 is a member (mechanism) that imparts an external force to the displacement portion 5 via the beam 2.
  • the external force applying unit 7 includes a coil 8 and a permanent magnet 9.
  • the coil 8 is fixed to the vicinity of the other end of the beam 2. Therefore, the coil 8 is displaced integrally with the beam 2.
  • the coil 8 is supplied with a current whose size is appropriately changed.
  • the permanent magnet 9 is arranged at a distance from the coil 8.
  • the permanent magnet 9 is fixed separately from the beam 2 (coil 8).
  • the permanent magnet 9 forms a static magnetic field, and the coil 8 is disposed in the static magnetic field.
  • the detection unit 6 detects the displacement of the displacement unit 5 due to the swing of the beam 2.
  • an electromagnetic force is generated by passing a current through the coil 8.
  • the magnitude of the electromagnetic force is determined by the value of the current flowing through the coil 8.
  • a force is applied to the coil 8 in a direction away from the permanent magnet 9, and a force directed downward (opposite to the displacement direction) is applied to the displacement portion 5 via the beam 2.
  • FIG. 2 is an enlarged side view showing the displacement unit 5 of the electronic balance 1.
  • FIG. 3 is a side sectional view taken along line AA in FIG. For convenience, FIG. 2 does not show the detection unit 6.
  • the electronic balance 1 includes the displacement unit 5 and the detection unit 6.
  • the displacement part 5 is a plate-shaped member (shutter) having a rectangular shape in a side view. As described above, the displacement portion 5 can swing in the vertical direction, and the swinging direction is orthogonal to the thickness direction. A slit 51 is formed in the displacement portion 5.
  • the slit 51 is disposed at the center in the vertical direction in the displacement portion 5 and penetrates the displacement portion 5 in the thickness direction.
  • the slit 51 extends along the vertical direction and the horizontal direction.
  • the width D1 of the slit 51 in the vertical direction (swing direction) that is, from the upper end edge (one end edge in the swing direction) of the slit 51 to the lower end edge (the other end edge in the swing direction) of the slit 51.
  • the width D1 is 0.4 mm or less.
  • the detection unit 6 includes a light emitting diode 61 and a photodiode 62.
  • the light emitting diode 61 is disposed with a distance from the displacement portion 5. Specifically, the light emitting diodes 61 are arranged with a gap in the horizontal direction with respect to the slits 51 of the displacement portion 5. The optical axis direction of the light emitted from the light emitting diode 61 is along the horizontal direction.
  • the photodiode 62 is disposed on the opposite side of the light emitting diode 61 with the displacement portion 5 (slit 51) interposed therebetween. That is, the photodiode 62 and the light emitting diode 61 are provided with the displacement portion 5 (slit 51) interposed therebetween.
  • the photodiode 62 is a two-divided photodiode formed in a plate shape, and includes a first light receiving surface 621 and a second light receiving surface 622.
  • the first light receiving surface 621 is arranged on the upper side of the photodiode 62 and faces the displacement portion 5.
  • the first light receiving surface 621 is formed in a rectangular shape in side view.
  • a light emitting element is mounted on the first light receiving surface 621.
  • the second light receiving surface 622 is disposed on the lower side of the photodiode 62 and faces the displacement portion 5.
  • the second light receiving surface 622 is disposed below the first light receiving surface 621 with a space therebetween.
  • the second light receiving surface 622 is formed in a rectangular shape in side view.
  • a light emitting element is mounted on the second light receiving surface 622.
  • the width D2 of the gap 623 between the first light receiving surface 621 and the second light receiving surface 622 in the vertical direction is a displacement portion. It is smaller than the width D1 of the five slits 51.
  • the width D2 of the gap 623 between the first light receiving surface 621 and the second light receiving surface 622 is, for example, 0.03 mm.
  • a gap 623 between the first light receiving surface 621 and the second light receiving surface 622 is disposed in a region facing the light emitting diode 61 in the optical axis direction.
  • the center of the gap 623 between the first light receiving surface 621 and the second light receiving surface 622 and the center of the slit 51 of the displacement portion 5 are the light from the light emitting diode 61. Located on the optical axis.
  • the light source B of the light emitting diode 61 emits light with high directivity. Light from the light source B is refracted in the process of passing through the outer surface of the light emitting diode 61 and travels toward the displacement portion 5. A part of the light from the light emitting diode 61 passes through the slit 51 of the displacement portion 5 and travels toward the photodiode 62. At this time, if there is no refraction of the light, the light can be captured in the same manner as it is emitted from the virtual point light source C.
  • the virtual point light source C is an apparent light source when it is assumed that there is no light refraction, and is an imaginary light source.
  • the virtual point light source C is located at a point farther from the displacement unit 5 and the photodiode 62 than the light source B.
  • the angle ⁇ formed by the vertical end edges of the slit 51 of the displacement portion 5 with respect to the virtual point light source C is between the first light receiving surface 621 and the second light receiving surface 622 with respect to the virtual point light source C. It is larger than the angle ⁇ 0 formed by both end edges of the gap 623.
  • the angle ⁇ is a line segment connecting the virtual point light source C and the upper edge of the slit 51 of the displacement part 5 and a line segment connecting the virtual point light source C and the lower edge of the slit 51 of the displacement part 5 in a side view. It is an angle to make.
  • the angle ⁇ 0 is a line segment connecting the virtual point light source C and the lower end edge of the first light receiving surface 621 and a line segment connecting the virtual point light source C and the upper end edge of the second light receiving surface 622 in the side view. Is an angle.
  • FIG. 4 is a block diagram showing a specific configuration of the control unit 20 and its peripheral members.
  • the electronic balance 1 includes a display 10 and a control unit 20 in addition to the coil 8, the light emitting diode 61, and the photodiode 62 described above.
  • the display device 10 includes, for example, a liquid crystal display screen. The display 10 displays the mass of the measurement object.
  • the control unit 20 includes, for example, a CPU (Central Processing Unit).
  • the control unit 20 controls each operation of the coil 8, the display 10, and the light emitting diode 61 based on the detection signal from the photodiode 62.
  • the control unit 20 functions as a current control unit 201, a calculation unit 202, a light amount control unit 203, and the like when the CPU executes a program.
  • the current control unit 201 determines the value of the current flowing through the coil 8 based on the detection signal from the photodiode 62.
  • the coil 8 is supplied with the current determined by the current control unit 201.
  • the magnitude of the electromagnetic force in the external force applying unit 7 is determined based on the value of the current flowing through the coil 8. That is, the current control unit 201 performs control to determine the magnitude of the electromagnetic force in the external force applying unit 7 based on the amount of light received by the photodiode 62.
  • the calculation unit 202 performs a process of calculating the mass of the measurement object based on the value of the current passed through the coil 8 determined by the current control unit 201 and causing the display unit 10 to display the calculated mass value.
  • the light quantity control unit 203 determines the light emission amount of the light emitting diode 61 based on the detection signal from the photodiode 62 so that the total amount of light received by the photodiode 62 is kept constant.
  • the light emitting diode 61 emits light with the light emission amount determined by the light amount control unit 203.
  • Control Unit As shown in FIG. 3, when light is emitted from the light source B of the light emitting diode 61, a part of the light passes through the slit 51 of the displacement unit 5 toward the photodiode 62. In the photodiode 62, light that has passed through the slit 51 of the displacement portion 5 is received by the first light receiving surface 621 and the second light receiving surface 622.
  • the amount of light received by the first light receiving surface 621 and the amount of light received by the second light receiving surface 622 are the same. If the displacement unit 5 is displaced upward due to the gravity of the measurement object (sample S) placed on the weighing pan 4, the amount of light received by the first light receiving surface 621 increases, and the second light receiving surface 622 The amount of light received decreases. On the other hand, if the displacement part 5 is displaced downward, the amount of light received by the first light receiving surface 621 decreases and the amount of light received by the second light receiving surface 622 increases.
  • the light amount control unit 203 determines the light emission amount of the light emitting diode 61 so that the total amount of light received by the photodiode 62 is kept constant.
  • the current control unit 201 calculates the difference between the amount of light received by the first light receiving surface 621 and the amount of received light by the second light receiving surface 622 based on the detection signal from the photodiode 62. . Then, the current control unit 201 performs feedback control for determining the value of the current flowing through the coil 8 so that the calculated difference in received light amount becomes zero. Specifically, the current control unit 201 divides the difference (difference received light amount) between the amount of light received by the first light receiving surface 621 and the amount of received light by the second light receiving surface 622 by the total amount of received light by the photodiode 62. Feedback control is performed to determine the value of the current that flows through the coil 8 so that the value (the value of the difference light reception amount with respect to the unit light reception amount at the photodiode 62) becomes zero. The coil 8 is supplied with the determined current.
  • the calculation unit 202 calculates the mass of the measurement object (sample S) based on the current value determined by the current control unit 201 and causes the display unit 10 to display the calculated mass value.
  • I represents the energy of the light emitting diode 61.
  • I 0 indicates the energy of light emitted perpendicularly (angle 0 °) from the light emitting diode 61
  • I ( ⁇ ) indicates the energy at the angle ⁇ from the light emitting diode 61
  • ⁇ 0 is The angle at which the light quantity of the light emitting diode 61 is 1 / e is shown.
  • I (Z) represents the incident energy per unit area at an angle ⁇ from the virtual point light source C in the displacement portion 5.
  • P + represents the incident energy at the first light receiving surface 621 of the photodiode 62.
  • P ⁇ indicates the incident energy at the second light receiving surface 622 of the photodiode 62.
  • P ⁇ indicates the incident energy at the first light receiving surface 621 of the photodiode 62 or the incident energy at the second light receiving surface 622 of the photodiode 62.
  • P indicates the energy difference between the incident energy at the first light receiving surface 621 of the photodiode 62 and the incident energy at the second light receiving surface 622 of the photodiode 62.
  • Equation (4) is a value obtained by dividing the difference between the amount of received light at the first light receiving surface 621 and the amount of received light at the second light receiving surface 622 (difference received light amount) by the total amount of received light at the photodiode 62 (photo This corresponds to the value of the difference received light amount relative to the unit received light amount at the diode 62). Further, when the formula (4) is differentiated by ⁇ , the following formula (5) is obtained.
  • This equation (10) shows the change in the signal intensity of the photodiode 62 with respect to the unit displacement amount of the displacement portion 5, and shows the mechanical sensitivity of the electronic balance 1.
  • FIG. 5 is a graph showing the relationship between the mechanical sensitivity of the electronic balance 1 and the width D1 of the slit 51 of the displacement portion 5.
  • the vertical axis indicates the mechanical sensitivity of the electronic balance 1
  • the horizontal axis indicates the width D ⁇ b> 1 of the slit 51 of the displacement portion 5.
  • the slit 51 of the displacement part 5 is formed so that the width D1 in the vertical direction (swinging direction) is 0.4 mm or less. Further, light with high directivity is emitted from the light emitting diode 61. Then, the light from the light emitting diode 61 passes through the narrow slit 51 having a width of 0.4 mm or less, and is received by the photodiode 62.
  • the current control unit 201 determines the value of the current passed through the coil 8 so that the value (the difference between the received light amounts at the two light receiving surfaces with respect to the unit received light amount at the photodiode 62) becomes zero. .
  • the coil 8 is supplied with the determined current.
  • the calculation unit 202 calculates the mass of the measurement object based on the current value determined by the current control unit 201. Therefore, the influence of noise on the calculated mass can be reduced, and as a result, the calculation accuracy of the mass of the measurement object by the calculation unit 202 can be improved.
  • the electronic balance 1 by setting the width D1 of the slit 51 of the displacement portion 5 to 0.4 mm or less, the value of the difference in the amount of light received at the two light receiving surfaces with respect to the unit amount of light received by the photodiode 62 (The change in the signal intensity of the photodiode 62 with respect to the unit displacement amount of the displacement unit 5 can be increased to reduce the influence of noise, and the measurement accuracy can be improved. Therefore, it is possible to improve the measurement accuracy without causing structural problems.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

An electronic balance (1) is provided with a displacement part (5) and a detection part (6). A slit (51) is formed in the displacement part (5), and a light-emitting diode (61) and a photodiode (62) are included in the detection part (6). The slit (51) in the displacement part (5) is formed such that a width D1 in the vertical direction (rocking direction) is not greater than 0.4 mm. Further, light having high directivity is emitted from the light-emitting diode (61). In addition, the light from the light-emitting diode (61) passes through the slit (51) having a narrow width of not greater than 0.4 mm, and is received by the photodiode (62). Therefore, measurement precision can be improved by magnifying a change of signal intensity of the photodiode (62) with respect to the unit displacement amount of the displacement part (5). As a result, measurement precision can be improved without causing a configuration failure.

Description

電子天秤electronic balance
　本発明は、発光ダイオードからの光をフォトダイオードにおいて受光し、当該受光した光の受光量に基づいて、測定対象物の質量を算出する電子天秤に関するものである。 The present invention relates to an electronic balance in which light from a light emitting diode is received by a photodiode and the mass of an object to be measured is calculated based on the amount of received light.
　通常、電子天秤は、測定対象物が載置される秤量皿と、支点を挟んで秤量皿と反対側に配置され、測定対象物の重力によって変位する変位部と、変位部の変位量を検出する検出部とを備えている。電子天秤では、変位部の変位が０になるように外力を付与しており、この外力の値に応じて、測定対象物の質量を算出している（例えば、下記特許文献１参照）。 Usually, the electronic balance is placed on the opposite side of the weighing pan with the fulcrum between the weighing pan on which the measurement object is placed, and the displacement part that is displaced by the gravity of the measurement object and the displacement amount of the displacement part are detected. And a detecting unit for performing the operation. In the electronic balance, an external force is applied so that the displacement of the displacement portion becomes zero, and the mass of the measurement object is calculated according to the value of the external force (for example, see Patent Document 1 below).
　具体的には、電子天秤は、コイル及び磁気回路を有する電磁力発生装置と、制御部とを備えている。また、検出部は、発光ダイオードと、発光ダイオードからの光を受光するフォトダイオードとを備えている。電子天秤では、変位部の変位に応じて、フォトダイオードでの受光量が変化する。電磁力発生装置では、コイルに電流を流して電磁力を発生させて、その電磁力を変位部に付与する。制御部は、フォトダイオードでの受光量に基づいて、変位部の変位が０となるように、コイルに流す電流の値を変化させる。そして、電子天秤では、その電流値に基づいて、測定対象物の質量を算出する。 Specifically, the electronic balance includes an electromagnetic force generator having a coil and a magnetic circuit, and a control unit. The detection unit includes a light emitting diode and a photodiode that receives light from the light emitting diode. In the electronic balance, the amount of light received by the photodiode changes according to the displacement of the displacement portion. In the electromagnetic force generator, an electric current is passed through a coil to generate an electromagnetic force, and the electromagnetic force is applied to the displacement portion. The control unit changes the value of the current passed through the coil based on the amount of light received by the photodiode so that the displacement of the displacement unit becomes zero. In the electronic balance, the mass of the measurement object is calculated based on the current value.
特許第５５６８９９７号公報Japanese Patent No. 5568997
　上記のような従来の電子天秤において、測定精度を向上させることが検討される。例えば、支点の構成や、変位部の配置を変更することで、単位重量の測定対象物を秤量皿に載置した場合における変位部の変位量を大きくすることが検討される。単位重量の測定対象物に対する変位部の変位量が大きくなれば、検出部によって変位部の変位を精度よく検出でき、その結果、測定精度を向上させることできる。しかし、このような変位部の変位量を大きくする構成にすると、衝撃に対する耐久性が低くなったり、装置が大型化するなどの不具合が生じる。 It is considered to improve the measurement accuracy in the conventional electronic balance as described above. For example, it is considered to increase the displacement amount of the displacement portion when the measurement object of unit weight is placed on the weighing pan by changing the configuration of the fulcrum or the arrangement of the displacement portion. If the amount of displacement of the displacement portion relative to the unit weight measurement object increases, the displacement of the displacement portion can be accurately detected by the detection portion, and as a result, the measurement accuracy can be improved. However, when the displacement amount of such a displacement portion is increased, problems such as low durability against impacts and an increase in the size of the device occur.
　本発明は、上記実情に鑑みてなされたものであり、構成上の不具合を生じることなく、測定精度を向上できる電子天秤を提供することを目的とする。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic balance capable of improving measurement accuracy without causing structural problems.
　本発明に係る電子天秤は、秤量皿と、変位部と、外力付与部と、検出部と、制御部と、演算部とを備える。前記秤量皿には、測定対象物が載置される。前記変位部は、支点に対して揺動可能に設けられ、前記秤量皿に載置された測定対象物の重力により一定方向に揺動するとともに、前記一定方向に延びるスリットが形成される。前記外力付与部は、測定対象物の重力により揺動する前記変位部に対して、当該変位部を逆方向に揺動させる力を付与する。前記検出部は、前記スリットを挟んで設けられた発光ダイオード及びフォトダイオードを有する。前記制御部は、前記発光ダイオードから前記スリットを介して前記フォトダイオードが受光する光の受光量に基づいて、前記外力付与部が前記変位部に付与する力を制御する。前記演算部は、前記外力付与部が前記変位部に付与する力に応じた値を測定対象物の質量として算出する。前記フォトダイオードは、前記一定方向に隙間を空けて並ぶ２つの受光面を有するとともに、前記隙間が、前記発光ダイオードに対して光軸方向に対向する領域に配置される。前記スリットの前記一定方向の幅は、０．４ｍｍ以下である。 The electronic balance according to the present invention includes a weighing pan, a displacement unit, an external force application unit, a detection unit, a control unit, and a calculation unit. An object to be measured is placed on the weighing pan. The displacement part is provided so as to be swingable with respect to a fulcrum, and is formed to swing in a certain direction due to the gravity of the measurement object placed on the weighing pan, and to form a slit extending in the certain direction. The external force applying unit applies a force that swings the displacement unit in the reverse direction to the displacement unit that swings due to the gravity of the measurement target. The detection unit includes a light emitting diode and a photodiode provided with the slit interposed therebetween. The control unit controls the force applied by the external force applying unit to the displacement unit based on the amount of light received by the photodiode from the light emitting diode through the slit. The calculation unit calculates a value corresponding to the force applied by the external force applying unit to the displacement unit as the mass of the measurement object. The photodiode has two light receiving surfaces arranged with a gap in the fixed direction, and the gap is disposed in a region facing the light emitting diode in the optical axis direction. The width of the slit in the certain direction is 0.4 mm or less.
　このような構成によれば、発光ダイオードからは、指向性の高い光が出射される。そして、その発光ダイオードからの光は、０．４ｍｍ以下の幅の狭いスリットを通過した後、フォトダイオードで受光される。 According to such a configuration, light with high directivity is emitted from the light emitting diode. The light from the light-emitting diode passes through a narrow slit having a width of 0.4 mm or less and is received by the photodiode.
　そのため、測定対象物の重力によって変位部（スリット）が変位すると、フォトダイオードにおいて、単位受光量に対する２つの受光面での受光量の差の値が大きくなる。 Therefore, when the displacement part (slit) is displaced by the gravity of the measurement object, the value of the difference between the received light amounts at the two light receiving surfaces with respect to the unit received light amount is increased in the photodiode.
　また、制御部は、そのフォトダイオードでの受光量に基づいて、外力付与部が変位部に付与する力を制御し、演算部は、その外力付与部の力に応じた値を測定対象物の質量として算出する。
　そのため、算出される質量に対するノイズの影響を軽減することができる。 The control unit controls the force applied by the external force applying unit to the displacement unit based on the amount of light received by the photodiode, and the calculation unit calculates a value corresponding to the force of the external force applying unit. Calculated as mass.
Therefore, the influence of noise on the calculated mass can be reduced.
　すなわち、本発明によれば、発光ダイオードから指向性の高い光を照射し、その光を０．４ｍｍ以下の幅の狭いスリットを通過させることにより、フォトダイオードでの単位受光量に対する２つの受光面での受光量の差の値を大きくしてノイズの影響を軽減し、測定精度を向上できる。そのため、構成上の不具合を生じることなく、測定精度を向上できる。 That is, according to the present invention, two light receiving surfaces with respect to a unit light reception amount of a photodiode are obtained by irradiating light with high directivity from the light emitting diode and passing the light through a narrow slit having a width of 0.4 mm or less. By increasing the value of the difference in the amount of received light at the time, the influence of noise can be reduced and the measurement accuracy can be improved. Therefore, it is possible to improve the measurement accuracy without causing structural problems.
　本発明によれば、発光ダイオードからの指向性の高い光は、０．４ｍｍ以下の幅の狭いスリットを介して、フォトダイオードで受光される。そのため、フォトダイオードでの単位受光量に対する２つの受光面での受光量の差の値を大きくすることにより、測定精度を向上できる。その結果、構成上の不具合を生じることなく、測定精度を向上できる。 According to the present invention, light having high directivity from the light emitting diode is received by the photodiode through a narrow slit having a width of 0.4 mm or less. Therefore, the measurement accuracy can be improved by increasing the value of the difference between the received light amounts at the two light receiving surfaces with respect to the unit received light amount at the photodiode. As a result, it is possible to improve the measurement accuracy without causing structural problems.
本発明の一実施形態に係る電子天秤を示した概略図である。It is the schematic which showed the electronic balance which concerns on one Embodiment of this invention. 図１の電子天秤の変位部を拡大して示した側面図である。It is the side view which expanded and showed the displacement part of the electronic balance of FIG. 図２のＡ－Ａ線に沿う側断面図である。FIG. 3 is a side sectional view taken along line AA in FIG. 2. 制御部及びその周辺の部材の具体的構成を示したブロック図である。It is the block diagram which showed the specific structure of the control part and its peripheral member. 電子天秤における機械的な感度とシャッタのスリット幅との関係を示したグラフである。It is the graph which showed the relationship between the mechanical sensitivity in an electronic balance, and the slit width of a shutter.
１．電子天秤の全体構成
　図１は、本発明の一実施形態に係る電子天秤１を示した概略図である。
　電子天秤１は、梁２と、支点３と、秤量皿４と、変位部５と、検出部６と、外力付与部７とを備えている。
　梁２は、長尺状に形成されており、水平方向に延びている。
　支点３は、梁２の中央部分を支持している。梁２は、支点３を中心として揺動可能である。
　秤量皿４は、梁２の一端部に設けられている。秤量皿４には、測定対象物であるサンプルＳが載置される。
　変位部５は、梁２の他端部に設けられている。変位部５は、梁２と一体となって揺動する。
　検出部６は、変位部５の揺動による変位を検出する。なお、検出部６及び変位部５の詳細の構成については後述する。 1. 1 is a schematic view showing an electronic balance 1 according to an embodiment of the present invention.
The electronic balance 1 includes a beam 2, a fulcrum 3, a weighing pan 4, a displacement unit 5, a detection unit 6, and an external force application unit 7.
The beam 2 is formed in an elongated shape and extends in the horizontal direction.
The fulcrum 3 supports the central portion of the beam 2. The beam 2 can swing around the fulcrum 3.
The weighing pan 4 is provided at one end of the beam 2. A sample S that is a measurement object is placed on the weighing pan 4.
The displacement part 5 is provided at the other end of the beam 2. The displacement part 5 swings integrally with the beam 2.
The detection unit 6 detects a displacement caused by the swinging of the displacement unit 5. The detailed configurations of the detection unit 6 and the displacement unit 5 will be described later.
　外力部付与部７は、梁２の他端部の近傍に設けられている。外力付与部７は、梁２を介して、変位部５に外力を付与する部材（機構）である。外力付与部７は、コイル８と、永久磁石９とを含んでいる。
　コイル８は、梁２の他端部近傍に対して固定されている。そのため、コイル８は、梁２と一体となって変位する。また、コイル８には、適宜大きさを変更した電流が流される。 The external force portion imparting portion 7 is provided in the vicinity of the other end portion of the beam 2. The external force imparting portion 7 is a member (mechanism) that imparts an external force to the displacement portion 5 via the beam 2. The external force applying unit 7 includes a coil 8 and a permanent magnet 9.
The coil 8 is fixed to the vicinity of the other end of the beam 2. Therefore, the coil 8 is displaced integrally with the beam 2. The coil 8 is supplied with a current whose size is appropriately changed.
　永久磁石９は、コイル８と間隔を隔てて配置されている。永久磁石９は、梁２（コイル８）とは別体として固定されている。永久磁石９は、静磁場を形成しており、その静磁場内にコイル８が配置される。 The permanent magnet 9 is arranged at a distance from the coil 8. The permanent magnet 9 is fixed separately from the beam 2 (coil 8). The permanent magnet 9 forms a static magnetic field, and the coil 8 is disposed in the static magnetic field.
　電子天秤１では、秤量皿４にサンプルＳが載置されると、サンプルＳの重力によって、梁２の一端部に対して下方に向かう力が加わる。梁２は、中央部（支点３の支持部分）を中心として、その一端部が下方に移動し、その他端部（変位部５）が上方に移動するように揺動する。検出部６は、梁２が揺動することによる変位部５の変位を検出する。 In the electronic balance 1, when the sample S is placed on the weighing pan 4, a downward force is applied to one end of the beam 2 due to the gravity of the sample S. The beam 2 swings so that one end portion thereof moves downward and the other end portion (displacement portion 5) moves upward with the central portion (supporting portion of the fulcrum 3) as a center. The detection unit 6 detects the displacement of the displacement unit 5 due to the swing of the beam 2.
　また、外力付与部７では、コイル８に電流が流されることにより、電磁力が発生する。電磁力の大きさは、コイル８に流される電流の値によって決定する。そして、コイル８に対して永久磁石９から離れる方向に力が付与され、梁２を介して、変位部５に対して下方（変位方向と逆方向）に向かう力が付与される。 Further, in the external force applying unit 7, an electromagnetic force is generated by passing a current through the coil 8. The magnitude of the electromagnetic force is determined by the value of the current flowing through the coil 8. A force is applied to the coil 8 in a direction away from the permanent magnet 9, and a force directed downward (opposite to the displacement direction) is applied to the displacement portion 5 via the beam 2.
　このとき、変位部５の変位が０となるように、コイル８に流す電流に対してフィードバック制御が行われる。そして、後述するように、コイル８に流す電流の値から、サンプルＳの質量が算出され、算出された質量の値が表示される。 At this time, feedback control is performed on the current flowing through the coil 8 so that the displacement of the displacement portion 5 becomes zero. Then, as will be described later, the mass of the sample S is calculated from the value of the current passed through the coil 8, and the calculated mass value is displayed.
２．変位部及び検出部の詳細構成
　図２は、電子天秤１の変位部５を拡大して示した側面図である。また、図３は、図２のＡ－Ａ線に沿う側断面図である。なお、便宜上、図２では、検出部６を省いて示している。 2. Detailed Configuration of Displacement Unit and Detection Unit FIG. 2 is an enlarged side view showing the displacement unit 5 of the electronic balance 1. FIG. 3 is a side sectional view taken along line AA in FIG. For convenience, FIG. 2 does not show the detection unit 6.
　電子天秤１は、上記したように、変位部５と、検出部６とを備えている。
　変位部５は、側面視矩形状の板状の部材（シャッタ）である。変位部５は、上記したように、上下方向に揺動可能であって、その揺動方向は、厚み方向と直交している。変位部５には、スリット５１が形成されている。 As described above, the electronic balance 1 includes the displacement unit 5 and the detection unit 6.
The displacement part 5 is a plate-shaped member (shutter) having a rectangular shape in a side view. As described above, the displacement portion 5 can swing in the vertical direction, and the swinging direction is orthogonal to the thickness direction. A slit 51 is formed in the displacement portion 5.
　スリット５１は、変位部５において上下方向中央部に配置されており、変位部５を厚み方向に貫通している。スリット５１は、上下方向及び水平方向に沿って延びている。
　具体的には、スリット５１の上下方向（揺動方向）の幅Ｄ１、すなわち、スリット５１の上端縁（揺動方向一端縁）から、スリット５１の下端縁（揺動方向他端縁）までの幅Ｄ１は、０．４ｍｍ以下である。
　図３に示すように、検出部６には、発光ダイオード６１と、フォトダイオード６２とが含まれる。 The slit 51 is disposed at the center in the vertical direction in the displacement portion 5 and penetrates the displacement portion 5 in the thickness direction. The slit 51 extends along the vertical direction and the horizontal direction.
Specifically, the width D1 of the slit 51 in the vertical direction (swing direction), that is, from the upper end edge (one end edge in the swing direction) of the slit 51 to the lower end edge (the other end edge in the swing direction) of the slit 51. The width D1 is 0.4 mm or less.
As shown in FIG. 3, the detection unit 6 includes a light emitting diode 61 and a photodiode 62.
　発光ダイオード６１は、変位部５と間隔を隔てて配置されている。具体的には、発光ダイオード６１は、変位部５のスリット５１に対して水平方向に間隔を隔てて配置されている。発光ダイオード６１から照射される光の光軸方向は、水平方向に沿っている。 The light emitting diode 61 is disposed with a distance from the displacement portion 5. Specifically, the light emitting diodes 61 are arranged with a gap in the horizontal direction with respect to the slits 51 of the displacement portion 5. The optical axis direction of the light emitted from the light emitting diode 61 is along the horizontal direction.
　フォトダイオード６２は、変位部５（スリット５１）を挟んで、発光ダイオード６１と反対側に配置されている。すなわち、フォトダイオード６２及び発光ダイオード６１は、変位部５（スリット５１）を挟んで設けられている。フォトダイオード６２は、板状に形成された２分割フォトダイオードであって、第１受光面６２１と、第２受光面６２２とを有している。 The photodiode 62 is disposed on the opposite side of the light emitting diode 61 with the displacement portion 5 (slit 51) interposed therebetween. That is, the photodiode 62 and the light emitting diode 61 are provided with the displacement portion 5 (slit 51) interposed therebetween. The photodiode 62 is a two-divided photodiode formed in a plate shape, and includes a first light receiving surface 621 and a second light receiving surface 622.
　第１受光面６２１は、フォトダイオード６２において上方側に配置されており、変位部５に対向している。第１受光面６２１は、側面視矩形状に形成されている。第１受光面６２１には、発光素子が実装されている。 The first light receiving surface 621 is arranged on the upper side of the photodiode 62 and faces the displacement portion 5. The first light receiving surface 621 is formed in a rectangular shape in side view. A light emitting element is mounted on the first light receiving surface 621.
　第２受光面６２２は、フォトダイオード６２において下方側に配置されており、変位部５に対向している。第２受光面６２２は、第１受光面６２１の下方に間隔を隔てて配置されている。第２受光面６２２は、側面視矩形状に形成されている。第２受光面６２２には、発光素子が実装されている。 The second light receiving surface 622 is disposed on the lower side of the photodiode 62 and faces the displacement portion 5. The second light receiving surface 622 is disposed below the first light receiving surface 621 with a space therebetween. The second light receiving surface 622 is formed in a rectangular shape in side view. A light emitting element is mounted on the second light receiving surface 622.
　上下方向における第１受光面６２１と第２受光面６２２との間の隙間６２３の幅Ｄ２（第１受光面６２１の下端縁から第２受光面６２２の上端縁までの幅Ｄ２）は、変位部５のスリット５１の幅Ｄ１よりも小さい。具体的には、第１受光面６２１と第２受光面６２２との間の隙間６２３の幅Ｄ２は、例えば、０．０３ｍｍである。第１受光面６２１と第２受光面６２２との間の隙間６２３は、発光ダイオード６１に対して光軸方向に対向する領域に配置されている。変位部５の変位が０の状態では、第１受光面６２１と第２受光面６２２との間の隙間６２３の中心、及び、変位部５のスリット５１の中心は、発光ダイオード６１からの光の光軸上に位置している。 The width D2 of the gap 623 between the first light receiving surface 621 and the second light receiving surface 622 in the vertical direction (the width D2 from the lower end edge of the first light receiving surface 621 to the upper end edge of the second light receiving surface 622) is a displacement portion. It is smaller than the width D1 of the five slits 51. Specifically, the width D2 of the gap 623 between the first light receiving surface 621 and the second light receiving surface 622 is, for example, 0.03 mm. A gap 623 between the first light receiving surface 621 and the second light receiving surface 622 is disposed in a region facing the light emitting diode 61 in the optical axis direction. When the displacement of the displacement portion 5 is 0, the center of the gap 623 between the first light receiving surface 621 and the second light receiving surface 622 and the center of the slit 51 of the displacement portion 5 are the light from the light emitting diode 61. Located on the optical axis.
　発光ダイオード６１の光源Ｂからは、指向性の高い光が照射される。光源Ｂからの光は、発光ダイオード６１の外面を通過する過程で屈折して変位部５に向かう。そして、発光ダイオード６１からの光は、その一部が変位部５のスリット５１を通過してフォトダイオード６２に向かう。
　このとき、光の屈折がなければ、光は、仮想点光源Ｃから出射されたのと同様に捉えることができる。
　仮想点光源Ｃは、光の屈折がないと仮定したときの見かけ上の光源であって、虚光源である。仮想点光源Ｃは、光源Ｂよりも変位部５及びフォトダイオード６２から離れた点に位置している。 The light source B of the light emitting diode 61 emits light with high directivity. Light from the light source B is refracted in the process of passing through the outer surface of the light emitting diode 61 and travels toward the displacement portion 5. A part of the light from the light emitting diode 61 passes through the slit 51 of the displacement portion 5 and travels toward the photodiode 62.
At this time, if there is no refraction of the light, the light can be captured in the same manner as it is emitted from the virtual point light source C.
The virtual point light source C is an apparent light source when it is assumed that there is no light refraction, and is an imaginary light source. The virtual point light source C is located at a point farther from the displacement unit 5 and the photodiode 62 than the light source B.
　また、仮想点光源Ｃに対して、変位部５のスリット５１の上下方向両端縁がなす角度αは、仮想点光源Ｃに対して、第１受光面６２１と第２受光面６２２との間の隙間６２３の両端縁がなす角度α０よりも大きい。角度αは、側面視において、仮想点光源Ｃと変位部５のスリット５１の上端縁とを結ぶ線分と、仮想点光源Ｃと変位部５のスリット５１の下端縁とを結ぶ線分とのなす角度である。角度α０は、側面視において、仮想点光源Ｃと第１受光面６２１の下端縁とを結ぶ線分と、仮想点光源Ｃと第２受光面６２２の上端縁とを結ぶ線分とのなす角度である。 In addition, the angle α formed by the vertical end edges of the slit 51 of the displacement portion 5 with respect to the virtual point light source C is between the first light receiving surface 621 and the second light receiving surface 622 with respect to the virtual point light source C. It is larger than the angle α 0 formed by both end edges of the gap 623. The angle α is a line segment connecting the virtual point light source C and the upper edge of the slit 51 of the displacement part 5 and a line segment connecting the virtual point light source C and the lower edge of the slit 51 of the displacement part 5 in a side view. It is an angle to make. The angle α 0 is a line segment connecting the virtual point light source C and the lower end edge of the first light receiving surface 621 and a line segment connecting the virtual point light source C and the upper end edge of the second light receiving surface 622 in the side view. Is an angle.
３．制御部及び周辺の部材の具体的構成
　図４は、制御部２０及びその周辺の部材の具体的構成を示したブロック図である。
　電子天秤１は、上記したコイル８、発光ダイオード６１及びフォトダイオード６２に加えて、表示器１０と、制御部２０とを備えている。
　表示器１０は、例えば、液晶表示画面を含んでいる。表示器１０には、測定対象物の質量が表示される。 3. FIG. 4 is a block diagram showing a specific configuration of the control unit 20 and its peripheral members.
The electronic balance 1 includes a display 10 and a control unit 20 in addition to the coil 8, the light emitting diode 61, and the photodiode 62 described above.
The display device 10 includes, for example, a liquid crystal display screen. The display 10 displays the mass of the measurement object.
　制御部２０は、例えば、ＣＰＵ（Central Processing Unit）を含む構成である。制御部２０は、フォトダイオード６２からの検出信号に基づいて、コイル８、表示器１０及び発光ダイオード６１の各動作を制御する。制御部２０は、ＣＰＵがプログラムを実行することにより、電流制御部２０１、演算部２０２及び光量制御部２０３などとして機能する。 The control unit 20 includes, for example, a CPU (Central Processing Unit). The control unit 20 controls each operation of the coil 8, the display 10, and the light emitting diode 61 based on the detection signal from the photodiode 62. The control unit 20 functions as a current control unit 201, a calculation unit 202, a light amount control unit 203, and the like when the CPU executes a program.
　電流制御部２０１は、フォトダイオード６２からの検出信号に基づいて、コイル８に流れる電流の値を決定する。そして、コイル８には、電流制御部２０１で決定した値の電流が流される。また、上記した外力付与部７での電磁力の大きさは、コイル８に流される電流の値に基づいて決定する。すなわち、電流制御部２０１は、フォトダイオード６２での受光量に基づいて、外力付与部７における電磁力の大きさを決定する制御を行う。 The current control unit 201 determines the value of the current flowing through the coil 8 based on the detection signal from the photodiode 62. The coil 8 is supplied with the current determined by the current control unit 201. Further, the magnitude of the electromagnetic force in the external force applying unit 7 is determined based on the value of the current flowing through the coil 8. That is, the current control unit 201 performs control to determine the magnitude of the electromagnetic force in the external force applying unit 7 based on the amount of light received by the photodiode 62.
　演算部２０２は、電流制御部２０１が決定したコイル８に流す電流の値に基づいて、測定対象物の質量を算出し、当該算出した質量の値を表示器１０に表示させる処理を行う。 The calculation unit 202 performs a process of calculating the mass of the measurement object based on the value of the current passed through the coil 8 determined by the current control unit 201 and causing the display unit 10 to display the calculated mass value.
　光量制御部２０３は、フォトダイオード６２からの検出信号に基づいて、フォトダイオード６２での全受光量が一定に保たれるように、発光ダイオード６１の発光量を決定する。そして、発光ダイオード６１では、光量制御部２０３で決定した発光量で光が出射される。 The light quantity control unit 203 determines the light emission amount of the light emitting diode 61 based on the detection signal from the photodiode 62 so that the total amount of light received by the photodiode 62 is kept constant. The light emitting diode 61 emits light with the light emission amount determined by the light amount control unit 203.
４．制御部による制御動作
　図３に示すように、発光ダイオード６１の光源Ｂから光が照射されると、その光の一部は、変位部５のスリット５１を通過してフォトダイオード６２に向かう。
　フォトダイオード６２では、第１受光面６２１及び第２受光面６２２において、変位部５のスリット５１を通過した光を受光する。 4). Control Operation by Control Unit As shown in FIG. 3, when light is emitted from the light source B of the light emitting diode 61, a part of the light passes through the slit 51 of the displacement unit 5 toward the photodiode 62.
In the photodiode 62, light that has passed through the slit 51 of the displacement portion 5 is received by the first light receiving surface 621 and the second light receiving surface 622.
　変位部５の変位が０の状態では、第１受光面６２１での受光量、及び、第２受光面６２２での受光量は同じである。そして、秤量皿４に載置された測定対象物（サンプルＳ）の重力によって、変位部５が上方に変位すれば、第１受光面６２１での受光量が増え、第２受光面６２２での受光量が減る。一方、変位部５が下方に変位すれば、第１受光面６２１での受光量が減り、第２受光面６２２での受光量が増える。
　このような電子天秤１での測定中において、光量制御部２０３は、フォトダイオード６２での全受光量が一定に保たれるように、発光ダイオード６１の発光量を決定する。 When the displacement of the displacement unit 5 is 0, the amount of light received by the first light receiving surface 621 and the amount of light received by the second light receiving surface 622 are the same. If the displacement unit 5 is displaced upward due to the gravity of the measurement object (sample S) placed on the weighing pan 4, the amount of light received by the first light receiving surface 621 increases, and the second light receiving surface 622 The amount of light received decreases. On the other hand, if the displacement part 5 is displaced downward, the amount of light received by the first light receiving surface 621 decreases and the amount of light received by the second light receiving surface 622 increases.
During the measurement with the electronic balance 1, the light amount control unit 203 determines the light emission amount of the light emitting diode 61 so that the total amount of light received by the photodiode 62 is kept constant.
　また、電流制御部２０１（図４参照）は、フォトダイオード６２からの検出信号に基づいて、第１受光面６２１での受光量と、第２受光面６２２での受光量との差分を算出する。そして、電流制御部２０１は、当該算出した受光量の差分が０となるように、コイル８に流す電流の値を決定するフィードバック制御を行う。詳しくは、電流制御部２０１は、第１受光面６２１での受光量と、第２受光面６２２での受光量との差分（差分受光量）を、フォトダイオード６２での全受光量で除した値（フォトダイオード６２での単位受光量に対する差分受光量の値）が０となるように、コイル８に流す電流の値を決定するフィードバック制御を行う。そして、コイル８には、当該決定した値の電流が流される。 Further, the current control unit 201 (see FIG. 4) calculates the difference between the amount of light received by the first light receiving surface 621 and the amount of received light by the second light receiving surface 622 based on the detection signal from the photodiode 62. . Then, the current control unit 201 performs feedback control for determining the value of the current flowing through the coil 8 so that the calculated difference in received light amount becomes zero. Specifically, the current control unit 201 divides the difference (difference received light amount) between the amount of light received by the first light receiving surface 621 and the amount of received light by the second light receiving surface 622 by the total amount of received light by the photodiode 62. Feedback control is performed to determine the value of the current that flows through the coil 8 so that the value (the value of the difference light reception amount with respect to the unit light reception amount at the photodiode 62) becomes zero. The coil 8 is supplied with the determined current.
　また、演算部２０２は、電流制御部２０１が決定した電流の値に基づいて、測定対象物（サンプルＳ）の質量を算出するとともに、当該算出した質量の値を表示器１０に表示させる。 Further, the calculation unit 202 calculates the mass of the measurement object (sample S) based on the current value determined by the current control unit 201 and causes the display unit 10 to display the calculated mass value.
５．電子天秤の測定精度
　以下では、電子天秤１の構成と測定精度との関係を数式を用いて説明する。
　図３に示す発光ダイオード６１からの光に関するエネルギーは、以下の式で表される。 5). Below, the relationship between the configuration of the electronic balance 1 and the measurement accuracy will be described using mathematical expressions.
The energy related to the light from the light emitting diode 61 shown in FIG. 3 is expressed by the following equation.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
　ここで、上記式（１）～（４）において、Ｉは、発光ダイオード６１のエネルギーを示している。具体的には、Ｉ０は、発光ダイオード６１から垂直（角度０°）に出た光のエネルギーを示し、Ｉ（θ）は、発光ダイオード６１からの角度θでのエネルギーを示し、θ０は、発光ダイオード６１の光量が１/ｅになる角度を示している。Ｉ（Ｚ）は、変位部５における仮想点光源Ｃからの角度θでの単位面積あたりの入射エネルギーを示している。Ｐ＋は、フォトダイオード６２の第１受光面６２１での入射エネルギーを示している。Ｐ－は、フォトダイオード６２の第２受光面６２２での入射エネルギーを示している。Ｐ±は、フォトダイオード６２の第１受光面６２１での入射エネルギー、又は、フォトダイオード６２の第２受光面６２２での入射エネルギーを示している。Ｐは、フォトダイオード６２の第１受光面６２１での入射エネルギーと、フォトダイオード６２の第２受光面６２２での入射エネルギーとの差分のエネルギーを示している。 Here, in the above formulas (1) to (4), I represents the energy of the light emitting diode 61. Specifically, I 0 indicates the energy of light emitted perpendicularly (angle 0 °) from the light emitting diode 61, I (θ) indicates the energy at the angle θ from the light emitting diode 61, and θ 0 is The angle at which the light quantity of the light emitting diode 61 is 1 / e is shown. I (Z) represents the incident energy per unit area at an angle θ from the virtual point light source C in the displacement portion 5. P + represents the incident energy at the first light receiving surface 621 of the photodiode 62. P− indicates the incident energy at the second light receiving surface 622 of the photodiode 62. P ± indicates the incident energy at the first light receiving surface 621 of the photodiode 62 or the incident energy at the second light receiving surface 622 of the photodiode 62. P indicates the energy difference between the incident energy at the first light receiving surface 621 of the photodiode 62 and the incident energy at the second light receiving surface 622 of the photodiode 62.
　式（４）は、第１受光面６２１での受光量と、第２受光面６２２での受光量との差分（差分受光量）を、フォトダイオード６２での全受光量で除した値（フォトダイオード６２での単位受光量に対する差分受光量の値）に対応している。
　また、式（４）をαで微分すると、下記式（５）が得られる。 Equation (4) is a value obtained by dividing the difference between the amount of received light at the first light receiving surface 621 and the amount of received light at the second light receiving surface 622 (difference received light amount) by the total amount of received light at the photodiode 62 (photo This corresponds to the value of the difference received light amount relative to the unit received light amount at the diode 62).
Further, when the formula (4) is differentiated by α, the following formula (5) is obtained.
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000005
　この式（５）に上記式（３）を用いると、下記式（６）が得られる。 When the above equation (3) is used for this equation (5), the following equation (6) is obtained.
Figure JPOXMLDOC01-appb-M000006
Figure JPOXMLDOC01-appb-M000006
　この式（６）に上記式（１）を用いると、下記式（７）が得られる。 When the above formula (1) is used for this formula (6), the following formula (7) is obtained.
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
　この式（７）に上記式（２）を用いると、下記式（８）が得られる。 When the above equation (2) is used for this equation (7), the following equation (8) is obtained.
Figure JPOXMLDOC01-appb-M000008
Figure JPOXMLDOC01-appb-M000008
　この式（８）を変数変換すると、下記式（９）が得られる。 When the equation (8) is converted into a variable, the following equation (9) is obtained.
Figure JPOXMLDOC01-appb-M000009
Figure JPOXMLDOC01-appb-M000009
　この式（９）をエラーファンクション（誤差関数）の式に変換すると、下記式（１０）が得られる。 When this equation (9) is converted into an error function equation, the following equation (10) is obtained.
Figure JPOXMLDOC01-appb-M000010
Figure JPOXMLDOC01-appb-M000010
　この式（１０）は、変位部５の単位変位量に対するフォトダイオード６２の信号強度の変化を示したものであり、電子天秤１での機械的な感度を示している。 This equation (10) shows the change in the signal intensity of the photodiode 62 with respect to the unit displacement amount of the displacement portion 5, and shows the mechanical sensitivity of the electronic balance 1.
　また、式（１０）から、図５に示すグラフが得られる。図５は、電子天秤１における機械的な感度と、変位部５のスリット５１の幅Ｄ１との関係を示したグラフである。図５では、縦軸が、電子天秤１での機械的な感度を示し、横軸が、変位部５のスリット５１の幅Ｄ１を示している。 Moreover, the graph shown in FIG. 5 is obtained from the equation (10). FIG. 5 is a graph showing the relationship between the mechanical sensitivity of the electronic balance 1 and the width D1 of the slit 51 of the displacement portion 5. As shown in FIG. In FIG. 5, the vertical axis indicates the mechanical sensitivity of the electronic balance 1, and the horizontal axis indicates the width D <b> 1 of the slit 51 of the displacement portion 5.
　図５から、変位部５のスリット５１の幅Ｄ１が小さくなるにつれて、電子天秤１での機械的な感度が大きくなることが確認できる。すなわち、変位部５のスリット５１の幅Ｄ１を小さくして、上記したように、第１受光面６２１での受光量と、第２受光面６２２での受光量との差分（差分受光量）を、フォトダイオード６２での全受光量で除した値（フォトダイオード６２での単位受光量に対する差分受光量の値）を大きくした結果、電子天秤１での機械的な感度が大きくなることが確認できる。特に、変位部５のスリット５１の幅Ｄ１が、０．４ｍｍ以下になると、電子天秤１での機械的な感度が急激に大きくなることが確認できる。
６．作用効果 From FIG. 5, it can confirm that the mechanical sensitivity in the electronic balance 1 becomes large as the width | variety D1 of the slit 51 of the displacement part 5 becomes small. That is, the width D1 of the slit 51 of the displacement portion 5 is reduced, and as described above, the difference (difference received light amount) between the amount of light received by the first light receiving surface 621 and the amount of received light by the second light receiving surface 622 is obtained. As a result of increasing the value obtained by dividing the total amount of light received by the photodiode 62 (the value of the difference amount of received light with respect to the unit amount of light received by the photodiode 62), it can be confirmed that the mechanical sensitivity of the electronic balance 1 increases. . In particular, when the width D1 of the slit 51 of the displacement part 5 is 0.4 mm or less, it can be confirmed that the mechanical sensitivity of the electronic balance 1 increases rapidly.
6). Effect
　本実施形態では、図３に示すように、変位部５のスリット５１は、上下方向（揺動方向）の幅Ｄ１が０．４ｍｍ以下となるように形成されている。また、発光ダイオード６１からは、指向性の高い光が出射される。そして、その発光ダイオード６１からの光は、０．４ｍｍ以下の幅の狭いスリット５１を通過した後、フォトダイオード６２で受光される。 In this embodiment, as shown in FIG. 3, the slit 51 of the displacement part 5 is formed so that the width D1 in the vertical direction (swinging direction) is 0.4 mm or less. Further, light with high directivity is emitted from the light emitting diode 61. Then, the light from the light emitting diode 61 passes through the narrow slit 51 having a width of 0.4 mm or less, and is received by the photodiode 62.
　そのため、秤量皿４上の測定対象物（サンプルＳ）の重力によって変位部５（スリット５１）が変位すると、フォトダイオード６２において、単位受光量に対する２つの受光面での受光量の差（第１受光面６２１での受光量と、第２受光面６２２での受光量との差分を、フォトダイオード６２での全受光量で除した値）が大きくなる。換言すれば、変位部５の単位変位量に対するフォトダイオード６２の信号強度の変化が大きくなる。 Therefore, when the displacement part 5 (slit 51) is displaced by the gravity of the measurement object (sample S) on the weighing pan 4, the difference in received light amount between the two light receiving surfaces with respect to the unit received light amount (first) in the photodiode 62. The difference between the amount of light received at the light receiving surface 621 and the amount of light received at the second light receiving surface 622 divided by the total amount of received light at the photodiode 62) increases. In other words, the change in the signal intensity of the photodiode 62 with respect to the unit displacement amount of the displacement portion 5 becomes large.
　また、電流制御部２０１は、その値（フォトダイオード６２での単位受光量に対する２つの受光面での受光量の差の値）が０となるように、コイル８に流す電流の値を決定する。そして、コイル８には、当該決定した値の電流が流される。また、演算部２０２は、電流制御部２０１が決定した電流の値に基づいて、測定対象物の質量を算出する。
　そのため、算出される質量に対するノイズの影響を軽減することができ、その結果、演算部２０２による測定対象物の質量の算出精度を向上できる。 In addition, the current control unit 201 determines the value of the current passed through the coil 8 so that the value (the difference between the received light amounts at the two light receiving surfaces with respect to the unit received light amount at the photodiode 62) becomes zero. . The coil 8 is supplied with the determined current. In addition, the calculation unit 202 calculates the mass of the measurement object based on the current value determined by the current control unit 201.
Therefore, the influence of noise on the calculated mass can be reduced, and as a result, the calculation accuracy of the mass of the measurement object by the calculation unit 202 can be improved.
　すなわち、電子天秤１によれば、変位部５のスリット５１の幅Ｄ１を０．４ｍｍ以下にすることで、フォトダイオード６２での単位受光量に対する２つの受光面での受光量の差の値（変位部５の単位変位量に対するフォトダイオード６２の信号強度の変化）を大きくしてノイズの影響を軽減し、測定精度を向上できる。そのため、構成上の不具合を生じることなく、測定精度を向上できる。 That is, according to the electronic balance 1, by setting the width D1 of the slit 51 of the displacement portion 5 to 0.4 mm or less, the value of the difference in the amount of light received at the two light receiving surfaces with respect to the unit amount of light received by the photodiode 62 ( The change in the signal intensity of the photodiode 62 with respect to the unit displacement amount of the displacement unit 5 can be increased to reduce the influence of noise, and the measurement accuracy can be improved. Therefore, it is possible to improve the measurement accuracy without causing structural problems.
　　　１　　　電子天秤
　　　３　　　支点
　　　４　　　秤量皿
　　　５　　　変位部
　　　６　　　検出部
　　　７　　　外力付与部
　　２０　　　制御部
　　５１　　　スリット
　　６１　　　発光ダイオード
　　６２　　　フォトダイオード
　２０１　　　電流制御部
　２０２　　　演算部
　６２１　　　第１受光面
　６２２　　　第２受光面
　６２３　　　隙間 DESCRIPTION OF SYMBOLS 1 Electronic balance 3 Support point 4 Weighing pan 5 Displacement part 6 Detection part 7 External force provision part 20 Control part 51 Slit 61 Light emitting diode 62 Photodiode 201 Current control part 202 Calculation part 621 1st light-receiving surface 622 2nd light-receiving surface 623 Gap

Claims (1)

  1. 　測定対象物が載置される秤量皿と、
    　支点に対して揺動可能に設けられ、前記秤量皿に載置された測定対象物の重力により一定方向に揺動するとともに、前記一定方向に延びるスリットが形成された変位部と、
    　測定対象物の重力により揺動する前記変位部に対して、当該変位部を逆方向に揺動させる力を付与する外力付与部と、
    　前記スリットを挟んで設けられた発光ダイオード及びフォトダイオードを有する検出部と、
    　前記発光ダイオードから前記スリットを介して前記フォトダイオードが受光する光の受光量に基づいて、前記外力付与部が前記変位部に付与する力を制御する制御部と、
    　前記外力付与部が前記変位部に付与する力に応じた値を測定対象物の質量として算出する演算部とを備え、
    　前記フォトダイオードは、前記一定方向に隙間を空けて並ぶ２つの受光面を有するとともに、前記隙間が、前記発光ダイオードに対して光軸方向に対向する領域に配置されており、
    　前記スリットの前記一定方向の幅が、０．４ｍｍ以下であることを特徴とする電子天秤。     A weighing pan on which a measurement object is placed;
    A displacement portion provided so as to be swingable with respect to a fulcrum, swinging in a certain direction due to the gravity of the measurement object placed on the weighing pan, and having a slit extending in the certain direction;
    An external force applying unit that applies a force that swings the displacement part in the opposite direction to the displacement part that swings due to the gravity of the measurement object;
    A detector having a light emitting diode and a photodiode provided across the slit;
    A control unit that controls the force applied by the external force applying unit to the displacement unit based on the amount of light received by the photodiode from the light emitting diode through the slit;
    A calculation unit that calculates a value according to the force applied to the displacement unit by the external force application unit as the mass of the measurement object;
    The photodiode has two light receiving surfaces arranged with a gap in the fixed direction, and the gap is disposed in a region facing the light emitting diode in the optical axis direction,
    The electronic balance according to claim 1, wherein a width of the slit in the certain direction is 0.4 mm or less.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013181979A (en) * 2012-02-29 2013-09-12 Mettler-Toledo Ag Measuring cell based on principle of magnetic force compensation using photoelectron position detector

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