Measuring instrument with reading device, and reading device

Abstract

Provided are a measuring instrument with a reading device capable of detecting the position of a pointer with a resolution higher than a resolution corresponding to the interval between adjacent sensor electrodes, and a reading device.　The measuring instrument with a reading device comprises: a rotating shaft; a metal pointer attached to the rotating shaft; a cover made of an insulator and covering the rotating shaft and the pointer; a plurality of sensor electrodes provided on the cover; a measuring circuit for measuring the capacitance of the plurality of sensor electrodes; and a control unit for calculating the position indicated by the pointer on the basis of the capacitance measured by the measuring circuit. The pointer has a tapered shape. The plurality of sensor electrodes extend away from the rotating shaft in a plan view, and are arranged radially around the rotating shaft. Each of the plurality of sensors has an isosceles trapezoidal or annular sectoral shape. The plurality of sensor electrodes have the same shape and size in a plan view. The control unit calculates the position of the pointer by interpolating a plurality of capacitances measured with respect to the plurality of sensor electrodes by the measuring circuit.

Description

Measuring instrument with reading device and reading device

[0001] The present disclosure relates to a measuring instrument with a reading device and a reading device.

[0002] A conventional remote measurement device for an analog measuring instrument includes a plurality of pointer detection sensors arranged along the scale of an existing measuring instrument for predetermined measurement units, a sensor selection unit that compares the output signals of each pointer detection sensor to identify the pointer detection sensor facing the measuring instrument's pointer, and a display that displays measurement values ​​that are pre-stored in a memory unit corresponding to the identified pointer detection sensor. The pointer position is determined by the position of the pointer detection sensor that outputs the largest output signal. The pointer detection sensor can be a magnetic sensor, an optical sensor, or a capacitance sensor (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 09-159490

[0004] In a remote measurement device for an analog measuring instrument, the position of the pointer is determined by the position of the pointer detection sensor that outputs the largest output signal, so it is not possible to detect the position of the pointer at an interval narrower than the interval (pitch) between the multiple pointer detection sensors. In other words, it is not possible to detect the position of the pointer with a resolution higher than the resolution determined by the interval (pitch) between the multiple pointer detection sensors.

[0005] Therefore, an object of the present invention is to provide a measuring instrument with a reading device that can detect the position of a pointer with a resolution higher than the resolution corresponding to the distance between adjacent sensor electrodes, and a reading device.

[0006] a measurement circuit that measures the capacitance of the plurality of sensor electrodes; and a control unit that calculates the position of the pointer based on the capacitance measured by the measurement circuit. The pointer has a tapered shape in plan view, with the needle width narrowing from the attachment portion attached to the rotary shaft toward the tip. The plurality of sensor electrodes extend in a direction away from the rotary shaft in plan view and are arranged radially around the rotary shaft. Each of the plurality of sensor electrodes has the shape of an isosceles trapezoid whose width in plan view is wider on the side farther from the rotary shaft than on the side closer to the rotary shaft, or the shape of an annular sector whose arc in plan view is longer on the side farther from the rotary shaft than on the arc closer to the rotary shaft. The plurality of sensor electrodes have the same shape and size as one another in plan view. The control unit calculates the position of the pointer by interpolating the plurality of capacitances measured for the plurality of sensor electrodes by the measurement circuit.

[0007] It is possible to provide a measuring instrument with a reader and a reader that can detect the position of a pointer with a resolution higher than the resolution corresponding to the distance between adjacent sensor electrodes.

[0008] 1 is a diagram showing an example of the configuration of a measuring instrument with a reading device 200 according to an embodiment. FIG. 1 is a diagram showing an example of the configuration of an analog meter 10. FIG. 1 is a diagram showing an example of the configuration of a reading device 100. FIG. 1 is a diagram showing an example of the configuration of a cross section taken along the arrows A-A in FIG. 1. FIG. 1 is a diagram showing an example of the components of the reading device 100. FIG. 1 is a diagram showing an example of the components of the reading device 100. FIG. 1 is a diagram showing an example of the components of the reading device 100. FIG. 1 is a diagram explaining an example of a method for calculating the position of a pointer. FIG. 1 is a diagram explaining an example of a method for calculating the position of a pointer. FIG. 1 is a diagram explaining an example of a method for calculating the position of a pointer. FIG. 1 is a diagram showing an example of the relationship between angle θ and an actual angle. FIG. 1 is a diagram showing an example of table data showing the relationship between angle θ and an actual angle (corrected angle). FIG. 1 is a diagram showing an example of the relationship between the outer diameter of a sensor electrode 140 and the upper and lower limits of the central angle between adjacent sensor electrodes 140. FIG. 1 is a diagram showing an example of the configuration of a substrate 110C and a sensor electrode 140 of a reading device 100 according to a first modified example of an embodiment. FIG. 1 is a diagram explaining an example of condition 3. FIG. 1 is a diagram showing an example of the configuration of a substrate 110C and a sensor electrode 140 of a reading device 100 according to a second modified example of an embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a reading device 100 according to a third modified example of the embodiment.

[0009] Hereinafter, a measuring instrument with a reading device and an embodiment to which the reading device of the present disclosure is applied will be described. In the following, the same elements will be given the same reference numerals, and duplicated explanations may be omitted.

[0010] In the following description, the XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to each other. The XYZ coordinate system is an example of a Cartesian coordinate system. Viewing the XY plane is referred to as planar view. In the following, the +Z direction may be referred to as up and the −Z direction as down, but these do not represent the universal up and down directions. In the following, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. Furthermore, terms such as parallel, right angle, orthogonal, horizontal, vertical, up and down, etc., are intended to allow for deviations to the extent that they do not impair the effects of the embodiments.

[0011] <Embodiment> Fig. 1 is a diagram showing an example of the configuration of a reading device-equipped measuring instrument 200 according to an embodiment. The reading device-equipped measuring instrument 200 according to an embodiment includes an analog meter 10 and a reading device 100. Fig. 2A is a diagram showing an example of the configuration of the analog meter 10. Fig. 2B is a diagram showing an example of the configuration of the reading device 100. Fig. 3 is a diagram showing an example of the configuration of a cross section taken along the line A-A in Fig. 1. Figs. 4A to 4D are diagrams showing examples of components of the reading device 100.

[0012] The reading device 100 is a device that can be attached to an existing measuring instrument after the existing instrument has been manufactured or installed. Here, an analog meter 10 will be used as an example of an existing measuring instrument. An existing measuring instrument is a device that has already been manufactured and completed.

[0013] The analog meter 10 is a gas meter as an example, but is not limited to a gas meter and may be a meter that indicates various physical quantities related to water, electricity, etc., or may be a speedometer of a moving object such as a vehicle. The analog meter 10 is installed in, for example, a factory, etc., and indicates the values ​​of various physical quantities.

[0014] <Analog meter 10> The analog meter 10 includes a housing 11, a dial 12, a rotating shaft 13, a pointer 14, and a cover 15. As an example, the analog meter 10 is a meter that is circular in a plan view. The analog meter 10 is not limited to being circular as long as the pointer 14 rotates around the rotating shaft 13. However, as an example, a configuration in which the analog meter 10 is circular in a plan view will be described here. In addition, as an example, the diameter of the analog meter 10 is 40 mm. The larger the diameter of the analog meter 10, the easier it is to arrange more sensor electrodes 140.

[0015] The housing 11 has, for example, a cylindrical shape with a bottom, an opening 11A provided at the top, and a space 11B communicating with the opening 11A. A metal dial 12 is disposed at the bottom of the space 11B. The dial 12 is a disc-shaped member, and letters, numbers, etc. for the gas meter are printed on the top surface.

[0016] The rotating shaft 13 is the axis of rotation of the hands 14 and is made of metal. As an example, the rotating shaft 13 is rotatably supported on the bottom of the housing 11 and extends in a direction (Z direction) that vertically passes through the center of the opening 11A in a plan view. The rotating shaft 13 passes through the center of the dial 12 in a plan view and rotates by an amount that corresponds to the gas pressure. Note that, hereinafter, the radial direction refers to the radial direction of the rotating shaft 13 in a plan view.

[0017] The hands 14 are rotatable in a plan view by the rotary shaft 13 that penetrates the dial 12, and indicate the value on the dial 12 according to the gas pressure. The hands 14 have a tapered shape in a plan view, with the needle width narrowing from the attachment portion attached to the rotary shaft 13 toward the tip. The hands 14 also have a weight on the opposite side of the rotary shaft 13 from the tip. The length from the rotary shaft 13 to the tip is longer than the length from the rotary shaft 13 to the end of the weight. The housing 11, dial 12, rotary shaft 13, and hands 14 are connected to ground (reference potential point).

[0018] The cover 15 is provided to close the opening 11A of the housing 11. The analog meter 10 has a waterproof structure that can prevent water from entering the space 11B. The cover 15 is, for example, a disc-shaped member made of transparent glass or resin. Because the cover 15 is transparent, the dial 12 and the pointer 14 can be seen from outside the analog meter 10.

[0019] The analog meter 10 can be read remotely using the reading device 100, but since it can also be viewed directly by an operator, it is preferable that the cover 15 is transparent. The cover 15 only needs to be transparent enough to allow the dial of the analog meter 10, including the pointer 14, to be visible.

[0020] <Reading device 100> The reading device 100 includes, as an example, a cover film 110A, three substrates 110B, 110C, and 110D, OCA (Optical Clear Adhesive) 120A, 120B, and 120C, a self-adhesive sheet 120D, an AS (Active Shield) electrode 130, a sensor electrode 140, an FPC (Flexible Printed Circuit) 150, a measurement circuit 160, a control unit 170, and a wireless communication unit 180. The substrate 110B is an example of an insulating layer that covers the multiple sensor electrodes 140. The substrate 110C is an example of an insulating substrate on which the sensor electrode 140 is provided. The self-adhesive sheet 120D is an example of an adhesive layer that attaches the insulating substrate (substrate 110C) to the cover 15.

[0021] As an example, the components from the cover film 110A to the sensor electrode 140 are stacked in the following order from top to bottom: cover film 110A, OCA 120A, AS electrode 130, substrate 110B, OCA 120B, sensor electrode 140, substrate 110C, OCA 120C, substrate 110D, and self-adhesive sheet 120D.

[0022] 3, the reading device 100 is attached to the upper surface of the cover 15 of the analog meter 10 by a self-adhesive sheet 120D. The reading device 100 can be peeled off from the cover 15 and can be attached to the cover 15 repeatedly.

[0023] <Cover Film 110A and OCA 120A (Mainly Figures 3 and 4A)> The cover film 110A is, for example, a transparent film made of PET (polyethylene terephthalate). The thickness of the cover film 110A is, for example, 0.1 mm. The cover film 110A is provided as the top layer to protect the three substrates 110B, 110C, and 110D, the OCAs 120A, 120B, and 120C, the self-adhesive sheet 120D, the AS electrode 130, and the sensor electrode 140.

[0024] An OCA 120A is attached to the lower surface of the cover film 110A. The cover film 110A and the OCA 120A are circular in plan view, and have a convex portion on the +Y direction side that is connected to the FPC 150. The OCA 120A is a transparent adhesive layer, and attaches the cover film 110A to the upper surfaces of the substrate 110B and the AS electrode 130. The OCA 120A has a thickness of 0.1 mm, for example, and a relative dielectric constant of 4.1, for example.

[0025] <Substrate 110B, AS electrode 130, OCA 120B (mainly Figures 3 and 4B)> The substrate 110B is, for example, a transparent film made of PET. The thickness of the substrate 110B is, for example, 0.05 mm, and the relative dielectric constant is, for example, 3.0. The AS electrode 130 and wiring 111B (see Figure 4B) are provided on the upper surface of the substrate 110B, and the OCA 120B is attached to the lower surface. The substrate 110B and the OCA 120B are circular in plan view and have a protrusion on the +Y direction side that is connected to the FPC 150. The OCA 120B is a transparent adhesive layer that attaches the laminate of the substrate 110B and the AS electrode 130 to the upper surfaces of the substrate 110C and the sensor electrode 140. The thickness of the OCA 120B is, for example, 0.1 mm, and the relative dielectric constant is, for example, 4.1.

[0026] The AS electrode 130 is a circular transparent electrode slightly smaller than the substrate 110B in plan view, and is made of ITO (Indium Tin Oxide) as an example. The AS electrode 130 is formed on the entire surface of a circular area slightly smaller than the outer edge of the substrate 110B in plan view, and is larger than the outer edge of the circular area in which all the sensor electrodes 140 are formed in plan view, and is formed without gaps throughout the entire circular area that includes the outer edge of the circular area in which all the sensor electrodes 140 are formed. In Figure 4B, the circular area in which the AS electrode 130 is provided is indicated by dots.

[0027] The AS electrode 130 is connected to an oscillator circuit in the measurement circuit 160 via wiring 111B formed around the AS electrode 130 on the upper surface of the substrate 110B and via an FPC 150, and is driven by an AC signal of the same frequency and phase as the AC components contained in the signals supplied to all of the sensor electrodes 140. The amplitude of the AC signal supplied to the AS electrode 130 is greater than the amplitude of the AC components of the signals supplied to the sensor electrodes 140. Note that the wiring 111B is, for example, a silver paste wiring with carbon paste printed around it to prevent migration.

[0028] The AS electrode 130 is provided to shield all of the sensor electrodes 140 from noise and to suppress the effects of parasitic capacitance. The AS electrode 130 is arranged in an overlapping state with a predetermined gap between it and all of the sensor electrodes 140 so as to be able to shield all of the sensor electrodes 140 from noise mainly from ground potential points such as the ground and to suppress the effects of parasitic capacitance between the AS electrode 130 and the ground potential points.

[0029] <Substrate 110C, OCA 120C, and Sensor Electrode 140 (Mainly Figures 3 and 4C)> The substrate 110C is, for example, a transparent film made of PET. The thickness of the substrate 110C is, for example, 0.05 mm, and the relative dielectric constant is, for example, 3.0. The sensor electrode 140 is provided on the upper surface of the substrate 110C, and the OCA 120C is attached to the lower surface. The substrate 110C and the OCA 120C are circular in plan view, and have a convex portion on the +Y direction side that is connected to the FPC 150. The OCA 120C is a transparent adhesive layer, and attaches the laminate of the substrate 110C and the sensor electrode 140 to the upper surface of the substrate 110D. The thickness of the OCA 120C is, for example, 0.025 mm, and the relative dielectric constant is, for example, 4.1.

[0030] A plurality of sensor electrodes 140 are provided within a circular region that is slightly smaller than the substrate 110C in a plan view. The sensor electrodes 140 are not provided in the center of the substrate 110C. More specifically, a plurality of sensor electrodes 140 are provided within an annular region that is included in the outer edge of the substrate 110C in a plan view. In a plan view, the center of the annular region coincides with the position of the rotation shaft 13. The positional accuracy of the center of the annular region affects the measurement accuracy. A mark may be provided in the center of the annular region to make it easier to align the center of the annular region with the position of the rotation shaft 13 when attaching the reading device 100 to the cover 15.

[0031] The multiple sensor electrodes 140 have a shape obtained by dividing the above-mentioned annular region evenly in the circumferential direction. Each sensor electrode 140 extends in a direction away from the rotation shaft 13 in a plan view and is arranged radially around the rotation shaft 13 in a plan view. As an example, each sensor electrode 140 has an annular sector shape in which the arc farther from the rotation shaft 13 is longer than the arc closer to the rotation shaft 13 in a plan view. The multiple sensor electrodes 140 have the same shape and size in a plan view. Furthermore, the spacing between adjacent sensor electrodes 140 is constant in the radial direction, and all sensor electrodes 140 are equally spaced in the circumferential direction. FIG. 4C shows an example of a configuration in which 30 sensor electrodes 140 are arranged radially.

[0032] 4C , the outer and inner radial ends of each sensor electrode 140 are arc-shaped, but may be linear. In this case, each sensor electrode 140 has an isosceles trapezoidal shape whose width in plan view is wider on the side farther from the rotation shaft 13 than on the side closer to the rotation shaft 13. The width of the sensor electrode 140 is the width in the direction perpendicular to the radial direction of the rotation shaft 13 in plan view.

[0033] The sensor electrodes 140 are transparent electrodes, and are made of, for example, ITO. The sensor electrodes 140 are self-capacitance type sensor electrodes. All of the sensor electrodes 140 are formed inside the circular outer edge of the AS electrode 130 in a planar view. The sensor electrodes 140 are connected to an oscillator circuit in the measurement circuit 160 via wiring 111C formed around the circular area on the top surface of the substrate 110C where all of the sensor electrodes 140 are formed, and via an FPC 150. The sensor electrodes 140 are driven by an AC signal having the same frequency and phase as the AC component contained in the signal supplied to the AS electrode 130. The amplitude of the AC signal supplied to the sensor electrodes 140 is smaller than the amplitude of the AC component of the signal supplied to the AS electrode 130. Note that the wiring 111C is, for example, a silver paste wiring with carbon paste printed around it to prevent migration.

[0034] <Substrate 110D, Self-Adhesive Sheet 120D (Mainly Figures 3 and 4D)> The substrate 110D is, for example, a transparent film made of PET. The thickness of the substrate 110D is, for example, 0.05 mm, and the relative dielectric constant is, for example, 3.0. A self-adhesive sheet 120D is attached to the underside of the substrate 110D. The substrate 110D and the self-adhesive sheet 120D are circular in plan view. The self-adhesive sheet 120D is a transparent, self-adhesive sheet that attaches the substrate 110D to the upper surface of the cover 15 of the analog meter 10. The thickness of the self-adhesive sheet 120D is, for example, 0.027 mm, and the relative dielectric constant is, for example, 3.0.

[0035] <FPC 150> The FPC 150 is a flexible substrate, and as an example, is a multilayer substrate having two conductive layers: a wiring layer connected to the wiring 111B of the substrate 110B, and a wiring layer connected to the wiring 111C of the substrate 110C. One end of one of the wiring layers of the FPC 150 is connected to the AS electrode 130 via the wiring 111B, and one end of one of the wiring layers of the FPC 150 is connected to the sensor electrode 140 via the wiring 111B. The other ends of the two wiring layers of the FPC 150 are connected to the measurement circuit 160.

[0036] <Measurement Circuit 160> The measurement circuit 160 is a measurement circuit that measures the capacitance of the multiple sensor electrodes 140. The measurement circuit 160 has an oscillator circuit that applies a (pulsating) voltage containing an AC component to the AS electrode 130 and the sensor electrode 140, a charge amplifier that converts the charge accumulated in the sensor electrode 140 into a voltage, and an ADC (Analog to Digital Converter) that converts the output voltage of the charge amplifier into a digital value. The output voltage of the charge amplifier represents the capacitance of the sensor electrode 140. The measurement circuit 160 measures the capacitance of each sensor electrode 140, digitally converts the voltage representing the capacitance, and outputs it to the control unit 170.

[0037] <Control Unit 170> The control unit 170 is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. The control unit 170 calculates the position pointed to by the pointer 14 based on the capacitance measured by the measurement circuit 160. The method for calculating the position of the pointer will be described later using Figures 5A to 5C.

[0038] The control unit 170 may be realized as an integrated circuit (IC) integrated with the measurement circuit 160, or as a separate IC from the measurement circuit 160. When the control unit 170 and the measurement circuit 160 are configured as separate ICs, the control unit 170 may be built into an IC that also performs other calculations. For example, a computer that monitors multiple various sensors (such as the analog meter 10 as a gas meter or meters that detect other physical quantities) may function as the control unit 170. The position of the pointer 14 of the analog meter 10 may be determined from the output of the measurement circuit 160.

[0039] <Wireless Communication Unit 180> The wireless communication unit 180 is connected to the control unit 170. The wireless communication unit 180 wirelessly transmits pressure data indicating the gas pressure to a management device that manages the gas pressure detected by the analog meter 10 serving as a gas meter. The reading device 100 detects the gas pressure at predetermined time intervals. The management device can remotely read the angle of the pointer 14 of the analog meter 10.

[0040] <Method of calculating the position of the needle> Figures 5A to 5C are diagrams illustrating an example of a method of calculating the position of the needle. In Figure 5A, the horizontal axis represents the index (1 to 60) of the sensor electrode 140, and the vertical axis represents the capacitance (unitless) of each sensor electrode 140. The capacitance shown in Figure 5A is raw data. Here, a case where there are 60 sensor electrodes 140 will be described as an example.

[0041] As an example, the measurement circuit 160 can simultaneously measure the capacitance of 16 sensor electrodes 140. The effects of noise and the like can be offset by calculating the difference between the simultaneously measured capacitances. As an example, the measurement circuit 160 simultaneously measures the capacitance of the sensor electrodes 140 with indexes 1 to 16, then simultaneously measures the capacitance of the sensor electrodes 140 with indexes 16 to 31. Next, simultaneously measures the capacitance of the sensor electrodes 140 with indexes 31 to 46, and then simultaneously measures the capacitance of the sensor electrodes 140 with indexes 46 to 1. Each time a measurement is performed, the sensor electrode 140 with the last index from the previous measurement is repeatedly measured, and the difference between the capacitances of adjacent sensor electrodes 140 with indexes 1 to 60 can be obtained from the simultaneously measured capacitances.

[0042] The 60 sensor electrodes 140, with indexes 1 to 60, are arranged radially in the counterclockwise direction in this order around the rotation shaft 13. The sensor electrode 140 with index 1 is adjacent to the sensor electrode 140 with index 60. The 60 sensor electrodes 140 are arranged at equal intervals within a 360-degree angular range around the rotation shaft 13. The relationship between the sensor electrodes 140 and the scale written on the dial is calibrated by software. Therefore, the rotational position of each sensor electrode can be determined so that it is easy to attach them.

[0043] When each sensor electrode 140 faces the pointer 14, the capacitance increases. This is because the electrode area of ​​the capacitor formed by the sensor electrode 140 and the pointer 14 increases. Therefore, of the 60 sensor electrodes 140, the sensor electrode 140 that overlaps the largest area in a plan view with the portion of the pointer 14 that is closer to the tip than the rotation axis 13 has the largest capacitance. The sensor electrode 140 that overlaps the largest area in a plan view with the portion of the pointer 14 that is closer to the tip than the rotation axis 13 is the sensor electrode 140 closest to the tip of the pointer 14, or the sensor electrode 140 located near the sensor electrode 140 closest to the tip of the pointer 14.

[0044] As an example, let us assume that the tip side of the pointer 14 is located at around index 15 of the sensor electrode 140. Therefore, the capacitance of the sensor electrode 140 at index 15 is at its maximum. At around index 46, the weight portion on the opposite side of the rotary shaft 13 from the tip of the pointer 14 is located, so the capacitance increases, but is still lower than the capacitance at the tip side.

[0045] Here, since raw data is easily affected by noise and the like, the control unit 170 obtains the difference value between the capacitances of two adjacent sensor electrodes 140 and calculates the position of the pointer 14 based on the difference value.

[0046] 5B shows an example of the distribution of difference values. As an example, the difference value is a value obtained by subtracting the capacitance of the sensor electrode 140 adjacent in the clockwise direction from the capacitance of each sensor electrode 140. For this reason, the horizontal axis of FIG. 5B shows E1-E60, E2-E1, ..., E57-E56, and E60-E59. E1 to E60 are sensor electrodes 140 with indexes 1 to 60.

[0047] The difference value of E1-E60 is the difference value obtained by subtracting the capacitance of the sensor electrode 140 with an index of 60 from the capacitance of the sensor electrode 140 with an index of 1. The difference value of E2-E1 is the difference value obtained by subtracting the capacitance of the sensor electrode 140 with an index of 1 from the capacitance of the sensor electrode 140 with an index of 2. The difference value of E3-E2 is the difference value obtained by subtracting the capacitance of the sensor electrode 140 with an index of 2 from the capacitance of the sensor electrode 140 with an index of 3. Similarly, the difference value of E60-E59 is the difference value obtained by subtracting the capacitance of the sensor electrode 140 with an index of 59 from the capacitance of the sensor electrode 140 with an index of 60.

[0048] Furthermore, adjacent difference values ​​are assumed to be A and B. When determining the position of the pointer 14, the control unit 170 searches for two difference values ​​A and B that satisfy the conditions that A > 0, B < 0, and A - B is the maximum. Searching for two difference values ​​A and B that satisfy this condition is equivalent to searching for three sensor electrodes 140: one sensor electrode 140 with the maximum capacitance and the two sensor electrodes 140 on either side of it. The one sensor electrode 140 with the maximum capacitance is the sensor electrode 140 that is closest to the position of the pointer 14.

[0049] A>0 and B<0 indicates that the sign of the difference value changes, and corresponds to the maximum capacitance value of the three adjacent sensor electrodes 140 being obtained at the central sensor electrode 140.

[0050] Furthermore, the maximum capacitance may be obtained not only from the sensor electrode 140 that overlaps the portion of the pointer 14 closer to the tip than the rotation axis 13, but also from the sensor electrode 140 that overlaps the weight portion of the pointer 14, or from a sensor electrode 140 whose capacitance has suddenly increased due to noise. The difference in capacitance between these sensor electrodes 140 and the adjacent sensor electrode 140 may be somewhat large.

[0051] Therefore, the conditions A>0 and B<0 can also be satisfied for the differential value based on the capacitance of the sensor electrode 140 that overlaps with the weight portion of the pointer 14, or for the differential value based on the capacitance of the sensor electrode 140 whose capacitance has suddenly increased due to noise.

[0052] To find adjacent difference values ​​A and B based on the capacitance of the sensor electrode 140 closest to the pointer 14, the control unit 170 searches for two difference values ​​A and B that satisfy the condition that A>0 and B<0, as well as the condition that A-B is maximum. This is because the three sensor electrodes 140 that provide the two difference values ​​A and B that maximize A-B are considered to include sensor electrodes 140 that overlap with the portion of the pointer 14 closer to the tip than the rotation axis 13.

[0053] Then, the control unit 170 calculates the angle θ representing the position of the pointer 14 using the two difference values ​​A and B that satisfy the conditions of A>0, B<0, and A-B being the maximum, according to the following equation (1): Equation (1) is an equation for determining the angle θ that gives the apex of the quadratic curve using the difference values ​​A and B. Because equation (1) uses the two difference values ​​A and B, it is essentially an equation for determining the angle θ representing the position of the pointer 14 by interpolating the three capacitances of three consecutive sensor electrodes 140.

[0054] In formula (1), i is 1 for E2-E1, 2 to 59 for E3-E2 to E60-E59, and 0 for E1-E60. φ is the central angle of the annular sector of the sensor electrode 140. As an example, when 60 sensor electrodes 140 are arranged, φ=6 degrees.

[0055]

[0056] The angle θ is a counterclockwise angle from the center of the multiple sensor electrodes 140 arranged radially, as shown in Figure 2B, with the boundary (straight line L) between the sensor electrode 140 with index 1 and the sensor electrode 140 with the maximum index as the reference (θ = 0 degrees).

[0057] In addition, when determining the angle θ, the control unit 170 may calculate the angle θ multiple times and calculate the average value as the position (angle) of the pointer 14 in order to reduce the influence of noise, etc.

[0058] In addition, the control unit 170 may calculate the position (angle) of the pointer 14 using, in addition to the adjacent difference values ​​A and B, the difference value B' that is next to the difference value B when viewed from the difference value A, and the difference value A' that is next to the difference value A when viewed from the difference value B.

[0059] The four consecutive difference values ​​are designated as A', A, B, and B'. The relationship between the difference values ​​A', A, B, and B' is as shown in FIG. 5B as an example. The difference value A is an example of a positive first difference value, and the difference value A' is an example of a positive second difference value. The difference value B is an example of a negative first difference value, and the difference value B' is an example of a negative second difference value. The difference values ​​A', A, B, and B' are consecutive in the order of the positive second difference value (A'), the positive first difference value (A), the negative first difference value (B), and the negative second difference value (B').

[0060] In this case, when determining the position of the hand 14, the control unit 170 searches for two difference values ​​A and B that satisfy the conditions that A > 0, B < 0, and (A + A') - (B + B') is the maximum. Then, the angle θ that represents the position of the hand 14 can be calculated based on equation (1). (A + A') is an example of the first sum, and (B + B') is an example of the second sum.

[0061] 5C shows an example of four consecutive difference values ​​A', A, B, and B', including difference values ​​A and B at which A-B is maximum. In FIG. 5C, the horizontal axis corresponds to the position in the arrangement direction of the radially arranged sensor electrodes 140. The positions of the five vertical ruled lines in the horizontal axis direction correspond to the positions of the five consecutive sensor electrodes 140.

[0062] When searching for difference values ​​A and B that maximize (A+A')-(B+B') based on four consecutive difference values ​​A', A, B, and B', it is possible to search for two difference values ​​A and B more stably than when searching for difference values ​​A and B that maximize A-B. In particular, it is possible to search for two difference values ​​A and B more stably in a situation where the capacitance of the sensor electrode 140 is likely to be affected by noise or the like.

[0063] 5C shows an example of angle θ obtained by substituting two difference values ​​A and B, which satisfy the conditions A>0, B<0, and (A+A')-(B+B'), into equation (1). The angle θ is located between two vertical ruled lines, and it can be seen that by interpolating the capacitance using equation (1), the position of the pointer 14 can be calculated with a higher resolution than that obtained by the sensor electrode 140.

[0064] <Correction of Angle θ> Fig. 6A is a diagram showing an example of the relationship between angle θ and actual angle. Angle θ is an angle representing the position of pointer 14 calculated by control unit 170 according to equation (1). The actual angle is an angle representing the actual position of pointer 14 when control unit 170 calculates angle θ. The angle of the actual pointer 14 can be obtained by directly observing and measuring analog meter 10.

[0065] For example, if the relationship between the actual angle of the pointer 14 and the angle θ calculated by the control unit 170 is measured in advance and the characteristics as shown in Fig. 6A are converted into data, the angle θ calculated by the control unit 170 can be corrected to the actual angle, thereby making it possible to determine a more accurate position (angle) of the pointer 14. In other words, the actual angle is used as the corrected angle (corrected angle) that represents the position of the pointer 14.

[0066] As an example, data of the mathematical expression (relational expression) representing the characteristic shown in FIG. 6A is stored in the internal memory of the control unit 170, and the control unit 170 calculates the angle θ based on equation (1), and then substitutes the angle θ into the mathematical expression representing the characteristic shown in FIG. 6A, thereby correcting the calculated angle θ to an actual angle.

[0067] Alternatively, instead of the relational expression, table data shown in Fig. 6B may be used. Fig. 6B is a diagram showing an example of table data showing the relationship between the angle θ and the actual angle (corrected angle). By using such table data to correct the angle θ calculated by the control unit 170 to the actual angle, a more accurate position (angle) of the pointer 14 can be determined.

[0068] <Outer diameter of sensor electrode 140 and upper and lower limits of the central angle between adjacent sensor electrodes 140> Figure 6C is a diagram showing an example of the relationship between the outer diameter of sensor electrode 140 and the upper and lower limits of the central angle between adjacent sensor electrodes 140. In Figure 6C, the horizontal axis represents the outer diameter (mm) of sensor electrode 140, and the vertical axis represents the central angle (degrees) of sensor electrode 140. The horizontal axis is represented by a lowercase x, and the vertical axis is represented by a lowercase y.

[0069] The outer diameter of the sensor electrode 140 is the diameter of an imaginary circle connecting the radially outer ends of all of the sensor electrodes 140 when multiple sensor electrodes 140 (30 sensor electrodes 140 in FIG. 4C ) are radially arranged as shown in FIG. 4C . The imaginary circle has a virtual center point. This virtual center point coincides with the position of the rotation axis 13 in a plan view. The central angle between the sensor electrodes 140 is the central angle of a circular sector. Even if the shape of the sensor electrode 140 is an isosceles trapezoid, the central angle can be considered to be the same as that of a circular sector.

[0070] The larger the outer diameter of the sensor electrodes 140, the easier it is to increase the number of sensor electrodes 140 and reduce the central angle between the sensor electrodes 140. Furthermore, the smaller the outer diameter of the sensor electrodes 140, the more difficult it is to increase the number of sensor electrodes 140, and the larger the central angle of the sensor electrodes 140 tends to be.

[0071] When the outer diameter of the sensor electrode 140 is set to various values, the central angles of the sensor electrode 140 of six outer diameters, 25 mm, 50 mm, 75 mm, 100 mm, 125 mm, and 150 mm, which provide upper and lower limits for the central angle of the sensor electrode 140 at which the error between the angle θ calculated based on equation (1) and the actual angle of the pointer 14 is less than 0.5 degrees, were investigated, and the graph shown in Figure 6C was obtained.

[0072] In Figure 6C, the six round markers represent the relationship between the upper limit of the central angle of the sensor electrode 140 at which the error between the angle θ calculated based on equation (1) and the actual angle of the pointer 14 is less than 0.5 degrees and the outer diameter of the sensor electrode 140 (25 mm, 50 mm, 75 mm, 100 mm, 125 mm, 150 mm).

[0073] In Figure 6C, the six square markers represent the relationship between the lower limit value of the central angle of the sensor electrode 140 at which the error between the angle θ calculated based on equation (1) and the actual angle of the pointer 14 is less than 0.5 degrees and the outer diameter of the sensor electrode 140 (25 mm, 50 mm, 75 mm, 100 mm, 125 mm, 150 mm).

[0074] Here, if the outer diameter of the sensor electrode 140 is x and the central angle of the sensor electrode 140 is y, the upper limit of the central angle is y=(0.0005x ２ -0.15x + 18), and the lower limit of the central angle is y = (0.0006x ２ -0.17x + 15).

[0075] If the outer diameter of the sensor electrode 140 is φ, the central angle of the sensor electrode 140 is (0.0005φ ２ -0.15φ+18) degrees, (0.0006φ) ２ It has been found that it is preferable that the angle be larger than −0.17φ+15 degrees.

[0076] <First Modification> Fig. 7A is a diagram showing an example of the configuration of the substrate 110C and sensor electrodes 140 of the reading device 100 according to a first modification of the embodiment. The substrate 110C and sensor electrodes 140 shown in Fig. 7A have a configuration corresponding to an analog meter 10 having a diameter of 100 mm. As an example, 60 sensor electrodes 140 are arranged radially. Fig. 7A shows an enlarged view of a portion of the center surrounded by a dashed square.

[0077] The enlarged view shows the rotary shaft 13 and the pointer 14 in addition to the sensor electrode 140. In the enlarged view, the portion of the pointer 14 extending downward and to the left from the attachment portion 14A of the pointer 14 to the rotary shaft 13 is the portion extending toward the tip of the pointer 14, and the portion extending upward and to the upper right is the weight portion.

[0078] As shown in the enlarged view, the width of the base portion of the pointer 14 extending from the mounting portion 14A toward the tip (the width perpendicular to the radial direction of the rotating shaft 13 in a plan view) is wider than the width of the inner end portion of one sensor electrode 140 in the radial direction.

[0079] More specifically, the total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotating shaft 13 is narrower than the width of the portion overlapping with the four ends of the pointer 14 (the base portion extending from the mounting portion 14A toward the tip) (Condition 1).

[0080] Furthermore, since the spacing between adjacent sensor electrodes 140 is constant in the radial direction and is equally spaced in the circumferential direction for all sensor electrodes 140, the above condition 1 can be rephrased as the following condition 2.

[0081] The total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotating shaft 13 and the width of the three gaps between the four sensor electrodes 140 is narrower than the width of the part overlapping with the four ends of the pointer 14 (the base part extending from the mounting part 14A toward the tip) (condition 2).

[0082] By setting the width of the pointer 14 and the sensor electrodes 140 so as to satisfy conditions 1 and 2, the base of the pointer 14 always overlaps with three or more sensor electrodes 140, and as explained using Figures 5A to 5C, two difference values ​​A and B can be obtained and the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the spacing between the sensor electrodes 140.

[0083] The widths of the pointer 14 and the sensor electrode 140 may be set to satisfy the following conditions 3 and 4.

[0084] <Condition 3> Figure 7B is a diagram illustrating an example of condition 3. Figure 7B is a cross section of analog meter 10 viewed from the radial outside toward the center, showing a cross section of the radially inner end of continuously arranged sensor electrodes 140 and a cross section of pointer 14 at the same radial position as the end. The width of pointer 14 is a, and the distance in the Z direction from sensor electrode 140 to pointer 14 is b.

[0085] Since the range where the density of the electric field lines is relatively high is 45 degrees, it is preferable that the four consecutively arranged sensor electrodes 140 be within a distance b from both ends of the needle 14 in the width direction. For this reason, it is preferable that the following condition be met:

[0086] The length L from the end E1 on one side (clockwise side) of the inner end in the radial direction of the rotating shaft 13 of the sensor electrode 140 that is located outermost on one side (clockwise side) of the circumference of the four sensor electrodes 140 arranged in succession to the end E2 on the other side (counterclockwise side) of the inner end in the radial direction of the rotating shaft 13 of the sensor electrode 140 that is located outermost on the other side (counterclockwise side) of the circumference of the four sensor electrodes 140 may be shorter than the sum of the width a of the part that overlaps with the four ends of the pointer 14 (the base part extending from the mounting part 14A toward the tip) and twice the Z-directional spacing b between the pointer 14 and the sensor electrode 140.

[0087] Here, the sensor electrode 140 located on the outermost side in the circumferential direction (clockwise side) is the sensor electrode 140 located at the end of the four sensor electrodes 140 in the clockwise direction.

[0088] The end E1 on one side (clockwise side) of the inner end in the radial direction of the rotation axis 13 of the sensor electrode 140 located outermost on one side (clockwise side) of the circumferential direction is the end located on the clockwise side in the width direction (direction perpendicular to the radial direction) of the inner radial end of the sensor electrode 140 located at the end in the clockwise direction.

[0089] The sensor electrode 140 located outermost on the other circumferential side (counterclockwise side) is the sensor electrode 140 located at the end of the four sensor electrodes 140 in the counterclockwise direction.

[0090] The end E2 on the other side (counterclockwise side) of the inner end in the radial direction of the rotation axis 13 of the sensor electrode 140 located outermost on the other side (counterclockwise side) of the circumferential direction is the end located on the counterclockwise side in the width direction (direction perpendicular to the radial direction) of the inner radial end of the sensor electrode 140 located at the end in the counterclockwise direction.

[0091] That is, the length L from the end E1 on one side (clockwise side) to the end E2 on the other side (counterclockwise side) in condition 3 is the length from end to end in the width direction of the four radially inner ends of the four sensor electrodes 140 arranged in succession.

[0092] When such length L satisfies condition 3, the base of the pointer 14 always overlaps with three or more sensor electrodes 140, and as explained using Figures 5A to 5C, two difference values ​​A and B can be obtained and the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the spacing between the sensor electrodes 140.

[0093] <Condition 4> The total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotation axis 13 and the width of the three gaps between the four sensor electrodes 140 may be narrower than the sum of the width of the part overlapping with the four ends of the pointer 14 and twice the distance between the pointer 14 and the sensor electrodes 140.

[0094] When the total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotation axis 13 satisfies condition 4, the base of the pointer 14 always overlaps with three or more sensor electrodes 140, and as explained using Figures 5A to 5C, two difference values ​​A and B can be obtained and the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the spacing between the sensor electrodes 140.

[0095] 7C is a diagram showing an example of the configuration of the substrate 110C and the sensor electrode 140 of the reading device 100 according to a second modification of the embodiment. The substrate 110C and the sensor electrode 140 shown in FIG. 7C have a configuration corresponding to the analog meter 10 having a diameter of 40 mm.

[0096] In the second modified example, no sensor electrode 140 is provided in the portion corresponding to approximately 4 o'clock to approximately 8 o'clock on the clock, and 20 sensor electrodes 140 are provided in the portion from approximately 8 o'clock through 12 o'clock to approximately 4 o'clock. As shown in Figure 2A, the portion without sensor electrodes 140 is the portion where there are no markings on analog meter 10, and the portion with 20 sensor electrodes 140 is the portion where there are markings on analog meter 10.

[0097] In sensor electrode 140 of the second modification, a position corresponding to approximately 8 o'clock on a clock is a position corresponding to the zero mark on analog meter 10 shown in Fig. 2A and is an example of a first position in the rotational direction. In sensor electrode 140 of the second modification, a position corresponding to approximately 4 o'clock on a clock is a position corresponding to the one mark on analog meter 10 shown in Fig. 2A and is an example of a second position in the rotational direction. If the clockwise rotation angle of the second position from the first position is less than 360 degrees, sensor electrode 140 does not need to be located in the section from the first position to the second position counterclockwise.

[0098] 7C , the pointer 14 is rotatable between a first position and a second position, which is a rotation angle of less than 360 degrees from the first position, in a circular region having a radius equal to the length from the rotation axis 13 to the tip of the pointer 14, with the rotation axis 13 as the center. The circular region has a first region through which the pointer 14 can pass between the first and second positions, and a second region other than the first region, and the multiple sensor electrodes 140 are arranged in the first region but not in the second region.

[0099] In the second modification, since it is not necessary to provide the sensor electrode 140 over 360 degrees, it is possible to limit the area where the sensor electrode 140 is provided to only the necessary area. In particular, when the sensor electrode 140 is made of a transparent electrode, the amount of expensive material used is reduced, which leads to cost reduction.

[0100] 7D is a diagram showing an example of the configuration of the reading device 100 according to a third modification of the embodiment. The cover film 110A, the substrates 110B, 110C, and 110D, the OCAs 120A, 120B, and 120C, the self-adhesive sheet 120D, the AS electrode 130, and the sensor electrode 140 of the reading device 100 according to the third modification are provided at the center of the top surface of the cover 15 of the analog meter 10, within a dashed circle shown in the center of the cover 15.

[0101] The diameter of the dashed circle including the cover film 110A, the substrates 110B, 110C, and 110D, the OCAs 120A, 120B, and 120C, the self-adhesive sheet 120D, the AS electrode 130, and the sensor electrode 140 is approximately one-third that of the cover 15, and the tip side of the pointer 14 and the scale on the dial 12 are located outside the dashed circle. The substrates 110B, 110C, and 110D are located closer to the rotary shaft 13 than the tip of the pointer 14 in the radial direction of the rotary shaft 13. In other words, the tip of the pointer 14 appears not to be covered by the substrates 110B, 110C, and 110D.

[0102] The FPC 150 extends to the outer periphery of the housing 11 in a section of the top surface of the cover 15 where there are no scales (the 6 o'clock position on a clock). An IC chip 190 is provided on the top surface of the FPC 150. The IC chip 190 incorporates a measuring circuit 160, a control unit 170, and a wireless communication unit 180.

[0103] The cover film 110A, substrates 110B, 110C, 110D, OCAs 120A, 120B, 120C, self-adhesive sheet 120D, AS electrode 130, and sensor electrode 140 within the dashed circle may be opaque because they do not overlap with the tip portion of the pointer 14 or the markings on the dial 12. If the cover film 110A, substrates 110B, 110C, 110D, OCAs 120A, 120B, 120C, self-adhesive sheet 120D, AS electrode 130, and sensor electrode 140 are opaque, costs can be reduced because less expensive materials are used, particularly compared to when the AS electrode 130 and sensor electrode 140 are made of transparent electrodes.

[0104] 7D shows a configuration in which the components from cover film 110A to sensor electrode 140 are arranged in the center of the upper surface of cover 15 (the portion closer to rotation axis 13 than the tip of pointer 14), so as not to overlap with the portion on the tip side of pointer 14 or the markings on dial 12. However, a configuration in which the components from cover film 110A to sensor electrode 140 are arranged along the outer periphery of the upper surface of cover 15, rather than being arranged in the center, so as not to overlap with the portion of pointer 14 that does not form the markings on dial 12 or the markings on dial 12.

[0105] <Effects> The measuring instrument with reading device 200 comprises a rotating shaft 13, a metal pointer 14 attached to the rotating shaft 13, an insulating cover 15 that covers the rotating shaft 13 and the pointer 14, a plurality of sensor electrodes 140 provided on the cover 15, a measurement circuit 160 that measures the capacitance of the plurality of sensor electrodes 140, and a control unit 170 that calculates the position pointed to by the pointer 14 based on the capacitance measured by the measurement circuit 160. The pointer 14 is attached to the rotating shaft 13, and the plurality of sensor electrodes 140 extend in a direction away from the rotating shaft 13 in a plan view. The sensor electrodes 140 are arranged radially around the rotation axis 13, and each of the sensor electrodes 140 has an isosceles trapezoid shape in which the width in plan view is wider on the side away from the rotation axis 13 than on the side closer to the rotation axis 13, or an annular sector shape in plan view in which the arc farther from the rotation axis 13 is longer than the arc nearer to the rotation axis 13, and the sensor electrodes 140 have the same shape and size as one another in plan view, and the control unit 170 calculates the position of the pointer 14 by interpolating the multiple capacitances measured for the multiple sensor electrodes 140 by the measurement circuit 160. Therefore, the position of the pointer can be detected with a higher resolution than the resolution corresponding to the spacing between adjacent sensor electrodes 140.

[0106] Therefore, it is possible to provide a measuring instrument with a reader 200 that can detect the position of the pointer with a resolution higher than the resolution corresponding to the distance between adjacent sensor electrodes 140 .

[0107] Alternatively, the control unit 170 may calculate a difference in capacitance between adjacent sensor electrodes 140, and determine two difference values ​​(A, B) where the difference value alternates between positive and negative and where the amount of change (A - B) between the two difference values ​​is equal to or greater than a predetermined threshold. Although capacitance changes due to noise, temperature changes, etc., using the difference value can cancel out changes that occur in all of the sensor electrodes 140 in the same way, allowing the position of the pointer 14 to be calculated with high precision.

[0108] Alternatively, the control unit 170 may calculate a difference in capacitance between adjacent sensor electrodes 140 and determine two difference values ​​(A, B) that alternate between positive and negative, and that maximize the amount of change (A - B) between the two difference values. Although capacitance changes due to noise, temperature changes, and the like, using the difference values ​​can cancel out similar changes in all sensor electrodes 140, allowing the position of the pointer 14 to be calculated with high accuracy. Furthermore, using the two difference values ​​(A, B) that maximize the amount of change (A - B) allows the position of the pointer 14 to be calculated based on the sensor electrode 140 closest to the pointer 14 and the sensor electrodes 140 on either side of it (or the two difference values ​​corresponding to them), even in the presence of significant noise.

[0109] Furthermore, the control unit 170 calculates the difference in capacitance between adjacent sensor electrodes 140, and when determining two difference values ​​(A, B) consisting of the positive first difference value (A) and the negative first difference value (B) that sandwich the boundary among the four difference values ​​(A', A, B, B') that successively follow the order of the positive second difference value (A'), the positive first difference value (A), the negative first difference value (B), and the negative second difference value (B'), the control unit 170 may determine two difference values ​​(A, B) such that the amount of change ((A+A')-(B+B')) between the first sum (A+A') of the positive first difference value (A) and the positive second difference value (A') and the second sum (B+B') of the negative first difference value (B) and the negative second difference value (B') is equal to or greater than a predetermined threshold. Although capacitance changes due to temperature changes and the like, by using the difference value, changes that occur in all of the sensor electrodes 140 are canceled out, making it possible to calculate with high precision the position of the pointer 14. In particular, by using the amount of change ((A+A')-(B+B')) that takes into account the positive second difference value (A') and the negative second difference value (B'), it is possible to cancel out changes in capacitance due to noise, temperature changes, and the like with higher precision, making it possible to calculate the position of the pointer 14 with higher precision.

[0110] Furthermore, the control unit 170 calculates the difference in capacitance between adjacent sensor electrodes 140, and when determining two difference values ​​(A, B) consisting of the positive first difference value (A) and the negative first difference value (B) that sandwich the boundary among the four difference values ​​(A', A, B, B') that successively follow the order of the positive second difference value (A'), the positive first difference value (A), the negative first difference value (B), and the negative second difference value (B'), the control unit 170 may determine the two difference values ​​(A, B) that maximize the amount of change ((A+A')-(B+B')) between the first sum (A+A') of the positive first difference value (A) and the positive second difference value (A') and the second sum (B+B') of the negative first difference value (B) and the negative second difference value (B'). Although capacitance changes due to temperature changes and the like, using the differential value cancels out similar changes in all sensor electrodes 140, allowing the position of the pointer 14 to be calculated with high accuracy. In particular, by using the amount of change ((A+A')-(B+B')) that takes into account the positive second differential value (A') and the negative second differential value (B'), changes in capacitance due to noise, temperature changes, and the like can be canceled out with higher accuracy, allowing the position of the pointer 14 to be calculated with higher accuracy. Furthermore, by using the two differential values ​​(A, B) that maximize the amount of change ((A+A')-(B+B')), even in the presence of large noise, the position of the pointer 14 can be calculated based on the sensor electrode 140 closest to the pointer 14, the sensor electrodes 140 on either side of that, and the sensor electrodes 140 on either side of those.

[0111] The control unit 170 may also perform an approximation by fitting a quadratic curve to the two calculated difference values ​​(A, B), and calculate the position of the apex of the quadratic curve as the position pointed to by the pointer 14. Using three capacitances makes it possible to approximate a quadratic curve, and the position of the pointer 14 can be calculated with high accuracy.

[0112] The control unit 170 may also store table data or a relational expression that indicates the difference between the calculated position (angle θ) of the pointer 14 and the actual position of the pointer 14, and may use the table data or the relational expression to correct the calculated position of the pointer 14. By correcting the angle θ to the actual angle, a more accurate position (angle) of the pointer 14 can be obtained.

[0113] Furthermore, the pointer 14 may have a tapered shape in plan view where the needle width narrows from the attachment portion attached to the rotating shaft 13 toward the tip. When each sensor electrode 140 has an isosceles trapezoidal or annular sector shape in plan view and the pointer 14 has a tapered shape in plan view, the multiple sensor electrodes 140 and the pointer 14 overlap on the attachment portion side of the pointer 14, making it easier to obtain multiple capacitances that change due to the presence of the pointer 14.

[0114] Furthermore, the total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotary shaft 13 may be narrower than the width of the portion that overlaps with the four ends of the pointer 14. Since the base of the pointer 14 always overlaps with three or more sensor electrodes 140, the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the spacing between the sensor electrodes 140.

[0115] Furthermore, the total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotary shaft 13 and the width of the three gaps between the four sensor electrodes 140 may be narrower than the width of the portion overlapping with the four ends of the pointer 14. Since the base of the pointer 14 always overlaps with three or more sensor electrodes 140, the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the spacing between the sensor electrodes 140.

[0116] Furthermore, the length from one end of the inner end of the outermost sensor electrode 140 on one side of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotary shaft 13 to the other end of the inner end of the outermost sensor electrode 140 on the other side of the four sensor electrodes 140 in the radial direction of the rotary shaft 13 may be shorter than the sum of the width of the portion overlapping with the four ends of the pointer 14 and twice the distance between the pointer 14 and the sensor electrodes 140. Since the base of the pointer 14 always overlaps with three or more sensor electrodes 140, the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the distance between the sensor electrodes 140.

[0117] Furthermore, the total width of the four inner ends of the four consecutively arranged sensor electrodes 140 in the radial direction of the rotary shaft 13 and the width of the three gaps between the four sensor electrodes 140 may be narrower than the sum of the width of the portion overlapping with the four ends of the pointer 14 and twice the distance between the pointer 14 and the sensor electrodes 140. Since the base of the pointer 14 always overlaps with three or more sensor electrodes 140, the position of the pointer 14 can be determined with a higher resolution than the resolution corresponding to the distance between the sensor electrodes 140.

[0118] The semiconductor device may further include a substrate 110B (insulating layer) that covers the plurality of sensor electrodes 140, and an AS electrode 130 that is provided on the side of the substrate 110B opposite to the side on which the plurality of sensor electrodes 140 are arranged, in a position that overlaps with the plurality of sensor electrodes 140. The AS electrode 130 can shield the plurality of sensor electrodes 140 from noise, suppress the effects of parasitic capacitance, and suppress malfunctions due to noise, etc.

[0119] Furthermore, signals of the same phase, frequency, and waveform may be applied to the multiple sensor electrodes 140 and the AS electrode 130. Waveforms expressed by functions of the same format are considered to be the same waveform even if the parameters are different. For example, sine waves are considered to be the same waveform even if they have different amplitudes, etc. The AS electrode 130 can shield the multiple sensor electrodes 140 from noise, suppress the effects of parasitic capacitance, and prevent malfunctions due to noise, etc. The amplitude of the signal applied to the sensor electrode 140 and the amplitude of the signal applied to the AS electrode 130 may be different. For example, sine wave signals that differ only in amplitude may be applied to the sensor electrode 140 and the AS electrode 130.

[0120] The watch also includes a dial 12 (metal plate) that faces the cover 15 across the hands 14, and a metal housing 11 that covers the sides of the cover 15, the sides of the dial 12, and the sides of the space between the cover 15 and the dial 12, and the dial 12 and the housing 11 may be held at ground potential (reference potential). Holding the dial 12 and the housing 11 at ground potential provides a shielding effect, which, combined with the active shielding provided by the AS electrode 130, can more effectively suppress malfunctions due to noise and the like.

[0121] The sensor device further includes a substrate 110C (insulating substrate) on which the sensor electrode 140 is provided, and a self-adhesive sheet 120D (adhesive layer) that attaches the substrate 110C to the cover 15, and the cover 15, the self-adhesive sheet 120D, the substrate 110C, the sensor electrode 140, the substrate 110B, and the AS electrode 130 may be transparent. The position of the pointer 14 can be read visually, and the position of the pointer 14 can also be read based on the capacitance of the reading device 100.

[0122] The device further includes a substrate 110C on which the sensor electrode 140 is provided, and a self-adhesive sheet 120D (adhesive layer) that attaches the substrate 110C to the cover 15, the cover 15 and the self-adhesive sheet 120D being transparent, the substrate 110C, the sensor electrode 140, the substrate 110B, and the AS electrode 130 being opaque, the dial 12 having a scale on the surface facing the pointer 14, and the substrate 110C being positioned so as not to overlap the scale in a planar view. The position of the pointer 14 can be read visually in the portion of the substrate 110C that does not overlap the scale in a planar view, and because a transparent electrode is not required, inexpensive materials can be used, resulting in cost reduction.

[0123] Furthermore, the substrate 110C may be positioned closer to the rotary shaft 13 than the tip of the pointer 14 in the radial direction of the rotary shaft 13. Because the tip of the pointer 14 is not covered by the substrate 110C and is visible, the position of the pointer 14 can be read visually with high precision even when an opaque sensor electrode 140 is used.

[0124] Furthermore, the pointer 14 is rotatable between a first position and a second position, the second position being a rotation angle of less than 360 degrees from the first position, in a circular region having a radius equal to the length from the rotation axis 13 to the tip of the pointer 14, with the rotation axis 13 as the center. The circular region has a first region through which the pointer 14 can pass between the first and second positions, and a second region other than the first region. The multiple sensor electrodes 140 are arranged within the first region, but may not be arranged within the second region. Since the sensor electrodes 140 do not need to be arranged over 360 degrees, the range in which the sensor electrodes 140 are arranged can be limited to only the necessary areas. In particular, when the sensor electrodes 140 are made of transparent electrodes, the amount of expensive material used is reduced, resulting in cost savings.

[0125] The reading device 100 comprises a substrate 110C (insulating substrate), a plurality of sensor electrodes 140 provided on the substrate 110C, a measurement circuit 160 that measures the capacitance of the plurality of sensor electrodes 140, and a control unit 170 that calculates the position of a pointer 14 that is placed on top of the plurality of sensor electrodes 140 based on the capacitance measured by the measurement circuit 160. The plurality of sensor electrodes 140 extend in a direction away from a virtual center point in a planar view and are arranged radially around the virtual center point. Each of the plurality of sensor electrodes 140 has the shape of an isosceles trapezoid whose width in a planar view is wider on the side farther from the virtual center point than on the side closer to the virtual center point, or the shape of an annular sector whose arc in a planar view is longer on the far side than on the arc closer to the rotation axis 13. The plurality of sensor electrodes 140 have the same shape and size as one another in a planar view. The control unit 170 calculates the position of the pointer 14 by interpolating the plurality of capacitances measured for the plurality of sensor electrodes 140 by the measurement circuit 160. Therefore, the position of the pointer can be detected with a resolution higher than the resolution corresponding to the interval between adjacent sensor electrodes 140 .

[0126] Therefore, it is possible to provide a reading device 100 that can detect the position of the pointer with a resolution higher than the resolution corresponding to the interval between adjacent sensor electrodes 140 .

[0127] Furthermore, if the outer diameter of the sensor electrode 140 is φ, the central angle of the sensor electrode 140 is (0.0005φ ２-0.15φ+18) degrees, (0.0006φ) ２ By setting the central angle in this manner, the position of the pointer 14 can be calculated with high accuracy.

[0128] The above describes an exemplary embodiment of the measuring instrument with a reading device and the reading device of the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0129] This international application claims priority based on Japanese Patent Application No. 2023-170072, filed on September 29, 2023, the entire contents of which are incorporated herein by reference.

[0130] REFERENCE SIGNS LIST 10 Analog meter 11 Housing 12 Dial 13 Rotating shaft 14 Pointer 15 Cover 100 Reading device 110A Cover film 110B, 110C, 110D Substrate 120A, 120B, 120C OCA 120D Self-adhesive sheet 130 AS electrode 140 Sensor electrode 150 FPC 160 Measuring circuit 170 Control unit 180 Wireless communication unit 200 Measuring instrument with reading device

Claims

1. A measuring instrument with a reading device comprising: a rotating shaft; a metallic pointer attached to the rotating shaft; an insulating cover covering the rotating shaft and the pointer; a plurality of sensor electrodes provided on the cover; a measurement circuit for measuring the capacitance of the plurality of sensor electrodes; and a control unit for calculating a position indicated by the pointer based on the capacitance measured by the measurement circuit, wherein the pointer is attached to the rotating shaft, the plurality of sensor electrodes extend in a direction away from the rotating shaft in a planar view and are arranged radially around the rotating shaft, and each of the plurality of sensor electrodes has the shape of an isosceles trapezoid whose width in a planar view is wider on the side away from the rotating shaft than on the side closer to the rotating shaft, or the shape of an annular sector whose arc in a planar view is longer on the side away from the rotating shaft than on the side closer to the rotating shaft, the plurality of sensor electrodes have equal shapes and sizes in a planar view, and the control unit calculates the position of the pointer by interpolating the plurality of capacitances measured for the plurality of sensor electrodes by the measurement circuit.

2. The measuring instrument with a reading device as described in claim 1, wherein the control unit calculates a difference in capacitance between adjacent sensor electrodes, and determines two difference values ​​where the difference value switches between positive and negative and where the amount of change in the two difference values ​​is equal to or greater than a predetermined threshold value.

3. The measuring instrument with a reading device as described in claim 1, wherein the control unit calculates a difference in capacitance between adjacent sensor electrodes, and determines two difference values ​​where the difference value switches between positive and negative and where the amount of change between the two difference values ​​is the largest.

4. The control unit calculates a difference value in capacitance between adjacent sensor electrodes, and when determining two difference values ​​consisting of the positive first difference value and the negative first difference value that sandwich the boundary among the four difference values ​​that successively lie on either side of the boundary where the difference values ​​switch between positive and negative, in the order of the positive second difference value, the positive first difference value, the negative first difference value, and the negative second difference value, determines two difference values ​​such that a change amount between a first sum of the positive first difference value and the positive second difference value and a second sum of the negative first difference value and the negative second difference value is equal to or greater than a predetermined threshold value.

5. The measuring instrument with a reading device as described in claim 1, wherein the control unit calculates a difference value in capacitance between adjacent sensor electrodes, and when determining two difference values ​​consisting of the positive first difference value and the negative first difference value that sandwich the boundary among the four difference values ​​that successively sandwich the boundary between positive and negative, in the order of the positive second difference value, the positive first difference value, the negative first difference value, and the negative second difference value, determines two difference values ​​that maximize the amount of change between a first sum of the positive first difference value and the positive second difference value and a second sum of the negative first difference value and the negative second difference value.

6. A measuring instrument with a reading device as described in any one of claims 2 to 5, wherein the control unit performs an approximation by fitting a quadratic curve to the two difference values ​​obtained, and calculates the position of the apex of the quadratic curve as the position indicated by the pointer.

7. A measuring instrument with a reading device as described in claim 6, wherein the control unit stores table data or a relational equation indicating the difference between the calculated position of the pointer and an actual position of the pointer, and corrects the calculated position of the pointer using the table data or the relational equation.

8. A measuring instrument with a reading device as claimed in any one of claims 1 to 7, wherein the pointer has a tapered shape in which the needle width narrows from the attachment part attached to the rotating shaft towards the tip.

9. A measuring instrument with a reading device as described in any one of claims 1 to 8, wherein the total width of the four inner ends of the four consecutively arranged sensor electrodes in the radial direction of the rotation axis is narrower than the width of the portion of the pointer that overlaps with the four ends.

10. A measuring instrument with a reading device as described in any one of claims 1 to 8, wherein the total width of the four inner ends of the four consecutively arranged sensor electrodes in the radial direction of the rotation axis and the total width of the three gaps between the four sensor electrodes is narrower than the width of the portion of the pointer that overlaps with the four ends.

11. A measuring instrument with a reading device as described in any one of claims 1 to 8, wherein the length from the one end of the inner end of the sensor electrode located outermost on one side of the four sensor electrodes arranged in succession to the other end of the inner end of the sensor electrode located outermost on the other side of the four sensor electrodes in the radial direction of the rotation shaft is shorter than the combined length of the width of the portion of the pointer overlapping with the four ends and twice the distance between the pointer and the sensor electrodes.

12. A measuring instrument with a reading device as described in any one of claims 1 to 8, wherein the total width of the four inner ends of four consecutively arranged sensor electrodes in the radial direction of the rotation axis and the width of three gaps between the four sensor electrodes is narrower than the total width of the portion of the pointer that overlaps with the four ends and twice the distance between the pointer and the sensor electrodes.

13. A measuring instrument with a reading device as described in any one of claims 9 to 12, further comprising: an insulating layer covering the plurality of sensor electrodes; and a shield electrode provided on the side of the insulating layer opposite to the side on which the plurality of sensor electrodes are arranged, in a position overlapping the plurality of sensor electrodes.

14. The measuring instrument with a reader according to claim 13, wherein signals of the same phase, frequency and waveform are applied to the plurality of sensor electrodes and the shield electrode.

15. A measuring instrument with a reader as described in claim 14, comprising: a metal plate facing said cover with said pointer in between; and a metal housing covering the sides of said cover, the sides of said metal plate, and the sides of the space between said cover and said metal plate, said metal plate and said housing being held at a reference potential.

16. A measuring instrument with a reader as described in claim 15, further comprising: an insulating substrate on which the sensor electrode is provided; and an adhesive layer for attaching the insulating substrate to the cover, wherein the cover, the adhesive layer, the insulating substrate, the sensor electrode, the insulating layer, and the shield electrode are transparent.

17. A measuring instrument with a reading device as described in claim 15, further comprising: an insulating substrate on which the sensor electrode is provided; and an adhesive layer that attaches the insulating substrate to the cover, wherein the cover and the adhesive layer are transparent; the insulating substrate, the sensor electrode, the insulating layer and the shield electrode are opaque; the metal plate has a scale on the surface facing the pointer; and the insulating substrate is positioned so as not to overlap the scale in a planar view.

18. The measuring instrument with a reader according to claim 17, wherein the insulating substrate is located closer to the rotating shaft than the tip of the pointer in the radial direction of the rotating shaft.

19. A measuring instrument with a reading device as described in any one of claims 1 to 18, wherein the pointer is rotatable in a rotation direction about the axis of rotation between a first position and a second position having a rotation angle of less than 360 degrees from the first position within a circular area having a radius equal to the length from the axis of rotation to the tip of the pointer, the circular area having a first area through which the pointer can pass between the first position and the second position, and a second area other than the first area, and the multiple sensor electrodes are arranged within the first area and not within the second area.

20. A reading device comprising: an insulating substrate; a plurality of sensor electrodes provided on the insulating substrate; a measurement circuit that measures the capacitance of the plurality of sensor electrodes; and a control unit that calculates a position indicated by a pointer placed on top of the plurality of sensor electrodes based on the capacitance measured by the measurement circuit, wherein the plurality of sensor electrodes extend in a direction away from a virtual center point in a planar view and are arranged radially about the virtual center point, each of the plurality of sensor electrodes has an isosceles trapezoid whose width in a planar view is wider on the side farther from the virtual center point than on the side closer to the virtual center point, or an annular sector shape whose arc in a planar view is longer on the far side than on the side closer to the rotation axis, the plurality of sensor electrodes have equal shapes and sizes to one another in a planar view, and the control unit calculates the position of the pointer by interpolating the plurality of capacitances measured for the plurality of sensor electrodes by the measurement circuit.

21. If the outer diameter of the sensor electrode is φ, the central angle of the sensor electrode is (0.0005φ ２ -0.15φ+18) degrees, (0.0006φ) ２ 21. The reader of claim 20, wherein the angle is greater than -0.17φ+15) degrees.

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