JPS61213601A - Electrostatic capacity type digital caliper - Google Patents

Abstract

PURPOSE:To take a measurement speedily with high precision by using an electrostatic capacity type encoder, providing electrodes on the reverse side of a main scale, and providing a sweeping means and a protection cover which remove foreign matter sticking on the reverse surface of the main scale or prevent it from sticking. CONSTITUTION:The main scale 2 which has one jaw formed at one end part and a slider 8 which is mounted in the main scale 2 and moved lengthwise are provided. This main scale 2 is provided with the 1st electrode, and the 2nd electrode is mounted on the slider 8 opposite the 1st electrode. An electrostatic capacity type encoder equipped with a circuit means sends out an output corresponding to the relative movement distance between the main scale 2 and slider 8 through the 1st and the 2nd electrodes. Then, a digital display device 34 displays the output value of the electrostatic capacity type encoder digitally. The slider 8 is provided with sweeping means 42 and 44 for sweeping foreign matter sticking on the reverse surface side of the main scale 2 and the main scale 2 is provided with the protection cover 18 which covers the reverse surface of the main scale 2 and prevent foreign matter from sticking thereupon.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a capacitance of 1t5! Digital calipers, especially those that maintain the ease of use of conventional calipers while providing digital display to enable extremely quick and highly accurate dimensional measurements, can be used for various dimensional measurements in all fields. It is.

[Background technology and its problems] A digital display type that has extremely high measurement accuracy compared to mechanical reading calipers with scales engraved on the main scale, and allows for quick reading without individual differences in reading when measuring length. Calipers are known.

Generally, such digital display type calipers have a pair of dials,
It is equipped with an encoder that operates in accordance with the relative movement of There is.

By the way, the encoders used to detect the relative movement amount of two objects have conventionally been photoelectric encoders,
Contact encoders, capacitive encoders, and the like are known.

However, the photoelectric encoder is inconvenient to handle because the light emitting device consumes a lot of power and the batteries used must be replaced frequently.Also, the clearance between the IJ4 long slit and the index slit is minute; Components for maintenance must be machined with high precision, which is difficult and increases manufacturing costs.

Furthermore, since parts such as a light emitter, two slits, a light receiver, and a lens are required, the device is large and requires a large ff1ffi.

Furthermore, since slits must be provided at intervals of several microns, manufacturing is difficult, and the clearance changes during use, which may lead to miscounts.

In addition, as the contact point type encoder is used, the contact portion is worn out, and there is a risk that contact failure may occur or noise may be mixed into the measurement signal, resulting in counting errors.

On the other hand, a capacitive encoder does not consume as much power as a photoelectric encoder, and does not consume contact parts like a contact encoder.

Furthermore, since the dimensional accuracy of the spacing between electrodes and the like can be relatively rough, manufacturing is easy and the manufacturing cost is low.

Further, since the number of parts is relatively small, there is an advantage that both size and weight are small.

For this reason, digital display calipers have the advantages of mechanical reading calipers that have been used for many years, but are capable of achieving higher accuracy and improved readability. It is preferable to use a capacitive encoder! However, when a digital display type caliper is actually manufactured using this capacitive FFI type encoder.

Furthermore, the following problems were found, and their solution was strongly desired.

That is, there is a foreign object between the first electrode provided on the main scale and the second electrode provided on the slider.

For example, if one person's sweat or the like adheres to the capacitor, the capacitance of the capacitor formed by the first electrode and the second electrode changes, which may interfere with measurement. That is, variations in the dielectric constant or short-circuit phenomena between electrodes or between cases occur, and miscounts and self-running phenomena are likely to occur.

This point is different from the case where capacitive encoders are used in other measuring instruments such as hide gauges and micrometers, and this is an inherent problem due to the structure of calipers, and when using Since the device is operated by grasping it with the hands, sweat from the hands may adhere to it, and considering the environment in which it is used,
Even when the scale is not in use, water droplets etc. scattered from other sources may adhere to the scale, or oil droplets etc. scattered from the 1 & panel etc. may adhere to the scale at the machine site. This often happens during use.

Second, in conventional calipers of this type, the first electrode provided on one length is provided on the same side as the digital display, that is, on the front surface of the length. It is not possible to add mechanical scales to the surface of the main scale, and it is not possible to provide the function of making reference measurements.

For this reason, even in the case of rough measurements that do not require precision, there are inconveniences such as having to temporarily suspend reading until the displayed value on the digital display becomes stable.

Thirdly, since the first electrode and the digital display are provided on the same surface side, it is necessary to store many parts on the surface side of the slider.
In addition, the size and shape of the built-in printed circuit board are restricted due to overall miniaturization and problems with the encoder configuration, so the display window of the display unit cannot be enlarged. The flexibility in adopting such things as the orientation and number of pieces is restricted, resulting in disadvantages and inconveniences in handling as a whole.

[Purpose of the Invention] The purpose of this JA Mei is to enable quick and highly accurate dimensional measurements while maintaining the ease of use of mechanical reading calipers that have been used for many years without significantly changing the way they are used. The objective is to obtain a capacitive digital caliper.

[Means and effects for solving the problems] The present invention has the following features:
In a digital caliper using a capacitive encoder, a first electrode is provided on the back side of the main scale, a digital display is provided on the front side, and a wiping means is provided to wipe away foreign matter adhering to the back side of the main scale. The slider is equipped with a protective cover on the back side of the main scale to prevent foreign matter from adhering to it, especially sweat, which is caused by unstoppable human sweating.This structure allows for miniaturization. In addition, it can withstand use even when used in the same way as a conventional caliper, and the disadvantages and inconveniences of the dinosaur capacitive digital caliper that have been proposed so far can be overcome by the structure and ergonomic characteristics of the caliper. This was resolved by considering and further integrating the issues.

This makes it possible to provide a caliper that can perform quick and highly accurate measurements while maintaining the ease of use of conventional mechanical reading calipers.

Specifically, the main scale includes a main scale having one jaw formed at one end, and a slider attached to the main scale and formed to be movable in the longitudinal direction of the main scale. 1 of 1 is provided with a pole, and the slider has a second electrode installed to face the first electrode, and the first electrode and the second electrode create a connection between the main scale and the slider. A capacitive encoder equipped with a circuit means for transmitting an output corresponding to a relative movement distance, and a digital display for digitally displaying the output value of the static 11L capacity Jl type encoder, wherein the electrode of t51 is provided on the back side of the main scale, and the digital display is provided on the front side of the slider,
The slider is provided with a wiping means for wiping off foreign matter adhering to the back side of the main scale, and the main scale is provided with a protective cover for covering the back side of the main scale to prevent foreign matter from adhering to the back side. It has a set configuration.

[Example J Fig. 1 is a perspective view showing one embodiment of the present invention, Fig. 2 is a wS
1 is a cross-sectional view taken along the line ■--■, and FIG. 3 is a cross-sectional view taken along the line ■--m in FIG.

One end of the main scale 2 in the figure, I-4, is also formed at the left end in the figure, and eyes aligned in the longitudinal direction on the surface side of the main scale 2. &6 is attached.

A slider 8 is mounted on the main scale 2 so as to be movable in the longitudinal direction of the main scale 2.

On this slider 8, the other jig -10, which is a pair with one jig -4 of the main scale 2, is fixed, and the other jig -10 is adjacent to the scale 6 at the upper part thereof. An indicator 12 for reading the eye 66 is provided at the site, and the approximate movement of the slider 8 can be read from these scales 6 and the wj mark 12.

A main beak 14 is provided at the top of one of the sliders 8, and a slider beak 16 that pairs with the main beak 14 is provided at the top of the slider 8.

Further, on the back side of the main scale 2, a protective cover 18 is slidably attached between the slider 8 and the rear end of the main scale 2, that is, the right end in the figure.

That is, the protective cover 18 is made of a waterproof and highly insulating material such as various plastics and rubbers, and corresponds to the back surface of the main scale 2, and has a second structure described below. It is made into an elongated plate-like body with a width larger than that of the receiving electrode as an electrode and approximately the same width as the main scale 2. A part of the plate-like body is extended vertically and bent in the width direction, and has a cross-section shaped like an opening. Joint part 2
0, and this engaging portion 20 is connected to the main scale 2.
is engaged with the slider 8 to protect the back surface of the main scale 2, that is, the receiving electrode, which will be described later, from foreign substances such as sweat. It is configured to be movable.

Furthermore, as shown in FIG. 2, the main scale 2 is provided with a groove 111122 on its surface side, and a depth spar 24 is slidably fitted into the groove 22. This depth par 24
has one end fixed to the slider 8, and the slider 8
T, :@ is configured to move along with the movement of.

This insulating material 28 prevents short circuits between the receiving electrodes 26 and the like.

Even if sweat or the like enters through any gap between the protective cover 18 and the main scale 2, if the amount is small, the receiving electrode 26 is protected by the insulating material 28 to prevent deterioration of characteristics. ing.

Further, a receiving electrode 26 constituting a first electrode is buried in the back side of the main scale 2 along the longitudinal direction of the main scale 2, and an insulating material 28 is provided so as to cover the surface of the receiving electrode 26. It is provided.

A transmitting electrode 30 and an output electrode 32, which constitute the 'ffi 2 electrodes, are provided in the slider 8 so as to face the receiving electrode 26.

Further, the slider 8 is provided with a digital display 34 and a solar cell 36 on its front side, and further has a solar cell 36 on its side side, that is, the top side in FIG.
A power storage device 38 and a measurement circuit 40 are installed inside the power storage device. At this time, slider 8
The solar cells 36 provided on the front side and the top side of the
Each power generation amount is set to a value sufficient to independently drive the digital display 34 and the measurement circuit 40.

The measurement circuit 40 includes a receiving electrode 2 which is the first electrode.
6 and a transmitting electrode 30 which is a second electrode, the capacitance signal detected by the output electrode 32 is measured, and an output corresponding to the relative movement distance between the main scale 2 and the slider 8 is sent out. These receiving electrodes 26, transmitting electrodes 1! Extreme 30. The output pole 32 and the measuring circuit 40 constitute an electrostatic encoder.

Inside the slider 8 and on the longitudinal direction fq side of the main scale 2, there is a removing means, which is a characteristic structural part of the present invention, for contacting the back surface of the main scale 2 and removing foreign matter adhering to the back surface. , that is, a removal member 4 made of an insulating material such as rubber.
A total of one pair of wiping members 44 made of a water-supplying material such as a sponge are attached to the inside of the cleaning member 2 and the removing member 42, respectively. The widths of the removing member 42 and the wiping member 44 are at least wider than the width of the insulating material 28 covering the receiving electrode 26, and are approximately equal to the width of the main scale 2, for example. Further, the removal member 42 is formed into a thin plate shape, and is brought into contact with the surface of the insulating material 28 in a bent state to have a linear contact portion, and its elastic force efficiently removes sweat and the like. It is made possible to exclude it.

As a result, as the slider 8 moves along the main scale 2, the wiping means temporarily removes the deposits such as sweat and water droplets with the wiping member 42 located on the outside, and then removes them on the inside. The wiping member 44 located at the front acts to absorb and wipe off residual sweat, etc., thereby completely removing sweat and the like.

FIG. 4 is a block diagram showing the circuit configuration of the capacitive encoder.

In the figure, the measurement circuit 40 includes a voltage application circuit 46 that sequentially applies an AC voltage with a predetermined phase shift to each of a plurality of transmitting electrodes 30 arranged at equal intervals in the slider 8, and The capacitance signal received by the receiving electrode 26 is detected by the output electrode 32, and by inputting this detection signal and analyzing its period, the relative shift vJEk between the transmitting electrode 30 and the receiving type 8i26 is determined. Period detection circuit 48 that sends out a corresponding signal
and an arithmetic circuit 50 which inputs the output signal of the period detection circuit 48 and the reference signal sent from the voltage application circuit 46 and calculates the moving distance of the transmitting electrode 30 from the reference position in the receiving TrL8i26. The output of the arithmetic circuit 50 is sent to the digital display 34 to display the measured value. At this time, the receiving electrodes 26 correspond to some of the plurality of transmitting electrodes 30 at regular intervals, and one end of each of the remaining transmitting electrodes 30 is grounded. Coupled Ml electrode (earth electrode) 27 to prevent negative effects due to capacitance interference from other sources.
are provided correspondingly to each other, and the output type 8i32
Since it is provided and built into the slider 8 side,
The output electrode 32 that outputs the detection signal and the measurement circuit 40 can be connected within the slider 8, so that when the slider 8 and the main scale 2 move relative to each other, wiring etc. are not exposed to the outside of the slider 8 and interfere with the movement. has been done.

Note that these circuit means are supplied with electric power generated by the solar cell 36 and stored in the capacitor 38.

FIG. 5 shows the receiving electrode 26. It shows the planar relative positional relationship of the transmitting electrode 30 and the output electrode 32, ffi
2rgJ when viewed from the direction indicated by arrow A. FIG.

That is, the capacitance signal transmitted from the transmitting electrode 30 is configured to be detected by the output electrode 32 via the receiving electrode 26.

Next, the operation of this embodiment will be explained.

When measuring, for example, the outer diameter of an object to be measured using the caliper according to the above-described embodiment, the slider 8 is first moved so that one jaw 4 and the other jaw 4 are in contact with each other. At this time, hold the caliper with your hand, but your hand is not connected to the receiving electrode 2.
The user only grasps the front side, which is not provided with the protective cover l8 made of plastic or the like, and sweat or the like does not adhere to the receiving electrode 26 on the back side.

Next, turn on the power to the encoder of slider 8.

A reset operation is performed to set the digital display 34 to show a zero value.

After that, move the slider 8 to move the object to be measured to one side.
-4 and the other jaw 10.

As a result, the capacitive encoder is activated to calculate the moving distance of the slider 8 and display it on the digital display 34.

Therefore, by reading this displayed value, the outer diameter of the object to be measured can be determined.

When performing standard measurements that do not require measurement accuracy, the encoder of the slider 8 is not powered on, and dimensions are measured using the scale 6 and index 12 in the same manner as a conventional mechanical caliper.

The above embodiment has the following advantages.

That is, since a capacitance type digital encoder is used to measure the relative movement distance between the slider 8 and the main scale 12, it is more accurate than conventional calipers, for example, a minimum reading value of 0. It is possible to measure 0.001 mm or more.

In addition, compared to the case of using a photoelectric encoder in which one emitter, slit, light receiver, lens, etc. must be arranged with high precision, the transmitter M, the pole 30, and the receiver electrode 26 are simply installed so as to face each other. Since it is only necessary to do the following, it can be formed compactly, and it is also easy to manufacture because it does not require precision in the relative positional relationship of each component unlike the photoelectric type.

Furthermore, compared to optical Trt, y1 encoder, qjt
Since the electric power is small, a small-capacity power source is sufficient, and a solar cell 36 can also be used as in this embodiment.

In addition, unlike a contact type encoder, the contacts do not touch each other, so there is no φ count error caused by friction between the contacts.

In addition, since the back surface of the main scale 2 is covered with the waterproof protective cover 18 made of plastic or the like, even if the caliper is held by hand, which is the original usage of calipers, or if it is placed in a poor working environment, it will not sweat. Adhesion of other foreign substances can be effectively prevented.

Therefore, changes in dielectric constant in each electrode, short circuit between electrodes, etc. do not occur.

Furthermore, since a wiping member 42 and a wiping member 44 as wiping means are provided inside the slider 8, even if the protective cover 18 is installed, there should be no problem.

If there are any deposits such as sweat, water droplets, oil, or dirt on the back surface of the main scale 2, these can be effectively removed, and these can be prevented from entering between the receiving electrode 26 and the output electrode 32, etc. In this case, the wiping action of the wiping means is performed in two stages: pushing away by the wiping member 42 and wiping by the wiping member 44.
Foreign matter such as sweat can be removed more completely.

Further, the receiving electrode 26 is provided on the back surface of the main scale 2, and the transmitting electrode 30. By installing the output electrode 32 and the measurement circuit 40 on the back side of the slider 8, the slider 8
This creates more space on the front side, increasing the degree of freedom in the design of component placement. Therefore, since the digital display 34 can be provided on the front side of the slider 8 and the solar cells can be arranged on two sides, the slider 8
The space on the front and back sides can be used effectively, which makes it easier to downsize the slider 8.

Furthermore, by providing the receiving electrode 26 on the back side of the main scale 2, when the measurer holds the main scale 2 at the 0 regular time, the palm of the measuring person who sweats a lot comes into contact with the front side of the main scale 2. The influence of sweat on the receiving electrode 26 can be further reduced, and together with the installation of the protective cover 18, the influence of sweat can be almost completely eliminated.

Furthermore, if the receiving electrode 26 is on the back side rather than on the front side, the chances of breathing heavily on the electrode surface during one operation are greatly reduced, and from this point of view as well, the adverse effects of moisture can be reduced.

Further, by providing the receiving electrode 26 on the back side of the main scale 2, it becomes easy to provide a visually visible mark @6 on the front side of the main scale 2, and by providing this scale 6, accuracy is required. In addition to being able to quickly carry out measurements that do not require accurate measurements, it can also be used as a guideline during measurement operations when making highly accurate measurements using an encoder, making it extremely easy to determine the location of the operation.

Furthermore, the solar cell 36 is used as a power source for the digital display 34 and the needle side circuit 40.

There is no need to replace the battery, and there is no inconvenience such as having to interrupt work to replace the battery.

Furthermore, since the solar cells 36 are provided on the surface and side surfaces of the slider 8, power generation will not be stopped even if light from one direction is blocked.

Furthermore, since the ILT storage device 38 is provided, the solar cell 36
Even if the light irradiated to the circuit is momentarily cut off, the power supplied to each circuit will not be interrupted.

Also, for calipers etc., due to the way they are used, the slider 8
It is also necessary to have small dimensions, light weight, and functional beauty, and according to this embodiment, all of these can be achieved.

In the above embodiment, an example was shown in which a capacitive i-type encoder was used, which analyzes the phase change of a capacitance signal, but this method measures the change in the capacitance value itself. Furthermore, although the surface of the receiving electrode 26 in the above embodiment is precisely the surface of the insulating material 28 that is integrally attached to the receiving electrode 26, in the present invention, the surface of the receiving electrode 26 is This does not necessarily mean the surface of the receiving electrode 26, but also includes the surface of the member 1, for example, the insulating material 28, which is provided in close contact with the surface of the receiving electrode 26. In other words, the transmission!
It also includes the surface of the member located at the receiving electrode 26 between the poles M and O.

5S6 and 7 show other embodiments of the removing member 42 and the wiping member 44, respectively, and FIGS. 6(a) and (b)
), the removal member 42 is made of rubber or other insulating elastic material, and the center portion in the width direction is a convex shape that is convex outward in the direction in which the slider 8 moves. A shaped part 52 is formed to facilitate wiping of foreign matter attached to the back surface of the main scale 2 by pushing it away to the left and right of the convex part 52. Also in this embodiment, the removal member 42
The t-contact with the surface of the insulating material 28 is a linear contact portion. In this embodiment, the tip of the convex portion 52 of the removal member 42 may be made thinner in order as shown by the chain line in the figure.

FIG. 7 shows a wiping member 44 made of a sponge or other water-absorbing elastic material and a spring member 54 such as a compression coil spring.
According to this embodiment, the main scale 2 is attached to the slider 8 to ensure contact with the main scale 2.
It is possible to effectively wipe off foreign matter adhering to the back surface of the device.

Further, FIGS. 8 and 9 show other different embodiments of the protective cover 18, respectively.

In FIG. 8, the main scale 2 is covered with a covering bag 56, which is a cylindrical member made of a thin vinyl film or the like, and in FIG. 9, one end is attached to the slider 8. i1 and the other end is fixed to the rear end of the main scale 2, and the bellows-equipped covering body 58 is formed of a bellows member near both ends to provide an expandable portion, and a grip portion is provided at the center thereof. Main scale 2
It is designed to cover the

This effectively eliminates the possibility that foreign matter such as sweat, water droplets, oil, or dirt may adhere to the back surface of the main scale 2, and also facilitates the measurement operation.

Note that the measurement operation can also be facilitated by forming a bellows-like part in the middle of the plate-like part of the protective cover 18 in the embodiment shown in FIG.

FIG. 1O is a diagram showing still another embodiment.

The receiving electrode 26 is located at the end in the width direction on the back surface of the main scale 2.
A groove 60 is provided along the groove 60, whereby sweat, oil, water droplets, etc. removed by the removal member 42 are temporarily accommodated in the groove 60, thereby eliminating the risk of them scattering to the outside.

Note that the 311160 is provided with a drainage hole 62 penetrating the back surface of the main scale 2, so that water droplets etc. accumulated in the groove 60 can be easily drained to the outside.

11(a) and Cb) show other different embodiments in which the insulating material 28 covering the receiving electrode 26 is provided with an inclined portion in the width direction. In FIG. 1(a), the center portion is higher. , is provided with an inclined part that descends toward the left and right, that is, upward and downward in Figure 1, and (b) in the figure is one end, that is,
A sloped portion is provided that descends from the upper end in the figure toward the other end, that is, the lower end in FIG.

In this case, although not shown, the fitting portion of the slider 8 with the main scale 2 is also formed in a shape corresponding to these #i oblique portions, and is of course configured to be movable. This makes it easier to remove water droplets and the like adhering to the surface of the insulating material 28.

[Effect of the Invention J As detailed above, the present invention uses a capacitance encoder, provides N, 8it- on the back side of the main scale, and provides a digital display on the front side. By providing a wiping means and a protective cover to eliminate or prevent foreign matter from adhering to the caliper, it has become possible to perform extremely quick and highly accurate dimensional measurements while maintaining the ease of use of conventional calipers. It is something.

[Brief explanation of the drawing]

:iS1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, FIG. 3 is a sectional view taken along the line m--m in FIG. A professional diagram showing the circuit configuration of a capacitive encoder, FIG. 5, shows the receiving electrode 26 in FIG. 2. Output electrode 32 and transmission? lj! i30 is a diagram seen through from the direction of the arrow in FIG. 2 to show the mutual positional relationship of the i30, FIG. Wiping member 4 in the figure
FIGS. 8 and 9 are views showing other embodiments of the protective cover 18 in FIG. 1, and FIGS. 1O and 11 are views showing other embodiments of the present invention. FIG. 3 is a diagram showing an example. 2...Main scale, 4...One jaw, 6...Scale,
8...Slider, 10...Other jaw, 12...
- Indicator, 18... Protective cover, 24... Depth bar, 26... Receiving electrode constituting the first electrode, 30...
・Transmission electrode 41 forming the second electrode, 32... Output electrode, 34... Digital display, 36... Solar cell,
42.44...Resistance member and wiping member as wiping means, 52... Convex portion.

Claims (12)

[Claims] (1) A main scale with one jaw formed at one end;
a slider attached to the main scale so as to be movable in the longitudinal direction of the main scale; the main scale is provided with a first electrode; and the slider is provided with a first electrode to face the first electrode. a capacitance type encoder comprising a second electrode installed in the main scale and a measuring circuit means for sending out an output corresponding to the relative movement distance between the main scale and the slider using the first electrode and the second electrode; In the device provided with a digital display that digitally displays the output value of the capacitive encoder, the first electrode is placed on the back side of the main scale, and the digital display is placed on the front side of the slider. In addition, the slider is provided with a wiping means for wiping off foreign matter adhering to the back side of the main scale, and the main scale is provided with a protection device for covering the back face of the main scale to prevent foreign matter from adhering to the back face. A capacitive digital caliper characterized by each having a cover. (2) In claim 1, the protective cover is made of a waterproof material that is movably attached to the main scale and extends in the longitudinal direction of the main scale along the first electrode. A capacitive digital caliper characterized by: (3) In claim 1, the protective cover is formed of a waterproof material extending in the longitudinal direction of the main scale along the first electrode, and one end thereof is attached to the slider. A capacitive digital caliper characterized by being fixed. (4) In claim 3, the protective cover is characterized in that at least one end thereof is provided with a portion that can be expanded and contracted in the longitudinal direction of the main scale along the first electrode. Capacitive digital caliper. (5) In any one of claims 2 to 4, the protective cover is formed from a thin plate-like member having a width at least equal to or larger than the width of the first electrode. Capacitive digital caliper. (6) In any one of claims 2 to 4, the capacitor is characterized in that the protective cover is composed of a highly flexible cylindrical member that covers the main scale. Type digital caliper. (7) In claim 1, the wiping means is formed from a highly flexible electrically insulating member having one end fixed to the slider. Capacitive digital caliper. (8) In claim 1, the wiping means includes a wiping means for wiping off foreign matter adhering to a portion of the back surface of the main scale where the first electrode is provided, and a wiping device for wiping off the foreign matter. A capacitive digital caliper characterized by comprising: a measuring means; (9) In claim 8, the removing means is characterized in that a central portion thereof in the width direction is formed in a convex shape outward in the direction of movement of the slider. Capacitive digital caliper. (10) The capacitive digital caliper according to claim 8, wherein the wiping means is made of a water-absorbing material. (11) The capacitive digital caliper according to claim 1, characterized in that a groove is provided on the back surface of the main scale along the first electrode. (12) The capacitive digital caliper according to claim 1, characterized in that the back surface of the main scale is formed with an inclined portion that slopes in the width direction thereof.