DE3727440A1 - Caliper - Google Patents

Abstract

A sliding caliper has a first measurement part and a second measurement part that can move in a longitudinal direction (x) relative to the first part. Flat measurement electrodes (14 to 17) are electrically insulated on the first measurement part. On the second measurement part, a plurality of flat measurement counter-electrodes (33, 34) transversely arranged to the longitudinal direction (x) are passed by the measurement electrodes (14 to 17) when the first measurement part moves relative to the second measurement part in the longitudinal direction. The measurement electrodes (14 to 17) and the measurement counter-electrodes (33, 34) form a condenser the capacitance (C) of which varies according to the relative displacement of both measurement parts. In order to simplify the construction, and therefore the manufacture of the sliding caliper, and to obtain a greater degree of freedom from the point of view of the geometric design of the measurement counter-electodes, the measurement counter-electrodes (33, 34) are formed as electrically conductive surfaces (47) that extend continuously in the longitudinal direction (x) and are provided with a coating (46) of dielectric material that intermittently covers at least parts of the surface (4) in the longitudinal direction (x).

Description

The invention relates to a caliper with a first measuring part and a longitudinally movable relative thereto second measuring part, with at least one on the first measuring part Electrically insulated, flat measuring electrode and a plurality of arranged on the second measuring part, areal measuring, extending transversely to the longitudinal direction Counter electrodes, past which the measuring electrode at relative Longitudinal movement of the first measuring part moves to the second measuring part  is, the measuring electrode and the measuring counter-electrodes one Form capacitor, the capacitance value depending on the relative movement of the two measuring parts to each other varies.

A caliper of the type mentioned, in which the distance recorded electronically between two measuring jaws, is evaluated and displayed is generally known.

If in the following we speak of a "slide gauge", then this is the invention only in relation to this application Illustrate the game more clearly. It understands themselves that the invention also in other mecha African / electrical length measuring devices can be used, so e.g. also with micrometers, probes and the like.

In the known calipers of the type mentioned a runner is arranged to be longitudinally displaceable on a rod. The The rotor and the rod are each protruding at 90 ° Provide measuring beak, between which the measurement object is enclosed will. The absolute position of the runner on the stick to measure in the longitudinal direction are conventional "electronic" Calipers with a capacitive measuring arrangement. This measuring arrangement consists of flat measuring electrodes, the surfaces of the rod sliding past each other and the runner are arranged. These flat measuring electrodes form the two plates of a capacitor, its capaci actual value is recorded and evaluated. With longitudinal displacement the runner on the stick changes the degree of Coverage of the electrodes on the rotor and the rod and hence the capacitance value of the capacitor thus formed.  

The known calipers are designed so that both on the rod as well as on the rotor the measuring electrodes as Insulated electrically conductive surfaces (islands) are formed are. In practice, this is achieved in such a way that the elec trically insulated surfaces by vapor deposition on an electrically represents non-conductive base body or by inserting punched strips in a non-conductive base or the like

The e.g. Measuring electrodes arranged on the rod must therefore not only isolated from each other but also isolated from the rod be. In order to achieve a capacitor measuring arrangement, the individual measuring electrodes of the rod, for example in Longitudinal direction 2.2 mm long and at a distance from example are arranged 2.54 mm, are connected to each other, so that the one or more electrodes of the runner to each individual electrode of the rod in capacitive and evaluable Can interact.

The known calipers have the disadvantage that they especially with regard to the arrangement of the many electrodes on the staff are extremely expensive because they are required isolation and subsequent wiring a very complex manufacturing process required. The very elaborate Manufacturing also necessarily brings a certain amount Sensitivity to mechanical loads with it.

The invention is therefore based on the object, a caliper of the type mentioned to further develop the their manufacture considerably simplified and at the same time their Robustness is increased significantly.  

According to the invention, this object is achieved on the one hand by that the measuring counter electrodes as continuous in the longitudinal direction, electrically conductive surface are formed with a the area in the longitudinal direction is at least partially discounted nu covering coating of dielectric material is provided.

The object underlying the invention is based on this Completely solved because now the entire conductive Surface, for example the rod of a caliper as a counter electrode works. It is obvious that this is the manufacture the caliper considerably simplified because only one suitable conductive surface of the rod with the dielectric Provide material, for example glued or printed need and the rod as a whole as a counter electrode works. A separate insulated embedding and wiring of Counter electrodes are therefore no longer required. This increases also the robustness of the slide gauge, in which the cross section the rod no longer has to be weakened by a groove, into which the counter electrodes are then to be inserted.

Another major advantage of coating with dielek trical material is that when coating, ins special printing almost any shape for the counter electrode can be selected.

In a preferred embodiment of the invention Leave area in the longitudinal direction without coating and there forms a first reference counterelectrode, which on the a first reference electrode faces the first measuring part. As an alternative or in addition, the area can be partially in  Be provided with a continuous coating in the longitudinal direction and form a second reference counterelectrode there, on the first measuring part faces a second reference electrode.

The above measures have the advantage that at Shift of the measuring parts to each other one of the Longitudinal displacement independent reference value is generated by which one the maximum capacity value (under activation the dielectric coating) and the other the minimum Corresponds to the capacitance value (without dielectric coating), where these are the two extreme values between which the Capacitance value between the measuring electrodes and the measuring counter electrodes when moving the two measuring parts to each other varies. In this way it is possible to measure disturbances, for example show the temperature dependence of the relative dielectric constant the coating, the age dependence of the plank averaging tricity constant and the like.

The object mentioned at the outset of the invention is further invented solved according to the invention in that the measuring counter electrodes as in Longitudinal, continuous, electrically conductive surface are formed with discontinuously in the longitudinal direction arranged depressions is provided.

In this way, too, the one on which the invention is based Task can be solved completely, because with this solution too variant the entire counter surface, for example the entire rod, acts as a counter electrode and separate electrodes no longer need to be embedded in the rod. The required deepenings can be easily, e.g. be introduced by electroerosion or it will be in  conversely on a reference surface increases by Electrode deposition applied. Again, in some ways Include the geometric design of the counter electrodes can be varied, although not to the same extent as this is the case when printing with a dielectric covering is.

It goes without saying that the second solution variant of the invention with discontinuously arranged depressions Reference electrodes and reference counter electrodes in the form of continuously existing or non-existent throughout Pre-recessed over the entire length of the second measuring part can be seen.

In preferred configurations of both solution variants the measuring electrodes and the measuring counter electrodes as transverse to Longitudinally arranged strips formed and in constant Distance from each other, as is known per se.

At the same time you can see the reference electrodes mentioned above before, a comb-like structure arises, which in both Solution variants can be easily applied or introduced.

It is also preferred if also known per se Way at least two measuring electrodes in an odd number Multiples of a quarter of the distance to each other in the longitudinal direction are arranged offset.

This measure has the advantage that by comparison the output signals of the two measuring electrodes determined can be in which direction the two measuring parts relative  are shifted towards each other. Another advantage of this The arrangement is as follows:

If the capacitive arrangement described in the introduction Measuring electrodes run past the measuring counter electrodes, see above theoretically there is a triangular shape of the capacity values depending on the longitudinal displacement. The reversal points of this triangular course, i.e. the points of the Longitudinal displacement, in which the measuring electrodes and the Cover the measuring electrodes completely or not at all, in practice, however, are rounded to roundings. Too to achieve a reproducible and linear measured value here, can with a measuring electrode arrangement at a distance of an odd multiple of a quarter of the distance switch to the other measuring electrode, which is in at this moment in the area of greatest linearity, namely in halfway between two reversal points. To this In this way, a strictly linear dependency is obtained overall over the entire measuring range.

In another embodiment of the invention at least two measuring electrodes in an even multiple the distance from each other offset in the longitudinal direction and electrically connected in parallel.

This measure has the advantage that a larger signal yield is possible because the effectively effective capacitor area is doubled. This is particularly important because with usual dimensions of calipers capacity values in pF range occur, so that a doubling of the evaluable  Measurement signals a considerable simplification for the further Signal processing means.

In further embodiments of the invention is a Numerous measuring counter electrodes are provided, their expansion is stepped in the longitudinal direction.

This measure has the advantage that a nonius-like arrangement arises in which the increase or decrease in area over coverage of the electrodes changes gradually, so that on this way a step-shaped signal function depending of the longitudinal displacement can be achieved with digital Evaluation means can be processed particularly easily.

In further embodiments of the invention Measuring counter electrodes profiled in the longitudinal direction.

This embodiment of the invention makes itself insbe especially when printing with a dielectric coating take advantage of existing possibility, the geometric design to be able to choose the measuring counter electrodes almost freely. By skillful geometric shaping of the measuring counter electrodes can either compensate for nonlinearities in this way or intentional non-linearities are generated, for example graded courses of the measurement signal.

In another group of embodiments, there are one Large number of measuring electrodes spaced transversely to the longitudinal direction arranged over an equal number of tracks of measuring Counter electrodes are movable.  

This also measures the variability in the form Design of measuring counter electrodes by printing with dielectri make use of chemical material, there is the advantage that a coding of the measurement result is possible by at each Measuring electrode a digital signal is generated by Link with the digital signals of the other measuring electrodes a relative or absolute signal for the respective longitudinal position of the measuring parts to each other.

Further advantages result from the description and the attached drawing.

It is understood that the above and the following features still explained not only in the respective specified combination but also in other combinations or can be used alone without the scope of the to leave the present invention.

Embodiments of the invention are in the drawing are shown and are described in more detail in the following description explained. Show it:

Figure 1 is a plan view of an electrode side of a slide of a slide gauge.

Fig. 2 is a plan view of an associated electrode side of a rod of a vernier caliper;

. Fig. 3 is a view of the runner which has been placed on the slider of Figure 2 shown in FIG. 1;

FIG. 4 shows an illustration in section, in the longitudinal direction, through the arrangement according to FIG. 3;

FIG. 5 shows a further illustration, in section, of a variant of the arrangement according to FIG. 4;

FIGS. 6 to 8, three curves of measuring signals to explain the arrangement according to Figures 1 to 5.

Fig. 9 shows a variant of an electrode array to form a vernier;

. 10 and 11 are waveforms for explaining the electrode drive UTHORISATION of FIG. 9;

. 12 to 14 are three variants of profiled in the longitudinal direction of electrodes;

Fig. 15 is a highly schematic view of a multi-lane electrode assembly according to the invention.

In Figs. 1 to 4 10 generally designates a rotor of a vernier caliper, which is provided with longitudinal guides 11 for a rod. The rotor 10 is provided with a first reference electrode 12 and a second reference electrode 13 , which extend in the longitudinal direction x of the rotor 10 over a relatively large length section. The reference electrodes 12 , 13 are preferably located next to the guides 11 and extend over almost the entire length of the rotor 10 .

Between the reference electrodes 12 , 13 are a first, a second, a third and a fourth measuring electrode 14 , 15 , 16 , 17 , which are strip-shaped and extend transversely to the longitudinal direction x . The first and the second measuring electrode 14 , 15 form a first pair and the third and fourth measuring electrodes 16 , 17 form a second pair. The Meßelek electrodes 14/15 and 16/17 of the two pairs are each offset by an equal first distance 18 , which can be 4.74 mm in a practical embodiment of the invention if the extension of the measuring electrodes 14 to 17 in the longitudinal direction x is 2.2 mm each. The pairs 14/15 and 16/17 of the measuring electrodes are offset from one another by a second distance 19 , which is preferably an odd multiple of a quarter of the first distance 18 .

FIG. 2 shows the rod 30 belonging to the rotor 10 of FIG. 1, also in a view of the surface provided with electrodes.

It can be seen from FIG. 2 clearly two comb-like structures which engage with, and at its base a first Gegenelek trode 31 and a second counter electrode 32 form the x passed through in the longitudinal direction, respectively. The interdigitated fingers of the comb-like structures alternately form a first measuring counter electrode 33 and a second measuring counter electrode 34 , specifically at a first distance 18 of, for example, 4.74 mm.

As can easily be seen in connection with FIG. 4, the electrodes in the rotor 10 and in the rod 30 can be designed differently, but need not be.

The rotor 10 consists of a metallic material which is provided with an insulating insert 40 . The measuring electrodes 14 to 17 and the reference electrodes 12 and 13 , which consist of an electrically conductive material, are embedded in this insulating insert 40 . By means of lines 41 and 42 , the measuring electrodes 14 to 17 , as well as the reference electrodes 12 and 13 are connected to an evaluation unit 43 . The rod 30 , which is also made of a metallic material, is also connected to the evaluation unit 43 via a connection 44 . The evaluation unit 43 is usually located on the rotor 10 and the connection 44 is represented by the metallic contact of the rotor 10 and the rod 30 on the very narrow mechanical guides 11 . The evaluation unit 43 is connected to a display unit 45 , for example a digital LCD unit.

As can be clearly seen from FIG. 4, the measuring counter electrodes 33 , 34 are formed on the rod 30 by a coating 46 on a metallic surface 47 of the rod 30 . The same applies to the reference counter electrodes 31 and 32 .

In embodiments of the invention, this can be done by gluing a comb-shaped dielectric adhesive tape according to FIG. 3 onto the bare surface 47 of the rod 30 or by applying a corresponding print made of dielectric material by screen printing or the like. This creates alternating capacitor areas of low capacitance (no adhesive tape or imprint, ie air as a dielectric) and high capacitance (adhesive tape or imprint with a high relative dielectric constant acts as a dielectric).

In the top view of FIG. 3 it can be seen that when the rotor 10 is moved in the longitudinal direction x, the reference electrodes 12 , 13 run continuously over the reference counter-electrodes 31 , 32 , namely the first reference electrode 12 runs over the uncoated in the longitudinal direction x Surface 47 , while the second reference electrode 13 runs over the longitudinally through coating 46 . The first reference electrode 12 with its associated first reference counterelectrode 31 therefore always shows a minimum capacitance value because the capacitor formed by the electrodes 12 , 31 has no minimum capacitance value, while this is the case with the second reference electrode 13 with the associated second reference counterelectrode 32 is the maximum value which is determined by the dielectric in the form of the continuous coating 46 .

When the rotor 10 is displaced longitudinally in the longitudinal direction x, the measuring electrodes 14 to 17 alternatively travel over coated and non-coated areas of the surface 47 , so that cyclically maximum and minimum capacitance values are produced, which are measured and evaluated in the evaluation unit 43 .

The parallel connection of the measuring electrodes 14/15 and 16/17 results in capacitors of double area and thus a signal of double amplitude.

In the variant shown in FIG. 5, the design of the rotor 10 is unchanged. The rod 30 a , however, is provided with successive increases 50 or depressions 51 , so that the distance between the electrode surface of the rotor 10 and the rotor 30 a fluctuates between a minimum value 52 and a maximum value 53 .

In one exemplary embodiment of the invention, the depressions 51 can be formed from the surface 47 by means of electroerosion or other material-removing methods, but alternatively, an application can also be carried out by means of electrode deposition or other galvanic methods in order to produce the distance variation 52/53 .

It is easy to see that when the rotor 10 is displaced longitudinally, the capacitance value also varies in this case between a minimum value (distance 52 ) and a maximum value (distance 53 ), because the capacitance value of a capacitor also depends on the distance between its planar electrodes.

Both in the electrode formation in FIG. 5 and in that in FIG. 4, signal profiles arise, as are shown in FIGS. 6 to 8.

Fig. 6 shows with curves 60 and 61 via the shift Längsver x invariant capacitance values C of the reference electrodes 12/31 and 13/32.

Fig. 7, on the other hand, shows with a curve 62 the dependency of the capacitance value C on the longitudinal displacement x in the pair 14/33 , 34 or 15/33 , 34 of the electrical system and it can be seen from FIG. 7 that for practical reasons the reversal points of the theoretically triangular The course can be ground to a rounded minimum 63, for example.

The same applies to the course 64 of the pair of measuring electrodes 16/33 , 34 and 17/33 , 34 shown in FIG. 8, which is offset in the longitudinal direction x by a quarter of the first distance 18 . At the location of the ground minimum 63 of the course 62 , a straight edge 65 is therefore measured at the course 64 . By selecting the more linear measurement signal, one can therefore eliminate measurement errors in the rounded areas of the curves 62 , 64 .

FIG. 9 shows a further variant of an electrode arrangement , in which ten measuring electrodes 70/0 to 70/9 are arranged equidistantly offset in the longitudinal direction x on a rotor. On a rod, also equidistantly offset in the longitudinal direction x , ten measuring counter electrodes 71/0 to 71/9 are arranged, which for the sake of clarity are shown in Fig. 6 next to the measuring electrodes 70/0 to 70/9 , but in the practical arrangement below.

While the measuring electrodes 70/0 to 70/9 have a constant extension in the longitudinal direction x , the length 72/0 to 72/9 of the measuring counter electrodes 71/0 to 71/9 decreases in steps, for example by 1 / 10 of a division. Are in a starting position, the measuring electrodes 70/0 to 70/9 and the measuring counter electrodes 71/0 to 71/9 in the position shown in Fig. 9, but with each other, a maximum capaci tity value is formed.

If, for example, the measuring counter electrodes 71/0 to 71/9 in FIG. 9 with fixed measuring electrodes 70/0 to 70/9 are moved to the right, for example by 1/10 division, it can be seen that the overlap of the respective Surfaces decrease linearly, namely by ten times a common width 73 multiplied with the longitudinal displacement x . After exceeding a longitudinal displacement x , which corresponds to the length 72/9 of the narrowest measuring counterelectrode 71/9 , the coverage decreases more slowly, because now only nine times the width 73 multiplied by the longitudinal displacement x is effective.

Overall, this results in a course 76 , as shown in FIG. 10, which is formed from a series of straight pieces 77 of decreasing incline.

If the course 76 is differentiated according to FIG. 10, a staircase function 78 is obtained , as is shown in FIG. 11. Such a staircase function 78 has the advantage in digital signal evaluation that the transition points can be recognized more easily by means of digital comparators than is the case with a continuous signal curve.

The arrangement of FIGS. 9 to 11 thus forms a vernier in which the area coverage and thus the capacitance value within a measuring point changes with the units of the respective measuring point in a more easily evaluable manner.

FIG. 12 shows a measuring counterelectrode 79 , which is provided with a profile 80 in the longitudinal direction x , in order to compensate for nonlinearities in this way, for example as with the ground minima 63 in FIG. 7, or to generate desired nonlinearities.

Fig. 13 shows a further measuring counter-electrode 91 , which is provided with a step profile 82 in the longitudinal direction x in order to also produce a stepped course of the capacitance value C in this way.

Fig. 14 shows a further measuring counterelectrode 85 with a continuous continuous staircase profile, which can pass over the entire length of the rod 30 .

Finally, FIG. 15 shows yet another arrangement in which four measuring electrodes 90/0 to 90/3 are arranged on the rotor offset with respect to one another transversely to the longitudinal direction x . Each measuring electrode 90/0 to 90/3 has a track of measuring counter electrodes 91 which are discontinuously applied in the longitudinal direction x as strips. The measuring electrodes 90/0 to 90/3 are connected to a decoder 92 , which determines an absolute or relative position of the rotor on the rod from the signal present at each measuring electrode 90/0 to 90/3 and from their logical combination with one another. The arrangement of the measuring counter-electrodes 91 can, for example, be chosen such that a two-off-four code, a BCD code or another suitable code results on the measuring electrodes 90/0 to 90/3 when the rotor is on moved the rod and alternatively a high or a low capacitance is applied to the measuring electrodes 90/0 to 90/3 due to the logical pattern of the measuring counter electrodes 91 .

Claims (12)

1. caliper with a first measuring part and a relative to it in a longitudinal direction ( x ) movable second measuring part, with at least one on the first measuring part arranged electrically isolated, area measuring electrode ( 14 to 17 ; 70 ; 90 ) and a variety of on second measuring part arranged transversely to the longitudinal direction ( x ) extending planar measuring counter electrodes ( 33 , 34 ; 71 ; 79 ; 81 ; 85 ; 91 , past which the measuring electrode ( 14 to 17 ; 70 ; 90 ) with relative longitudinal movement of the first measuring part is moved to the second measuring part, the measuring electrode ( 14 to 17 ; 70 ; 90 ) and the measuring counter-electrodes ( 33 , 34 ; 71 ; 79 ; 81 ; 85 ; 91 ) forming a capacitor whose capacitance value ( C ) varies as a function of the relative movement of the two measuring parts to one another, characterized in that the measuring counter electrodes ( 33 , 34 ; 71 ; 79 ; 81 ; 85 ; 91 ) are designed as an electrically conductive surface ( 47 ) which is continuous in the longitudinal direction and which is provided with a coating ( 46 ) of dielectric material which at least partially discontinuously covers the surface ( 47 ) in the longitudinal direction ( x ). 2. Caliper according to claim 1, characterized in that the surface ( 47 ) is left in regions in the longitudinal direction ( x ) without coating ( 48 ) and forms a first reference counter electrode ( 31 ) there, which on the first measuring part has a first reference electrode ( 12 ) faces. 3. caliper according to claim 1 or 2, characterized in that the surface ( 47 ) is partially in the longitudinal direction ( x ) with a continuous coating ( 46 ), and there forms a second reference counter electrode ( 32 ) on the the first measuring part faces a second reference electrode ( 13 ). 4. caliper with a first measuring part and a relative to it in a longitudinal direction ( x ) movable second measuring part, with at least one on the first measuring part arranged electrically isolated, area measuring electrode ( 14 to 17 ; 70 ; 90 ) and a variety of on arranged second measuring part, extending transversely to the longitudinal direction ( x ), planar measuring counter electrodes ( 33 , 34 ; 71 ; 79 ; 81 ; 85 ; 91 ), past which the measuring electrode ( 14 to 17 ; 70 ; 90 ) relative longitudinal movement of the first measuring part is moved to the second measuring part, the measuring electrode ( 14 to 17 ; 70 ) and the measuring counter-electrodes ( 33 , 34 ; 71 ; 79 ; 81 ; 85 ; 91 ) forming a capacitor whose capacitance value ( Z ) varies depending on the relative movement of the two measuring parts to one another, characterized in that the measuring counter-electrodes ( 33 , 34 ; 71 ; 79 ; 81 ; 85 ; 91 ) are designed as an electrically conductive surface ( 47 ) which is continuous in the longitudinal direction ( x ) , d ie with intermittently arranged recesses ( 51 ) in the longitudinal direction ( x ). 5. caliper according to claim 4, characterized in that the surface ( 47 ) is left in regions in the longitudinal direction ( x ) without a recess ( 51 ) and forms a first reference counter electrode ( 31 ) there, which on the first measuring part a first reference electrode ( 12 ) faces. 6. caliper according to claim 4 or 5, characterized in that the surface ( 47 ) is partially in the longitudinal direction with a continuous recess ( 51 ) and there forms a second reference counter-electrode ( 32 ) which on the first measuring part a second Reference electrode ( 13 ) faces. 7. caliper according to one of claims 1 to 6, characterized in that the measuring electrodes ( 14 to 17 ) and the measuring counter-electrodes ( 31 , 32 ) are arranged as strips arranged transversely to the longitudinal direction ( x ) and at a constant distance ( 18 ) are arranged to each other. 8. caliper according to one of claims 1 to 7, characterized in that at least two measuring electrodes ( 14/16 , 15/17 ) in an odd multiple of a quarter of the distance ( 19 ) to each other in the longitudinal direction ( x ) are arranged offset. 9. caliper according to one of claims 1 to 8, characterized in that at least two measuring electrodes ( 14/15 , 16/17 ) in an even multiple of the distance ( 18 ) to each other in the longitudinal direction ( x ) arranged offset and electrically connected in parallel. 10. Caliper according to one of claims 1 to 9, characterized in that a plurality of measuring counter electrodes ( 71/0 to 71/9 ) is provided, the extent of which is stepped in the longitudinal direction ( x ). 11. Caliper according to one of claims 1 to 10, characterized in that the measuring counter electrodes ( 79 ; 81 ; 85 ) are profiled in the longitudinal direction ( x ). 12. Caliper according to one of claims 1 to 10, characterized in that a plurality of measuring electrodes ( 90/9 to 90/3 ) are arranged at a distance transversely to the longitudinal direction ( x ), which over a same plurality of tracks of measuring counter electrodes ( 91 ) are movable.