Capacitive displacement sensor

Details Capacitive displacement sensor Capacitive displacement sensor

2000-11-28

2003-02-25

Oda, Christine (Department: 2858)

Electricity: measuring and testing

Impedance, admittance or other quantities representative of...

Lumped type parameters

Reexamination Certificate

active

06525546

ABSTRACT:

TECHNICAL FIELD
The invention relates to a capacitive sensor for length and angle measurement.
BACKGROUND ART
Since the coming out of capacitive displacement sensor for large displacement measuring in the seventies of the century, due to its advantages on low power consumption, high integration, small volume, and low cost etc, extensive applications had been achieved rapidly on digital display measuring tools and other length measuring devices. However, because of its lower resolution and measuring precision in comparison with the sensors like the gratings and synchronous inductor etc, therefore a certain limitation occurs in aspects of high precision measurement. While the simplest and most effective method for raising resolution and precision of capacitive displacement sensor is reduction of the spacings between the emitting electrodes
12
of a subsidiary scale and reduction of the spacings among the reflecting electrodes
10
of a main scale simultaneously, as shown in FIG.
6
. According to arrangement for the prior art's emitting electrodes
12
of subsidiary scales, in a pitch T of the subsidiary scale, 2N (N is an integer, 2N=8 to be set in the drawing) emitting electrodes transmitting different signals are involved. If the various emitting electrodes
12
in a pitch T are numbered as
1
,
2
,
3
,
4
,
5
,
6
,
7
,
8
according to the position sequence, there are a plurality of emitting electrodes
12
with a pitches T, and emitting electrodes in each pitch T must have gaps S and a receiving electrode
11
is placed on one side of the emitting electrode. If the spacing t between the emitting electrodes
12
were reduced according to aforesaid form of arrangement, then the gaps between the adjacent emitting electrodes shall be extremely small so its technological difficulty is obvious. Moreover since there is a gap S between the adjacent emitting electrodes
12
, therefore discontinuity of signals shall be presented while the reflecting electrode
10
on the main scale traverses two emitting electrodes
12
, thereby precision of the sensor is influenced. In the patents (CN87102624) (CN1038421), it was proposed to take out the emitting electrodes on the subsidiary scale originally concentrated in a pitch T respectively, then to dispose them on the same positions of different pitches T separately so that each emitting electrode being broadened, and improving its resolution but not increasing the technological difficulty. But a group of emitting electrodes in this kind of arrangement shall correspond to multiple reflecting electrodes respectively, so that no complete signal can be synthesized on a reflecting electrode. A reflecting electrode must be coupled with a receiver electrode once again to compose a complete synthesized signal. However the variation of capacitance is directly proportional to the square of the distance between both capacitor plates, thus an extremely high parallelism of the main scale and the subsidiary scale is required, otherwise the precision cannot be reached, consequently its application shall be rather difficult. Furthermore, when the reflecting electrode is traversing the overlapping portions of two emitting electrodes, the sensor precision shall also be influenced due to said signal discontinuity.
DISCLOSURE OF THE INVENTION
An object of the invention is to propose an improved capacitive displacement sensor, which can not only improve the resolution and precision of capacitive displacement sensor, meanwhile the fabrication technological difficulty is also not excessively increased, and the applicable function of improved capacitive displacement sensor can be conveniently extended.
The capacitive displacement sensor of the invention comprises a main scale and a subsidiary scale arranged in a relatively mutual movable mode;
2
N (N is an integer) emitting electrodes
12
are disposed on the said above subsidiary scale for transmitting different signals, said emitting electrodes
12
being perpendicular to the subsidiary scale and arranged in each pitch T; a receiving electrode
11
, said above emitting electrodes
12
and reflecting electrodes
10
opposing the receiving electrode
11
are installed on the said main scale; and an electronic circuit for measuring the relative displacement by means of the coupling capacitance between said above emitting electrodes
12
, receiver electrode
11
, and reflecting electrodes
10
,
wherein, the adjacent emitting electrodes
12
in the same pitch T of the subsidiary scale are arranged on both sides of the receiver electrode
11
respectively, and all the emitting electrodes
12
transmitting different signals still are involved in a pitch T, the geometrical gaps of adjacent emitting electrodes
12
along the longitudinal direction of said subsidiary scale being zero, i.e. the neighboring sides between the adjacent emitting electrodes
12
located on a straight line. Corresponding to arrangement of the emitting electrodes
12
in each pitch T, the arrangement sequence of the emitting electrodes
12
in another pitch T separating several pitches with the said above pitch T is alternatively arranged with the aforesaid emitting electrodes
12
, and the gap among the neighboring two groups several pitches T.
A plurality of units formed according to the mode of arranging emitting electrodes on both sides of receiver electrode
11
respectively, and the geometric gaps between the adjacent emitting electrodes being zero may be disposed, along subsidiary scale wherein a spacing of several pitches T occurred among the two adjacent pitches, and the arrangement sequences of the emitting electrodes
12
in the two adjacent units are alternatively allocated.
The form of reflecting electrodes
10
of the main scale may be a tumbled letter “T” shape relatively to the main scale.
Also, a pitch of the reflecting electrodes
10
may equal a pitch T of the emitting electrodes
12
.
The reflecting electrode
11
may be rectangular shape, its length may be integer times of the pitch T of emitting electrodes
12
.
Furthermore, both ends of receiver electrode
11
may be T/
2
shorter than the both outer ends of emitting electrode
12
respectively.


REFERENCES:
patent: 4841225 (1989-06-01), Meyer

Affiliated with

Also associated with

Rating

Capacitive displacement sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Capacitive displacement sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Capacitive displacement sensor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3175447