DE19643538A1 - Magnetic encoder for absolute length measurement - Google Patents

Abstract

The encoder consists of two parallel tracks (1) of alternate North and South magnetised elements. A sensor, e.g. Hall probe, is connected by a lead (3) to a processor (4) and display (5). The encoder has a single-turn track with alternating North and South pole elements for fine position sensing. The second track is a multi-turn track with cyclic sequential code for coarse position sensing. The sensor has two probes for the single-turn track with half the encoder spacing and a number of probes (2N) for the multi-turn track at half the encoder spacing.

Description

The invention relates to a device for measuring length with an element that contains path information.

Devices for measuring length are in a variety of forms and execution known. In the present inventions it's all about working very precisely, at least partially controlled electronic length measuring devices, Here, for example, incrementally evaluating magnetic Length measuring systems are known. It should also be mentioned well-known arc tangent evaluation with microcontrollers.

All of these higher quality length measuring devices have the Disadvantage that they do not record the value absolutely. Stand for example, they are not under tension, they are adjusted, see above that it only returns to zero when a measurement begins must be asked.  

The present invention is based on the object Develop device of the type mentioned above, with the an absolute length measurement is possible with regard to Path and angle.

The path information leads to the solution of this task encoded on the element and a sensor for the element Registration of the route information is assigned.

The path information on the element should be absolute, d. that is, the sensor detects without reference to other parameters the exact position. The sensor is defined with a Distance moved over the encoded tape. He dedicates that position information coded there and gives the data preferably to an electronic evaluation unit. Of the The advantage of the absolutely measuring system is that the sensor can also be moved in the de-energized state without the route information is lost. After being back the current route information is available when the system is switched immediately available.

The whole thing is effected by the coding, which is preferred done magnetically and be from at least two code tracks stands. Both code tracks are preferably parallel to one another arranged, with a code track as a single turn track (ST- Track) and the other code track as a multi-turn track (MT track) is trained. Singleturn track means that the code track alternately magnetized with north and south poles. This Code track is used for the fine recording of the length measurement. The However, rough recording is done through the multiturn track which is determined in which field the singleturn track the sensor or the corresponding scanner of the Sensors. For this, the MT code track is with a cyclically sequential code that magnetizes this rough Position information transmitted.  

For the single-turn track, two scanners, their Output signals two sines offset by 90 ° to each other signals are. For the MT code track, however, are one A plurality of scanners are provided which correspond to the number of Corresponds to bit width. However, even those are preferred double the number of bit width used on sampler, so that the multiturn track is scanned twice, whereby the active scanner block always safely within a pole division sits.

With the help of the evaluation unit, the signals that the Sensor delivers, first processed (analog amplifier, Filters etc.). The processed signals can be digital siert (comparator, A / D converter) and with the help of a Microcontroller processed to route information or will be charged. This information can then be stored in one Display or otherwise (e.g. parallel, serial) to a higher-level station (Control, etc.) are passed on. The area of application the device for length measurement according to the invention unlimited.  

Further advantages, features and details of the invention result from the following description more preferred Exemplary embodiments and with reference to the drawing; this shows in

Figure 1 is a schematically illustrated plan view of a device for length measurement according to the invention.

FIG. 2 shows a side view of the device according to FIG. 1;

Fig. 3 is a plan view of a part of an element which includes a routing information;

Fig. 4 is a plan view of arrangements of scanners on a sensor.

According to FIG. 1, a device for measuring length according to the invention has an element 1 to which a sensor 2 is assigned, which can be moved along the element 1 . The sensor 2 is connected via a line 3 to an evaluation unit 4 , which in the present exemplary embodiment has a display 5 for displaying the length measurement.

In Fig. 2 it can be seen that the element 1 , which contains the path information, is band-shaped in the embodiment. It essentially consists of a magnetic tape 6 , which is glued to a surface 8 via an adhesive tape 7 . A further adhesive tape 9 is then applied to the magnetic tape 6 and a cover tape 10 is applied to this. The element 1 could, however, also be designed in the form of a rail or the like.

The sensor 2 may be in the direction of the double arrow 11 are moved over the item 1, wherein the scanning of the element 1 is contactless, there is an air gap 12 is formed between the sensor 2 and the magnetic tape 6 and the cover strip 10th

Element 1 has two code tracks 13 and 14 , code track 13 being referred to as a multi-turn track (MT track) and code track 14 as a single-turn track (ST track). Both code tracks 13 and 14 are arranged parallel to one another. The ST track 14 is alternately magnetized with magnetic north and south poles. It has a pole pitch P. The MT track 13 also has a pole pitch P which is the same as that of the ST track. However, the MT track is encoded with a so-called "cyclically sequential code" (see "Technical Measurement" tm 9/94 p. 343) with a bit width N, z. B. the "logical one" is assigned to the north pole and the "logical zero" to the south pole. The measuring length of the system is thus

ML = (2 ^N ) × P

In Fig. 4 2 sensor 15 are shown punctiform. In addition, the representation is enlarged compared to element 1 from FIG. 3, as can be seen from the comparison of the pole pitch P.

The scanner 15 are arranged in rows corresponding to the code tracks 13 and 14 . The ST code track 14 is read in by two magnetoresistive scanners at a distance of P / 4. The output signals are two sine signals offset by 90 ° to each other. If the amplitudes and offset values of the electrical signals are the same, an arc value can be used to find an angle value which uniquely and absolutely determines the dimension within a pole pitch P. This makes a fine determination of the length measurement.

The rough position is determined with the MT track, ie in which of the ST track fields the corresponding scanners are located. For this purpose, the above-mentioned sequential code is scanned with N scanners (preferably Hall elements) which have a spacing P. Since the borders between the north and south poles are not necessarily equidistant, ambiguous codes can occur in the transition area between the pole divisions. Therefore, the MT track 13 is preferably scanned twice. That is, 2 × N scanners at a distance of P / 2 are used. In this way it is possible to switch between two scanning blocks, so that the active scanner block is always securely seated within a pole pitch P.

Reference list

1

element

2nd

sensor

3rd

management

4th

Evaluation unit

5

Display

6

Magnetic tape

7

duct tape

8th

surface

9

duct tape

10th

Masking tape

11

Double arrow

12th

Air gap

13

MT code track

14

ST code track

15

Scanner
P pole pitch
N bit width
ML measuring length
B total width of the element

1

Claims (11)

1. Device for length measurement with an element ( 1 ) which contains path information, characterized in that the path information on the element ( 1 ) encodes and the element ( 1 ) is assigned a sensor ( 2 ) for detecting the path information. 2. Device according to claim 1, characterized in that that the coding is magnetic. 3. Device according to claim 1 or 2, characterized characterized in that the element is a ribbon. 4. Device according to one of claims 1 to 3, characterized in that the sensor ( 2 ) is connected to an evaluation unit ( 4 ). 5. The device according to at least one of claims 1 to 4, characterized in that on the element ( 1 ) at least two code tracks ( 13 , 14 ) are provided. 6. The device according to claim 5, characterized in that the code tracks ( 13 , 14 ) run parallel to each other. 7. Apparatus according to claim 5 or 6, characterized in that an ST code track ( 14 ) is magnetized alternately with north and south poles. 8. Device according to one of claims 5 to 7, characterized in that an MT code track ( 13 ) is magnetized with a cyclically sequential code. 9. Device according to one of claims 5 to 8, characterized in that the sensor ( 2 ) scanner ( 15 ) for each code track ( 13 , 14 ). 10. The device according to claim 9, characterized in that two scanners ( 15 ) are provided for the ST code track ( 14 ). 11. The device according to claim 9 or 10, characterized in that a number of scanners ( 15 ) is provided for the MT code track ( 13 ), which corresponds to twice the bit width (N).