DE8906663U1 - Device for measuring length and angle - Google Patents

Description

Device tension IfHnoen— or angle measurement

The invention is directed to a device for measuring length or angle, which is designed primarily for battery operation for use "on site" and is provided with an optoelectronic scanning device and a measuring body that can be moved past it and which carries a scanning pattern for modulating light that is sensed for evaluating the body position for measuring purposes.

A well-known hollow tape measure of this type (DE-OS 33 9f> 13?) is equipped with a slactronic circuit which, by means of a scanning device, detects markings applied to a measuring tape that can be pulled out of the tape housing. A pulse shaper or trigger connected downstream of the scanning device generates a pulse sequence corresponding to the markings, which are added up in a counter connected downstream. The sum of the pulses, which represent the length of the measuring tape pulled out, is transmitted to a display device and displayed by this in a viewing window on the tape measure housing. With such measuring devices, there is a considerable need to design them as handy, portable devices that are suitable for field use "on site", with the power supply being provided by one or more batteries.

This gives rise to the problem underlying the invention, namely to be able to optically record a scanning pattern marked on a measuring tape, measuring tablet or disk with minimal power consumption in reflected or transmitted light and at the same time to achieve a high measurement resolution. To solve this problem, according to the invention, in a device with the features mentioned at the beginning

It is proposed that the scanning device is connected to a sequence control which, in time with the scanning period, activates one or more light sources simultaneously to irradiate the scanning pattern within a scanning period which corresponds at most to the time required for the light sources and associated photo sensors to oscillate and for their interrogation.

In optoelectronic scanning of surface-imaged

In order to produce an image pattern, it is generally unavoidable to expose it to a light stream from a light source or photoemitter. The photoemitter in particular is characterized by a relatively high energy or power consumption in order to be able to emit light of sufficient intensity. According to the invention, this unfavorable fact is counteracted by the fact that the scanning is carried out within regularly recurring scanning intervals (preferably scanning periods), whereby the photoemitter is activated to emit light within a scanning period that is chosen to be as short as possible compared to the scanning period. In other words, the photoemitter is only activated by the sequence control to emit light for as long as is necessary to achieve a reliable scanning result. This results in an extremely short period of time in which the photoemitter consumes (battery) energy compared to the length of the scanning interval after which the irradiation of the surface image pattern with light begins periodically. As a result, a number of parallel light sources can be used, along with associated photo sensors or detectors, without drastically increasing the power consumption for optoelectronic scanning.

An advantageous development of the invention consists in the fact that the sequence control is connected to the output of the photoelectric sensor and/or - in the case of battery operation - to the battery and the sampling duration and/or sampling period duration varies depending on the output level (that of the photoelectric sensor or the battery). In the first alternative, the output level of the photodetector itself serves as a measure for the length of the sampling duration; this is stretched until a stable, clear output signal is present at the output of the photodetector. This represents a practical implementation option in order to keep the sampling time as short as possible. The second alternative (battery operation) addresses the problem that as the energy stored in the battery is consumed, the control power that can be derived from it for the light source or photoemitters decreases. This results in a delay in the transient response of the light detector or photosensor. Through the above-mentioned further development, the sampling time can now be extended (if necessary) until a stable or at least processable output signal is available at the output of the finally steady-state light sensor. Overall, this achieves an adaptive control of the sampling time, whereby available energy or power resources play a significant role.

Adaptation or control parameters.

In order to supply the output signals of the photo sensors to the storage and evaluation unit only in their stable, steady state, in a further development of the invention the query of the photo sensors is carried out with a delay compared to the time of activation of the light sources by a period of time which corresponds to the swing-in time of the photo sensors.

eneotechnik. In terms of circuit technology, this is realized in that the sequence control generates a first pulse signal to activate the light sources (activation pulse) and a second pulse signal to query the photo sensors (query pulse) in such a way that the query pulse begins with a time delay compared to the activation pulse that corresponds to the settling time of the photo sensors. In a special development of this idea, the query pulse is generated within the time window formed by the activation pulse and ends at the same time as the activation pulse. This allows the query pulse to be conveniently derived from the rising or falling initial edge of the activation pulse for the light source.

It is within the scope of the invention that the sequence control is connected on the input side to a clock generator for generating the sampling period. In order to bring about an orderly interaction between the sequence control, the optoelectronic scanning device and, if applicable, the downstream storage and evaluation electronics or unit, the latter should be synchronized in time with the sampling intervals. Accordingly, one embodiment of the invention consists in the fact that the photo sensor system is followed by a storage and/or evaluation unit, which is controlled by the sequence control in time with the sampling period to query the photo electronics.

In order to make the measurement result quickly and precisely visible to the user, the measuring device according to the invention is provided with a liquid crystal display that is controlled by the storage and/or evaluation unit. The advantage of using liquid crystal displays is their extremely low energy consumption.

A cost-effective and technologically practical implementation of the scanning device consists in the fact that it has known optocouplers, each of which consists of light-emitting diodes and phototransistors assigned to them. The special development of the phototransistor into a Darlington transistor circuit has the advantage that a sufficiently high current is available at the light sensor or photoemitter designed in this way in order to be able to directly control downstream electronic units, possibly connected in parallel, in particular inputs of the storage and evaluation unit.

A structural implementation of the invention, which above all enables easy handling, consists in the measuring body being designed as an angle-adjustable disk or as a flexible measuring tape or rigid measuring rod - each adjustable relative to a device housing - and its scanning pattern being angle- or length-coded. This is done expediently by arranging several tracks next to each other in parallel, each corresponding to a binary position of digital code words, with an opto-coupling device consisting of a light source and photoelectric devices being assigned to each track, which are each controlled in parallel by the activation output of the sequence control or queried by the corresponding inputs of the storage and evaluation unit. In this arrangement, several parallel bits of code patterns with a processing width are scanned, with each opto-coupler being assigned a different bit. B. flat scanning or code mast. It is exposed to light from the photo emitter and the photo detector or sensor reacts to the light modulation.

tion behavior of the sample area with a corresponding output signal. By connecting the control inputs of the light sources in parallel to the sequence control that feeds their control signals, and querying the outputs of the light sensors from the storage and evaluation device at the same time (in parallel), circuitry, and above all copper and cable expenditure, is saved. When querying the outputs of the sensors optically coupled to the light source in multiplex operation,

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A narrow, elongated device housing is naturally desirable, especially for length measurement. Due to the large number of coded scanning tracks running next to one another on the measuring body, the opto-couplers assigned to these must also be arranged next to one another in a corresponding manner, each with a light source and photosensor. This raises the problem that the length measuring device becomes wide and unwieldy. This is counteracted by a particularly advantageous embodiment of the invention in that the scanning tracks are offset from one another in their longitudinal direction by a distance which corresponds to the spatial distance of the light sources and/or photosensors. For example, the tracks are alternately offset or not offset, with the second, fourth, sixth, etc. track starting in the longitudinal direction, so that the assigned opto-couplers can be arranged in two rows one behind the other in the longitudinal direction.

30

A version of the length measuring device according to the invention which is particularly suitable for manual applications consists

in that one or more measuring tongues that can be pulled out from the device housing are designed as the measuring body, the scanning φ patterns of which represent absolute coding of the extension length - preferably ff in the binary-coded decimal system (BCD). An exemplary, practical implementation of this is that one measuring tongue can be pulled out at each of the opposite ends in a common housing.

When used specifically as a length measuring device, the

The length of the device housing must be taken into account when calculating the measurement result. It is also desirable to be able to display the length measurements that are often different in different countries on a display as required. For this purpose, the device according to the invention is provided with a calculator for adding a fixed value to the measurement result derived from the position of the measuring body and/or for converting and, if necessary, displaying the measurement result in different length or angle measurements. The fixed value can then correspond to the length of the device's base housing and be added up. Commercial calculators, e.g. customer-specific logic circuits or microcomputers, can easily be influenced by an external switching device so that they can convert the measurement coding of the scanning pattern into centimetres or

Convert inch measurement.

The range of uses is increased if one or more spirit levels are provided in a housing wall to form a spirit level. If the measuring device according to the invention is provided with a display for the measurement result, it is particularly advantageous to arrange at least one spirit level in the immediate vicinity of the display.

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In connection with the above-mentioned absolute coding of the extension length, the advantage remains that the initial withdrawal no longer has to be scanned optoelectronically and taken into account in the processing electronics; instead, a measuring body can be adjusted and only then the supply voltage for the scanning and evaluation electronics can be switched on - which - due to the absolute coding - can clearly detect and process the measuring body adjustment. In the context of the invention, the tracks bz·*. Max-correction running next to each other correspond to x parallel bits of a digital code, whereby they binary modulate the light emitted by the light source during the scanning time, e.g. reflect or not reflect or let through or not let through. The modulation result reflecting the measuring body position is detected and passed on by the light sensor.

Important features, details and advantages of the invention emerge from the following description of a preferred embodiment of the invention and from the drawing. Here:

Fig. 1 a basic block diagram of the

optoelectronic circuit used in the measuring device according to the invention,

Fig. 2 a pulse diagram of the associated sequence control,

Fig. 3 an embodiment of an optoelectronic scanning unit (optocoupler) for reflex operation,

• » · t

Fig. 4 a timing diagram of the input/output behavior of this sampling unit,

Fig. 5 an example of a scanning pattern with absolute coding of the heg length,

Fig. 6 is a perspective view of a length measuring device designed according to the invention,

IC Fig. 7 a sectional view along the line A-A in Fig. 6,

Fig. 8 a cutting position according to line B-B

in iUg. 7,
15

Fig. 9 in plan view with the broken-off part of the length measuring device according to Fig. 6, and

Fig. 10 shows an enlarged view of the partially extended measuring tongue according to

Fig.9.

According to Fig. 1, a clock generator 1 outputs a rectangular clock signal to a sequence control 2, the period duration of which corresponds to the sampling period duration T (see Fig. 2). Synchronously with the clock signal, the sequence control 2 generates a first pulse signal with the time duration t± at a first output 16 and a second pulse signal with the time duration t ₂ at a second output 17. In the example, the inputs of twelve optical scanning units 3, for example photoelectric optocouplers, are connected in parallel to the first output 16.

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They are therefore activated by the first pulse signal with the duration t _x . The twelve outputs 4 of the sensor parts of the optical units 3 are each connected to an input 5 of the storage and evaluation device 6, so that a parallel, i.e. simultaneous, reading of the sensors in the optical units 3 by the storage and evaluation devices β is possible. A control input 7 of the storage and evaluation device 6 is connected to the second output 17 of the sequence control 2, which supplies the second pulse signal with the duration t ₂ . The second pulse signal has the function of controlling the storage and evaluation device 6 to query the outputs 4 of the optical units S-. A preferably digital display device 9 is controlled via an output 8 of the storage and evaluation device 6, the display of which shows the scanning result of the optical units 3.

The optical units 3 are essentially formed as optocouplers from a photoemitter (light source) and a photodetector or sensor that senses its light beam (see Fig. 3). This is indicated in Fig. 1 as an example for the optical units 3 numbered I and XII by means of oblique arrows, the course of which corresponds to the path of the emitted light from a carrier medium 10 for optical codes to the

photodetector reflected light.

In Fig. 2, the respective course over time t of the square wave signal output by the clock generator 1 with the period duration T and the first and second pulse signals output by the sequence control 2 with the durations tj and t ₂ are shown. Accordingly, with each falling edge 11 of the square wave signal from the clock generator 1, the Bo-

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ginn (starting edge 12) the first impulse signals from the
Sequence control 2 is initiated. This pulse signal has the duration tj. From the rising initial edge 12 \

derived and delayed by the time te ., the rising initial edge 13 of the second pulse signal

the sequence control 2. The second pulse signal has the duration t ₂ · According to Fig. 2, the first pulse signal t^ and the second pulse signal t ₂ end at approximately the same time, and the latter begins in the time window of the first pulse signal
.10t1 _.

As schematically outlined in Fig. 3, an optical unit 3 consists essentially of a light source 14, in the example shown a light-emitting diode, and an optical

Sensor 15, as shown, for example, a photo

Darlington transistor. The light source 14 sends light to the carrier medium 10 (shown in section) according to the dashed line for a scanning pattern; the light incident on the carrier medium 10 is - depending on the coding - either

reflected or absorbed. When reflected, it essentially reaches the optical sensor 15 as shown by the dashed line, which generates an output signal in response.

According to Fig. 4, the optical sensor has a
Input signal Ue of the light source delayed response. This results in a delay time te, which the optical sensor needs to oscillate according to the input signal of the light source. The input signal

Ue of the light source with the pulse duration t^ is, as above
executed from the first output 16 of the sequence control 2
(see Fig. 1). After the delay time te

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t ff ♦ ·

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the output signal of the optical sensor, influenced by the coding of the scanning pattern on the carrier medium 10, is stable until the pulse duration t^ has ended. This period is marked in Fig. 4 with t ₂ and corresponds approximately to the pulse duration of the signal from the second output 17 of the sequence control 2, which is fed to the control input 7 of the storage and evaluation device 6 (cf. Fig. 1 and 2). The pulse duration t ₂ is dimensioned such that the storage and evaluation device 6 - according to Fig. 1 - can reliably read the output 4 of the optical signal 3 in parallel.

In Fig. 5, a scanning pattern is shown in sections which is imaged flatly on the carrier medium 10, which e.g.

B. in the BCD code can form a scale for measuring length. Such a carrier medium 10 can serve as a measuring tape for a tape measure, as is disclosed, for example, in the DE-OS 33 26 137 mentioned at the beginning. The processing width of the BCD code is - to simplify the drawing - limited to ten parallel bits in the example shown. These form ten parallel tracks I' - X' running side by side, each of which - when expanded to twelve �Ogr;«««« T' _ VTT' _ vnn olnom Hoi- OntnVonnler T — XII CremHß

Arrangement according to Fig. 1 can be scanned. The scanning takes place here in reflection mode. If a light beam from the light source falls on a part of the BCD-coded area on the carrier medium 10 that remains bright (white in Fig. 5), the incident light is reflected back to the optical sensor. This then generates an output signal Ua according to Fig. 4. If, conversely, emitted light falls on a light-absorbing part within the coded area,

Before this, no reflection to the optical sensor takes place, so that it does not react with an output signal as shown in Fig. 4.

The optoelectronic circuit arrangement just explained is, according to the invention, inserted or housed in a length measuring device 20 within its elongated outer housing 21 (cf. the box housing 22 for housing the scanning device in Figs. 7 and 9). To pick up a length to be measured, a lifting tongue 23 is arranged so that it can be pulled out at each of the two opposite ends of the outer housing 21. Raised above the rest of the surface of the outer housing 21 is a toggle switch 24 to start the scanning and evaluation electronics, adjacent to this is a display 25 to show the length measurement result, and immediately adjacent to the latter is a spirit level to form a spirit level. As can be seen in particular from Figs. 7 and 8, the measuring tongues 23 are mounted so that they can be moved in the longitudinal direction 28 by means of roller bearings 27.

Above the broad sides of the measuring tongues 23 are

Box housing 22, which contains the opto-couplers or other optical scanning units 3 or I - XII according to FIGS. 1 and 3

Due to the arrangement according to Fig. 9 and 10, the scanning units I - XII or opto-couplers 3 can apply light to the upper broad side of the measuring tongues 23, which are provided with a scanning pattern (I' - XII') for light modulation. The scanning pattern corresponds in principle to that shown in Fig. 5, but has the following differences: The binary positions for the digital absolute coding representing tracks I', II', III' etc. are

alternately offset from one another in the longitudinal direction 28, in that the ones with even Roman reference numbers II'/ IV, VI' etc. are offset by the distance s (see Fig. 10) in the direction of the center of the outer housing 21. Accordingly, according to the front view of Fig. 7, the scanning units or opto-couplers II, IV etc. assigned to the offset tracks II', IV etc. are arranged in the second row behind the scanning units I, III, V, VII etc., each named with an odd Roman numeral, i.e. in the first row. This advantageously allows the total width b of the outer housing 21 (see Fig. 8) to be limited to a size that is convenient for handling.

Claims (15)

Protection claims 1. Device for measuring length or angle, in particular in battery operation, with an optoelectronic scanning device and at least one measuring body which can be moved past it and which carries a scanning pattern for modulating light which is sensed to evaluate the position of the measuring body for the measurement result, characterized in that the scanning device (I - XII) ; is connected to a sequence control (2) which, in the If cycle of the scanning period (T), activates one or more |! light sources (14) simultaneously to irradiate the fu scanning pattern (I' - XII') within a scanning period pj (tjj) which is at most the necessary time Id (t _e , t ₂ ) for the oscillation of the light sources (14) together with the associated photo sensors (15) as well as for their query (5, 6). 2. Device according to claim 1, characterized in that the sequence control (2) is connected on the input side to the output of the photo sensor and/or - in the case of battery operation - to the battery and the sampling duration (t^) and/or sampling period duration (T) varies depending on the output level of the latter. 3. Device according to claim 1 or 2, characterized in that the sequence control (2) generates a first pulse signal (t ₁ , 16) for activating the light sources and a second pulse signal (t ₂ , 17) for querying the photosensor system (15) in such a way that the query pulse (t ₂ , 17) begins with a delay compared to the activation pulse (t _1# 16) by a time which corresponds to the transient response time (t _e ) of the photosensor system (15). • · · · i · · · · tll IM · * t · · t · ti Ii &igr; : , &igr; • · · · · · ·· Il Il I • · ♦ « ··· ti 4. Device according to claim 3, characterized in that the interrogation pulse (t ₂ , 17) is generated within the time window (tjj) formed by the activation pulse (tj_, 16) and ends simultaneously with the activation pulse (t _x , 16). 5. Device according to one of the preceding claims, characterized in that the sequence control (2) is connected at the input to the clock generator (1) compartment pearling time (T). 6. Device according to one of the preceding claims, characterized in that the photo sensor system (15) is followed (5) by a storage and/or evaluation unit (6) which is controlled (7) by the sequence control (2) in time with the sampling period (T) to query the photo sensor system (15). 7. Device according to claim 6, characterized in that a liquid crystal display (9, 25) is connected downstream (8) of the storage and/or evaluation unit (6). 8. Device according to one of the preceding claims, characterized in that the light sources are implemented by means of light-emitting diodes (14) and the photosensors are implemented by means of phototransistors (15) each associated with a light-emitting diode. 9. Device according to one of the preceding claims, characterized in that the measuring body is designed as an angle-adjustable disc or as a flexible measuring tape or A rigid scale (23) - adjustable relative to a device housing (21) - is implemented, and its scanning pattern (I' - XII') is angle- or length-coded.
5 10. Device according to claim 6 and claim 9, characterized in that the scanning pattern (I' - SII') has a plurality of adjacent tracks (I', II', etc.) which each correspond to one unit of digital code _words and that j' of a track (I', II' etc.) of a light source (14) and a photo sensor (15) e£r*d, each of which is connected in parallel to the activation (16) asu: sequence control (2) controlled or queried by corresponding inserts <5) of the storage and evaluation unit (?) . 11. Device according to claim 10, characterized in that the 3 traces (I', II' etc.) are offset from one another in their longitudinal direction (28) by a distance (s) that corresponds to the spatial dimensions of the light sources and/or photo sensors (I - XII). 12. Device according to one of the preceding claims, for length measurement, characterized in that one or more measuring tongues (23) which can be pulled out of the device housing are provided as the measuring body, the scanning patterns (I' - XII') of which represent absolute coding of the extension length, preferably in the binary-coded decimal system (BCD). 13. Device according to one of the preceding claims, characterized by a calculating unit for adding a fixed value to the value determined by the measuring body position ■ · · derived measurement result and/or to display the measurement result in different length or angle dimensions. I5 14. Device according to one of the preceding claims, characterized by one or more in a housing wall f inserted spirit level vials (26). 15. Device according to claim 14, characterized in that 10 at least one spirit level (2G) in the immediate vicinity of a display (25) for the measurement result ¹ is embedded.