DE3823992C2 - Benchmark for length measuring devices - Google Patents

Description

The invention relates to a yardstick for lengths measuring devices according to the preamble of Claim 1 (DE 36 20 118 A1).

At the known scale, the temperature of standards above seperate, by the standards fixed temperature sensors and the tempera arithmetic change in length of the scales considered. The construction of the Temperature sensor so solved that discrete platinum resist stands PT 100 built into the scale bracket the. However, this is disadvantageous for several reasons. Because the sensors are not directly at the point of interest namely near the scale division itself be brought and the temperature transition from Scale on the feeler not as fast or off done well enough, this type of approach bring measurement errors arise. Also the tempe rature conductivity for coordinate measuring machines mostly used glass scales relatively bad. It can therefore local temperature gradients in the measure Train the rod with only one or two sensors alone cannot be grasped. This creates in particular Especially with long scales, length measurement errors in not negligible size.

DE 25 07 731 B2 shows Measuring resistors for resistance thermometer, where one thin metallic resistor layer on an insulating Base material deposited becomes.

It is the object of the present invention in a benchmark for linear encoders with probes to measure the temperature of the scale this way to design or attach that the scale temperature is recorded as precisely as possible.

This task is carried out by the im Features specified claim 1 solved.

Achieved by this one that the temperature of the scale exactly at the place of interest is measured. In addition, the Temperature transition from the base material of the measure bes on the sensor directly without any intermediate scarf more or less poorly conducting measures materials. The connection between scale and feeler is also permanently ensured.

The sensors resemble a metal film stands can preferably be evaporated. Chromium, aluminum, for example, come as the material um, nickel or platinum in question. Conventional photo Electrically readable scales are made of glass and have a vapor-deposited chrome partition. This Material is also suitable for the sensor.  

It can be useful several graduation marks of the scale division electrically par to connect allel or in series. By this measure can set desired resistance values for the tempe temperature sensor can be realized and can be used in particular Parallel connection a calibration of the Simply by interrupting the supply line individual tick marks can be made.

Further advantages of the invention will become apparent from the following description of Ausführungsbeispie len with reference to FIGS. 1-3 of the accompanying drawings. The figures each show a different exemplary embodiment of a scale with an integrated temperature sensor. Portions of a scale are shown in each case, with a view of the scale division.

On the scale ( 11 ) shown in Fig. 1 according to an embodiment, individual stri che of the scale division ( 12 ) itself are used as a measuring resistor. As a rule, the graduation marks of a photoelectric incremental scale, as shown in FIG. 1, are a few micrometers, e.g. B. 8 microns wide and consist of a chrome layer of 0.1 microns thick. With a line length of 12 mm, such a scale stroke has an internal resistance of about 2000 ohms.

The scale line ( 16 ) has a slightly longer length than the other scale lines and at the ends in contact fields ( 15 a and 15 b), each of a pair of conductors ( 13 a / 14 a) and ( 13 b / 14 b ) are connected with a much higher layer thickness. Since two pairs of conductors are used for each measuring point, temperature measurement using the so-called four-line method is possible. ie via the conductor ( 13 a / 13 b), the measuring resistor ( 16 ) is supplied with a constant current, while the two conductors ( 14 a / 14 b) are used to derive the temperature-dependent voltage dropping at the measuring resistor ( 16 ). As can be seen from Fig. 1, several re measuring points are realized on the surface of the scale in this embodiment. The other measuring points have the same structure as the sensor described above and are designated in Fig. 1 with ( 17 ) and ( 18 ).

In the scale ( 31 ) shown in Fig. 2 according to a further embodiment also serve as the respective lines of the scale division itself as a measuring resistance. Here, however, several scales are connected electrically in parallel by the two contact fields ( 35 a and 35 b) arranged in the longitudinal direction on both sides of the scale division ( 32 ).

The parallel connection of 20 scale marks made of chrome allows z. B. to reach the usual resistance value of 100 ohms for temperature measurements. The dependency of resistance on the nature of a single scale stroke is also reduced. The parallel connection also makes it possible to deduct the total resistance of the sensor formed from the scale lines ( 36 a- 36 i) by simply interrupting the electrical connection of individual scale lines to the contact fields. This is done, for example, for the scale ( 36 i) at the point marked with the arrow ( 37 ). A comparison of the total resistance may be necessary if not, only temperature changes of the scale, but whose temperature is to be measured absolutely. In the exemplary embodiment according to FIG. 2, the contact fields ( 35 a and 35 b) are again connected to two pairs of lines ( 33 a / 34 a and 33 b / 34 b) in order to be able to measure using the four-wire method.

In the exemplary embodiment according to FIG. 3, all between the two with ( 27 a) and ( 27 b) designated stri surface of the scale division (22) together with two sides of the division ( 22 ) on the scale ( 21 ) extending in the longitudinal direction ( 26 a and 26 b) the measuring resistor. The conductor tracks ( 26 a and 26 b) are electrically connected to one another via the graduation marks ( 27 a and 27 b). The two parallel conductor tracks ( 26 a, b) of the measuring resistor are connected, for example, over 1000 chrome lines of scale scale ( 27 ), which have a total resistance of 2 ohms when connected in parallel. If each conductor track ( 26 a, b) is also made of chrome and has a width of 3.75 mm and a length of 500 mm, its resistance is approx. 200 ohms. The total resistance of the network is then 101 ohms and can be compared very easily and with high precision by interrupting individual lines of the scale division, as indicated by the arrow ( 28 ).

Since the resistance network formed in this way extends over a relatively long area of the division ( 22 ), the temperature measurement value is integrated into this section of the scale ( 21 ). Also in this embodiment example contact fields ( 25 a and 25 b) are provided via which the temperature sensor is connected to the supply line pairs ( 23 a / 24 a and 23 b / 24 b).

Claims (4)

1. Scale for length measuring devices with one or more temperature sensors for detecting the temperature of the scale, the temperature sensors being applied to the surface of the scale, characterized in that individual graduations ( 16 , 17 , 18 , 36 a-i) of the scale division ( 12 , 22 , 32 ) are themselves temperature sensors and these graduation marks ( 16 , 17 , 18 , 36 a-i) are designed as metal film resistors. 2. Scale according to claim 1, characterized in that the metal film resistors on the Surface of the scale are evaporated. 3. Scale according to claim 1, characterized in that several of the graduations used as temperature sensors ( 36 a-i) of the scale division ( 32 ) are electrically connected in parallel or in series. 4. Scale according to claim 1, characterized in that the multiple graduation marks ( 27 ) of the scale division ( 22 ) and metal films ( 26 a, b) extending in the longitudinal direction of the scale form a temperature sensor.