Abstract: A system for removing trapped air layers is disclosed for use in a measuring apparatus such as a length measuring apparatus for measuring dimensions of a test object supported on a measuring surface. According to this invention, the measuring surface defines in the region beneath the resting surface of the test object a plurality of openings which are connected to a source of subatmospheric pressure in order to draw off any trapped air layer present between the measuring surface and the resting surface of the test object. In the illustrated embodiment, these openings are connected with an external suction line by means of channels defined in the measuring table.

Abstract: The disclosed guide device utilizes no rigidly mounted external guide elements. However, a guide element freely slidable on an air cushion on a flat base can be lowered from the interior of a slide element (by removal of the air cushion) onto the base. Once the guide element has been lowered, it is fixed by subpressure onto the base and takes over the function of a rigidly mounted guide. The guide element, which was previously freely slidable on the base, is now exactly positionable along the guide of the guided element. If the displacement path is to be increased, then the slide piece element is fixed by subpressure on the base, the guide element is again acted upon with compressed air and driven within the slide piece in a displacement direction and at the end of the interior space is again fixed to the base. Now the slide piece is again released and can on its air cushion be further positioned exactly in the displacement direction. This stepwise movement is limited only by the size of the base.

Abstract: A photoelectric measuring apparatus includes a measuring scale and a scanning unit including at least one photosensitive element for generating a scanning signal in response to light incident on the scanned region of the scale. First and second light sources are included, as well as a mechanism for selecting either of the first and second light sources such that light from the selected light sources is directed at the scanned region of the scale. A slider mechanism, a turntable, a movable mirror, or a movable prism can be used to select either the first or second light sources. In addition, a circuit is disclosed which provides separate first and second balancing circuits for the respective light sources, such that rebalancing the measuring instrument is not required when the selecting mechanism is used to select a different light source.

Abstract: An inductive measuring device comprises a rotor and a stator, each of which has an electrical conductor mounted thereon. Opposed grooves are formed in the conductor side of the stator and the rotor, the slip rings and contact brushes are mounted in respective grooves such that both the slip rings and the contact brushes are mounted internally between the rotor and the stator, thereby protecting the slip ring and brushes from damage and fouling and reducing the size of the measurement device and the need for external adjustment.

Abstract: A longitudinal measuring instrument, preferably with digital path coverage, which is constructed according to the Abbe principle. The measuring instrument includes a stationary scale, a displaceably mounted scanning unit for scanning the scale, and a measuring spindle sleeve mounted on the scanning unit, said measuring spindle comprising at least two bars which surround the scale.