Position measuring apparatus with multiple scanning locations
AssigneeDr. Johannes Heidenhain GmbH
InventorsAlfons Ernst, Walter Schmitt, Norbert Huber
Life of this patent
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Abstract
A measuring device is provided in which a graduated plate is scanned in at least two scanning locations. The scanning signals from the different scanning locations are transmitted to a testing circuit which determines whether the phase displacement between the scanning signals exceeds a limit value. If the limit value is exceeded, one of the scanning locations is weighted higher than the other. The weighting is implemented by increasing the components of the signals from one scanning location while decreasing the components from the signals from the other scanning location.
Claims7
In a position measuring apparatus including a measurement embodiment, and a plurality of scanning devices arranged to scan said measurement embodiment at a plurality of different scanning locations, each of said scanning devices generating scanning signals corresponding to each of said scanning locations, wherein the improvement comprises:
- evaluating circuit means including a testing circuit for evaluating said scanning signals from said scanning locations and detecting the occurrence of predefined conditions from said scanning signals;
- and
- weighting means for unequally weighting said scanning signals from said different scanning locations when said testing circuit evaluates said scanning signals and detects the occurrence of at least one of the following conditions (a) the phase displacement between said scanning signals from said different scanning locations exceeds a predetermined tolerance range, and (b) the amplitude of the sum of the signals from said different scanning locations exceeds a predetermined tolerance range.
Dependencies are inferred from the claim text.