Digital electrical length or angle measuring device

• US 4,412,206 A
• Filed: 09/18/1980
• Issued: 10/25/1983
• Est. Priority Date: 09/21/1979
• Status: Expired due to Term

• Current Assignee: Dr Johannes Heidenhain GmbH
• Original Assignee: Dr Johannes Heidenhain GmbH
• Inventors: Schwefel, Ernst
• Primary Examiner(s): Sloyan, T. J.
• Application Number:
  US06/188,276
• Time in Patent Office: 1,132 Days
• Field of Search: 340/347 M, 340/347 P, 250/231 SE, 250/237 B, 371/51
• US Class Current: 341/2
• CPC Class Codes: H03M 1/26 with weighted coding, i.e. the weight given to a digit depends on the position of the digit within the block or code word, e.g. there is a given radix and the weights are powers of this radix

Abstract

A digital electrical length or angle-measuring device connects digitalized scanning signals of at least one coarser revolution code group to first addressing inputs of one or more fixed value stores containing binary-stored calculated variants of the digitalized signals in form of tables, and the variants are alternately connected to outputs of the store in dependence upon the logical condition of the control signal which is derived from the respective higher resolution code groups and which is connected to a second addressing input of the store.

Claims

1. Digital electrical measuring device, particularly an absolute measuring device with means for scanning at least one value representation with code groups of different resolutions and with means for adding unambiguously higher resolution code groups to coarser resolution code groups, wherein the improvement comprises means for connecting digitalized scanning signals (code values CW) of at least one coarser resolution code group (C₂ -C_n) to first addressing inputs (SE) of at least one fixed value storage (S) containing integral, non-rounded off, binary-stored calculated variants of such digitalized signals (CW) in tabular form;

and means for alternately connecting such variants of the digitalized signals (CW) to outputs (SA) of said storage (S), in dependence upon the logical state of a control signal which is derived from the respective higher resolution code groups (C₁) and which is connected to a second addressing input (SE) of said storage (S), said variants including (CW+1)/2 for preceding signals and (CW+0)/2=CW/2 for non-preceding signals when the resolution of a higher resolution code group is double the resolution of a coarser resolution code group so that the calculated variants are dependent on a function of the resolution of the code groups, whereby a resolution of N-2 bits is achieved when a coarse resolution code is interconnected with an intermediate resolution code and a fine resolution code.

2. Digital measuring device as defined in claim 1, wherein one-step codes are used.

3. Digital measuring device as defined in claim 1, wherein said measuring device comprises a length measuring device.

4. Digital measuring device as defined in claim 1, wherein said measuring device comprises an angle measuring device.

5. Digital measuring device as defined in claim 2, wherein a parity signal is derived from at least one of the coarser resolution digitalized signals (C₂ -C_n) by double scanning at least one trace and is synchronized by a fine resolution digitalized signal (C₁).

6. Digital measuring device as defined in claim 5, wherein said fine resolution digitalized signal (C₁) has a 1:

1 grid track and two scanning signals are produced which are phase shifted relative to one another by 90°

, a further subdivision being effected by forming of linear combinations.

7. Digital measuring device as defined in claim 6, and further comprising resistance network means operative for forming said linear combinations.