| 摘要 |
The relative position of two elements is measured by reading a coded strip (11) fixed to one of the elements. The strip (11) carries code elements in a pseudo-random binary sequence (PRBS) which can be read by a photo-detector array (15). The array (15) and suitable optics if necessary enable enough successive code elements of the PRBS to be read simultaneously to identify the position along the PRBS. The array (15) has several detecting elements for each code element or bit of the PRBS, so that the fine position of transitions or markings of the PRBS can be measured within one PRBS bit length. A comparator (17) compares the output of the array (15) with a portion of the PRBS from a PRBS generator (21). The generated PRBS is serially shifted through a register (18) and a counter (22) stores the number of shifts needed until a match is found. Applications are described in micrometers, pressure sensors, shaft encoders and others. |
