| 摘要 |
<p>The apparatus and method are able to concentrate the metrological core in a limited-size single piece of equipment, a bislider, for locally interpolated differential error recovery. A bislider is a low CTE spacer keeping two read-heads (2, 4) at fixed and invariant relative distance; when the bislider slides over the scale (1), two signals are produced by the read-heads. If required, thermometers may be applied to connections (6) for the compensation of the bislider expansion. The goal of the apparatus is to stabilize the scale measurements over time, in spite of possible thermo-mechanical (local or general) expansion / contraction of the linear encoder line grating spacing, by a method according to which the differences are recorded of simultaneous readings yielded by the two read-heads when the bislider is at positions where both readings are nominally multiple of the bislider length. These values permit the performing of a recovery procedure periodically, or when significant variations due to e.g. thermal drift are suspected. The recorded X2-X1 values, the resulting recovery values, and the difference between recorded and recovery values, are registered in suitable look-up tables.</p> |
