> ------------------------------------- > The article has a good picture of the "cercle repetiteur", which > also appears > on page 41 of L'Aventure du Metre, but I can not figure out how > it works. > Somebody, tell me how it works; what is repeated? > > Robert Bushnell
Robert: He doesn't explain it at all well in the book, and I'm sure I don't completely understand it. Here goes, though: The two scopes on the repeater are focused on separate targets, then locked in place on the graduated circle. The angle between the scopes, as shown on the circle's graduated scale, is noted. The circle is then rotated to the right, so that the scope that initially focused on the lefthand target is now focused on the righthand target, and the angle between them is maintained. The new reading is noted as well. The other scope is then decoupled and turned back to focus on the lefthand target, and the first step is repeated. Doing this several times produces a cumulative reading of the angle separating the two targets, and that number is then divided by the number of repetitions. The final result is therefore an average. According to Alder, "This method has the advantage of reducing the uncertainties inherent in any single angle observation and of minimizing the impact of irregularitiews in the manufacture of the calibrated gauge." Got it? David Owen
