Q. An automatic or self-winding watch in which energy comes from winding a spring automatically as a result of natural motion of the wearer's arm. This makes manual winding unnecessary. It does not use a battery.
My automatic watch has an analog meter on the face or dial that is linked to the spring. As the spring is wound, the dial on the meter mechanically moves from ‘0' to ‘40' indicating how much reserve time (in hours) the spring can keep the watch going. Can I use this watch on Shabbos?
A. Most Poskim forbid winding a mechanical watch on Shabbos mainly because it is considered "fixing a vessel," or, according to the Chazon Ish, also an act of "building." In the case of a wound and ticking watch, neither of these reasons applies, therefore Da'as Torah 338:3 writes that the custom is to be lenient. However, Mishna Berura (338:15) is stringent even regarding the winding of a ticking clock, unless there is an urgent need. This is the accepted custom today (see Shemiras Shabbos Kehilchasah 28:19).
Self-winding watches are different mainly because you don't specifically have intention to wind them as you move your hands, therefore many Poskim permit the use of self-winding watches, while they are still working (see Shemiras Shabbos K'hilchoso 28:28).
However in your particular case where there is an added analog monitoring device that changes numbers as the watch is moved, the opinion of Horav Shlomo Miller Shlit"a is that one should avoid wearing it on Shabbos (It would become muktze too).
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a
Important Numbers
