Storage scopes can be set to record negative time from the trigger point so no need to estimate anything. :) The thing I remember though was that the delay changed with the record length and I had to change the record length to get the full 2 sec to 1/500 sec. Cumbersome. Also by measuring the "power" of the trace would get the integration for the value under the trace. By measuring the maximum voltage of the original and calculating the same area with perfectly straight ideal edges the actual time could be found. Andy On Jan 28, 2011, at 3:20 PM, David Dyer-Bennet <dd-b@xxxxxxxx> wrote: > > On Fri, January 28, 2011 13:46, Andy wrote: >> I did this to measure the shutter speed of my LF copal shutters. It worked >> very well and has been useful a number of times. While the lens is in >> spec, I measured almost a half stop error at the fastest shutter speeds. >> It also showed that they become more repeatable after 3 or 4 practice >> exposures. Such is life with old mechanical devices. >> >> the tricky part was to set the trigger on the o-scope and determining the >> area under the curve as this is the only way to measure all of the light. > > Cut out along the trace, and weigh the bit you cut out. Another lovely > lovely old trick for getting quite good approximations to things that are > fairly hard to do with high precision. > > -- > David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ > Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ > Photos: http://dd-b.net/photography/gallery/ > Dragaera: http://dragaera.info >
