Hi Hristijan, Here is the data sheet for the 32.768kHz crystal on the shimmer: http://www.eea.epson.com/portal/pls/portal/docs/1/1349455.PDF, specifically the Epson FC-135 32.7680KA-A3. So the frequency tolerance is ±20ppm. The data sheet also specifies the additional influence temperature fluctuations has on this. As the timestamp is determined directly from this crystal you should be able to figure you how much it can drift over any specified time period.
Mike On Tue, Mar 6, 2012 at 2:55 PM, Hristijan Gjoreski < [email protected]> wrote: > Hi, > > I have a question about the internal clock inside the Shimmer. > > Our scenario is the following: > > Two shimmers should start logging data into the SD card during a whole day > (16 hours). These data should be synchronized between the two sensors. > I already have a shimmer application that logs the acceleration data and > the LocalTime (Internal clock 32kHz) in each data sample. > Therefore, I have timestamps for the data. > Because I know the starting time of the logging and the internal clock > timestamp, I can calculate the "real time" timestamp of the data sample. > This way I can synchronize the both sensors data. > Am I correct, or I am missing something? > > Will the two sensors be synchronized after 16 hours of working? > In other words, how much will differ internal clocks in both sensors after > working the whole day? > > Thanks, > Hristijan > > ______________________________**_________________ > Shimmer-users mailing list > [email protected] > https://lists.eecs.harvard.**edu/mailman/listinfo/shimmer-**users<https://lists.eecs.harvard.edu/mailman/listinfo/shimmer-users> >
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