If the clocks used for sampling have different frequency (more likely than not) you would get different time number of samples. To verify this you could use the fact that clock frequency usually varies with temperature (check data sheet for used crystal), move one into sunlight another info shadows, wait for temperature to stabilize, measure, switch places, wait and measure again...
/RogerL -- Roger Larsson, Research Engineer Division of Mobile Networking and Computing Luleå University of Technology ________________________________________ Från: [email protected] [[email protected]] för Omar Bouzid [[email protected]] Skickat: den 27 augusti 2010 10:58 Till: '[email protected]' Ämne: [Tinyos-help] Timestamping the start and the end of a sampling process Dear all, After posting my problem to TinyOs mailing list and searching a lot in TinyOs-help and following some hints, I still cannot find a solution to my problem which is described below: I'm using tinyos-2.x and three micaz platforms equipped with MTS310 sensor board and once they receive a start sample command from BS, they will start sample the mic sensor immediately. Each mote timestamps the start and the end of the sampling process in order to compute the sample interval. My question is: Why I always do receive different lengths of sample intervals (for example, with a STDEV of 601.1724757, 325.9728201 and 472.9102405 for the three motes)? First I was using CounterMicro32C component and Counter.get() command to timestamp the start and the end of the sampling process and then I tried to use CounterToLocalTime component as well. But in both cases I still have the same problem. So, please share with me this problem and let me know your suggestions ASAP. Any hint might be useful for me and take me a step forward. Thanks in advance, Omar _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
