[Shimmer-users] SD Log Firmware: Synchronisation Help

[chin w.h. (whc1g10)]

Hi all,
In the SD Log Firmware User Manual (Section8.1, page 25), is there a numerical mistake for the timestamp column in the second table (center table) of Figure 3?
Shouldn't it starts with 67916 and followed by 68756 (instead of 67196, 68556 as printed in the manual) Can anyone confirm this?

Also, does anyone know how to determine the interval of the offset? (i.e, in the example of page 24, Figure 2, why starts with -1010.44 for the offset? why is the starting value not -1010.0?)

Any help is much appreciated. Thanks

Best wishes,
Ken

[Niamh O'Mahony]

Hi Ken,

There is a typo in Fig. 3 - the first entry of the column you refer to
should read 67916. The other values in that column are correct. Thanks for
pointing this out. Also, the second element of the Timestamp column in
Figures 1 - 3 should read 3020 (instead of 3220).

The offsets are determined by calculating a linear fit to the available
timestamp and offset data; e.g. use a least square error criterion to
estimate a and b, for y = a*x + b (with x -> timestamp and y -> offset). In
the example, the offset of -1010.0 corresponds to a message time of 3660.
The first sample in the right-hand column of Figure 2 has a timestamp of
2380 (occurring before the first offset message). Thus, after calculating a
linear fit to all of the offset datapoints, the estimated value for a
timestamp of 2380 is -1010.44.

I hope this helps to clear up any confusion.

Best regards,
Niamh

-----Original Message-----
From: shimmer-users-***@eecs.harvard.edu
[mailto:shimmer-users-***@eecs.harvard.edu] On Behalf Of chin w.h.
(whc1g10)
Sent: 16 June 2013 21:34
To: shimmer-***@eecs.harvard.edu
Subject: [Shimmer-users] SD Log Firmware: Synchronisation Help

Hi all,
In the SD Log Firmware User Manual (Section8.1, page 25), is there a
numerical mistake for the timestamp column in the second table (center
table) of Figure 3?
Shouldn't it starts with 67916 and followed by 68756 (instead of 67196,
68556 as printed in the manual) Can anyone confirm this?

Also, does anyone know how to determine the interval of the offset? (i.e, in
the example of page 24, Figure 2, why starts with -1010.44 for the offset?
why is the starting value not -1010.0?)

Any help is much appreciated. Thanks

Best wishes,
Ken
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