this can include very brief interruption of battery power due to mechanical shock or
vibration.
REC
may accompany a
CHG
timestamp if the logger’s non-volatile status indicates that
it should be sampling. The date/time in the logger’s real time clock is corrupted, but the
logger makes an attempt to reconstruct a valid setting as nearly as possible, using data
already recorded in the memory. The result will not be exactly correct, but at least
allows the logger to continue collecting data, while the timestamp alerts the user to a
possible problem with the sample times. It may later be possible to reconstruct the true
sample times by correlating the data with an external influence at a known time
There is also an event stamp which routinely appears in user data, but only in a TWR
data logger which is used for recording wave bursts.
BST
indicates the start of a recorded wave burst in a TWR data logger. Wave bursts
are a special case, with some differences when compared to other stored data. Each
individual reading is still stored as a 3-byte, 24-bit number, with the most significant byte
first. However, there is not a reading from every channel in the logger within the burst;
a burst contains
only
readings from the pressure channel. The number of readings
present will be the wave burst length. The time between the readings within the burst is
determined by the wave burst sampling rate.
The wave burst is usually followed by a timestamp to ensure synchronization of the
following data. This will typically be for tidal averages, in which the stored data reverts
to its normal format of one reading per channel, until another wave burst occurs.
The remaining timestamp types are much less common, and may be associated with
one of a number of rare faults or unusual situations.
RTC
shows that the RTC date/time was changed, in a way which may affect the sample
time sequence. It is always accompanied by
TIM
timestamps showing the date/time
both before and after the change was made, and a synchronizing timestamp with the
sample data if necessary. This is not commonly seen, because RBR software does not
permit date/time changes while the logger is sampling.
LUK
indicates a system restart, in which the internal real time clock contained a valid
date/time, but one or more of the programmed parameters was not valid. Non-volatile
storage of the programmed parameters is normally very robust, and this is not a
common occurrence.
November 5, 2010
Rev1.4
56
