MoTeC SDL - Manual (Page 8)

6 Overview
When the logging memory is full the SDL begins to overwrite the oldest data,
which ensures that the most recent data is always available. This is referred
to as cyclic logging.
Power
The SDL power can be turned off at any time without losing the logged data.
The SDL uses FLASH memory which does not require an internal battery to
keep it alive.
Logging Rate
The SDL can store any value at up to 200 times per second, which can be
individually set for each logged item.
The rate at which the values are logged is very important – the value must be
logged fast enough to record all variations in the reading. If the value is
logged too slowly then the readings can be totally meaningless. For example
suspension position normally needs to be logged at 100 times per second or
more.
Note, however, that if a value is logged faster than necessary it will not
improve the accuracy of the logged data, it will just reduce the total logging
time available. For example, the engine temperature only needs to be logged
at once per second.
Logging Time
The maximum logging time is dependent the number of items logged and the
rate at which they are logged. The configuration software will report the
logging time, taking these factors into account.
Logging Rates
The logging Rate may be individually set for each value between 1 to 200
times per second.
Start and Stop Logging Conditions
Two options are provided; the default is to log data while the engine is
running. The condition is to start when Engine RPM >= 200 rpm for 2
seconds. Logging will stop when Engine RPM < 200 rpm for 20 seconds. This
requires that the Engine RPM channel is present in the configuration.
The alternative is to specify start and stop logging conditions to suit the
application. For example logging might start when the vehicle exceeds 50