Where to place "log:flush()" without disturbing intervall? 
Why should such a place exist?
The csv log module used in rawpoint accepts 3 buffer_mode values
'os' - output is buffered by the OS, written to the card when the OS thinks it needs to, or when log:close() or log:flush() is called. This is the default.
'table' - output is kept in a Lua table until log:flush() or log:close() is called. May use all available RAM unless the script takes steps to avoid this.
'sync' - output file is opened, written and closed each time log:write() is called. log:flush() is ignored.
The assumption is that 'os' will generally minimize disturbance, since the OS will probably try to write optimally sized chunks. Scripts that do the equivalent of 'sync' have been reported to have much less consistent intervals, which isn't surprising since it would likely involve a lot of writes smaller than an allocation unit on the SD card.
If you have enough memory and don't care about losing everything in a crash, then 'table' would have the minimum impact.
