What is the technique generally used for timestamping data in datalogger memory?

Hello all

What is the technique generally used while timestamping data in datalogger memory?Is each data timestamped?
Or only the time,say, when the logging starts?And the subsequent time is then calculated based on the logging interval?
Is there a chance of losing the time sync if this is done?
And a seperate RTC would be required,right?


I think I should give some more info regarding what I am planning to do.

I was thinking for storing the data in an external EEPROM.
For the first reading, I would save the time,obtained from an RTC or
the uC itself.Then when the EEPROM is being read ,(to transfer the data
to the PC),the subsequent times would be
calculated,either by the uC and the data along with the time
,transferred to the Pc,or the time calculation would be done in the Pc
itself.
After a memory read,for the next reading,time would be saved again.i.e.
time will be saved in the EEPROM only after a download takes place.
Downloading would be done every few hours.Logging every few seconds.


I need the data and the real time when viewing the past data on the
PC,either as a chart or a tabular.


Is the above thing a bad idea?What would be a good way of doing this?


What should I do during power downs?Have a battery running for the
RTC?I havent decided on the RTC chip yet.Any suggestions?


I hope what I have said is clear.




Thanks.

Re: Timestamping data

Hi

If your time semp is costant you need not to save time stemp from RTC

But if your time stemp is random you need to save the time of sample

All the best

Bobi