Help: Recording ASCII data to an SD card

I'm a total novice at Arduino and am looking for some feedback/advice on the best way to record ASCII data output from an RS232 port onto an SD card. I think this can be done with an Arduino but have a few questions before I sink my teeth in:

  1. The instrument (an analytical balance) outputs ASCII-formatted data from an RS232 port at ~1 Hz but does not output a time stamp. Is there a way to write this ASCII data to an Arduino while simultaneously recording a time stamp from the Arduino?

  2. The balance will be deployed overnight so 1 Hz data is overkill for this purpose. Is there a tutorial that goes through how to automatically average the 1 Hz data to a 10 min average?

  3. Someone suggested I use a Raspberry Pi instead - would this be easier? Are there any other platforms/methods that would be easier?

CONTEXT: the ultimate goal is to create a dewfall meter that can accurately and precisely measure the mass of dew as it accumulates overnight. On top of the balance is a tray containing artificial turf so as dew collects on the turf the balance will detect the additional mass.

  1. Yes. You will just need RS232 to TTL Serial conversion hardware.

  2. Probably not but anyone who has taken high-school math can tell you how to average values.

  3. No. RaspberryPi requires knowledge of Linux programming. Arduino is much simpler. If you already know Linux programming then you would probably be using a spare Linux PC.

Thanks for the quick reply - this seems like it won't be too hard! I have very little programming experience so it's not the math that's tricky it's the coding.