Thermocouple data graphing in Libreoffice Calc - real time clock shield required

Hey everyone, Im still fairly new to Arduino, but have been learning a lot lately! I have been searching for this particular topic, but haven't found anything like what I want to do.

I have an idea for a project that takes thermocouple data, displays it on a LCD, whilst also sending the data serially to Excel or Libreoffice Calc to be displayed as a x-y plot as a line (x being time, y being temp). I want to be able to see temp changes as they happen, so a datalogger is out (from what I have learned so far). So my question is - do I need a RTC shield to do this?

Any advice is hugely appreciated

So my question is - do I need a RTC shield to do this?

whilst also sending the data serially to Excel or Libreoffice Calc to be displayed as a x-y plot as a line (x being time, y being temp).

If the Arduino is connected to the PC, you can ask the PC what time it is. I'm not sure that Excel can do real-time plots. Processing can, and can also write to a csv file that Excel can open later.

As long as the timing isn't really critical I'd just let Excel read the PC time and use that. I think this will introduce small timing errors as serial data is buffered here and there, but maybe not and maybe that won't matter to your application.

Another way to get pretty accurate timing is to have the Arduino attach the value from millis() to each sample then have Excel simply add that offset value to the time the job was started. This will be very accurate.

Similarly just ensure that the Arduino samples every N mS in which case the offset from the start is implied.


Rob

Please provide more hints as to what you're trying to accomplish. What OS are you using, and are you doing short runs or ...?

For a permanent installation RRDTool is the most packaged way of performing continuous logging of data.

If you want to use Excel you can use its OLE interface to fill cells in real time.

I want to build a coffee roast logger, that enables me to track the the temp changes during the roast with a graphical depiction of the pertinent temperatures. Each roast takes approx 13 mins. I am using Ubuntu (Natty) as my OS.