dean is right on the money - no pun intended. If a volt/current data logger is out of your price range: like : www.instserv.com/daqpro_data_logger.htm - Before the self contained dataloggers were commercially available, I stuck an A-D card in an old PC - wrote a very simple BASIC program that sampled the A-D card with an Amp probe attached - download the text file to Excel and analyze it.