Which driver are you using? <a href="http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=014FBD5290E626D9E0440003BA7CCD71" target="_blank">this one</a> or <a href="http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=E3B19B3E9184659CE034080020E74861" target="_blank">this one</a> Did you look at the Dual Channel example? It shows you how to program for the second channel.