Istvan has a really great point (and usually does). You need to reference set your instrument. If you don't do a reference measurement against a known value, then you have absolutely no idea whether your measurement is good, bad or ugly. In the land of SI it is always best to check twice (or three times) and cut once. So many times I have been told that any number of checks have been made only to find out later that they were made wrong or the instrument was out of calibration. Best Regards, Michael C. Greim And all this science they don't understand Is just my job six days a week..... We will either find a way or make one -Hannibal In the middle of every difficulty lies opportunity -Al Einstein ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu