Thanks very much, Camacha; it looks like the main thing I was missing was the bracketed element and the proper field name. For anyone interested, I modified Camacha's code a bit to log the value every second to a .txt file for later importing into excel. It's probably sloppy, but gets the job done for now. My hope is to eventually do away with the archaic Logomatic and Flight Recorder UNTIL ship:electriccharge < 50 { WAIT 1. SET partlist to ship:partstagged("mag"). //be sure to tag the part SET foo to partlist[0]:getmodule("DTMagnetometer"). SET output to foo:getfield("|b|"). LOG output + "," + round(longitude,2) + "," + round(latitude,2) + "," + round(altitude,2) to magb.txt. }.