Crap, I hope I'm not replying to myself. Was just measuring watts with my Wavetek 52 and had the dt 9939 measuring dc volts on a cheap Chinese voltage standard on the other desk. The 9939 went to sleep and when I powered it back up by pressing the backlight button, the voltage reading was incorrect. I turned the dial to the millivolts scale and measured 200 millivolts at a power supply and the reading was the same as my Agilent u1252b. I returned to the other desk, turned the dial to volts and plugged the meter back into the Chinese voltage reference and the reading was correct. This is driving me nuts.