If its likely still in cal after being in storage for ? years, it likely doesn't matter. In general, its best never to turn off high accuracy devices once they are in a stable state. Aging of references is more reliable [ i.e., reduced uncertainty] when the device is kept under power. Its a bigger issue with 7.5 digit DMM and more. The EDC calibrators were made to be portable, however in the specs the shortest term accuracy rating, ~ 1 hr of 5ppm suggests to me the unit performs best if left powered on, if used as a reference. If may not hold at 5ppm to a year, but it likely may be better than its 30ppm or so, worse case. With the unit on, the quiescent operating temp of the device plus stable lab temperatures eliminates thermal shock as one factor to destabilize your reference's setting. At 01:27 AM 8/9/2013, Joseph Gray wrote: >Since the VS330 is designed to be a portable voltage standard, is it better >to leave it on all the time or not? The manuals for other models don't say, >but they do talk about the short power up time to achieve rated accuracy. >So far, I have left it on. >

Marv, Thanks for your thoughts. I'll leave it on. Joe Gray W5JG On Sat, Aug 10, 2013 at 7:17 AM, Marv @ Home <marvin.gozum@comcast.net>wrote: > If its likely still in cal after being in storage for ? years, it likely > doesn't matter. > > In general, its best never to turn off high accuracy devices once they are > in a stable state. Aging of references is more reliable [ i.e., reduced > uncertainty] when the device is kept under power. Its a bigger issue with > 7.5 digit DMM and more. > > The EDC calibrators were made to be portable, however in the specs the > shortest term accuracy rating, ~ 1 hr of 5ppm suggests to me the unit > performs best if left powered on, if used as a reference. If may not hold > at 5ppm to a year, but it likely may be better than its 30ppm or so, worse > case. With the unit on, the quiescent operating temp of the device plus > stable lab temperatures eliminates thermal shock as one factor to > destabilize your reference's setting. > > > > At 01:27 AM 8/9/2013, Joseph Gray wrote: > >> Since the VS330 is designed to be a portable voltage standard, is it >> better >> to leave it on all the time or not? The manuals for other models don't >> say, >> but they do talk about the short power up time to achieve rated accuracy. >> So far, I have left it on. >> >> > ______________________________**_________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/volt-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts> > and follow the instructions there. > >