Uref1        Uref2        rel. to cal    rel. to 0°

For Andreas - never did such a crazy experiment before. I rotated my double LTZ reference on every of the six sides and measured the deviation relative to the 3458A. At least 2min between measurements for stabilization (sufficient). Obviously, no appreciable drift occured in the 3458A in between the whole run. I have seen a drift of max. 1ppm during rotation. Thermal root cause, not magnetic, because drift to consecutive stable value is slow, not instantaneous. Here's the table: Uref1 Uref2 rel. to cal rel. to 0° 01.01.2010 7,1762318 7,1479788 0° 7,1762295 7,1479862 -0,3 1,0 0,0 0,0 90° 7,1762330 7,1479892 0,2 1,5 0,5 0,4 180° 7,1762375 7,1479893 0,8 1,5 1,1 0,4 270° 7,1762329 7,1479848 0,2 0,8 0,5 -0,2 Back Side 7,1762370 7,1479932 0,7 2,0 1,0 1,0 Front Side 7,1762372 7,1479918 0,8 1,8 1,1 0,8 360° 7,1762292 7,1479848 -0,4 0,8 0,0 -0,2 acal dcv 7,1762295 7,1479845 -0,3 0,8 0,0 -0,2 regards Frank.

> For Andreas - never did such a crazy experiment before. Thanks for doing the experiment. For me its just a missing spec in the datasheet which seems to be important for heated references. Others could be the relative humidity for plastic cases or power-on hysteresis on low power devices. I found this effect by accident when I missed 30uV between calibration location and home between the two LM399 references. Unfortunately I had not payed attention to the orientation of the devices at the calibration. The most weird thing I observed is the fact that the two Keithleys show exact the same reading of my 7V references when the one instrument is orientated in 0 degrees and the other in 90 degrees. So I am wondering what the guys at the calibration lab are doing when they have not much space on the table or if this result is by luck. When I have built my reference and pre-aged I will compare your LTZ1000 with 12K/1K setpoint to my LTZ1000A which will have 12K5/1K (UPW50) setpoint. If the effect depends on the difference between environment and setpoint temperature I should be worse. If it depends on heater power I could have had luck. By the way: can you estimate the room temperature which was during the experiment? >From your description of thermal shielding I got the impression that on the 0 degrees orientation is with the legs of the LTZ above the metal can. Or did I mis-interpret the description? On the other side the PCB could be mounted vertically in the case. So how is the orientation of the LTZ with respect to the 0 degrees? best regards Andreas

Hi Andrea: I have a friend who does equipment calibration and the orientation is very important to him, although not to all calibration people. He told me about the case of a crystal oscillator where the access was by removing the bottom cover. In that case he needed to mount the instrument into an empty rack and lay on a jury rigged mechanics creeper to get to the bottom. An easier way would be to put the instrument on the bench on it's side, but the cal would not be a cal. Have Fun, Brooke Clarke http://www.PRC68.com Andreas Jahn wrote: > >> For Andreas - never did such a crazy experiment before. > Thanks for doing the experiment. > > For me its just a missing spec in the datasheet which > seems to be important for heated references. > > Others could be the relative humidity for plastic cases > or power-on hysteresis on low power devices. > > I found this effect by accident when I missed 30uV > between calibration location and home between the > two LM399 references. Unfortunately I had not > payed attention to the orientation of the devices > at the calibration. > > The most weird thing I observed is the fact > that the two Keithleys show exact the same > reading of my 7V references when the one > instrument is orientated in 0 degrees and the > other in 90 degrees. So I am wondering what > the guys at the calibration lab are doing when > they have not much space on the table or if this result is by luck. > > When I have built my reference and pre-aged > I will compare your LTZ1000 with 12K/1K > setpoint to my LTZ1000A which will have > 12K5/1K (UPW50) setpoint. If the effect > depends on the difference between environment > and setpoint temperature I should be worse. > If it depends on heater power I could have > had luck. > > By the way: can you estimate the room temperature which was during the > experiment? > >> From your description of thermal shielding I got > the impression that on the 0 degrees orientation > is with the legs of the LTZ above the metal can. > Or did I mis-interpret the description? > On the other side the PCB could be mounted > vertically in the case. > So how is the orientation of the LTZ with respect > to the 0 degrees? > > best regards > > Andreas > > > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > -- Have Fun, Brooke Clarke http://www.PRC68.com