Obviously its not possible to have large attachments so resent without the screen photo. With best regards Andreas ----- Original Message ----- From: "Andreas Jahn" <Andreas_-_Jahn@t-online.de> To: "Randy" <randallgrayevans@yahoo.com> Cc: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Saturday, February 04, 2012 5:31 AM Subject: Re: [volt-nuts] Fluke 731B replacement >I use the attached cirquit: > > its an amplifier with 10000 fold amplification and around 0.1 .. 10Hz > bandwidth. > together with a Oscilloscope with 2mV/div you will get 0.2uV/div > capability. > > I use 2 standard electrolytic caps (1000uF + 2200 uF) > of good quality which are selected for leakage current > at 10V charge voltage with precharge for a couple of days. > > All is powered by 2 * 9V block NiMH batteries. > All within a metal box (the cakes have been taken out). > > The noise floor level with 8*Eneloop (around 10V input voltage) is around > 0.12uVpp. > (Screen photo is 1 sek/div and 0.2uV/div on my old HAMEG). > So with this cirquit comparative measurements of different references can > be > made. > > With best regards > > Andreas > > > ----- Original Message ----- > From: "Randy" <randallgrayevans@yahoo.com> > To: "Andreas Jahn" <Andreas_-_Jahn@t-online.de> > Cc: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Saturday, February 04, 2012 4:17 AM > Subject: Re: [volt-nuts] Fluke 731B replacement > > > It is the "Thaler" unit. I got it from a cancelled project. Do you have > an > easy test to check the noise level? The Linear Tech app note by Jim > Williams is too expensive for me ($400 input cap). > > Randy > > Sent from my iPhone > > On Feb 3, 2012, at 2:25 PM, "Andreas Jahn" <Andreas_-_Jahn@t-online.de> > wrote: > >> Hello Randy, >> >> is your VRE310 a "new" part (branded APEX) or is it a old "Thaler" >> reference? >> >> Some months ago I bougth 2 VRE3050A but the measured noise is well above >> the typical value in the data sheet. >> So if you have a APEX part it would be interesting for me wether the >> VRE310 is more quiet in low frequency noise (0.1 .. 10Hz). >> For a 10V part it should be about 6uVpp typical. >> >> Do you plan to heat the reference? Or how do you intend to get near to >> the >> 731B specs? >> >> With best regards >> >> Andreas Jahn >> >> ----- Original Message ----- From: "Randy Evans" >> <randallgrayevans@yahoo.com> >> To: <volt-nuts@febo.com> >> Sent: Friday, February 03, 2012 5:58 PM >> Subject: [volt-nuts] Fluke 731B replacement >> >> >> I am planning on building an equivalent Fluke 731B transfer Standard >> using >> a VRE310 10V Precision reference and LTC5400 Quad resistor as a precision >> 10:1 divider, plus ancillary circuits. However, before starting the >> detailed design I modeled the Fluke 731B circuit in LTSpice. The 1V, >> 1.018V and 1.019V outputs are fine but the 0 to 999uV delta E adjustment >> circuit for the delta V, 1.018 + delta E and 1.019 + delta E outputs does >> not work per the circuit modeled from the schematic. I have double and >> triple checked my LTSpice schematic per the Fluke 731B schematic but I >> can't see any difference. Maybe I am just too close to the forest to see >> the trees. >> >> Note: The Fluke 731B schematic from the manula I have does not show the >> value of the delta E adjustment pot but the parts list shows a value of >> 5K >> ohms. >> >> Does anyone have any ideas? I can forward the LTSpice schematic I am >> using >> to anyone that might be interested, just send me your e-mail address. >> >> Thanks, >> >> Randy Evans >> _______________________________________________ >> 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. >