[volt-nuts] Fw: Fluke 731B replacement

Andreas Jahn Andreas_-_Jahn at t-online.de
Sat Feb 4 04:39:53 UTC 2012

Obviously its not possible to have large attachments

so resent without the screen photo.

With best regards


----- Original Message ----- 
From: "Andreas Jahn" <Andreas_-_Jahn at t-online.de>
To: "Randy" <randallgrayevans at yahoo.com>
Cc: "Discussion of precise voltage measurement" <volt-nuts at 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 at yahoo.com>
> To: "Andreas Jahn" <Andreas_-_Jahn at t-online.de>
> Cc: "Discussion of precise voltage measurement" <volt-nuts at 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 at 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 at yahoo.com>
>> To: <volt-nuts at 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
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