[volt-nuts] Fluke 731B replacement

Randy randallgrayevans at yahoo.com
Sat Feb 4 03:17:09 UTC 2012

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).


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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