[volt-nuts] Fluke 731B replacement

Andreas Jahn Andreas_-_Jahn at t-online.de
Fri Feb 3 22:25:50 UTC 2012

Hello Randy,

is your VRE310 a "new" part (branded APEX) or is it a old "Thaler" 

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 

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.


Randy Evans
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