Joel Setton | 18 Dec 16:41 2014

The "averaging reference"


In my search for the Perfect Volt, I'm thinking about building a 
reference voltage generator which would average the voltages generated 
by 8 or 10 REF102CP chips (with a simple resistor network), mounted in a 
temperature-controlled box.
Among all the experts on this list, does anyone have any experience with 
such a project? It looks good on paper, but what kind of stability can I 
reasonably expect?

Many thanks!

Joel Setton

Andrea Baldoni | 13 Dec 19:35 2014

Agilent 34970A (34401A) self test error 606

Hello all.

Following the thread on time-nuts about the ebay seller yixunhk and afraid to
have been a victim of their way to do business, I decided to thoroughly test an
Agilent 34970A unit I bought from them some years ago in "almost-new" shape and
practically never used since then.

The 34970A is a data acquisition unit with builtin multimeter identical
to 34401A, with some math function absent in 34401A like the direct measurement
of RTDs. The ADC is a "Multislope III" and you may find it in other instruments
as well, like the E3631A power supply.

I took the opportunity to use it to watch the temperature of an experiment, so
I connected a 100R platinum RTD and begun.
After an hour I noticed a sudden 10x or more increase in noise, so much that
the measure could not be read easily while was still to the tenth of C just
a moment before.
After having excluded cabling pickup, sensor defects, and so on, I launched the
self-test and got Error 606.

I left the instrument on for a full day, to let it stabilize and maybe dry up
from the moisture, even if it has always been kept in the lab, and repeated
the test with the same error. The test imply a power cycle and the error
didn't wanished just with that.

Today I was ready to do further checks, but after a cold start, the noise is
normal (I think, being +-17PPM worst case in the two wire 100R range measuring
a 100R precision resistor at 6.5 digits resolution) and the self test pass.
(the 34401A noise with the same resistor is much better, +-2.5PPM worst case,
but I expected this because of relays in switch units and wiring issues in my
(Continue reading)

Frank Stellmach | 10 Dec 23:54 2014

LTZ1000 VS LM399


obviously, you also have missed these long and exhausting discussions on 
EEVBLOG about those two references:

The difference between both is much more distinct:

The LM399 is about 1-2 orders of magnitude less stable than the LTZ1000 
and appropriately selected external components.

The LM399 is good for stabilities of about 20ppm/yr. and <1ppm/K T.C., 
i.e. 6 1/2 digits class DMMs.

The LTZ1000 plays in totally different league of the 8 1/2 digit DMMs, 
calibrators and voltage standards, i.e. < 1ppm/yr. and < 0.02 ppm/K can 
be achieved on intelligently selected components.

The LM399 is fixed on 95°C oven temperaturer, including the buried Zener 
and all oven temperature and reference determining resistors.
The LTZ1000 on the other hand can be operated at 45°C, and the oven and 
reference determining resistors can be chosen for optimum performance, 
which is not true for the resistors-in-silicon of the LM399.
These differences explain the ultra stability of the LTZ1000.

Therefore, you may average as many LM399 as you like, you will hardly 
(never) achieve the ultra performance of a single LTZ1000.
If the averaging follows a 1/sqrt(N) law, then more than 400EA LM399 
(Continue reading)

Jan Fredriksson | 10 Dec 16:20 2014

LTZ1000 VS LM399

I have been off the list for a while, but noticed that there where
some posts on the LTZ1000 and LM399 about a month ago.

I just have a comment; the requirements on these two references
(standard datasheet implementations) are very much opposites:

- LTZ1000 requires very stable resistors but is practically immune to
supply voltage variations.

- LM399 does not require high stability resistors but requirements on
stable supply voltage are high.

On the $ of one LTZ1000 board, you can get a number of LM399
paralelled & averaged.
But one LTZ1000 runs on less power than one LM399

my 2c
Dallas Smith | 8 Dec 05:16 2014

Fluke 720a Switching Center

To volt-nuts,

I uploaded my metrology switching center project for my Fluke 720a to 

  ( in windows explorer. 

This simplifies the different wiring configurations that the Fluke 720a 
is used for.


Ludger.Lenzen | 7 Dec 15:19 2014

Datron 1281 calibration enable key

I am searching for the calibration enable key for my Datron 1281.
At EBAY one key for the Wavetek 4808 Calibrator is offered.

Does anybody know if this key fits also to the Datron 1281?

Thanks for Help.

PeLuLe / Germany
Ludger.Lenzen | 7 Dec 00:42 2014

Does the Wavetek 4808 Calibration Enable Key fit to the Daltron 1281

Dan Kemppainen | 4 Dec 22:00 2014

Re: volt-nuts Digest, Vol 64, Issue 4


We have the professional Eagle at work. I also own a pro copy at home. 
The learning curve is a bit steep, but we have done some pretty neat 
stuff with it. It's more than paid for itself at home and at work. It's 
not really a cheap cad package, but it's also not the high end cad. Sort 
of a middle of the road. Same sort of issues with CAD/CAM packages for 
CNC also.

As for auto routers, none of them really work all that well IMO. Even 
the high end cad packages struggle with it. It's really hard to do in an 
autorouter what a good RF or analog engineer does in his mind, so that's 
to be expected I guess.

As for upgrading, we also experienced upgrade issue going from Ver5 to 
Ver7. And from Ver3.5 to Ver4.16, and from 2 to...
This last upgrade from Ver5 to Ver7 we had trouble with 126 of about 
1000 schematic/board sets. About half of those were things guys had done 
stupid. However the XML format allowed editing of most of the files, and 
after about 2 days everything was upgraded successfully to ver7. So, 
yeah, pretty painful.

The one thing I will say about Eagle, is the few questions I've had were 
answered with a quick phone call. Not sure if KiCAD has phone support or 
not. In a business environment, that can be worth a lot.

When you do the new board with KiCAD, be sure to post some results to 
your induction list. I'd like to hear how it works out...

(Continue reading)

Mark Sims | 4 Dec 02:26 2014

PC board layout software [WAS: HP-419...]

Another package that has a good reputation and is fairly inexpensive is DIPTRACE.  It is supposed to be
easier to learn than most packages.  Their size limits are based upon pin count, not board size.  Their
non-commercial free version is limited to 500 pins/2 layers.  A local university recently evaluated
several programs and chose DIPTRACE.
I've never seen a "real" PCB package that did not have a rather steep learning curve,  lots of frustrating
warts,  etc.   Having a decent sized installed base and active community is essential... 		 	   		  
Mark Sims | 3 Dec 17:46 2014

HP-419 and Fluke 845 Modifications

Eagle has a freeware version that is for non-commercial projects of smaller physical size.   It is a very
stable program... it has never crashed on me.  Eagle has LOTS of community support.  
All the PCB services that I mentioned can fab boards directly from Eagle .BRD files so you don't even have to
mess with making Gerber files.  They all have a preview function,  but OSHPARKs is the best.  You can submit
files to OSHPARK,  preview them there, and not submit an order if you just want to verify your design. 		 	   		  
Mark Sims | 3 Dec 05:38 2014

HP-419 and Fluke 845 Modifications

OSHPARK.COM is in the US and will do three boards for $5/sq inch... with no setup or shipping charges.
For larger boards or quantities and make nice boards for dirt cheap
(particularly for boards under 5x5 or 10x10 cm).  They can  be 1/10th the cost of OSHPARK.