Hi Alf,

Look at this item on ebay. This guy makes little reference boards for
a good price. I have had conversations with him and got some good info
on standards.

http://cgi.ebay.com/10V-L-STANDARD-V...QQcmdZViewItem

If the link doesn't work search ebay on "voltage reference".

I built a little standard using a different chip than he used. I used
an LT1019A and trimed it in.

I have a small spread sheet comparing his board with mine and the 731B
transfer standard if you would like me to send it to you.

He had sent me one of his boards to play with. I found that they move
quite a bit with temperature. Temperature is the biggest problem in
maintaining a stable reference with those chips. I have a fluke 731B
transfer standard to reference to, using an hp 3456 voltmeter to
measure things with.

The board he has is not a bad deal as he sends it out calibrated. If
you can duplicate his temperature you will do pretty good but probably
not quite as good as he advertises.

A good pre regulated supply is important to feed the reference chip
too.

73
Gary K4FMX


On Fri, 14 Apr 2006 19:47:03 -0700, Alfred Green wrote:

I have recently aquired a nice 5.1/2 digit DVM, and would like to assess
the absolute accuracy. Many years ago I had a 'Standard Cell', but that
got lost in one of my several relocations.
What is a good alternative these days? I would think that there is a
semiconductor device that has a known threshold. I am familiar with the
Wheatstone bridge method to measure voltage without affecting the reference.
Once I have a good DC reference, getting AC & RMS calibration is fairly
easy.
Having a GPS locked time and frequency reference, I am used to being at
the 1e-10 accuracy level for those, but if I can get to 1e-5 for analog
voltage I would be very happy.
Any suggestions gratefully received.

73 Alf NU8I
Scottsdale AZ DM43an
160m - 10 Gigs