AD5791 & LTZ1000 in a box

[Grandchuck]

The box was needed to get the best results.  Also, learned that ground loops can be a problem.  As the picture shows, the output connectors have been removed as they were causing problems.

My Florida lab is nearly an ideal environment because the AC holds the temp and humidity fairly constant.

Expensive project, but good results!

I have new connectors ordered and hope to get rid of the wires.

[TiN]

Welcome to forum! 

Is it just reference ADI board in box, or your own design? Interested minds like to know  .

[Grandchuck]

Thanks!  Long time reader.

Yes, it is just the ADI board in a box.

[branadic]

Which one? The old version with an additional LTZ board you build or the new one with the AD/LT-LTZ board on top?

-branadic-

[Grandchuck]

The new one.

[Grandchuck]

Help! I am becoming a voltnut.  Two meter pics are attached.  The first one is with the AD5791 programmed for 10 volts and the second one is one bump up (19 microvolts more).  So all is working well.  The drift is wobbling around very little (a few microvolts).

The meter is new (to me) so I have to learn some things.  I found LabView stuff for mean, standard deviation and intend to pursue that route.  So far, have not got any of that working.  Also, not able to read the cal ram data.  The meter came with a USB to GPIB adapter, so perhaps just a matter of learning how to use it (having a driver issue).

I also cobbled up a 10 kohm (within 1 ohm) resistor and now will try a 4 wire measurement.  Might as well be an ohmnut too.

[babysitter]

So, let the 19µV "BUMP" become a valid alternative unit of voltage!

Cant wait to see the first 79kBUMP Batteries marketed.

[Grandchuck]

As an update, I have run a few 24 hours power off and then back on cycles to determine if there would be any hysteresis. There wasn't any that was measurable.

My particular LTZ1000 performance has agreed with the Long-Term Stability graph shown on the first page of the data sheet.  It has aged enough that it is reliable.

Now for the effect of temperature.  I applied medical cold pack (0 F) to the metal cabinet that houses the DAC and LTZ1000 assembly.  The temperature (measured on the outside of the metal box with a Fluke IR thermometer) dropped from 86 F to 75 F.  The output was set at 10 volts and it went up by 3 ppm.  I have repeated this a few times and it is consistent.  There was no measurable hysteresis effect from the temperature cycling.

All in all the results are good and it is nice to have a reliable voltage standard.  Since my lab is temperature controlled, the temperature effect is not an issue for me.

I am still learning about the 3458A and have had some success with the USB/GPIB interface.  All of the AD571 evaluation software is working now (the Measure DAC Output finally works).