Feasible? Convert Fluke 5440B A9 Into Stand Alone DC Standard

[Rax]

Have you made sure, that the 732As oven is running properly?
Frank

From all the data and logs you collected, denimdragon, this part is conspicuously missing (unless I missed it). And it's likely one of the most relevant parts of the puzzle at this early juncture. It's also one of the easiest to assess - just hookup a decent ohmmeter at the OVEN TEMP THERMISTOR jacks and also log those readings.

I'm embarked on a similar project - much more invested, as it required repair with "oven heart surgery"  (a joint venture with bdunham7), and it's still under work - and you'll notice the oven ramps up pretty slowly. You do want to make sure it stabilizes before drawing any conclusions on stability and whatnot.

My 732A sample stabilizes at 4.52k (and very slightly fluctuating change) which is pretty much dead on center to where it should be (between 4k and 5k).

Don't underestimate the 5440B either, from my experience with my 5440A (also a project that ate my soul for a few months, but I deem good now), I feel the only real (functional) difference between the ultimate spec of the 5440A and the 732A is that the latter is supposed to be continuously powered to have its spec guaranteed (other than that, they're essentially very similar). Honestly, the 5440A doesn't seem to need it. It's an amazing performer.

[Rax]

I just need [...] the Vishay resistors.

I highly recommend a place which may actually be local to you - TCC in Houston. They make the top shelf Vishay resistors to your spec, affordably (relatively), and they are overall a mind blowing option and opportunity, frankly. I can go into more detail, but I cannot recommend them enough. Feel free to contact me offline (or here) for further detail.

I have no affiliation whatsoever with them, btw. I just think if we use their services - as we should - they'll thrive and provide their excellent service and product to us voltunut hobbyists forever (hopefully).

[Rax]

I also have nearly everything to build one of the LTZ1000 references from here.

Use this: https://www.eevblog.com/forum/metrology/agilent-keysight-03458-66509-dcv-reference-pca-for-3458a/. Disregard what the link is telling you, it's a comprehensive guide on building a great performing LTZ1000(A) reference, front to end - particularly if you live in the US. The first post accrues essential steps - fell free to ask questions and I (and I'm sure others) will be happy to help.

[Rax]

[...] and the Vishay resistors.
They seem to be difficult to acquire from what I have read.

As per my post just above - not at all. You actually may be just about located uncannily right vs. everyone else (in the world, mind you). You can order your resistors from TCC - https://webdirect.texascomponents.com/ProductDetails.asp?ProductCode=Z201%5FCustom%5F0%2E25 (so, .25% tolerance, which is of less importance, and .2ppm TC, which is far more important) for about $22 each, no minimum quantity, on any value you want (or calculate - see the main thread I posted above), and ready within a few days.

Best resistors there are (outside of Fluke's magic sauce). Best of all? You get to drive to pick them up when ready! Lucky SOB.

You're welcome

[Rax]

On your configuring your lab, bench, and planning - typically, you'd expect the 732A to be the traveling 10V reference - carrying the precious low-uncertainty 10V from a suitable (very important aspect) lab to your environment - that then can, as Frank suggests, serve aligning your 5440 with the truth of the lab you used.

While evaluating that pursuit, make sure the TUR and all credentials of the labs you use are proper and exceeding your own references. I've realized very quickly that my local preferred lab cannot calibrate my standards from a certain point of my trajectory (and standards at hand), and I've filtered the labs I trust vs. those I don't by how honest they are with their claims and how forthcoming with their assessments. The lab I like, but can't really use, is the one that volunteered all the relevant information, showing both competence and honesty in the process. I'd effusively recommend them any day for the appropriate application.

[chuckb]

Just wanted to second the good comments about Texas Components. No affilliation with me.
I ordered five VHD200 (hermeticly sealed Vishay dividers) and they arrived 3 weeks later. I ordered an exsisting part (1k/16k) so that may have helped.
Cost $65 each. I'm checking temp co and stability right now.

[denimdragon]

As per my post just above - not at all. You actually may be just about located uncannily right vs. everyone else (in the world, mind you). You can order your resistors from TCC - https://webdirect.texascomponents.com/ProductDetails.asp?ProductCode=Z201%5FCustom%5F0%2E25 (so, .25% tolerance, which is of less importance, and .2ppm TC, which is far more important) for about $22 each, no minimum quantity, on any value you want (or calculate - see the main thread I posted above), and ready within a few days.

Best resistors there are (outside of Fluke's magic sauce). Best of all? You get to drive to pick them up when ready! Lucky SOB.

You're welcome

Rax, yes I am familiar with TCC. They are 7 miles North of
me, and it's a straight shot. I am pretty luck to be so close.
I order the KX board from OSHpark this morning and it should
me here by next week. That will give me enough time to order
the rest of the components.

On your configuring your lab, bench, and planning - typically, you'd expect the 732A to be the traveling 10V reference - carrying the precious low-uncertainty 10V from a suitable (very important aspect) lab to your environment - that then can, as Frank suggests, serve aligning your 5440 with the truth of the lab you used.

While evaluating that pursuit, make sure the TUR and all credentials of the labs you use are proper and exceeding your own references. I've realized very quickly that my local preferred lab cannot calibrate my standards from a certain point of my trajectory (and standards at hand), and I've filtered the labs I trust vs. those I don't by how honest they are with their claims and how forthcoming with their assessments. The lab I like, but can't really use, is the one that volunteered all the relevant information, showing both competence and honesty in the process. I'd effusively recommend them any day for the appropriate application.

The lab I have been using is a pretty decent lab. They are
currently waiting for there 732A/Bs to get back. I've discussed
the 732A being "verified" against their 732s, and was told that
he could verify my 732A. In order to truly have the 732A Cal'd,
wouldn't I have to send it in to a national lab or Fluke?

Just wanted to second the good comments about Texas Components. No affilliation with me.
I ordered five VHD200 (hermeticly sealed Vishay dividers) and they arrived 3 weeks later. I ordered an exsisting part (1k/16k) so that may have helped.
Cost $65 each. I'm checking temp co and stability right now.

Hi chuckb, what has the results been so far concerning the
drift logging?

[acstd90]

Not sure where you have stopped on the 5440B but two fixes that cause strange errors are to replace the two capacitors C33 & C38 on the A10 board (when they get old they create issues "Normally intermittent guard failures) There is also a large resistor on the A17 regulator that gets hot over the years and increases in value over the years and as it increases in value it gets hotter. You will see it as the board will look burned under the resistor. The fix is to use a resistor mounted up off the board and increase the wattage by 2 times. Also I am going from memory a long time ago but there are two or three yellow electrolytic caps on the A14 guard crossing board that will cause problems.