Fluke SL935 Resistance Standard project (rare prototype teardown included)

[ManateeMafia]

They need to be organized by slot number.

[Dr. Frank]

As far as I know, the 732B runs a 45°C, it's described somewhere in the manual, I think.
The 5440B at least also keeps its reference ovenized at 50°C, and its resistors at about 55°C, so that the T.C. of the resistors is eliminated, as well as any power dissipation (esp. at 1kV output).

Therefore, the stability is greatly increased, and I don't think, that the drift is greatly enhanced at these temperatures, as resistance wires are much more stable compared to silicon structures, at comparable temperature elevations. Therefore, drift should be < 1ppm/yr. as well.

Compare that to Edwin Pettis' very interesting description of PWW technology.

Frank

[Edwin G. Pettis]

For a precision wire wound resistor, the operating temperature is not particularly a concern, whether operated at 23°C or 60°C or something else, as long as the resistor is rated for that temperature and properly processed (if intended as a reference resistor) it will remain stable with stable temperature, the higher temperatures do not affect the wire as far as aging characteristics and if processed correctly, the remaining stresses, whatever they may be, will also be stabilized to a high degree.  A well designed and processed PWW resistor will exhibit very minimal drift as long as its environment is also stable.  The resistor must be designed for the specific intended use, a standard off the shelf resistor, even a very good one, will not be quite as stable in the short term at least.

If you are going to insist on a high standard performance level, you are going to have to specify the conditions and pay for the extra needed processing to achieve it.  You cannot compare one grade of resistors against another with different performance parameters and expect the same levels.  You aren't going to get an SR-104 for $100, maybe a good used one for $2,000, you have to pay for the performance you want, it doesn't come cheap.  It is apples and oranges, they are all resistors but they are not all the same.

I have built high performance resistor standards in the past, they cost a lot more than the regular grade resistors I normally sell and take time to manufacture.  Just because they are PWW resistors and similar, they are not the same.

[nidlaX]

Goddam. TiN always delivers!

[TiN]

Some first checks..

1 Ohm : Median 1.000059 Ohm vs 3458A, TC <2ppm/K over 3C span, can't tell, readings too noisy
10 KOhm : Median 9999.990 Ohm vs 3458A, TC <0.3ppm/K over 3C span

No special processing/connections, no shielding from drafts, etc. Oven not connected to anything. 3458A ACAL ALL every 0.4c, so essentially it's comparison of SL935 vs HP's 40K reference resistor TCR  .

I'll need to code some python to use 6221 as reversible current source to get much better data off 1 ohm, with Delta-measurement method.

[VintageNut]

Some first checks..

1 Ohm : Median 1.000059 Ohm vs 3458A, TC <2ppm/K over 3C span, can't tell, readings too noisy
10 KOhm : Median 9999.990 Ohm vs 3458A, TC <0.3ppm/K over 3C span

No special processing/connections, no shielding from drafts, etc. Oven not connected to anything. 3458A ACAL ALL every 0.4c, so essentially it's comparison of SL935 vs HP's 40K reference resistor TCR  .

I'll need to code some python to use 6221 as reversible current source to get much better data off 1 ohm, with Delta-measurement method.

The micro-ohm errors in the 1-ohm measurement can have very long time constants to settle to zero IF you can get all of the connections of the circuit to be at the same temperature (no thermal gradients). Otherwise you are measuring the 1 ohm resistor and some number of thermocouples.

The 6221 can help, but the uncertainty of the 6221 is not metrology-grade.

[TiN]

Uncertainty of 6221 wouldn't matter in bridge configuration or even in simpler setup with two 3458A's monitoring both resistor and current source.

[e61_phil]

Uncertainty of 6221 wouldn't matter in bridge configuration or even in simpler setup with two 3458A's monitoring both resistor and current source.

Isn't your HP3245A a better 100mA source?

[Cerebus]

Two pages and still no reply.

This is a torture.

 

No, this is torture - three pages and not a glimpse of the insides!

[Pipelie]

I got a offer for this unit last year.
The price was acceptable, but the unit is incomplete, and  no Fluke WW resistors  inside at all . So,no,Thanks.
Frankly, I was disappointed when I Saw what‘s inside.

[TiN]

I got a offer for this unit last year.
The price was acceptable, but the unit is incomplete, and  no Fluke WW resistors  inside at all . So,no,Thanks.
Frankly, I was disappointed when I Saw what‘s inside.

Well, I'm sure happy that you didn't snag it, otherwise this thread wouldn't happen.
But it would be interesting to know why disappointment?

Unit is complete enough for me, as I just received 732B-7001 today, which is a perfect match now. Just add some water batteries...

[TiN]

Pics removed, thread derailed. 

[manganin]

(Sorry)

[Vgkid]

I mean if it works. :hide

[TheSteve]

Ouch - why post that crap in TiN's thread?

[Macbeth]

Because it's hilarious? 

I'm sure TiN will appreciate good humour, though the purveyor of "10.00000V 2ppm" crap on ebay that relies on the sellers extreme lack of soldering skills and his belief in God will be offended.

ETA: 6ppm to 2ppm. OMG! http://www.ebay.com/itm/10-Volt-10-V-DC-Prec-Voltage-Reference-Standard-Nulled-to-Fluke-732A-or-732B-/251756273626   

[TheSteve]

Oh I get it. It's just that the Fluke is a work of art even if portions were hand assembled, that other voltage ref is just junky sadness.

[manganin]

No way a real R&D prototype or even a mockup. Fluke is the major player in the high end voltage standards but not in resistance metrology. Who would buy a thermostated 742A for $6K?

Must be some DIY enthusiast in the service department who has access to spare parts / leftovers.

Total spend just bit over 1K$ for something that should be good enough as transfer standard for 3458A/5700A/5720A calibrations. I wish there would be room inside to put LTZ module as well...

Good deal if you find a totally smashed 732B needing a new enclosure. Or an LTZ1000 based "732B" would be cool too.

I think that the Fluke divider hybrids find better use in some ratio related application rather than as a mediocre resistance standard. 14 pcs total !!!



And sorry again. I know that religion and politics should be kept out of the forum. But I couldn't help myself...

[Echo88]

Indeed, the SL935 shown here is nothing more than a prototype nobody would dare to sell to customers. "Work of Art" 

If TheSteve would like to invest in art, i suggest this: https://en.wikipedia.org/wiki/Artist%27s_Shit

[TiN]

Too bad there is no "Unthank post" button. After all this is electronics community section, not the general chat.
And calling Fluke not a player in metrology is fun, sure folks at Everett will have good laugh reading this. 

People and market seem not to mind using Fluke resistors in 720A, 752A's, which are still up for today's standards.
Are these resistors from 5700A worse? Maybe. Ask that question in 5 years if you really care that much, when we see actual data.

Would I buy such a unit as stated "thermostated 742A for $6K"? No, not really. And why 6K? Why not 3K or 15K?
I've heard IET charges more for magical SR104, no?

Something tells me that people here that able to measure visible difference between SR104 and 10xF5700 network array can be count on one hand (me excluding, I don't pretend to have time or gear for that).
If you guys not interested, let's get this prototype project closed and all move to this magical thread.

I've got a tool to transfer calibrations for 5700A. No SR104 replacement or magical best in the world resistor statements were made. 

[VintageNut]

Tin

As always, without exception, I thoroughly enjoy following your projects.

This particular Fluke resistance box is very interesting. It shows intelligent design and access to lots of the best resistors fluke uses.

Please continue to share what you are doing with this resistance box.

[CalMachine]

Tin

As always, without exception, I thoroughly enjoy following your projects.

This particular Fluke resistance box is very interesting. It shows intelligent design and access to lots of the best resistors fluke uses.

Please continue to share what you are doing with this resistance box.

I agree.  I thoroughly enjoyed seeing what was inside of that Fluke prototype and was intrigued by this prototype in particular.  I would take what some people are saying, with a grain of salt...  It, clearly, wasn't a production item.

[Echo88]

I might have been a bit harsh. Of course the stability/accuracy of those paralleled resistors should be very good and TiNs teardowns are always worth the read. I just expected a working glorious device after 3 pages of guessing and it looks more like what i would build in my sparetime, if i would work at fluke and had those resistor-networks laying around. 

[manganin]

Fluke is the major player in the high end voltage standards but not in resistance metrology [products].

And calling Fluke not a player in metrology is fun, sure folks at Everett will have good laugh reading this. 

Fluke has one of the best primary level labs in the whole world, but their best resistance standard product is still the 742A. The small size and low temperature coefficient makes it an excellent transfer unit also used in the highest level. But even though sometimes marketed as a replacement for the SR104, there is a magnitude difference in stability.

People and market seem not to mind using Fluke resistors in 720A, 752A's, which are still up for today's standards.

All those products rely on regular relative adjustment or calibration with more stable standards. But I agree that Fluke (or their subcontractor) makes very good resistors.

Too bad there is no "Unthank post" button.

My intention was not to be rude, but challenge you to think how to get the best out of the purchase. I think in this case the value of the complete instrument is less than the sum of those high end parts it was made of. The divider hybrids alone are probably worth the money that you paid. How about building ten new instruments instead of stacking all together to make one mediocre standard resistor? Especially for you it would be easy to find a number of new interesting metrology applications.

And sorry for injecting noise in this thread with the "Totally looks like" meme.

[TiN]

Thanks, I'll go with mediocre standard resistor, as I don't have SR104, nor seeing it for sale anywhere in <1K$. Also SR104 is useless as 1 ohm, without current comparator or bridge, none of which I have yet.
SR104 without calibration is just a box with wire and oil tank too.

And anyhow, my purpose was clear from the start, and that was never a replacement for SR104, which is not really a primary standard anymore since the QHR adopted, unless I got that wrong too?