Author Topic: Statistical arrays  (Read 9823 times)

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Offline dietert1

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Re: Statistical arrays
« Reply #75 on: July 03, 2019, 09:58:03 pm »
Sorry, i would rather prefer learning from industry leaders who have been applying thin film technology in precision measurement for many years.

I got somewhat impressed that 6 $ plus proper wiring of that part gets me a voltage divider with less than 0.5 ppm change of the division ratio during an 18°C oven cycle. Which is less than 0.03 ppm/°C. And this is the worst of six parts and still so good that i can't really measure the residual change. I know that number doesn't appear in the data sheet. Please don't tell me you know how long the adjustment will last if i don't touch the part anymore. I think right now nobody can tell.

Regards, Dieter
 

Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #76 on: July 04, 2019, 02:32:50 am »
Well dietert1, considering that you haven't been playing with this part for very long, you don't know what the longer term drift is and since Vishay doesn't specify longer term drift, you can accept that if Vishay doesn't provide longer term drift, there is no significant improvement over time or they would have said so.  I know quite well the performance limitations of many resistor technologies and I also know very well how well my precision wire wound resistors perform.

Carefully read the NOMCA data sheet from Vishay, the information I quoted is directly from their own data sheet, so no you don't have to believe what I said because it is in their data sheet quite plainly.

As far as resistors go, I have nearly 46 years in the resistor business, I think I know a tad more about the subject than you think.....I have the instruments that can measure resistance better than most anybody here and to a very high accuracy traceable to NIST, my uncertainty is 0.15 PPM on my primary reference.

However, you are most welcome to believe whatever you wish.
« Last Edit: July 04, 2019, 06:10:44 pm by Edwin G. Pettis »
 

Offline TiN

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Re: Statistical arrays
« Reply #77 on: July 04, 2019, 04:46:17 am »
Edwin G. Pettis

Quote
my uncertainty is 0.15 PPM on my primary reference.
Aww, beat me by 0.01 ppm there  ;D

Jokes aside, how possible would it be to order small qty (10-20?) of PWW network for purpose of 7V/10V and such, but with custom values per network? I'd be interested, and probably some others too to make it into a batch? One could find out precise values using calibrated decades like RS925, and then specify final divider, like 7.1426kohm/20.5216kohm as example. Of course, each network's precise value would be different, matched to specific LTZ circuit.  :popcorn:
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Offline branadic

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Re: Statistical arrays
« Reply #78 on: July 04, 2019, 05:48:07 am »
Well, if the TDP / NOMCA networks were really that bad in aspect of longterm stability and noise I'm pretty sure they wouldn't be used in Wavetek/Fluke 7000 and 7001 and if TaN resistor networks were bad in general Fluke wouldn't have used them in 732B and 732C and replaced the former single wirewound resistors by resistor network. So please not another flame war on resistor technology.

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Offline dietert1

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Re: Statistical arrays
« Reply #79 on: July 04, 2019, 06:22:21 am »
Sorry Mr. Pettys, we understand that you prefer wire wound resistors and you are not at all interested in thin film technology or statistical arrays.
At least one of your statements above was plain false. Analog Devices offers the AD587 reference part, which is well known for its good long term stability (Geller reference). Know what, the 10 V to 7 V divider within that part is based on thin film technology. No wire wound resistors there.

Resistor arrays offer exactly what TiN is asking for: A configurable voltage divider that supports many different division ratios and pretty fine adjustment. And yes, this needs implementation and measurement instead of general wisdom and reading between the lines.

Regards, Dieter
 

Offline Kleinstein

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Re: Statistical arrays
« Reply #80 on: July 04, 2019, 02:08:04 pm »
The specs for long term stability (some are shown in the environmental tests) are not that good. However with something like long term aging this is usually only a best guess, nothing easy to measure and check for every unit.  I am not 100% sure one can use the TDP series to directly use for the SMD version. The SMD version is much more sensitive to board stress.
Especially with the DIP versions, Fluke may have done some selection up front, to get better than typical units.

Especially in a cost critical or small size case wire wound resistors may not such a good alternative. Even if only replacing 2 resistors such an SMD array can be cost and size effective. For some cases there may be better alternatives like the MORN series (4 resistor in SSOP8) with better specs.
When using several resistors in a series and / or parallel configuration the relative TC matching is expected to improve (at least on average and in most cases). However one can still have bad luck and get a relatively poor matching.

The resistor excess noise may in some cases become a problem - but at least from the specs (< - 30dBi) the NOMCA arrays are not that bad, despite the small size. For a LM399 based reference the extra noise should not be a big issue - for a LTZ1000 based reference, one may notice some additional noise. For the resistors directly at the LTZ1000 excess noise should not be relevant with thin film resistors.
The TaN Arrays HP was / is using in there DMMs tend to be larger area with thus a chance for lower noise and possible better matching.
 

Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #81 on: July 04, 2019, 04:02:58 pm »
My statements were directly based on the Vishay NOMCA data sheet, there was no interpretation involved.  Comparing the AD587's internal resistors to the NOMCA is not valid, they are not identical even if they are using the similar Ta2N resistors which is generally used in most ICs.  That is the same as claiming all precision wire wound resistors are the same which they are definitely not.  Just because I specialize in wire wound technology doesn't mean I don't know how the other resistor technologies work.

The networks you refer to in the the 7000 are not identical to the NOMCA arrays, the manufacturing processes are not the same so you cannot compare the two.

I specifically stated that in my opinion, the NOMCAs are not well suited to a voltage booster circuit requiring low PPM performance.  So far all I've seen is mainly measurements on the arrays and none done on an actual booster circuit, those are two entirely different operating conditions.  Let's see what your measurements come up with in an actual booster circuit first before throwing rocks at the windows.

For that matter, I have made matched tracking TCRs of resistors down to <0.2PPM/°C which has been independently verified over long term period.  No it is not easy to achieve, the physical circuitry details are just as important, if not more important, than the resistors themselves.  Creating a very low tracking TCR depends on a lot more than just the resistors themselves, thermals can be very complex to control and can completely wipe out the low tracking TCRs of the resistors.
 

Offline Magnificent Bastard

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Re: Statistical arrays
« Reply #82 on: July 04, 2019, 05:34:41 pm »
The AD587 (et. al.), as well as the LT5400 are made with silicon-chromium resistors that are passivated with silicon-nitride.  The ratio of silicon-chromium to silicon-nitride is adjusted to minimize absolute TCR.  The Fluke 7000 series uses Vishay TDP networks, which are nickel-chromium elements that are passivated with tantalum-nitride.  Same as above, they tweak the ratio of nickel-chromium to tantalum-nitride in order to minimize the absolute TCR.  NOMCA are made with a 100% tantalum-nitride process, and they are self-passivating.  During the tantalum sputtering process, the percentage of nitrogen in the chamber is controlled to minimize the absolute TCR.  Because of the way they are made; where the resistors are sputtered onto a substrate in a controlled environment; adjacent resistors will track very well in TCR (and hence are valuable as a ratio device).  In resistor networks, the resistors have a tendency to track each other over time because resistor drift is driven by temperature, and the resistors on a network are nearly the same temperature.

Most of the evils that engineers have experienced with networked resistors have to do with the thick film process, which is totally different than thin-film or metal film.  The data sheets for these metal/thin film parts are VERY conservative.  The tracking TCR is related to R1 against any other resistor in the network (over 6-sigma); but resistors that are next to each other (and closer to the center of the network) WILL track each other far better than data-sheet specs say they will; and the networks can be selected for additional needed performance.  Once built and operating, the ratio of such a network will track within 1ppm/a, but usually much better than that.  You DO have to follow some common-sense rules when you are designing such a ratio device.  Even though two networks come from the same batch, they often TCR track very well, but you cannot rely on this; only that resistors within an individual network will track.  You have to make certain that each network in a multi-package divider shares responsibility for both the upper and lower legs of the ratio divider.  The resistors closer to the ends of the network (R1/R8 or R1/R7) are not going to track as well as the resistors closer to the center of the network; and this is all due to package strain.  A statistical array of at least 3 networks will perform better than just one network...  (and so on and so forth...)  You can figure out all of these rules on your own through testing; but don't forget to test for humidity, which can have bigger effects than temperature.
 
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Offline try

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Re: Statistical arrays
« Reply #83 on: July 04, 2019, 06:44:15 pm »
As far as resistors go, I have nearly 46 years in the resistor business, I think I know a tad more about the subject than you think.....I have the instruments that can measure resistance better than most anybody here and to a very high accuracy traceable to NIST, my uncertainty is 0.15 PPM on my primary reference.

Well, Edwin, claiming 46 years in the resistors business and having instruments that can measure resistance better than most anybody does not seem to be sufficient at all when it comes to delivering 10k Ohm flat with 10 ppm precision to a customer.

OK, mistakes can happen.
But refusing to deliver a free replacement shipment upon delivering the requested measurement proof is pretty disappointing.

« Last Edit: July 04, 2019, 06:47:58 pm by try »
 

Offline dietert1

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Re: Statistical arrays
« Reply #84 on: July 04, 2019, 07:23:33 pm »
While TCs within a Nomca package resemble better than TCs between different packages, in my measurements i have not seen that resistors close to each other resemble better. Neither have i seen that "inner" resistors are matching better than resistors near the ends of an array.

Apparently resistance tolerances within each array are very small, like +/- 0,005 %. This means it is very difficult to tune a Nomca divider for division ratio by using a certain combination of it's resistors. So when making a 7 -> 10 V booster with a Nomca array, additional tuning resistors are necessary to get close. A usual 1% 100 ppm/K MF resistor that one may have around is not good enough. If it gets its TC attenuated by 200 it will still ruin anything tuned to 0,1 ppm/K or better.

The reference booster resistor array of the HP 3456A has lots of different resistor values organized like a binary DAC. They get so close that in the end a usual  potentiometer is good enough for tuning.

Regards, Dieter
 

Online antintedo

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Re: Statistical arrays
« Reply #85 on: July 04, 2019, 07:34:14 pm »
While TCs within a Nomca package resemble better than TCs between different packages, in my measurements i have not seen that resistors close to each other resemble better. Neither have i seen that "inner" resistors are matching better than resistors near the ends of an array.
Thanks for your input, that was my observation as well. Since chip layout of NOMCA is not symmetrical, did you perhaps observe any patterns? For example in my test of 5 samples the resistor between pins 2 and 15 was almost always an outlier.

I will try to eliminate this and re-test, but it has to wait until the weekend.
So much for that - I'm still trying to setup a decent thermal chamber with a controller. However I tested a few more samples with my previous setup. The TCR pattern between resistors was similar but tracking much better. I edited the original post to include the results of 1 more sample that I had time to check for repeatability.

Regarding recent discussion, I was curious about 1/f noise of thin films, especially NOMCA vs larger models. I did a quick test dividing LTZ1000 voltage by 2 and measuring 0.1-10Hz pp noise within 1 minute period.

LTZ1000: 0.15 ppm
noname THT 3.3k metal film: 0.16 ppm
NOMCA 10k, 3 samples tested, 6 resistors used every time: 0.22-0.25 ppm
S102K (refurbished) 11k, 6 resistors used: 0.16 ppm

Additionally, long time ago I found this publication containing 1/f noise tests of various resistor types and models. Seems like a lot of models achieve good performance with almost no 1/f noise, even in SMD 0402 size.
 

Offline dietert1

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Re: Statistical arrays
« Reply #86 on: July 04, 2019, 09:14:40 pm »
My Nomca TC measurement results.
There is one measurement (R7 in array "B") that exhibits hysteresis. So that measurement may have some problem and be the reason why that part violates the 5 ppm tracking spec. I'm already using the part as a 13:1 divider for a LTZ1000 reference, leaving R7 unconnected.

Regards, Dieter
 
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Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #87 on: July 04, 2019, 11:15:21 pm »
Since Try can't seem to get on with it:

Appears Try is still suffering from a malady mostly of his own making.  The original order was shipped in December, 2016, and while I tried to talk him out of ordering ±10PPM resistors he insisted, note that he requested no additional special handling of the resistors, even so I still guaranteed them to meet transfer standard specs (ESI) which I later sent him a copy of the specs which using his own numbers was still within spec.  As is standard industry practice, the resistors are guaranteed to meet said initial specifications before leaving the factory.  The initial readings were indeed -2PPM and -6 PPM when shipped.

I received this reply from Try on 1-18-2017: “I measured the one you marked 10k -2ppm. It was either spot on or exactly 10k + 0ppm on my 34401A with four wire measurement.”  He did not mention the other resistor and I was rather surprised at how close his meter read it, that should mean his meter also read the other resistor at -6PPM.  I did not hear again from Try until nearly 14 months later when he wrote to say he thought that both resistors had drifted some but could not get a calibrated reading on them, using several nondescript resistors and an out-of-cal (5 years) 3458A…..that’s okay it should be in the ball park at least.  The figures he gave me was somewhere around 20-30 PPM higher than original.  I offered to re-calibrate them for the cost of postage so he would have accurate readings again, he refused and claimed they were out of spec…..well yes they were probably not within ±10PPM by this time but as they were standard processed resistors that was not unexpected plus there was no way of knowing what had happened to them in the ensuing 14 months.

The standard guarantee for a transfer standard is that the standard will maintain it’s given tolerance for 60 days after manufacture assuming it was handled properly.  There was another batch of e-mails at a much later time which mostly just rehashed what had been said earlier.

I believe the offer of re-calibration was sufficient and reasonable, since Try insisted only on replacement a good year and a half later, I would only offer replacements if the resistors were beyond specifications for a transfer standard of which I had sent him a copy of the standard specifications and guarantee.

He also complained about the pricing, a mere $28.38 for ±10 PPM resistors, I think he got more than he paid for.  All he really needed was calibration of the resistors to accurate known values and he’s back in business with calibrated references.  Now if he thought he was going to get resistors that would hold ±10 PPM indefinitely and for that price, I think he was just off his gourd a bit.

I will still do the re-calibration for the cost of postage even now but I cannot be held responsible for his turning down the offer repeatedly.
 

Offline dietert1

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Re: Statistical arrays
« Reply #88 on: July 05, 2019, 06:27:12 am »
Mr. Petty, considering your story, i understand the measurements try showed above are those same two resistors you mentioned and that they exhibited a difference of 3.7 ppm between each other after 18 months while you determined 4 ppm in the start? So this means the resistors - though worse than expected - were still useful for making a voltage divider, where a possible 40 ppm drift cancels.

I guess the same applies to the Nomca parts i tested. I got those from Mouser two weeks ago and we may probably assume they have been in stock for years. And they still exhibit tracking with 0,6 to 1 ppm (stdev of 8 resistors). Isn't that remarkable?

If there is anybody with a similar set of wire wound resistors from Mr. Petty, what is the stdev after some years? The result will depend somewhat on how the parts were treated/used. And i would really like to know the TCs of those two resistors mentioned above ..

Regards, Dieter
 

Online MiDi

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Re: Statistical arrays
« Reply #89 on: July 05, 2019, 11:25:52 am »
A bit off-topic, but seems to fit here:

Could a precision DAC used in "multiplying" configuration be a serious replacement for precision custom resistor dividers/networks in boost amplifier (e.g. AD5781/-91)?

Relying upon Datasheets, these DACs seem to outperform even the best resistor dividers/networks and they are ootb trimmable down to ppm...
« Last Edit: July 05, 2019, 11:48:27 am by MiDi »
 

Offline dietert1

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Re: Statistical arrays
« Reply #90 on: July 05, 2019, 01:30:30 pm »
Yes, i was waiting for that. Just combine a AD587 reference with a PT1000 temperature sensor, a humidity sensor, a Cortex M0 microcontroller and some smart firmware to automatically fine tune the reference including support for teach-in. That should result in a near perfect voltage standard without heating and with slow aging. The firmware could even predict and compensate aging drift.

So lets stop putting wire wound resistors into dry boxes, TEC boxes etc. and do some real work instead.

Regards, Dieter

PS: I just have a 10 KOhm econistor in the dry box. Room humidity is and was 32 % for hours, while temperature increased about 1 °C. While from the temperature increase i would expect a resistance change of about 2.2 ppm the part exhibits a resistance change of -49 ppm after drying for some hours. Anybody wants to fill their voltage reference box with silica gel?
« Last Edit: July 05, 2019, 02:13:24 pm by dietert1 »
 

Offline Kleinstein

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Re: Statistical arrays
« Reply #91 on: July 05, 2019, 04:22:55 pm »
.....
PS: I just have a 10 KOhm econistor in the dry box. Room humidity is and was 32 % for hours, while temperature increased about 1 °C. While from the temperature increase i would expect a resistance change of about 2.2 ppm the part exhibits a resistance change of -49 ppm after drying for some hours. Anybody wants to fill their voltage reference box with silica gel?

Silca gel is not just for lowering humidity. If left in normal air for some time it mainly works to buffer humidity changes - so that rel humidity would change less/slower, even in a not so hermitic sealed case.

With the NOMCA arrays in an epoxy type case - they may react to humility changes too. With wires wound types it really depends on the materials used - nor wire wounds are equal.
 

Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #92 on: July 06, 2019, 05:36:23 pm »
This is the data on the SR-1 transfer standards, not only do my resistors exceed these specs but the cost is far lower.  Notice their initial accuracy is ±20PPM and calibration is only accurate to ±10PPM.  You also appear to not understand the definition of initial accuracy: “Initial Accuracy: The specifications stated in the TEGAM instrument catalogs and data sheets are intended as acceptance specifications and are guaranteed for 60 days from the date of shipment.”  You seem to think that initial accuracy is held indefinitely, no transfer standard does that.


http://www.ietlabs.com/pdf/Datasheets/TegamSR1.PDF

Note the initial accuracy is ±20 PPM and long term is ±50 PPM and calibration is only to 10 PPM, according to Try even after 2.5 years they are still within specifications.  He has nothing to complain about and I even offered a free calibration which he refused twice so I think it is time Try moved on.  He never presented any evidence that the resistors were out of spec.  He also bought a lot of other resistors from me and has never complained about those.  My standard off-the-shelf resistor exceeds the SR-1 specifications and for a lot less money and without post operation processing.

Just for your information, some time back Vishay was chasing after me to become a field applications engineer for them, Felix Zandman interviewed me himself, I turned them down in the end for personal reasons.  The job entailed flying all over the country and at that time I could not do that.  Vishay knew that I had the knowledge they needed, they approached me.  Your erroneous claim that I don’t know about Vishay technology is full of hot air.
 

Offline branadic

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Re: Statistical arrays
« Reply #93 on: July 06, 2019, 05:43:33 pm »
Come on, this thread is about statistical arrays and not about Edwin G. Pettis, if you don't have anything to contribute please be silent., Thanks.

-branadic-
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Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #94 on: July 06, 2019, 06:08:22 pm »
I'd be happy to Branadic, I didn't start this nonsense, dietert1 and Try interjected all this nonsense so please feel free to jump them first, it is only fair that I get to re-but them.

Measuring resistors on a DVM  is not a valid technique for determining how a given resistor will perfect in a given circuit under actual operating conditions.  Yes you get a bunch of data on how it is performing under test conditions which may have some indirect bearing on the circuit performance but if you want to know how that divider is going to work under actual conditions, make an actual circuit and try it, see what the end result is, then if it isn't performing as expected you can trace the source.  A resistor under actual operating bias and environmental conditions is not the same as hooking it to the front end of a DVM.
 

Offline dietert1

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Re: Statistical arrays
« Reply #95 on: July 06, 2019, 06:23:21 pm »
Dear Mr. Pettis, from your table i understand that buying two resistors from you to make a voltage divider will result in a division ratio with up to 10 ppm/K on the division ratio. This worst case happens if one resistor has +5 ppm/K, the other one -5 ppm/K and it means up to 180 ppm change on the division ratio in an 18°C temperature cycle.
I think i demonstrated above that a Nomca thin film resistor array, when wired correctly, will give you a small fraction of a ppm/K on the division ratio and an overall variation of less than 0.5 ppm with a 18°C cycle. The thin film array is a much superior solution, about 360 times better. Hard to understand what you want to contribute.

In the meantime i finished drying the 10 KOhm econistor (my example of a qualified wire wound resistor). The final result of the humidity test going from 32% RH down to about dry was -60 ppm after about 24 hours. Only then the econistor exhibited a hysteresis free 18°C cycle with a TC of 2.67 ppm/K. The negative sign of the 60 ppm resistance change is interesting. It means this huge humidity effect is not surface conductivity, but probably carrier size. Carrier gets bigger by water absorption, wires get stressed to be slightly longer and slightly thinner. Carrier shrinks when dry and resistance shrinks as well.
Started a similar test on Nomca thin film array, but drying is very slow. Effect on resistance is -12 ppm after 8 hours, yet only 0.21 ppm on division ratio (with 13:1 divider example).

Regards, Dieter
« Last Edit: July 06, 2019, 06:29:32 pm by dietert1 »
 

Offline Kleinstein

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Re: Statistical arrays
« Reply #96 on: July 06, 2019, 07:01:46 pm »
With the comments on wire wound resistors a possible important point got slightly hidden. The NOMCA arrays seem to have noticeable noise:
....
Regarding recent discussion, I was curious about 1/f noise of thin films, especially NOMCA vs larger models. I did a quick test dividing LTZ1000 voltage by 2 and measuring 0.1-10Hz pp noise within 1 minute period.

LTZ1000: 0.15 ppm
noname THT 3.3k metal film: 0.16 ppm
NOMCA 10k, 3 samples tested, 6 resistors used every time: 0.22-0.25 ppm
S102K (refurbished) 11k, 6 resistors used: 0.16 ppm

Additionally, long time ago I found this publication containing 1/f noise tests of various resistor types and models. Seems like a lot of models achieve good performance with almost no 1/f noise, even in SMD 0402 size.

This essentially means the arrays are not good enough for a 7 to 10 V step for a LTZ based reference. The resistor noise in this case seems to be about as much as the LTZ, even with using 3 resistors in parallel each.
They may still be OK with a LM399 based reference, or to set the temperature in an LTZ1000 circuit, at least from the noise side. A still open point is aging. Specs here are tricky, as there is no good and easy way to measure upfront and small differences in the protective layer / epoxy could make quite some difference.

Though not specified much different, there are also NOMCT arrays, using NiCr resistors. These may be better with TC matching / noise, but from what I have read so far could show a little more aging.

With wire wound resistors, there are also set available with TC matching better than the absolute TC. Even without this, chances are good that at least the 2 nd order part will compensate. Especially similar value resistors can be made from the same wire spool to give good matching.

With the resistor arrays the TC matching can on average improve with the statistical use of more resistors, but the worst case does not improve that much. Best case there are 4 resistors on each side. This would be on average an improvement by about a factor of 2 (maybe a little more as there is finite number of resistors and thus more gain than the normal square root N). Without individual matching / selecting the expected divider TC is thus more like 2 ppm/K, maybe often better if the initial specs are rather conservative or for a larger temperature range.
 
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Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #97 on: July 06, 2019, 07:04:03 pm »
No you are totally incorrect, you are confusing tolerance with TCR, the tolerance of those two resistors were within ±10 PPM as requested, the TCR would have been <1.0PPM°C, probably close to 0.85 PPM/°C, but that is not the tracking TCR, since both were made of the same wire the tracking TCR (ignoring external factors such as thermal differentials) would be likely less than 0.5PPM/°C (conservatively under real operating conditions)).  The tracking is affected by external environmental conditions which I have no control over and yes film resistors would have similar effects even on the same substrate but possibly smaller because they are much smaller physically but they are also affected by factors which have little to no effect on wire wounds.  Tracking is a very difficult specification to work out since it involves much more than just the resistors, each situation is different.

Yes you very well may be getting pretty close tracking on your NOMCA chip under those conditions, I am not particularly disputing your results, the question is how stable is it over time, your one off only shows that this one chip has these current specifications at this time.  The TCR and tracking TCR of my resistors do not shift significantly over time unless the resistors are subjected to extraordinary conditions.  Your calculations concerning my parts are quite incorrect.  I have demonstrated 0.1PPM to 0.2PPM ratio tracking over long term time by one of my customers, that is not to say everyone is going to achieve that low tracking value, it takes effort on the part of the customer as well.

Econistors are not equivalent to mine, their specs are not equal and as stated, all precision wire wound resistors are NOT the same.  If you are going to compare something against my resistors, then use my resistors but stop making erroneous comparisons thank you.

The table I posted is NOT mine, it is the SR-1 transfer resistor data table from ESI/Tegam/IET, my specifications are better than those which I said in the other posting, please read it more carefully.

It is this kind of misinterpretation which causes problems, it would be much better if you asked a question directly instead of posting first without comprehension.  Yes resistors, like most other components are much more complex that most people understand and when you're chasing PPMs, it gets even more difficult.
 

Offline Edwin G. Pettis

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Re: Statistical arrays
« Reply #98 on: July 06, 2019, 07:18:23 pm »
In general I agree with you, Kleinstein, those statements are accurate.
 

Offline Andreas

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Re: Statistical arrays
« Reply #99 on: July 06, 2019, 08:00:56 pm »
In the meantime i finished drying the 10 KOhm econistor (my example of a qualified wire wound resistor). The final result of the humidity test going from 32% RH down to about dry was -60 ppm after about 24 hours.

Hello,

usually I measure time constants for drying of epoxy in the order of 3-7 days at room temperature.
So it would be interesting what happens after the 24 hours.

Lars also stated 0.5-2ppm change for 8E16 resistors for each % relative humidity.
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1379236/#msg1379236

when I compare the humidity in Colorado with that of my region here I have minimum 30% more humidity.

with best regards

Andreas

 


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