Author Topic: T.C. measurements on precision resistors  (Read 240563 times)

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Offline lars

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Re: T.C. measurements on precision resistors
« Reply #775 on: December 20, 2017, 08:44:54 pm »
Hi Try,

Sorry I were sloppy. As you already figured out the temperature is °C and humidity %RH. All resistors (not dividers) are in ppm (parts per million). The resistor values are relative, that is I have applied an offset to scale it readable on the graph. So what you can for example see is that the 100kohm have about 50ppm seasonal variation for about 30%RH variation.

100, 1k, 10k and 100kohm are 8E16 wire wound resistors but the 1Mohm are standard 1% 50ppm/C 0.25W metal film through hole unknown brand. As can be seen it has higher drift per year but not so high seasonal variation. From the scale it has about +20ppm/year drift. I have tested very few MF and it is a lot of brands and types available so I have no idea what is reasonable to expect. What I have seen is that Yaego MF0207 0.1% (thick film) of 1Mohm have had up to 1000ppm/year (0.1%/year)! For lower values the Yaego MF0207 were better, down to below 100ppm/year. For Thin films I have mostly seen 5-20ppm/year for both through hole and SMD0805 I have tested. But as I said I have to little experience to say anything generic. Also remember this is tested without load on the resistors. The resistors normally have been mounted on FR4 boards. Many are in boxes as the attached picture. Between the measurements they are stored in a paper box in my lab with a room temperature of 16-32°C.

The resistors were tested with an HP3456A with 4W OC. But the results are relative to two very stable old GR1440 and series/parallel dividers as SR1010 and DIY but also checked against L&N 40xx, hermetic BMF's from Vishay and AE and old Tettex standards from 100ohm to 1Mohm. The GR1440's have a long term drift that the last 20 years have been below my measurement uncertainties.

Lars
 

Offline bopcph

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Re: T.C. measurements on precision resistors
« Reply #776 on: January 02, 2018, 03:20:55 pm »
The only way to get rid of this is to use materials that are immune to humidity such as metal, glas and ceramics which ends up in hermetic packages.

But it's not humidity only, there are a lot of materials that exibit gas in some way.

Will you care to tell my mass spectrometer that metal, glas and ceramics are immune to humidity ?!?
Yes, water doesn't penetrate any of the 3 materials (ceramics general speaking, I can find a significant number of ceramic type that does)
but you can "store" a significant and measurable amount of water in the surface of all 3 materials.

Even the super glossy polished stainless steel inner surface of my MS will suck serveral 100 ug water from my controlled lab environment
(20 degC, +/- 0.5 - 30-35%RH) if left open for just a few hours.
No, its not like a foggy mirror, you can't see it, and yes the SS is well beyond the dew point  ;)
 
For information:
You can get some epoxies that are quite immune to water - depends on how much you want to pay.


 

Offline Magnificent Bastard

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Re: T.C. measurements on precision resistors
« Reply #777 on: January 02, 2018, 05:27:01 pm »
You can get some epoxies that are quite immune to water - depends on how much you want to pay.

Can you elaborate?  Manufacturer and P/N please!
 

Offline Andreas

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Re: T.C. measurements on precision resistors
« Reply #778 on: January 11, 2018, 09:11:16 am »
Hello,

and here the remaining three 70K 8G16 resistors.
following conditioning has been made:

#4   baked 4 days then 6 days room temp     (so no longer reduced hysteresis visible after 6 days room temp)
#5   baked 4 d / room temp 6 d / cycling 4 d   (this candidate has rather low hysteresis but largest T.C.)
#6   baked 4 d / room temp 6 d / cycling 4 d   (again large hysteresis)

And finally the overview of the measured 8G16 70K resistors.
Compared to other PWW resistors or metal foil resistors these have a rather large stray of the parameters T.C., hysteresis and ageing drift. Compare also here:
http://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg848965/#msg848965

with best regards

Andreas



« Last Edit: January 11, 2018, 04:55:42 pm by Andreas »
 

Offline Andreas

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Re: T.C. measurements on precision resistors
« Reply #779 on: January 13, 2018, 04:37:34 pm »
Hello,

first result of a 120 Ohms econistor 8G16. Datecode 1522

box T.C. measured 8.7 ppm/K over 30 deg C.
hysteresis: deviation up to 45 ppm from LMS approximation.
drift: 10.5 ppm over 4 days.

so around the performance of a 15ppm/K RC55Y metal film resistor. But much more hysteresis than the metal film.
See RC55Y (1K) measurements on bottom of the post here:
http://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg462301/#msg462301

with best regards

Andreas
« Last Edit: January 13, 2018, 05:36:54 pm by Andreas »
 
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Offline cellularmitosis

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Re: T.C. measurements on precision resistors
« Reply #780 on: January 15, 2018, 03:47:18 pm »
Andreas, I hope to be able to contribute to this thread soon!  I spent the weekend spinning up a little rig to measure resistor tempco: http://www.eevblog.com/forum/projects/mini-tempco-characterization-rig/

Edit: fixing number of minor gridlines in chart
« Last Edit: January 15, 2018, 04:34:06 pm by cellularmitosis »
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Offline TiN

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Re: T.C. measurements on precision resistors
« Reply #781 on: January 16, 2018, 12:24:35 am »
Good. Details and setup? Do tell.
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Offline Pipelie

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Re: T.C. measurements on precision resistors
« Reply #782 on: January 16, 2018, 02:03:53 am »
Hello,

some results of my brand new VHP101 & VHP202Z,  I'm afraid there is only 20% chance you will get an almost zero TC resistor from the batches your order or so.   |O
 
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Offline cellularmitosis

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Re: T.C. measurements on precision resistors
« Reply #783 on: January 16, 2018, 02:30:25 am »
Good. Details and setup? Do tell.

Sure!  I put all of the details in another thread: http://www.eevblog.com/forum/projects/mini-tempco-characterization-rig/
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Offline TiN

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Re: T.C. measurements on precision resistors
« Reply #784 on: January 16, 2018, 02:33:29 am »
Why would you expect zero TC from VPG H/HZ? :) They are specified at 2ppm at best, which your number confirm well with margin.  :-+
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Offline cellularmitosis

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Re: T.C. measurements on precision resistors
« Reply #785 on: January 16, 2018, 06:33:34 pm »
Why would you expect zero TC from VPG H/HZ? :) They are specified at 2ppm at best, which your number confirm well with margin.  :-+

I just measured a 9K9850 VHP202Z at -1.3ppm/K.  What a bummer.  Now I understand what they mean by "0.2 +/- 2 ppm/C".  That means it could be as bad as 2ppm/C.

https://github.com/cellularmitosis/logs/tree/master/20180115-vhd202z

http://www.vishaypg.com/docs/63120/hzseries.pdf

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Offline Alex Nikitin

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Re: T.C. measurements on precision resistors
« Reply #786 on: January 16, 2018, 07:39:20 pm »
Why would you expect zero TC from VPG H/HZ? :) They are specified at 2ppm at best, which your number confirm well with margin.  :-+

I just measured a 9K9850 VHP202Z at -1.3ppm/K.  What a bummer.  Now I understand what they mean by "0.2 +/- 2 ppm/C".  That means it could be as bad as 2ppm/C.



For this particular resistor you can just add about 3.3 Ohm of copper wire in series and get very close to a zero tempco in this temperature range  ;) .

Cheers

Alex
 

Offline cellularmitosis

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Re: T.C. measurements on precision resistors
« Reply #787 on: January 16, 2018, 08:17:04 pm »
HMM, that’s a creative solution. At 40 AWG that’s only one meter of wire.
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Offline mimmus78

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Re: T.C. measurements on precision resistors
« Reply #788 on: January 16, 2018, 08:54:24 pm »
Any idea how much copper wire can be stable?

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Online Kleinstein

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Re: T.C. measurements on precision resistors
« Reply #789 on: January 16, 2018, 11:06:47 pm »
If not bend too much, the resistance of copper can be relatively stable - it just has the TC as intended in this case.
 

Offline Magnificent Bastard

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Re: T.C. measurements on precision resistors
« Reply #790 on: January 17, 2018, 03:08:03 am »
Pure Nickel wire ("Ni200") with a heavy high-temperature coating is much more corrosion resistant than copper, and also has a very high TC (~0.6%/oC).  If you are looking for time stability of more than a few decades, Nickel is the way to go (and you can even consider ordering gold plating on the wire for even better stability).  If you need a lot of resistance, then you might switch to BALCO wire.
 

Offline Alex Nikitin

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Re: T.C. measurements on precision resistors
« Reply #791 on: January 17, 2018, 03:40:53 am »
Any idea how much copper wire can be stable?

Inviato dal mio ONEPLUS A5010 utilizzando Tapatalk

There are published designs of copper wire based temperature sensors with better than 10mK stability, so in absence of strong thermal shocks a better than 50ppm long-term stability should be possible. In the practical case of this 3.3 Ohm compensation resistor it's potential instability is reduced by 1/3000 times ratio to the main resistor value, so should not be a problem.

Cheers

Alex
 

Offline texaspyro

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Re: T.C. measurements on precision resistors
« Reply #792 on: January 17, 2018, 04:26:43 am »

There are published designs of copper wire based temperature sensors with better than 10mK stability, so in absence of strong thermal shocks a better than 50ppm long-term stability should be possible.


The SR104 resistor temperature sensor uses a copper resistor for temperature compensation.
 

Offline branadic

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Re: T.C. measurements on precision resistors
« Reply #793 on: January 17, 2018, 06:11:30 am »
Hi all,

we X-rayed some PWW resistors today. Here is what the 8G16D from Rhopoint looks like. You can fairly see the strain-relief construction, but also how they try to decrease inductance, two seperate winding sets with opposite winding direction.

-branadic-

EDIT: Date code is 1722
« Last Edit: January 17, 2018, 07:07:50 pm by branadic »
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Offline Andreas

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Re: T.C. measurements on precision resistors
« Reply #794 on: January 17, 2018, 06:27:06 am »
Hello,

thanks Branadic,

Question: which date code did you use. Same batch as my 1522 above?

From the construction there should be low influence from the housing to the resistor windings.
(The sealing is only done from one side).
So I do not understand why I have that large hysteresis.

So is it the silicone rubber sealing directly on the windings or something else.

I think its time to measure a "naked" 8G16

with best regards

Andreas
 

Offline branadic

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Re: T.C. measurements on precision resistors
« Reply #795 on: January 17, 2018, 06:41:22 am »
Will answer that question tomorrow, as the resistors are still at work for further x-ray pictures.

-branadic-
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Offline mimmus78

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Re: T.C. measurements on precision resistors
« Reply #796 on: January 17, 2018, 06:55:59 am »
Any idea how much copper wire can be stable?

Inviato dal mio ONEPLUS A5010 utilizzando Tapatalk

There are published designs of copper wire based temperature sensors with better than 10mK stability, so in absence of strong thermal shocks a better than 50ppm long-term stability should be possible. In the practical case of this 3.3 Ohm compensation resistor it's potential instability is reduced by 1/3000 times ratio to the main resistor value, so should not be a problem.

Cheers

Alex
Copper is ok also from a EMF point of view as resistors leads are also of copper if I'm not wrong. Or not?

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Offline Dr. Frank

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Re: T.C. measurements on precision resistors
« Reply #797 on: January 17, 2018, 08:51:10 am »
Hi all,

we X-rayed some PWW resistors today. Here is what the 8G16D from Rhopoint looks like. You can fairly see the strain-relief construction, but also how they try to decrease inductance, two seperate winding sets with opposite winding direction.

-branadic-

Great!!!
I assumed, that the 120 Ohm type would be wound extremely tight to the outer case, but that seems not to be the case.
I've seen the same big hysteresis (and apparent T.C.) like Andreas on this value; the rest of the set was ok.
So there are other explanations to be found.
What about x-ray of a 12k econistor, in comparison?

Frank
 

Offline branadic

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Re: T.C. measurements on precision resistors
« Reply #798 on: January 17, 2018, 09:07:30 am »
Be patient, further images of 1k, 12k and 70k (complete resistor set) will follow. I also need to think about possible reasons for that large hysteresis.

-branadic-
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Offline Edwin G. Pettis

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Re: T.C. measurements on precision resistors
« Reply #799 on: January 17, 2018, 11:45:38 am »
Let's start with the questions about the G.R. resistor first, the rubber silicone filling in theory was put there to help absorb stress between the windings and the bobbin/shell, the problem I found was if the shell is overfilled with the silicone (i.e. no gap between it and the shell) it does just the opposite.  After quite a bit of digging I found that silicone rubber has an COE of 900 microinches/°C, somewhat higher than I thought it would.  So as the resistor gets hotter, everything is expanding and within a certain range, the silicone does absorb some of the stress but after that point it begins 'spreading' the stress around from the expansion against the outer shell and actually increases stress on the windings (even if you've cooked the resistor silly).  I found through actual measurements that this stress takes quite a bit of time to relax and even over a period of days just sitting, the resistors did not return to the original starting points, albeit the differences became smaller with time, almost none of the test resistors went back to the starting resistance.  I also had these tests confirmed by another independent tester.  So that becomes another variable in the stability equation.

Next, the question of how snug the windings are, as indicated in the X-ray, if you look closely at the X-ray, particularly the lower winding, you will see rater uneven, even sloppy turns of wire, not the even turns one would expect, that indicates that the tension of the wire was essentially uncontrolled during winding and during calibration the turns in the upper pi was likely loosened by the calibrator when searching for the correct resistance point.  I noticed that the wire size used in this resistor was unusually small for a 120R0 resistor, not the best idea.  To some degree, loose turns are good except when they are too loose and sloppy, this can cause problems (not so much in low ohms), the wire must be wound with a certain minimum tension, without that the resistors become inconsistent, this tension is taken care of later on.  In the resistor X-rayed, the less than great winding may be because of an inexperienced winder.

Also a problem is kinks or loops in the wire (often caused by insufficient tension while winding or by jerky feed of the wire from the spool), there appears to be a rather sharp bend in the wire at the top weld joint, these can affect the TCR, another point is that G.R. uses alloy 180 ribbon to connect the resistance wire to the lead, this is used by multiple manufacturers as an intermediary since Evanohm cannot be directly welded to a copper lead.  While it is a relatively small resistance, it is also of a higher TCR than Evanohm and is in series with the resistor at both ends, this will cause a slight hyperbolic curve in the TCR line particularly with lower resistances.  The main reason for using the ribbon is the attachment between the lead and Evanohm, as far as 'relieving' stress on the weld, yes and no, while molding the lead/ribbon into the bobbin does substantially prevent external applied stress on the lead from getting to the weld joint, it doesn't protect the weld joint from stress applied inside the resistor and like all welds of this tiny physical size, various factors come into play that can affect the weld joint, in turn affecting the overall apparent TCR of the resistor.

Not to throw bricks at the competition, but I'm trying to illustrate the complexity of the interaction of all the materials that can go into the making of a precision wire wound resistor and also applies to the film/foil resistors as well, there are no absolute solutions to completely fix any of the various causes of stress on the resistor/element.  Each set of materials has its own characteristics and interactions and when you're working in the lower PPM range, everything becomes important and more difficult to adjust for.

Finally, variables change with wire size used, larger wire sizes must be handled differently than smaller wire and the techniques used for winding varies with the size, how the wire is wound onto the bobbin can also affect the resistance.  One other 'myth' I'll pop while I'm at it, the misbelief that reverse winding the pi has a significant effect on overall inductance, it doesn't, measurements indicate that while there is a small reduction in overall inductance, it is not really that significant when it comes to AC signals.  The coupling between pi is quite loose and therefore has little cancelling effect because they are next to each other in series so the flux lines do not cancel significantly, not to mention that the Q of resistors is exceedingly low.

« Last Edit: January 17, 2018, 12:38:57 pm by Edwin G. Pettis »
 


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