Low ohm precision resistor standard and testing

[HighVoltage]

Thanks gamalot for the clarification, it makes sense now.

Your Hioki low resistance meter looks very good!
They are just sooo expensive.

[quarks]

because of the HIOKI RM3545 shown here,  I just updated my old "Resistance Comparison" chart, which I made several years ago, with some of the other gear shown here (and left in the FLUKE 8508A for reference)



Keithley 2460 is not fully shown here, because of the odd accuracy specs <2 Ohm and >20MOhm (which I did not calculate)


edit: found an error in HIOKI RM3545 graph and corrected it

[HighVoltage]

Thanks quarks for this nice chart.
And it becomes very clear now, why the 34470A is not suited for a 1 mOhm measurement as I have tried.

Also a surprise how much better the Fluke 8508A is in comparison to the Keysight 3458A for the full range.

[onemilimeter]

And it becomes very clear now, why the 34470A is not suited for a 1 mOhm measurement as I have tried.

Hi... quite sad to read this ... Is this "the 34470A is not suited for a 1mOhm measurement" mainly because of the low test current 1mA at 100-ohm range? Thanks.

[e61_phil]

Today I tried to measure a 1mR Isabellenhütte PBV 0.5% shunt on the 34470A. It showed 0.0010 Ohms.

[VintageNut]

Today I tried to measure a 1mR Isabellenhütte PBV 0.5% shunt on the 34470A. It showed 0.0010 Ohms.

What is the uncertainty of the measurement according to the datasheet?  You are only using 10 counts of a 10,000 count range.

[e61_phil]

Today I tried to measure a 1mR Isabellenhütte PBV 0.5% shunt on the 34470A. It showed 0.0010 Ohms.

What is the uncertainty of the measurement according to the datasheet?  You are only using 10 counts of a 10,000 count range.

I know it is nonesense to measure 1mR directly with the 34470A. I did it only because of the wired measurements HighVoltage took.

[HighVoltage]

Today I tried to measure a 1mR Isabellenhütte PBV 0.5% shunt on the 34470A. It showed 0.0010 Ohms.

What is the uncertainty of the measurement according to the datasheet?  You are only using 10 counts of a 10,000 count range.

I know it is nonesense to measure 1mR directly with the 34470A. I did it only because of the wired measurements HighVoltage took.

Thank you for making this measurement on your 34470A
It seems yours is at least better calibrated in this low ohm area than mine and I will have my meter definitely calibrated by Keysight Germany, in the next few weeks.

[HighVoltage]

Does anyone have any experience with the ex ussr milli-ohm standard resistors?

I got my first USSR precision resistor with a 1 Ohm nominal value.
No papers and no info was given by the seller.
So I can only go by what is written on the label

Model P3030 from 1986
It seems the 6 mm studs are pure silver or at least silver plated.

Measurements:
1.000068 Ohm - Keithley 2460 SMU
1.00005 Ohm - Agilent 3458A

I will keep this one hooked up to the Keithley 2460 SMU to take some Data over the next few days.
It will be interesting to see, how stable this one will be in comparison to the Burster resistors.

[e61_phil]

Can you tell me which uncertainty is achievable at 1R with the Keithley SMU?

I think a (or better two) 3458A can achieve 52ppm with an external current source (100mA) within 1 year specifications. Is the SMU better?

[manganin]

I got my first USSR precision resistor with a 1 Ohm nominal value. No papers and no info was given by the seller. So I can only go by what is written on the label

Soviet foil technology! Better initial adjustment accurary but less stable than the Krasnodar factory wire wound P321 (which unfortunately also suffers from the Soviet quality: there are very good examples, but you need to buy ten to find one.)

[HighVoltage]

Can you tell me which uncertainty is achievable at 1R with the Keithley SMU?

I think a (or better two) 3458A can achieve 52ppm with an external current source (100mA) within 1 year specifications. Is the SMU better?

I don't think the SMU is better than 52 ppm at 1 Ohm.
If I remember right, the Ohm uncertainty was something like 0.04% + 1 mOhm on the datasheet of the SMU. (I will have to look it up.)

But the 2460 SMU has 1 uOhm resolution in the 2 Ohm range, and the 3458A has 10 uOhm resolution in the 100 Ohm range.

[HighVoltage]

I got my first USSR precision resistor with a 1 Ohm nominal value. No papers and no info was given by the seller. So I can only go by what is written on the label

Soviet foil technology! Better initial adjustment accurary but less stable than the Krasnodar factory wire wound P321 (which unfortunately also suffers from the Soviet quality: there are very good examples, but you need to buy ten to find one.)

It seems you know these soviet resistors.
Thanks for this explanation.
Is the quality issue found in all ranges of the P321 or more in the lower or upper ranges.
May be I will get a 1 Ohm P321 and compare it to this P3030

[quarks]

Can you tell me which uncertainty is achievable at 1R with the Keithley SMU?

I think a (or better two) 3458A can achieve 52ppm with an external current source (100mA) within 1 year specifications. Is the SMU better?

if you look in my comparison chart above, you can see that 2460 accuracy is much worse than 3458

[e61_phil]

if you look in my comparison chart above, you can see that 2460 accuracy is much worse than 3458

Sorry, but I can't. The specifications for 1R are missing (best volts and amps combination for 1R).

And it seems to me, that you already calculated the best possible resistance uncertainty using volts and amps and not resistance measurement. Is that right? Because, the 3458A has about 10x15ppm+5ppm=155ppm uncertainty at 1R. If one combines 100mA (40ppm) and and 100mV (12ppm) you achieve 52ppm.

[quarks]

if you look in my comparison chart above, you can see that 2460 accuracy is much worse than 3458

Sorry, but I can't. The specifications for 1R are missing (best volts and amps combination for 1R).

And it seems to me, that you already calculated the best possible resistance uncertainty using volts and amps and not resistance measurement. Is that right? Because, the 3458A has about 10x15ppm+5ppm=155ppm uncertainty at 1R. If one combines 100mA (40ppm) and and 100mV (12ppm) you achieve 52ppm.

maybe I got your initial question wrong, but for me it is clear that the 3458A is much better than a 2460 for 1 Ohm

in my comparison chart I used resistance 1 year accuracy specs from the datasheets

[e61_phil]

maybe I got your initial question wrong, but for me it is clear that the 3458A is much better than a 2460 for 1 Ohm

It wasn't clear to me, that the Keithley SMU is in no range better than 100ppm. Therefore, 1R is also much worse than the 3458A.
I had a look into the datatsheet now.

in my comparison chart I used resistance 1 year accuracy specs from the datasheets

I read about 50ppm in your chart. The datasheet says 155pmm for 1R and 1year.

[quarks]

in my comparison chart I used resistance 1 year accuracy specs from the datasheets

I read about 50ppm in your chart. The datasheet says 155pmm for 1R and 1year.

3458A 1 year spec is 15ppm + 5ppm in the 10 Ohm range and for 1 Ohm this makes 65ppm

[e61_phil]

in my comparison chart I used resistance 1 year accuracy specs from the datasheets

I read about 50ppm in your chart. The datasheet says 155pmm for 1R and 1year.

3458A 1 year spec is 15ppm + 5ppm in the 10 Ohm range and for 1 Ohm this makes 65ppm

Yeyp, sorry. I interchanged ppm of reading and ppm of range.

[HighVoltage]

The Russian based Model P3030 1 Ohm resistor was now for almost 48 hours on the Keithley 2460 SMU at 100mA bias current.
And it shows a significant drift of 48 uOhm over 171.000 readings.
But may be that is normal?
And I dont know how much drift is contributed by the SMU.

I have also ordered a Burster 1 Ohm resistor for comparison purpose.

[2N3055]

The Russian based Model P3030 1 Ohm resistor was now for almost 48 hours on the Keithley 2460 SMU at 100mA bias current.
And it shows a significant drift of 48 uOhm over 171.000 readings.
But may be that is normal?
And I dont know how much drift is contributed by the SMU.

I have also ordered a Burster 1 Ohm resistor for comparison purpose.

Well,
it looks like you have P-P 48 ppm drift+noise on 1 Ohm..
Noise is 9.686 ppm RMS, roughly it looks like about 20 ppm P-P.. So median drifted about 20 ppm.
Keithley 2460 has Extended specs +-40 ppm/°C of reading.... (0,1% /°C of +-0,04%)... on 20 Ohm/100mA range..
Keithley alone could have drifted that much with change in temp of less than 0.5°C.

But that noise looks high.. 100mA range on 2460 is specified at 100nA RMS noise..
So contribution to noise from SMU should be in 100nV range RMS on 1Ohm resistor.. You seem to have 100x more noise..

Maybe cabling, external disturbances?
Did I calculate wrong?

Regards,

Sinisa

[HighVoltage]

Maybe cabling, external disturbances?
Regards,

Sinisa

I also suspected the cable and made a new one.

Well, I also got a new resistor to play with.
This is a Russian P321 1 Ohm in good condition, was suppose to be "new".
But it came without any paperwork.

I made a cable, Silver plated copper with crimped lugs (Low EMF) and PTFE insulation.
The shield is grounded to the 2460 SMU

The results are much better already, with close to 100.000 readings.
Pk/Pk is only 26 uOhm.

[HighVoltage]

Finally I got a Burster 1240-1, a 1 Ohm calibration resistor, "Made in Germany"
Condition: looks like new, came in original box.
Thank you eBay !

This one was made on 12.05.2000
Has a listed tolerance of 0.025% and a stated Imax of 1.5A
I have tested this resistor on my Keithley 2460 with 100 mA for a few hours.

Here are the results:
- Measured average value: 1.000 081 Ohm
- Pk to Pk over 6841 readings: 19.6 uOhm
I think I can be very happy with this resistor and first results.

[alm]

Noise for the Burster looks very similar to the P321. Still, the 3 uVrms noise seems high compared to the SMU specifications, suggesting that improvements are still possible with better shielding.

I think it is hard to make any statements about short-term drift since it appears to be buried in the noise of the setup. Averaging might help, or just measure over larger intervals.

[HighVoltage]

I think it is hard to make any statements about short-term drift since it appears to be buried in the noise of the setup. Averaging might help, or just measure over larger intervals.

OK, I turned the "Filter" ON and had it run over night.
Now we can see a drift of 34 uOhm
The temperature did fall about 1.5 °C in the same time.

May be it is time for me to get a temperature chamber.