At 100 M Ohm I would not expect more than 6.5 digit performance.
Well, bridge like ESI 242D and older versions of this system.
There is one in unknown condition on bay now for 3K. If you get it, fix it, calibrate it, than you can get 3458A or better performance.
Hi all
I am wondering what best to get for measuring resistance with very high precision.
There are all the well known Keysight, Keithley, Fluke, Transmille etc. 8.5 digit multimeters that would be fine.
But is there something more special that has a lower price tag than the $10.000-ish tags these meters usually have?
Any ideas?
several years ago I opened a similar topic, most likely there should still be some useful information in it
https://www.eevblog.com/forum/chat/help-wanted-low-and-high-ohm-measuremet/msg169139/#msg169139
(Anyway, a slightly defective ESI DC801 is sitting on my bench. Does somebody have the schematic of the non-A, non-B, non-bigger-character-suffix? The meter inside is by the way a HP 37-419 null detector, so the schematic of this would be great!)
What utter nonsense....I have used, calibrated and repaired 242D systems since 1973! I have consistently been able to calibrate a 242D to within 1 PPM from 100 ohms to 1 Megohm, slightly increasing to 2 PPM towards the top end of 11Megohms and gradually increasing to 5 PPM on the lowest range mainly due to resolution limitations. They are completely traceable to primary standards with low uncertainty. I don't know where you're getting your information but it either incorrect or those 242Ds you've fussed with were not properly calibrated. My system 242D is fully traceable through the SR-104 with uncertainty as low as under 0.5 PPM against it. The uncertainty does increase slightly the farther you go from the 10K range but it is still quite small. A 3458A only comes close to a 242D at a 10K cardinal point if directly calibrated against an SR-104, beyond that, the 3458A is not as accurate as a 242D. It does take skill and experience to achieve such performance.....and don't both quoting the manual to me, those are conservative specifications and the 242D is quite capable of better performance, I've got the years of experience to know so. Each 242D system is a bit unique so quoting just how long a 242D will maintain that 1 PPM accuracy depends on each bridge. If you're worried about it, a quick check against the SR-104 will take care of that.
What utter nonsense....I have used, calibrated and repaired 242D systems since 1973! I have consistently been able to calibrate a 242D to within 1 PPM from 100 ohms to 1 Megohm, slightly increasing to 2 PPM towards the top end of 11Megohms and gradually increasing to 5 PPM on the lowest range mainly due to resolution limitations. They are completely traceable to primary standards with low uncertainty. I don't know where you're getting your information but it either incorrect or those 242Ds you've fussed with were not properly calibrated. My system 242D is fully traceable through the SR-104 with uncertainty as low as under 0.5 PPM against it. The uncertainty does increase slightly the farther you go from the 10K range but it is still quite small. A 3458A only comes close to a 242D at a 10K cardinal point if directly calibrated against an SR-104, beyond that, the 3458A is not as accurate as a 242D. It does take skill and experience to achieve such performance.....and don't both quoting the manual to me, those are conservative specifications and the 242D is quite capable of better performance, I've got the years of experience to know so. Each 242D system is a bit unique so quoting just how long a 242D will maintain that 1 PPM accuracy depends on each bridge. If you're worried about it, a quick check against the SR-104 will take care of that.
If you are looking for good accuracy, an older 3456A will give you very good performance at a very good price point, a lot of bang for the buck. Unless you can justify the cost or real need, instruments like the 242D and 3458A tend to be too costly for the hobbyist unless you have deep pockets, calibration is not cheap if you intend on keeping them at peak performance and you will find very few calibration shops that will calibrate an 242D to capability and not just spec, same thing goes for the 3458A.
I've got a 3456A sitting on my bench near the 242D, it is checked against the 242D/SR-104 and my Vref often, so far, it is holding calibration better than the 1 day spec of 10 PPM at 122 days since I calibrated against the Vref.....not too shabby for a 30+year old DVM. I have not tweaked it because I'm curious what the drift will be for 6 months, just to compare it against manual specs.
What utter nonsense....I have used, calibrated and repaired 242D systems since 1973! I have consistently been able to calibrate a 242D to within 1 PPM from 100 ohms to 1 Megohm, slightly increasing to 2 PPM towards the top end of 11Megohms and gradually increasing to 5 PPM on the lowest range mainly due to resolution limitations. They are completely traceable to primary standards with low uncertainty. I don't know where you're getting your information but it either incorrect or those 242Ds you've fussed with were not properly calibrated. My system 242D is fully traceable through the SR-104 with uncertainty as low as under 0.5 PPM against it. The uncertainty does increase slightly the farther you go from the 10K range but it is still quite small. A 3458A only comes close to a 242D at a 10K cardinal point if directly calibrated against an SR-104, beyond that, the 3458A is not as accurate as a 242D. It does take skill and experience to achieve such performance.....and don't both quoting the manual to me, those are conservative specifications and the 242D is quite capable of better performance, I've got the years of experience to know so. Each 242D system is a bit unique so quoting just how long a 242D will maintain that 1 PPM accuracy depends on each bridge. If you're worried about it, a quick check against the SR-104 will take care of that.
If you are looking for good accuracy, an older 3456A will give you very good performance at a very good price point, a lot of bang for the buck. Unless you can justify the cost or real need, instruments like the 242D and 3458A tend to be too costly for the hobbyist unless you have deep pockets, calibration is not cheap if you intend on keeping them at peak performance and you will find very few calibration shops that will calibrate an 242D to capability and not just spec, same thing goes for the 3458A.
I've got a 3456A sitting on my bench near the 242D, it is checked against the 242D/SR-104 and my Vref often, so far, it is holding calibration better than the 1 day spec of 10 PPM at 122 days since I calibrated against the Vref.....not too shabby for a 30+year old DVM. I have not tweaked it because I'm curious what the drift will be for 6 months, just to compare it against manual specs.
Edwin,
initially I did not intend to spread the word about it you but with you bragging about your measurement abilities while simultaneously failing to meet the specs I think others should be aware of my negative purchase experience with you.
This is what I wrote to you 2/27/2018 20:19:
Hello Edwin,
I hope you are doing well!
Unfortunately I have an issue with your resistors, they are off specification.
In your email dated on Christmas Eve (12/24/2016 18:30) you stated:
...The two 10Ks were about -2 PPM and -6 PPM from nominal....
When measuring them with PTB at the maker fair on 8/27/2017 they were 10,000 441 and 10,000 397 kOhm.
As the 3458A they used this time hadn't been calibrated/adjusted* for some time I waited for a arrival of a friend.
Last Friday we both went to the university department he had worked for.
We had a 3458A in there, 5 years old and never calibrated since.
We measured 10,000 485 kOhm and 10,000 491 kOhm.
By comparing to a Vishay VHP in 10k my friend had measured at work with his annually calibrated 3458A we were able to determine that the 3458A at university was reading roughly 16ppm too high.
But even then, the real value of your resistors would rather measure an adjusted 10,000 325 kOhm and 10,000 331 kOhm.
I just measured them on my 34401A that I adjusted to PTB specs at the maker fair and they were both at 10,000 34 kOhm.
I have to assume that the two candidates have either never exhibited the resistances you indicated or that they drifted roughly 35 ppm in just nine months.
The following pictures shows one of the two 10k resistors specified 10ppm (your writing!) that I purchased from you at the end of 2016. I just measured it. They are both way off spec.
Now I have to read in this thread that you have a 3456A on your bench which you could have used to verify the resistor you produced for me what you obviously not bothered to do for a client order in the 10ppm precision range.
Conclusion:
Please do not claim high precision. You are probably a good source for PWW resistors in the 0,1% or 0,01% class and are delivering a good service that you do not charge for by producing PWW resistors with resistances as per customer specification.
I always enjoyed reading your contributions and still do with a grain of salt but the former confidence is gone.
I hope that the bunch of knowledge you acquired will show up in your PWW products sometime in the future.
And as opposed to my last email to you where I hinted to you that I ordered and paid 10ppm class and received two classes below:
You can continue to ignore it - no problem.
Greetings from Germany
try
* The 3458A had been calibrated in the voltage ranges shortly before the fair but not in the Ohm ranges.
Last Friday we both went to the university department he had worked for.
We had a 3458A in there, 5 years old and never calibrated since.
We measured 10,000 485 kOhm and 10,000 491 kOhm.
By comparing to a Vishay VHP in 10k my friend had measured at work with his annually calibrated 3458A we were able to determine that the 3458A at university was reading roughly 16ppm too high.
But even then, the real value of your resistors would rather measure an adjusted 10,000 325 kOhm and 10,000 331 kOhm.
I just measured them on my 34401A that I adjusted to PTB specs at the maker fair and they were both at 10,000 34 kOhm.
try
* The 3458A had been calibrated in the voltage ranges shortly before the fair but not in the Ohm ranges.