Will we ever see a 9.5 digit dmm?

[Zucca]

After reading the thread about Tek retiring the K2002, I am wondering if anyone will develop a 9.5 digit device?
What will be the next step in precision EE devices?

[coromonadalix]

i dont think so,  beyond 8.5 digits,  if it was needed, we would have seen some ...  and calibrate theses ........  would be astronomicaly pricey

imagine at 120,000,000 counts   getting an absolute value of say 100,000,000  what reference would you use beyond 8.5 digits famous ltz1000 to do 9.5 digits and get 1,000,000,000   ?

[Sensorcat]

I also don't think so, because the need for 9.5 digits resolution is so specific to certain tasks, perhaps in science. There's no point in creating a generic instrument, a DMM, for this. If you need it, you can create an instrument for the particular application, taking advantage of everything the application may offer to reach that goal, like tailored acquisition/integration time, perhaps multiple acquisitions for each measurement, tailored probe interface, etc., etc. Everything that a generic instrument would not have, because it then loses it's versatility.

[bdunham7]

After reading the thread about Tek retiring the K2002, I am wondering if anyone will develop a 9.5 digit device?
What will be the next step in precision EE devices?

Yes, you could whack another digit on any of the current 8.5-digit models.But what is the point of a billion-count DMM with tolerances greater than 1ppm?  The old Fluke 8842A is a 5.5-digit device with a maximum error (99%) at 10V of 5 counts.  That's impressive, IMO.  Show me an 8.5-digit DMM with a 5 or 10 count tolerance rather than another digit.

[Zondar]

It's not quite the same thing, but if you have a spare U.S. $350,000, NIST can provide a programmable voltage standard good to at least a part in 10^10 over -10V to 10V. You could make do with that.

https://www.nist.gov/sri/standard-reference-instruments/sri-6000-series-programmable-josephson-voltage-standard-pjvs

NIST says no tire-kickers need apply. 

For what more normal people might buy (at least those with already-deep pockets), even the market for 8.5 digits seems too thin to support more.

[oPossum]

.

[Kleinstein]

Already the current 8.5 digit DMMs are not 100x more accurate than a typical digit 6.5 meter. The noise is barely there, usually a bit more averaging / time needed than with 6 digit meters. Many modern meters are not directly quantization limited, but more noise limited and via the computer interface provide extra digits. So the effective counts are kind of set by the RMS noise.
Already for testing the stability and linearity one needs lower noise. So at the high end with relatively slow meters you can't expect the last digits to be accurate. The given resolution is the noise limit, not the accuracy.

Another limiting point are the voltage references and naturally the external voltages to measure. Even if you have a super stable  voltage reference in the meter, essentially all voltages to measure would not be as stable. At some 10% of the range or just at the limit to not have a lower range the reference noise is already a bit less critical and good resolution with a not so great reference still makes some sense.

One may get a 9 digit meter in the sense of more than 200 million counts. Or a noise of less than 5 ppb of the range (at least with low input voltage and some time for averaging). That would be something like a factor 2 up from the currently best DMMs.

One can already get beyond the 8.5 digit resolution with specialized resistance bridges and for voltages with cryogenic JJAs at a rather high price.
Still speciallized instruments - not a DMM.

[5U4GB]

After reading the thread about Tek retiring the K2002, I am wondering if anyone will develop a 9.5 digit device?
What will be the next step in precision EE devices?

Yes, you could whack another digit on any of the current 8.5-digit models.

You could do it right now with only a software change. Who's going to be able to prove your ninth digit isn't showing the correct value?

In fact it wouldn't surprise me if there weren't already some 13-digit meters on Aliexpress, powered by 50,000mAh 18650s and with 500,000lm backlights.

[tszaboo]

If it's only for the resolution, and linearity then it should be possible.
 I think we can improve on the voltage reference, by double ovenizing the circuits, so the reference resistors and support circuit would be oven controlled as well. A Fluke 732 has 0.3ppm 30 day accuracy, where a 3458A has 4ppm (from the top of my head). So an order of magnitude improvement is possible. Also 32 bit ADCs exist now.
That being said, I also don't think a generic DMM with that makes sense, it would be just too expensive. Current ranges are always going to be a lot worse, resistance ditto. And I don't think you want to pay so much for a generic instrument where most of the features you don't use. But perhaps something like a Keithley 2182A, with more digits.

[laichh]

This topic was discussed some time ago:

https://www.eevblog.com/forum/metrology/9-digit-multimeter-feasible/

https://electronics.stackexchange.com/questions/450454/why-isnt-there-any-9-5-digit-multimeter-or-higher

[MadTux]

So like 6 1/2 digits of useful data and 3 digits of noise?