Products > Test Equipment
7.5 digit bench DMMs comparison
Kjelt:
--- Quote from: Jay_Diddy_B on September 24, 2016, 02:19:04 am ---Calibration doesn't imply accuracy either. Calibration is not adjustment. Calibration is confirming that meter is inside the specifications. Calibration improves confidence.
--- End quote ---
As discussed in another topic with someone from a cal lab if you do not ask explicitly for adjustment and the meter is within a one year accuracy you are right.
If you ask explicitly for readjustment with the calibration they will do this but since they have double work they will charge you double. For a cheap lab with cal instruments suitable for 6,5 digits dmm this will already cost you the price of half the new meter (400-500) , i do not want to know how much an official 7,5 or 8,5 adj +cal will set you back for, probably the price of a brand new 6,5 digit dmm.
Dr. Frank:
--- Quote from: Dragony on September 23, 2016, 10:37:35 pm ---I found a suspiciously good comparison of DMM7510 vs 34470A. The DMM7510 is the clear winner. Can someone say if its plausible, or is it Keithley Propaganda?
http://imgur.com/gallery/Wbx7q
--- End quote ---
Clear winner in which aspect?
These tests are not well-grounded.
The absolute readings / uncertainty will depend on the passed time of usage, after last calibration, and this is not defined in his 'test'. The 7510 may be freshly calibrated, and the 34470A may have had last calibration one year ago. So that's an invalid comparison. In the end, both instruments are still well inside their 24h specs!
If you look closely to the StD statistics of the different DCV ranges (100mV, 1V, 10V), which is in practice identical to rms noise, you will see, that in contradiction to his final noise testing, the 34470A and the 7510 always show nearly identical StD.
He estimates the noise from the graphic display, obviously.
In this case, he could better have used the statistical function, again, w/o disturbing the cables, as he claims to have done during the uncertainty testing.
Also, a measurement on a single NPLC number gives a limited picture only.
NPLC 1 gives always noisy readings, not worth 7 digits, so NPLC 10 or better NPLC 100..500 (or averaged equivalents) would tell the interesting facts about noise performance for 7 1/2 digits.
TiN had organized a big noise comparison test, over a broad range of NPLC numbers for each instrument, which gives much more illuminative pictures on these instruments.
https://xdevs.com/article/dmm_noise/
But as far as I can see, still no contribution on a 7510, what a pity.
But anyhow, the comparison to the superior 3458A might give you a better understanding of that parameter testing.
To my opinion, and experience, the real performance of 7 1/2 digits instruments in terms of noise, stability specification and linearity do not justify at all their high price, twice or four times than of comparable modern 6 1/2 digit instruments. See also my already linked 465/470 comparison tests.
Anyhow, all their user interfaces, digitizing and nice graphical features are a big pro over old boxes like the 3458A.
So, if you are crazy enough, i.e. going volt-nuts, and spend 2 .. 4k $/€/SFr, I could fully understand that ;)
If you decide to buy Keysight '465A or '470A, don't forget to order the digitizing option, the additional 2M memory (recommended for digitizing) currently is for free.
The 7510 already comes with more and better features on this aspect, I think.
Frank
EEVblog:
--- Quote from: Dragony on September 23, 2016, 10:10:42 pm ---As far as I have found out so far the only available rather recently released 7.5 DMMS are Keithley DMM7510 and Keysight 34470A. Do you know any other ones?
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When you are looking at this high end you really shouldn't consider anything else unless you have a very specific niche requirement for something.
What's wrong with 6.5 digit BTW?
HighVoltage:
I have the Keysight 34470A for a while now and like it a lot for my VoltNuts addiction.
The calibration of this one is 1 1/2 years old
Now I have brand new Keithley DMM7510
This one was calibrated in 8/2016
In the next few days I will make some comparison measurements between the two.
But so far I see the following on my LTZ1000A reference:
The 34470A reads about 18 uV high
And the DMM7510 is about 20 uV low
What is really impressive with the 7510 is how quick it is warmed up to show a stable reading.
I have not measured it, but it is less then one minute, it seems.
Both instruments are recommended.
The handling is just very different.
If you are in to low current measurements, the 34470 has a 1 uA current range and the DMM7510 has a 10 uA current range.
And the 34470A is just amazing, in measuring this low current.
I have not tested this on the Keithley meter.
Mickle T.:
--- Quote from: Dragony on September 23, 2016, 10:37:35 pm ---I found a suspiciously good comparison of DMM7510 vs 34470A. The DMM7510 is the clear winner. Can someone say if its plausible, or is it Keithley Propaganda?
http://imgur.com/gallery/Wbx7q
--- End quote ---
It's a Keithley Propaganda.
--- Quote ---[–]NorthBus ... 1 year ago
I'm an analog hardware engineer from the Keithley 7510 project team ...
https://www.reddit.com/r/electronics/comments/2t6935/keithley_7510_gsmdmm_released_75_digit_1_plc_45/
--- End quote ---
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