Author Topic: Keysight B2980A series electrometer/picoammeter review/teardown  (Read 5632 times)

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Offline Kirill V.

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #25 on: April 01, 2020, 09:42:44 pm »
Stunts in the measurement were known in the previous era. Then what are the advantages of this particular electrometer over its predecessors? It can demonstrate an unsurpassed level of accuracy and sensitivity with the direct measurement method?
And it is very strange that with such a high sensitivity it is not possible to connect the source as close as possible to the input amplifier...
 

Offline guenthert

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #26 on: April 01, 2020, 10:09:32 pm »
How is it useful to use the resolution of this electrometer? I'm interested in a specific example where you really need a resolution of 10 aA without accuracy
  Accuracy of the meter is in most cases irrelevant.  Who cares whether a current is 2.02fA or 2.03fA?  Chances are the instrument is attached to a sensor measuring some other physical property and the whole system will have to be calibrated in place and probably frequently.
 

Offline TiN

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #27 on: April 01, 2020, 11:29:14 pm »
Relative measurements also don't care about accuracy. E.g. if electrometer used as a detector to find null between two current sources. Resolution and noise floor is important in this case, accuracy is not.
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Offline thm_w

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #28 on: April 01, 2020, 11:59:20 pm »
https://xdevs.com/doc/HP_Agilent_Keysight/B2987A/img/bem_ehigh_1.jpg

Wonder what is the deal here, three resistors are through hole mount, then there is the one white resistor surface mounted with no isolation routing. Maybe hand selected and solder after the fact?
 

Offline Kirill V.

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #29 on: April 02, 2020, 10:46:15 am »
This device is called a meter and not an indicator or null-meter. Therefore, it is necessary to know its accuracy, it is a formality of Metrology.
If you can't offer specific examples, I'll come up with an example specifically. I am a consumer and I need to measure 50 aA current. I read the data sheet of this meter and see that the manufacturer promises accurate and reliable measurement of currents with a resolution of 10 aA. Since they do not explain anything, I conclude that we are talking about a direct measurement method: source-cable-meter - look at the display and see the result. Can this electrometer really meet my needs in reality? And what abs. accuracy can I expect when measuring attoampere currents?
 

Offline Kirill V.

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #30 on: April 26, 2020, 01:52:24 pm »
Well, no one could answer. Now I am interested in the following question: the manufacturer loudly declares that this electrometer can measure resistance up to 10^15 Ohms. I know that back in the 60s, devices were able to measure up to 10^18 Ohms. In other words, Keysight is proud of the achievements of the last century?
 

Offline TiN

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #31 on: April 26, 2020, 04:48:26 pm »
Your posts more like statement, rather than a questions. You could surely see B2980A specifications and determine accuracy and reliability of the measurements by yourself in few minutes and simple excel spreadsheet. There is everything one need in specs to do so. If you need accurate measurement of 10 aA source, you are in territory of metrology field, not commercial instrumentation. You can buy something specifically designed for that, if your project have such needs.

Keysight probably proud that anyone can buy commercial instrument that you can put on the bench and measure high resistances/low currents without need of whole lab filled with vacuum equipment, ultraclean chambers, triple shielded boxes and sapphire insulators, like you often needed back in 60s. :)
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Offline Kirill V.

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #32 on: April 26, 2020, 05:45:13 pm »
This means that they are betting on Commerce and not on the best technical characteristics. I am trying to understand where the technique of electrometric measurements has gone today.
American companies are actively taking over the market and I am trying to understand what they offer.

 
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Offline shodan@micron

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #33 on: June 26, 2020, 06:25:39 pm »
Keysight B2985A noise floor test on 2pA range:

Output on, without cable, triax closed on RFI75-1 cap.



Null box emulator:





Output on, with N1412A cable, with null box emulator:


My lab in Instagram. LXI Instruments Data Logger apps.
I'm need tank of Bose-Einstein condensate....
 
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Offline Kleinstein

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #34 on: June 26, 2020, 07:19:06 pm »
The test with the cable seem to have a less stable temperature. There is also quite some drift residual settling in the current. This adds to the low frequency noise.  Extra capacitance at the input can also add to the noise - so a long cable does not really help, even of very high quality.

There is a chance the drift seen with the cable could be from dielectric absorption (either in the cable or meter irself, with lust less waiting time before).
 

Offline shodan@micron

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #35 on: June 26, 2020, 08:31:27 pm »
The test with the cable seem to have a less stable temperature.
Create a stable ambient temperature environment is too difficult for me.

B2985A is very temperature sensitive tool, it can detect very small wind flow. I'm doing test twice!! to get stable readings.

Remember, when you working with B298*A series electrometer:
  • do not enter to the room
  • do not open windows and door's
  • kick out the cats from the room
  • turn off the music!
Maybe then... you are get stable readings..... >:D

Unstable example:
« Last Edit: June 26, 2020, 09:04:26 pm by shodan@micron »
My lab in Instagram. LXI Instruments Data Logger apps.
I'm need tank of Bose-Einstein condensate....
 
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Offline shodan@micron

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #36 on: July 05, 2020, 08:33:36 am »
Keysight | B2980A Series Femto/Picoammeter and Electrometer/High Resistance Meter - Data Sheet

Ok...



Hm.... Keysight  you are liars !!! :-DD
My new "conventional electrometer" at 466$USD is superior!
Yours B2985 10k$USD too slow.
My lab in Instagram. LXI Instruments Data Logger apps.
I'm need tank of Bose-Einstein condensate....
 
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Offline bsw_m

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #37 on: July 05, 2020, 09:56:09 am »
So in ranges 2nA and higher B2985A really faster, that V7-49. But in pA ranges V7-49 is faster: 1pA range settling time 1s, 10pA and higher settling time is 100ms.
This is not a totally lie, these are marketing flaws  :-DD
« Last Edit: July 05, 2020, 10:01:30 am by bsw_m »
 
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Offline Kleinstein

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #38 on: July 05, 2020, 11:05:38 am »
As far as I can see the B2985A has higher ADC resolution. So one a fixed range one can get higher resolution or one could use a higher range to get a comparable resolution. To make use of higher ADc resolution one may have to add intentional filtering to reduce the noise and this adds to the settling, though it could probably be done better. In most real world application one has slow settling of the DUT anyway. One you are looking for fA's and below it often takes many minutes to hours for the DUT to settle.

There if often settling with more than one time constant: a fast part from classical RC time constants that may be fast (seconds to 0.1 - 1%) and than a slower process than may take minutes to hours to get down to below 0.01 % settling.

The "conventional" electrometer mentioned by HP is likely a Keithley meter.  A Rusian meter would be a exotic one on the US market.
 
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Offline shodan@micron

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Re: Keysight B2980A series electrometer/picoammeter review/teardown
« Reply #39 on: July 05, 2020, 02:53:03 pm »
Kleinstein, i use 2985 arround 2 years.
After touch to old, low cost, USSR electrometer, i've start thinking about sell 2985 and buying more sensitive old-stock USSR electrometer.

About resolution - i need extremely long time to get high resolution with 2985, it need's a day's of measurement and post-processing huge data massive, because 2985 is very noisy stuff.
My lab in Instagram. LXI Instruments Data Logger apps.
I'm need tank of Bose-Einstein condensate....
 


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