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12 bit Keysight... when?

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Wolfgang:

--- Quote from: Martin72 on December 23, 2023, 05:35:26 pm ---
--- Quote from: PELL on December 23, 2023, 02:15:03 am ---I guess because they have the best 10-bit ADC converter on the market.

The important thing about a scope resolution is the "Effect Number Of Bits" or "ENOB".

Many 12bits scope only has around 6~8bits of ENOB (depending on bandwidth and sample rate), while Keysight can easily reach this number with their 10bit ADC. One of my main guesses they actually design a 12bit ADC, but only say "it is 10bit" when marketing.

Surely one day they will reach 12bit, but I don't think they will announce before they polish enough.

--- End quote ---

The Keysight 10bit converter is not bad - or it is generally hardly "better"...


Edit: Not in the picture: Siglent SDS7000 H12:  7.5bits (3Ghz), 7.3Bits (4Ghz)
Siglent SDS2000X HD: 8.7bits/8.4bits(100/350Mhz)

--- End quote ---

Another point is the advertising method about resolution. Many bits on paper look nice, but the only thing that really counts is effective bits (ENOB). These figures are *always* below what the ADC can deliver,
and that means that the ENOBs of 12bit ADCs are around 10 at best.

See here: https://electronicprojectsforfun.wordpress.com/to-enob-or-not-to-enob/

It has become a fashion to brag about resolution (e.g., R&S claims "up to 18bits" for their MXO4 and 5), but not to give ENOB numbers. That is deliberately misleading. Keysight and even Rigol are serious and
have their ENOB values documented. Ironically, R&S even has a paper discussing their pro scopes and why ENOB is important. Only their own marketing department did not get it :) for the MXO4 and 5.

The R&S paper is here:
https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1er03/ENOB_Technical_Paper_1ER03_1e.pdf


2N3055:

--- Quote from: Wolfgang on January 17, 2024, 02:00:06 pm ---
--- Quote from: Martin72 on December 23, 2023, 05:35:26 pm ---
--- Quote from: PELL on December 23, 2023, 02:15:03 am ---I guess because they have the best 10-bit ADC converter on the market.

The important thing about a scope resolution is the "Effect Number Of Bits" or "ENOB".

Many 12bits scope only has around 6~8bits of ENOB (depending on bandwidth and sample rate), while Keysight can easily reach this number with their 10bit ADC. One of my main guesses they actually design a 12bit ADC, but only say "it is 10bit" when marketing.

Surely one day they will reach 12bit, but I don't think they will announce before they polish enough.

--- End quote ---

The Keysight 10bit converter is not bad - or it is generally hardly "better"...


Edit: Not in the picture: Siglent SDS7000 H12:  7.5bits (3Ghz), 7.3Bits (4Ghz)
Siglent SDS2000X HD: 8.7bits/8.4bits(100/350Mhz)

--- End quote ---

Another point is the advertising method about resolution. Many bits on paper look nice, but the only thing that really counts is effective bits (ENOB). These figures are *always* below what the ADC can deliver,
and that means that the ENOBs of 12bit ADCs are around 10 at best.

See here: https://electronicprojectsforfun.wordpress.com/to-enob-or-not-to-enob/

It has become a fashion to brag about resolution (e.g., R&S claims "up to 18bits" for their MXO4 and 5), but not to give ENOB numbers. That is deliberately misleading. Keysight and even Rigol are serious and
have their ENOB values documented. Ironically, R&S even has a paper discussing their pro scopes and why ENOB is important. Only their own marketing department did not get it :) for the MXO4 and 5.

The R&S paper is here:
https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1er03/ENOB_Technical_Paper_1ER03_1e.pdf

--- End quote ---

R&S is "selling" Hires mode as real bits..

Siglent for instance not only publishes ENOB figures but unlike some others also specifies how published number was measured.
From datasheet for SDS2000X HD :
ENOB*1 (typical):
(350 MHz) 8.4-bit, (200 MHz) 8.6-bit, (100 MHz) 8.7-bit
* 1:99.99 MHz input(100 MHz model uses 49.99 MHz),-0.5 dBFS,20 mV/div,50 Ω input impedance

Many manufacturers have the all the numbers, marketing don't care. 

Generally speaking marketing always speaks only off things that they can leverage as perceived advantage. They emphasize what they have...
While Keysight is talking it's ass off how important wfms/s is when talking about Megazoom scopes, they don't even mention it on Infinium-S series. Cause it has really low wfms/s because it is long memory analytical scopes. In datasheets for those it is all about how large memory is great..
So which one is true?

David Hess:

--- Quote from: 2N3055 on January 17, 2024, 02:45:01 pm ---Generally speaking marketing always speaks only off things that they can leverage as perceived advantage. They emphasize what they have...
While Keysight is talking it's ass off how important wfms/s is when talking about Megazoom scopes, they don't even mention it on Infinium-S series. Cause it has really low wfms/s because it is long memory analytical scopes. In datasheets for those it is all about how large memory is great..
So which one is true?
--- End quote ---

Marketing may also drive engineering.

During the Tektronix 22xx and 24xx era of DSOs, engineering came up with a way for the DSO to indicate that aliasing was likely present; just compare the trigger frequency with the sample rate.  So they had a prototype with an indicator to show when aliasing was present.  Leaving aside how useful this might be to inexperienced users, and keep in mind that everybody was an inexperienced user as far as DSOs back then, this feature was obviously dropped because it implied that Tektronix DSOs suffered from aliasing when their competitors did not.

Is there any actual use for the ENOB specification?  I would rather know the SFDR (spurious free dynamic range) which is directly observable with an FFT, and very likely where they are calculating the less useful ENOB from anyway.

Oscilloscopes used to specify aberrations, which is roughly equivalent to settling time.  I imagine these specifications would look especially bad on 12-bit and higher resolution instruments, some of which will never settle.  One reason sampling oscilloscopes are useful at lower frequencies is overload immunity and instant settling time.

tooki:

--- Quote from: 2N3055 on January 17, 2024, 02:45:01 pm ---
--- Quote from: Wolfgang on January 17, 2024, 02:00:06 pm ---It has become a fashion to brag about resolution (e.g., R&S claims "up to 18bits" for their MXO4 and 5), but not to give ENOB numbers. That is deliberately misleading. Keysight and even Rigol are serious and
have their ENOB values documented. Ironically, R&S even has a paper discussing their pro scopes and why ENOB is important. Only their own marketing department did not get it :) for the MXO4 and 5.

The R&S paper is here:
https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1er03/ENOB_Technical_Paper_1ER03_1e.pdf

--- End quote ---

R&S is "selling" Hires mode as real bits..

--- End quote ---
How do you figure, given that the MXO 4 and 5 have 12-bit resolution all the time (the native resolution of the ADCs) and have a "high def" mode you can enable on top of that?

Wolfgang:

--- Quote from: tooki on January 17, 2024, 08:08:42 pm ---
--- Quote from: 2N3055 on January 17, 2024, 02:45:01 pm ---
--- Quote from: Wolfgang on January 17, 2024, 02:00:06 pm ---It has become a fashion to brag about resolution (e.g., R&S claims "up to 18bits" for their MXO4 and 5), but not to give ENOB numbers. That is deliberately misleading. Keysight and even Rigol are serious and
have their ENOB values documented. Ironically, R&S even has a paper discussing their pro scopes and why ENOB is important. Only their own marketing department did not get it :) for the MXO4 and 5.

The R&S paper is here:
https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1er03/ENOB_Technical_Paper_1ER03_1e.pdf

--- End quote ---

R&S is "selling" Hires mode as real bits..

--- End quote ---
How do you figure, given that the MXO 4 and 5 have 12-bit resolution all the time (the native resolution of the ADCs) and have a "high def" mode you can enable on top of that?

--- End quote ---

Lets stick to physics:

- There are never more bits than an ADC can provide. Everything else is done by boxcar averaging and oversampling. While this can reduce noise, it will only make the inherent nonlinearities of the ADC more visible  >:D
These nonlinearities create spikes in the spectrum, automatically reducing dynamic range and also the resulting ENOB.

Most serious ADC chips have ENOB specs, depending on sampling rate, signal frequency, amplitude, ... The R&S MXO uses a Texas Instrument ADC (not even a bad one), and this one has ENOB values around 10
according to its datasheet. So - soory - no magic anywhere, except for the marketing guys who may plead incompetent.

An extreme (low frequency) example of a huge discrepancy between ADC resolution bits and useful bits are 24-32bit ADC used for digitizing. *Several* of the lower bits just drown in noise, still these ADCs are in the worlds best multimeters.
Its the linearity that makes an ADC premium.

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