Products > Test Equipment
Siglent SDS1000X HD 12bit DSO's
Performa01:
--- Quote from: robert.rozee on April 02, 2023, 10:53:42 am ---hopefully folks won't deride this as a silly question... but what practical usage advantage does a 12-bit scope have over an 8-bit scope?
it seems to me that 12-bits gets you a 16x vertical zoom advantage, but i can't see that as being something that would be of much value in most usage cases. and how much useful information do those extra 4 bits really carry?
--- End quote ---
First we should consider the fact that even on an entry level DSO, the vertical screen height (in pixels) is at least twice as much as the net number of levels in an 8-bit ADC. Thus, every data point is actually drawn as a line that is two (or even more) pixels high if you utilize a full screen waveform display.
This is an issue especially for the XY-mode, where this problem exists not only for the vertical direction, but also horizontally. Each display dot is actually a square of 2 x 2 pixels on an 8-bit scope. The sole reason why it still looks decent is the DPO technology, mixing a picture from thousands of single acquisitions.
The above have been only the visual effects so far.
Dynamic range is another important consideration, especially when using math, as has already been mentioned before. It makes a difference if we have a guaranteed genuine dynamic range of 49 dB or 72 dB – and this difference can be demonstrated quite easily. I have once shown a few examples in the SDS2000X HD thread…
--- Quote from: robert.rozee on April 02, 2023, 10:53:42 am ---a distinct disadvantage seems to be the loss of features at a given price point, as manufacturers need to cut costs elsewhere to pay for the 12-bit hardware. for instance: all else being equal, would you rather your 4-channel scope have a single shared 12-bit ADC, or 4 independent 8-bit ADC?
--- End quote ---
Well, this is not a valid question. If you need (or even only want) 12 bits, then you don't care.
Apart from that: few DSOs have independent ADCs per channel these days. Most of the better ones have two ADCs for four channels. At Siglent, the only exception currently is the SDS6000A (8-bit) and the SDS6000 H10/12 Pro (10/12 bit, available in China only), which use four independent 5 GSa/s ADCs.
--- Quote from: robert.rozee on April 02, 2023, 10:53:42 am ---i also wonder if much of the advantage of a 12-bit ADC could be achieved with front-end improvements that allow precise DC offsetting (even if only on 1 of the 4 channels) that gives you a view into a narrow vertical band (for example, dial in a 5v offset so you you can look at a 4.95v to 5.05v band without distortions due to over-driving of the front end).
--- End quote ---
A precise offset would be nothing new. I've already demonstrated several times, how we can measure for instance 205V with better than 0.08% accuracy even with the entry level SDS1104X-E (8-bit).
The overload issues on the other hand, are inherent to the split path input buffer design, universally used in all higher bandwidth scopes. This won't change anytime soon, because it is the prerequisite for accurate and stable DC offsets.
Performa01:
--- Quote from: robert.rozee on April 03, 2023, 12:20:29 am ---
--- Quote from: Martin72 on April 02, 2023, 10:13:10 pm ---https://www.electronicdesign.com/technologies/test-measurement/article/21805339/whats-really-the-difference-between-a-12bit-and-8bit-oscilloscope
--- End quote ---
good article, although i was a little puzzled by this part:
"Most modern, mid-range oscilloscopes include a high-resolution mode, which increases the number of bits by filtering. In essence, bandwidth is traded off for the increased dynamic range. Basically you get one additional bit for each halving of the scope’s bandwidth. Therefore, to achieve a 4-bit increase, it would reduce the scope’s bandwidth by 16:1. So if you start with a 1-GHz scope, increasing the resolution to 12 bits with the high-resolution mode would reduce the scope’s bandwidth to below 100 MHz."
my understand was that for each ONE bit increase, it required 4x oversampling, leading to a bandwidth [addendum: i should probably be talking about 'sample rate' here, not 'bandwidth'] reduction of 256:1 to get the extra 4 bits. perhaps we are instead seeing 10-bit ADCs being used with a further 2 bits then obtained in software to give us the final 12 bits. i shall need to research this point some more - if the author is correct then i have a few (abandoned) projects i need to revisit!
--- End quote ---
The resolution enhancement goes along with the oversampling. For instance, four times oversampling results in four times more resolution = 2 bits of additional resolution and at the same time only one fourth of the bandwidth.
Best example for this is the Siglent SDS2000X Plus in 10-bit mode. It utilizes four times oversampling for two additional bits of resolution and at the same time the bandwidth drops to about 100 MHz, because with all four channels in use, the sample rate is limited to 1 GSa/s per channel, therefore Nyquist is at 500 MHz and one fourth of that is 125 MHz.
The confusing part might be that the noise reduction is only 3 dB per doubling of the sample frequency. So it is only 6 dB for four times oversampling, thus resulting in an ENOB enhancement of only one bit.
Long story short: we have to distinguish resolution and ENOB – and this is why physical 12-bit ADCs are the superior solution compared to HiRes/ERES oversampling approaches, even when we ignore the bandwidth reduction caused by oversampling.
nctnico:
Remember: In the end you can't turn an 8 bit ADC into a 12 bit ADC just by oversampling. Getting extra bits relies on linearity and having enough & good noise to work with. Neither is guaranteed (and more likely not there in practical situation).
Also keep in mind that an oscilloscope is not a precission instrument. A 12 bit ADC gives extra resolution to look at small wiggles in a signal (which typically get removed by hires / eres BTW) but it doesn't give extra accuracy.
electr_peter:
SDS1000X HD would be very welcome seeing positive feedback on SDS2000X HD. According to datasheets, SDS1000X HD is the same as SDS2000X HD with lower parts count but with almost all capabilities of bigger brother (missing zone trigger, lower sample rate).
SDS2000X HD firmware currently is better developed than Rigol DHO(HDO)1000/4000, likely SDS1000X HD will be similar. Main attraction is 12 bit ADC in nice form factor and many features. If price is expected to be in 800-1000 USD range or even lower, this will be a no brainer.
Martin72:
Yepp, and if this price will come true, I wonder what else is "slimfasted" in comparison to the 2kHD...
One instead two ADCs, ok.
No inbuild awg, ok.
But same solid case, screen, maybe the same good encoders.
Where else could they have done to make it (if the price will come) appx 2500 bucks cheaper.
But that´s only guessing, time will tell and the first launched one in the hands of a teardowner...
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