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Help me understand oscilloscope peak acquisition mode

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Performa01:
You might want to read the section "Peak Detect" in my review document part 2 (SDS1104X-E Review 26-50):

https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/msg1371771/

This is for the little SDS1104X-E, but the working principle is the same on all higher class models too. So you should easily be able to reproduce the examples given in that article.

EDIT: Maybe you shoud read the section about the Normal Acquisition mode first, to see the problem that can be solved by peak detect.

rf-loop:

--- Quote from: Performa01 on December 05, 2023, 11:39:19 am ---You might want to read the section "Peak Detect" in my review document part 2 (SDS1104X-E Review 26-50):

https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/msg1371771/

This is for the little SDS1104X-E, but the working principle is thesame on all higher class models too. So you should easily be able to reproduce the examples given in that article.

EDIT: Maybe you shoud read the section about the Normal Acquisition mode first, to see the problem that can be solved by peak detect.

--- End quote ---

Manual have this:
"The oscilloscope acquires the maximum and minimum values of the signal within the sample interval" (However, it does not specify exactly how they are displayed.)

If the logic of the sentence is strictly interpreted, I could add it as an extension: "or maybe not" (based to SDS2kXHD).

For now, under Deeper investigation... (after I get SDS2kX+ on my table)

Performa01:

--- Quote from: rf-loop on December 05, 2023, 01:07:14 pm ---Manual have this:
"The oscilloscope acquires the maximum and minimum values of the signal within the sample interval" (However, it does not specify exactly how they are displayed.)

--- End quote ---
My document states:

--- Quote ---Peak detect mode uses a different strategy for data decimation: instead of using every nth sample from the ADC stream, one min/max pair out of 2n samples is stored. This way we cannot miss a transition; on the other hand we don’t get a faithful reproduction of the input signal anymore.

--- End quote ---

So the fuzziness of the description in the manual is the definition of "sample interval".

It should be obvious, that it cannot be the raw sample interval, which might be as short as 500 ps at 2 GSa/s.
It is the decimated sample interval instead, which is now twice as wide as for decimation in normal mode, because it contains a sample pair (min/max) instead of a single sample.

rf-loop:

--- Quote from: Performa01 on December 05, 2023, 02:11:46 pm ---
--- Quote from: rf-loop on December 05, 2023, 01:07:14 pm ---Manual have this:
"The oscilloscope acquires the maximum and minimum values of the signal within the sample interval" (However, it does not specify exactly how they are displayed.)

--- End quote ---
My document states:

--- Quote ---Peak detect mode uses a different strategy for data decimation: instead of using every nth sample from the ADC stream, one min/max pair out of 2n samples is stored. This way we cannot miss a transition; on the other hand we don’t get a faithful reproduction of the input signal anymore.

--- End quote ---

So the fuzziness of the description in the manual is the definition of "sample interval".

It should be obvious, that it cannot be the raw sample interval, which might be as short as 500 ps at 2 GSa/s.
It is the decimated sample interval instead, which is now twice as wide as for decimation in norml mode, because it contains a sample pair (min/max) instead of a single sample.

--- End quote ---

If set sample interval 100us. (decimated samplerate 10kSa/s)
Now if example OP use 10kHz signal he get as he have explained. And his signal was 10kHz. One full wave in every 100us sample interval and now important - IF this is sample interval in this matter.

It's quite sloppy to talk in User Manual about a sample interval but not say that it's not the same as a sample interval but something else, like 2*sample interval. If I think 10kSa/s, it really means that the time between samples is 100us, which is also the sample interval.

Now if we think about this R&S axle. There it takes the minimum and maximum that is within that one interval when it reads the undecimated samples of the ADC (the ADC actual sample rate). +
But Siglent does NOT work like this example. And at least I no longer know how it works exactly, because now I have SDS2kX+ in front of me.
It looks like it can detect the 200us interval, but... more tests are needed.

RoGeorge:

--- Quote from: AJ528 on December 04, 2023, 08:19:48 pm ---"The oscilloscope acquires the maximum and minimum values of the signal within the sample interval so that the peak (maximum – minimum) in the interval is obtained". While I understand the intent of peak acquisition mode, I'm confused how Siglent is implementing it.

For example, let's say that during the sample interval there is a maximum value of +1 V and a minimum value of -1 V. The manual says peak = (maximum - minimum) = (1 - (-1)) = 2 V. Does that mean the oscilloscope plots a point at 2V?

--- End quote ---

That in the user manual is some wrong phrasing.

For each "sample" in peak mode, the oscilloscope always displays 2 points, the max and the min value.  Not added, not subtracted, but both the min and the max one after another.  Always pairs of dots, even when max == min.

For your example with +1 and -1 in the same interval, it will display two consecutive dots, one display dot at -1V, followed by another dot at +1V.

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