So now we have to start carefully distinguishing between memory depth and record length. Marketing will of course advertise the former rather than the later because it will be larger.
How does this limitation make sense for performance when the same amount or even less of the data would be processed? What requires more processing when a smaller part of the acquisition record is displayed and the sample rate did not change?
You can capture a longer timebase and zoom in. That's essentially the same as what you're asking for.
So now we have to start carefully distinguishing between memory depth and record length. Marketing will of course advertise the former rather than the later because it will be larger.
It has always been record length.
Why they made this choice is not understood by me, but it might be because they want two buffers of memory available (plus scratchpad for trigger correction or other management), and alternately stream one or the other to the processor. Or, it might simply be a marketing decision, to not compete with their higher-end models and offer the full memory space in normal acquisition.
In the Siglent, the full record length is available by increasing the timebase, and Siglent have made the decision that the true acquisition length should always set the memory depth. This appears to be a technical decision rather than a marketing decision, but doesn't seem to imply any hardware or software limitation. If you want to capture the full 200Mpt, simply zoom the instrument out, capture the data, and zoom in. If the instrument was continuously capturing the 200Mpt samples, then it would need to acquire and potentially process all of those while displaying only 0.01% of the actual acquisition. This would reduce the acquisition rate considerably.
Honestly I prefer that the acquisition record be the same size as or lightly larger than the viewed area unless I specify otherwise if it means a higher acquisition rate. Maybe Dave will go back and see how the acquisition rate changes at different time/div settings when the record length is being limited.
I tend to disagree with Dave here that it's a crippling and insane decision to not always capture the full memory. At least for lower sampling rates, it would take very long to fill the whole buffer. E.g. at 1MSa/s, it would need 200s to fill the buffer. I'd think nobody would accept a single shot mode that needed more than a second to display a signal after the trigger. On the Keysight scopes that people like to present as the gold standard, you usually only have less than 2MPts or so which kinda eliminates this problem due to a simple lack of deep memory.
Of course there would be cleverer ways to solve this by e.g. dynamically limiting the memory to ensure a relatively quickly (few hundred milliseconds) reaction in single trigger mode dependent on the sample rate. I'm sure that even then people would complain about the incomprehensible memory usage. So Siglent went the easy way. IMHO this is a reasonable decision and actually having a permanent history is a cool feature, isn't it?
You can capture a longer timebase and zoom in. That's essentially the same as what you're asking for.
No it isn't.
It's of no use whatsoever when the event only happens infrequently and you just managed to capture one and want to know what happened before/after.
QuoteOf course there would be cleverer ways to solve this by e.g. dynamically limiting the memory to ensure a relatively quickly (few hundred milliseconds) reaction in single trigger mode dependent on the sample rate. I'm sure that even then people would complain about the incomprehensible memory usage. So Siglent went the easy way. IMHO this is a reasonable decision and actually having a permanent history is a cool feature, isn't it?The way Siglent implemented it: no; it is half assed. For example R&S and Yokogawa allow to trade-off record length and history depth manually to have maximum control.
I tend to disagree with Dave here that it's a crippling and insane decision to not always capture the full memory. At least for lower sampling rates, it would take very long to fill the whole buffer. E.g. at 1MSa/s, it would need 200s to fill the buffer.
QuoteOf course there would be cleverer ways to solve this by e.g. dynamically limiting the memory to ensure a relatively quickly (few hundred milliseconds) reaction in single trigger mode dependent on the sample rate. I'm sure that even then people would complain about the incomprehensible memory usage. So Siglent went the easy way. IMHO this is a reasonable decision and actually having a permanent history is a cool feature, isn't it?The way Siglent implemented it: no; it is half assed. For example R&S and Yokogawa allow to trade-off record length and history depth manually to have maximum control.
The question in my mind is: is this something that could be changed in software so that the trade-off could be added as a feature? Or is this tied to hardware.
I think this is likely a couple of hours of work for Siglent to change. All the functionality is there in the software; it just needs to be wired a bit differently. The changes come down to adding an auto / fixed memory setting and create a hidden zoom function which is set the memory length selected by the user.
I tend to disagree with Dave here that it's a crippling and insane decision to not always capture the full memory.
I'm a newbie looking for my first scope which I'm saving up for ^_^. I was really set on the SDS1104X-E because of the great price, but this is really disturbing. Do we think Siglent will listen and fix this in a firmware update? (can it be fixed in firmware?)
Also can someone make a video showing how to use the dual display mode hack to get the sampling we want?
I'm a newbie looking for my first scope which I'm saving up for ^_^. I was really set on the SDS1104X-E because of the great price, but this is really disturbing. Do we think Siglent will listen and fix this in a firmware update? (can it be fixed in firmware?)
Also can someone make a video showing how to use the dual display mode hack to get the sampling we want? (maybe demonstrating with trigger/single shot)
Thanks guys. Maybe I will end up still getting the aforementioned model. I really dislike the visual layout of the Rigol's with the dual columns of buttons on either side and tiny on-screen icons, and the two shades of blue in the channels. Siglent looks really clean.