Siglent SDS 1102CML scope Re 1sec/div Horiz sweep for Educational Demo - Page 1
Forum section: electronics / testgear

author: Fran3
author_rank: Newbie
timestamp: January 10, 2020, 01:51:56 pm
content: Just got a Siglent SDS 1102CML scope and am learning its features.I'm setting up a simple educational demo feeding different DC levels into the scope to show how it responds by moving the beam vertically as it sweeps horizontally.I have set up a 1-second per division horizontal sweep...But the scope stores/illuminates the sweep path...I just want to see a "dot" moving across the screen...I'm guessing there a menu setting somewhere that turns off "storage" so the scope just sweeps a point of light across the screen much like the old CRT scopes.Any suggestions on how to do this?Also...With either zero DC or 1 volt DC as the input...I want to manually trigger the sweepBut I can't seem to find the trigger setting to do this.I've setup Edge Trigger on CH 1 on the rising edge and "Single" Mode (which I assume to be one sweep only)Then I press the "Force" button to start the sweep...But nothing happens.the "Auto" mode will show the sweep but I can't start it when I want it to start... and it stores the trace as opposed to showing the "dot" moving across the screen.Any tips would be helpful.Thanks

author: tautech
author_rank: Super Contributor
timestamp: January 11, 2020, 04:49:26 am
content: Quote from: Fran3 on January 10, 2020, 01:51:56 pmNot possible.There is no analog signal path to the display unlike a CRO where the raster can be slowed enough to produce the result you'd like.Instead you need apply a different way of thinking when using a DSO primarily as it acquires a series of data points then subsamples it to the display.So there are a few things to understand to see why DSO's are so different to CRO's which are primarily the sampling rate, memory depth and how they are each influenced by different timebase settings plus the effects or interpolation vs dot mode.Exercise.Connect the probe to the 1 KHz compensation output and select the Acquire menu. Watch the reported sample rate change with timebase setting adjustments while remembering the max acquisition rate is 1 GSa/s.Now speed up the timebase to show the rise time well magnified then select Display menu>Dots and while the acquisition is still running we have enough overlaid data points to show a continuous trace yet if we select Stop only the last series of data points will be shown.The displayed dots in Single or Stop mode represent the memory depth available at any given timebase setting for the scope to reconstruct a waveform from.QuoteFurther to above, all behaviour outside Auto triggering mode is determined by trigger level vs signal input and selection of Normal or Single mode.Other things that confuse with DSO's vs CRO's is the actual trigger point where in this model (CML+) it's NOT at the far left of the display but in the middle however you can place it where you like yet it may shift off the display but can easily be centered again with a press of the H-Pos control.Also a vertical trigger level indicator is visible on the left of the display and between H-Pos and trigger level we set the conditions the waveformmustmeet before anything is displayed in Normal or Single modes.Use of a channels 0V level to the peak of a waveform WRT the # of graticules and input setting gives us the amplitude values just like a CRO or we can engage Measurements and specify a channel and measurement type.Oh, and welcome to the forum.

author: Fran3
author_rank: Newbie
timestamp: January 12, 2020, 11:25:41 pm
content: Thank you Tautech. Reading your post I learned some stuff about the scope.I do understand storing and displaying individual samples of the input.However they could have "emulated" the single dot moving across the screen at 1-div/sec as we would have seen in an old CRO...but in most, if not all, real world applications that is probably not necessary.That said, I can make my task work with the slow sweep path being displayed so no problem there.Regarding manually triggering a single sweep of a DC voltage equal to either zero or X...I can obtain my goal using an external trigger wired to a push button switch connected to a DC source.So, we are good. Thanks again for your response.BTW, what is "WRT" ?Thanks :-)

author: nctnico
author_rank: Super Contributor
timestamp: January 12, 2020, 11:40:30 pm
content: No roll mode? Roll mode (if supported) shows the signal as a continuous trace on the screen scrolling from right to left.

author: tautech
author_rank: Super Contributor
timestamp: January 13, 2020, 12:24:47 am
content: Quote from: Fran3 on January 12, 2020, 11:25:41 pmWith respect/regard to.You will have discovered the auto Roll mode at timebase setting above 50ms/div which 'sort of' allows for how you want to operate the scope and in effect it gives you the info you want to see just not how you've been used to.Keep discovering what it can do and how it does it however many DSO's are a little different how you get the visual feedback at slow timebase settings. Faster is usually fine just using a hint of Persistence so to emulate the phosphor decay in a CRO.