Learning how to use external trigger and sweep function - Page 1
Forum section: electronics / beginners

author: bsas
author_rank: Regular Contributor
timestamp: March 18, 2018, 01:55:27 am
content: Hi all, brand new noob/dumb question for youI am trying to do a simple audio sweep in my function gen (sine, 10Hz-15kHz, 200mVpp, 5sec, log).My idea is to try to learn how to use external triggering. So, the whole idea is to make the function generator to send a pulse at the beginning of the sweep and another at the end, so, my oscilloscope can start and stop the collection of data at the right moments. Nice idea, but, no clue how to do it with my equipmentI already tried a bunch of stuff and some scope tutorials, but no luck. Can anyone help me how?Scope: - Rigol DS1054Z (unlocked)Gen: Siglent SDG2042X (unlocked)The scope has a port called "Trigger Out" and obviously 4 channels. The function gen has "Counter", "AUX In/Out", and "10Mhz In/Out".Thanks!

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 18, 2018, 02:06:02 am
content: Unfortunately the DS1054z does not have an external trigger input. So if you want "external triggering" you need to use one of the four channels for the ext trig ... making it effectively a "3 channel + ext trig" scope.But for what you are doing, if I understand you correctly, you don't really need ext trig on the scope, you can just set the scope for a slow horizontal sweep rate and trigger from the same channel you are using to display the FG signal, then use the "single shot" sweep mode on the scope. Then play with the "Timeout" or other Advanced Trigger modes so that you can trigger only on the slowest frequency at the beginning of the sweep.Then you wind up with something like this: (first one in Normal acquire mode, second one in High Res acquire mode)

author: bsas
author_rank: Regular Contributor
timestamp: March 18, 2018, 05:02:46 am
content: Quote from: alsetalokin4017 on March 18, 2018, 02:06:02 amI am fine sacrificing one channel on the scope, I just need 2 for my things anyway for now. If so, how do I do it?I know I don't necessarily need to do that way, I just want to learn how to do it

author: llkiwi2006
author_rank: Regular Contributor
timestamp: March 18, 2018, 05:18:53 am
content: Quote from: bsas on March 18, 2018, 05:02:46 amPlug your trigger input into a channel you are not using, and set the trigger input on the scope to that channel. Then just set your trigger level and/or other settings like you would normally.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: March 18, 2018, 08:07:00 am
content: If I understand them correctly, the external trigger is just a "trigger only" channel. They are a channel that can only be used for triggering. Think of the DS1052 is a 2.5 channel (3 can trigger 2 can analyze) scope. The 1054 as a 4 channel (that can trigger and analyze) scope.

author: David Hess
author_rank: Super Contributor
timestamp: March 18, 2018, 05:28:15 pm
content: Quote from: alsetalokin4017 on March 18, 2018, 02:06:02 am4 channel oscilloscopes usually rely on one of their 4 inputs to serve as an external trigger input. That would be a problem with a 2 channel oscilloscope where you would have to sacrifice one of the vertical inputs for this function so they usually include one or sometimes even two external trigger inputs which are completely separate from the vertical inputs.As far as bsas' question, if the function generator can produce a trigger output indicating the start of the sweep from its auxiliary output, then connect it to any vertical input of the 4 channel DS1054Z, usually the forth one but it doesn't matter, and set the triggering to use that source. I have done this exact thing with my function generators and oscilloscopes to do swept scalar and vector network analysis and it works fine.

author: bsas
author_rank: Regular Contributor
timestamp: March 19, 2018, 04:54:25 am
content: Quote from: David Hess on March 18, 2018, 05:28:15 pmCool! So, any idea how to do that with my function gen? Thanks!

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: March 19, 2018, 05:05:03 am
content: One (of multiple) ways to do it with SDG2042X and DS1054Z. Connect generator channel 1 (note that channel numbers are arbitrary) output to scope channel 1 input. Connect generator Aux In/Out to scope channel 2. Set scope to trigger mode to Normal, on negative going edge pulse on channel 2, trigger level greater than 0V and less than 5V. Set generator parameters as desired, and in addition under sweep settings, set source (sweep trigger source) to Manual, and Trig Out to On. Then on page 2 of the sweep settings menu on the generator, press the button for Trigger to initiate a sweep. When you press the Trigger button, the sweep starts, and the generator emits a 40uS negative pulse from the Aux In/Out connector on the back of the generator.You can also set the scope to just trigger off of the same channel it receives the waveform on, however on the SDG2000X generators (not sure how others work), once you set up sweep mode, the generator always outputs a fixed frequency waveform (either the start frequence, stop frequency, or center frequency) on the output channel, and doesn't actually start the sweep until triggered. So you won't be able to get a sweep start synchronized capture by just triggering the scope on the same input (at least not without more complex triggering).

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: March 19, 2018, 05:21:52 am
content: Since learning, another way (previous and other ways would be more useful, but still will work, and since playing around, throwing it out there). Everything else still set the same, on the generator change the sweep Source setting from Manual, to External. This will revert the generator's Aux In/Out from an output, back to an input. Then instead of hooking the generator Aux In/Out to the scope second input channel, hook it in to the scope's Trigger Out on the back of the scope (so you have generator Aux In/Out to scope Trigger Out, and generator channel 1 output to scope channel 1 input). Now press the trigger 'Force' button on the front of the scope. This causes the scope to trigger, and send a trigger output to the generator, which causes the generator to initiate the sweep. Definitely not the most efficient way, but works.