An osciloscope that can trigger on two channels independently (!) - Page 1
Forum section: electronics / testgear

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: May 30, 2025, 08:11:57 pm
content: Doing a project with my son and playing with my old Tektronix Type 453 oscilloscope, I realised it can trigger on two channels independently.Is that cool or not? Was this a regular feature back in those days?I don't think modern digital scopes can do this at all (well, perhaps there are exceptions... Let me know in the comments).

author: electr_peter
author_rank: Unknown
timestamp: May 30, 2025, 08:34:40 pm
content: There are ways to trigger on two unsynchronized channels with digital scope (OR trigger; digital patter trigger; independent time base) and analog scope (choped or alternate trigger). Tek does some something of the latter.EEVblog #1235 - How To Align Signals On A Digital Oscilloscope

author: David Hess
author_rank: Super Contributor
timestamp: May 30, 2025, 08:41:07 pm
content: Quote from: RBBVNL9 on May 30, 2025, 08:11:57 pmIt was a regular feature because of how channel switching and trigger selection work on CRT oscilloscopes.Very early oscilloscopes had the trigger pickoff after the vertical channel switch for simplicity, so the channels triggered independently all of the time, and in ADD mode the trigger source becomes the added inputs. Later oscilloscopes with trigger source selection between the input channels kept the "vertical" source, so independent triggering and ADD mode still worked.I do not know what others did, but later when Tektronix implemented a fully independent channel switch for the trigger source, they duplicated the behavior of older designs with a vertical input even though there was no connection to the actual vertical source. Their early DSOs which had analog channel switches also support independent triggering. On my 2230 and 2232 DSOs, I usually leave the trigger source set to VERTICAL by default duplicating the operation of the earliest oscilloscopes.

author: nctnico
author_rank: Super Contributor
timestamp: May 30, 2025, 09:25:59 pm
content: GW Instek oscilloscopes have this feature (alternating trigger). And this is very handy indeed to get two unrelated signals visible on screen. But just like on an analog scope, the traces have no hard relation as they are acquired sequentially.

author: egonotto
author_rank: Super Contributor
timestamp: May 30, 2025, 09:26:39 pm
content: Hello,the DSO 2074G (Hantek (DSO3064A ?)) can trigger from all active channels (it is a 4 channel 70 MHz USB Oscilloscope) with individual timebaseBest regardsegonotto

author: sonpul
author_rank: Regular Contributor
timestamp: May 30, 2025, 09:42:19 pm
content: As far as I know, Uni-t oscilloscopes can do something similar. The mode is called Multi-Scopes.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: May 31, 2025, 03:45:09 pm
content: Thanks for the various replies!Noting that also (some) older Tek scopes could do this using the name "composite triggering", I checked it up in the manual of my 2465A and indeed: "Use a composite A-Trigger source only to compare asynchronous signals.To generate a composite trigger, select Vert trigger source, a trigger mode other than Auto Lvl, and Alt vertical mode.". So yes, I have two analogue scopes that can do this! Given that I have four analogue scopes and two of them have this, it must be not so rare after all ;-)Seeing the replies (here and to the YouTube channel), I see Hantel and Uni-T are digital scopes that can do this, too. As far as I know, my digital scopes cannot (some R&S, Keysight and Siglent models). But maybe I'm simply not aware of it, or maybe it will be a nice firmware update;-))

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: May 31, 2025, 03:54:55 pm
content: You are right in not having previously noticed the feature. The label says "NORM" trigger, which usually means something else on scopes.And even this scope, to the left it has a paddle switch to select AUTO or NORM trig, in the usual meaning we are accustomed to for scopes.Not very clear, IMHO

author: Wrenches of Death
author_rank: Regular Contributor
timestamp: May 31, 2025, 06:51:25 pm
content: Quote from: David Hess on May 30, 2025, 08:41:07 pmI've still got a number of four bay Tek 7704A's around here. With two 7B92A dual bases plugged in, you have four independent time bases. Plug in a couple of 7A26 vertical amplifiers and you have four channels, each with their own time base.I still remember how disapointed the first time I used my new "high tech" digital scope to find out limited it was with only one time base.WoD

author: David Hess
author_rank: Super Contributor
timestamp: May 31, 2025, 08:17:07 pm
content: Quote from: Wrenches of Death on May 31, 2025, 06:51:25 pmI have plenty of 4-bay mainframes and 7B92A timebases and I do not think that works. Alternate pairs mode will assign one 7B92A to one 7A26, but the delaying and delayed timebases of each 7B92A are still linked together.Update: The 5000 series 5B12N and 5B42 can operate as dual timebases, with one sweep for the left vertical and one sweep for the right vertical, but not split between channels of the same timebase. The 547 tube oscilloscope can split its timebases between channels in some cases.

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: May 31, 2025, 11:04:26 pm
content: the owon vds1022i also has alt trigger mode, it does come in handy every once in a while. it seems like it's a simple thing to implement since such a low cost device can do it, so i wonder why it isn't a more common thing