(Siglent SDS1104X-E) How is trigger frequency counted during blind time? - Page 1
Forum section: electronics / testgear

author: Spacemarine
author_rank: Newbie
timestamp: May 04, 2019, 11:10:29 am
content: After getting the Siglent SDS1104X-E, i have done some reading about DSO blind time and it's implications. One thing is still unclear to me: As I understand it, after each filling of the memory depth, the DSO needs some time to process the collected data. During that time it is unable to respond to new signals.But how can it measure the trigger frequency during this time? Or does it ignore the trigger during blind time? But in this case, shouldn't the appearant frequency change if the recorded signal becomes so short that only one trigger is visible before the DSO becomes blind?I'm also interested how other scopes handle this, not only the siglent.

author: rf-loop
author_rank: Super Contributor
timestamp: May 04, 2019, 11:38:26 am
content: Quote from: Spacemarine on May 04, 2019, 11:10:29 amSignal, via ADC, to digital trigger system is continuous. Independent of blind time.So it can count continuously.Blind time do not stop this red marked signal (data stream, digitized analog input signal).How data stream is stored to memory and handled for display. There is also blind time.You can imagine trigger counter signal is one extra output from this Digital Trigger Circuit what do not sleep when scope have "blind time".Also same if we talk about bit older analog trigger systems in digital oscilloscopes.Signal, via analog side pathway, to analog trigger system is continuous. Independent of blind time.So it can count continuously.Even when digital acquisition system have blind time this analog side pathway to trigger comparators and also trigger counters works continuously. In old analog trigger system it is perhaps more easy to understand that blind time do not affect this side pathway where from can take signal to trigger counter.Conventional analog side pathway trigger system (fun is this text in image).

author: Spacemarine
author_rank: Newbie
timestamp: May 04, 2019, 12:11:44 pm
content: Thanks, that makes it clear!

author: 2N3055
author_rank: Super Contributor
timestamp: May 04, 2019, 12:30:28 pm
content: rf-loop made a nice post that explains it well.On Keysight 3000 it is pretty much the same, trigger circuit runs continuously regardless os state of acquisition engine.Trigger event detector can trigger with frequency of up to 25 MHz (ideal case), despite acquisition engine being much slower..That makes retrigger time of pure trigger engine as fast as 40 ns, although acquisition engine cannot go faster than one acquisition every 1 us in ideal circumstances. Hence max acquisition rate off 1MWfms/s

author: Spacemarine
author_rank: Newbie
timestamp: May 04, 2019, 02:04:58 pm
content: Quote from: 2N3055 on May 04, 2019, 12:30:28 pmBut it can count much faster, right? The frequency counter goes much higher.

author: Old Printer
author_rank: Frequent Contributor
timestamp: May 04, 2019, 02:33:32 pm
content: This is an excellent article about waveform update rates and trigger blind time, from a member here exiled, but not forgotten. P.I.P. Wuerstchenhundhttps://forum.allaboutcircuits.com/xfa-blogs/wuerstchenhund.471615/

author: 2N3055
author_rank: Super Contributor
timestamp: May 04, 2019, 02:41:19 pm
content: Quote from: Spacemarine on May 04, 2019, 02:04:58 pmfrequency counter seems to have separate path and goes to 1GHz