| Products > Test Equipment |
| Oscilloscope Zoom Out Quirk |
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| 2N3055:
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| SilverSolder:
--- Quote from: 2N3055 on May 11, 2020, 02:15:47 pm --- --- Quote from: SilverSolder on May 11, 2020, 01:26:12 pm --- --- Quote from: Wuerstchenhund on May 11, 2020, 12:42:57 pm ---[...] And if you make it a habit to always capture as long as sensible/possible then you are unlikely to find yourself in the situation that you need to access data which isn't instantly available and without having to stop the scope. --- End quote --- I guess that the Agilent/Keysight idea is to do that automatically, even if you have the scope set at a faster timebase. Can't really be argued that it is a harmful idea, and it is useful often enough that I noticed the behaviour and started using it. --- End quote --- Yes, 3000T doesn't really do it in RUN mode, and when you STOP, you get only 400us at full sample rate. If your problem domain is jumping between 2ns/div to 10us/div you're golden. I use it all the time on stopped acquisitions in that time scale. If you need to capture 10ms, you have to slow down. None of that is supporting Nico's scenario: Capturing in constant RUN mode, with triggers happening every 10-20 seconds (or when he presses the button on DUT), he's looking at one SPI packet full screen (10 something micro seconds), and then if that SPI packet is not right, he pulls back to 100 ms around the trigger and looks at the state of some other inputs to figure out state of device at he moment. And once he's happy with analysis, he presses the button on DUT for another go.. While staying in RUN mode all the time. No STOP or SINGLE. To make sure he can do that, he keeps scope in manual memory mode, sets it to some large memory setting, so on every trigger event scope will get enough of data. I do the same thing on Pico (3000T is not perfect for this). I set Pico to 100MS mem depth, set it to 10ms/div (100ms total) , zoom in to area arround trigger (or wherever the packet is in full capture), press RUN and off we go...At the bottom of screen, I will also have full decoded table of whole capture, where I can click and screen will zoom in and jump to that packet..When I'm ready to move forward I press button on DUT for next cycle. I don't see how is what I do more complicated (in fact it's less steps and more intuitive), and result is the same. --- End quote --- When you set the scope in manual memory mode to capture more data, is the "punishment" then that you get less waveform updates per second? |
| SilverSolder:
--- Quote from: Wuerstchenhund on May 11, 2020, 02:31:13 pm ---[...] Testing doesn't mean just poking something with an instrument to see what's coming out. --- End quote --- Well, most of the time that statement is accurate... but it seems very cut and dried unless you are in a controlled environment. Say you are repairing an unfamiliar and undocumented piece of equipment, you have absolutely no idea what is causing some obscure fault - so you are looking for clues. You might be following the "golden rule" of checking the supply voltages first, for example. So you might look for excessive noise on the lines. But at what frequency? Depends on the circuitry sipping the juice as much as the PSU, right? Could be 60Hz, 120Hz, or several megahertz. Taking a look around using different timebases suddenly seems more like a prudent strategy of elimination rather than random probing? --- Quote ---Testing properly means working methodologically, you have to spend some time thinking about what you have, what you want to achieve, what you ideally expect, what problems/issues you may encounter and how to address them, and then develop a test strategy which will give you the desired data in a reasonable amount of time and with reasonable effort. And then you go and execute your strategy. And if your strategy was sensible you get the data you need. If not, you re-strategize and execute again. Simples. --- End quote --- Sure, but that could describe playing chess or any other difficult activity... in other words, the description is not enough information to actually play the game well! |
| 2N3055:
--- Quote from: SilverSolder on May 12, 2020, 01:51:25 pm --- --- Quote from: 2N3055 on May 11, 2020, 02:15:47 pm --- --- Quote from: SilverSolder on May 11, 2020, 01:26:12 pm --- --- Quote from: Wuerstchenhund on May 11, 2020, 12:42:57 pm ---[...] And if you make it a habit to always capture as long as sensible/possible then you are unlikely to find yourself in the situation that you need to access data which isn't instantly available and without having to stop the scope. --- End quote --- I guess that the Agilent/Keysight idea is to do that automatically, even if you have the scope set at a faster timebase. Can't really be argued that it is a harmful idea, and it is useful often enough that I noticed the behaviour and started using it. --- End quote --- Yes, 3000T doesn't really do it in RUN mode, and when you STOP, you get only 400us at full sample rate. If your problem domain is jumping between 2ns/div to 10us/div you're golden. I use it all the time on stopped acquisitions in that time scale. If you need to capture 10ms, you have to slow down. None of that is supporting Nico's scenario: Capturing in constant RUN mode, with triggers happening every 10-20 seconds (or when he presses the button on DUT), he's looking at one SPI packet full screen (10 something micro seconds), and then if that SPI packet is not right, he pulls back to 100 ms around the trigger and looks at the state of some other inputs to figure out state of device at he moment. And once he's happy with analysis, he presses the button on DUT for another go.. While staying in RUN mode all the time. No STOP or SINGLE. To make sure he can do that, he keeps scope in manual memory mode, sets it to some large memory setting, so on every trigger event scope will get enough of data. I do the same thing on Pico (3000T is not perfect for this). I set Pico to 100MS mem depth, set it to 10ms/div (100ms total) , zoom in to area arround trigger (or wherever the packet is in full capture), press RUN and off we go...At the bottom of screen, I will also have full decoded table of whole capture, where I can click and screen will zoom in and jump to that packet..When I'm ready to move forward I press button on DUT for next cycle. I don't see how is what I do more complicated (in fact it's less steps and more intuitive), and result is the same. --- End quote --- When you set the scope in manual memory mode to capture more data, is the "punishment" then that you get less waveform updates per second? --- End quote --- If you set the scope to acquire 250ms worth of data every time it triggers, you get 4 triggers per second... It's that simple. |
| SilverSolder:
--- Quote from: tautech on May 11, 2020, 04:11:57 pm ---[...] Certain members have used this arse backwards capture analysis MO to attack brands that don't support it [...] --- End quote --- Which is of course silly, because any instrument has a large feature matrix of which this is only one item. In the long run, most manufacturers end up having all the popular features implemented one way or another. I know we shouldn't compare with cars, but since we love cars, it's hard not to... - if you are having an argument about which is best, standard or automatic gearbox, the answer inevitably depends on... who is driving the car. |
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