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| MSO5000 Bode Plot Capability: Is it Good Enough? [Many tips about a 1st scope] |
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| mawyatt:
Regarding the Bode plotting capability within various DSOs. Here's one that honestly we did not think possible, or ever attempted. This is the injection locking of an oscillator which requires the Bode function to correctly surmise the correct response in the presence of the oscillator signal, which is close to the measurement frequency!! We've added a snip from Razvi which is referenced in the thread, and note the Bode response curves from the measurements!! https://www.eevblog.com/forum/projects/injection-locked-peltz-oscillator-with-bode-analysis/msg4424434/#msg4424434 If you are in to non-linear dynamics, the injection locking phenomenon is fascinating, and having an instrument capable of displaying such is something we did not expect and required no post processing, this is right from the DSO:-+ Best |
| 2N3055:
--- Quote from: Fungus on October 02, 2022, 09:51:05 am --- And they've added a hires mode that will reduce noise to within spitting distance of a Siglent in a pinch thanks to the beast's massive sample rate. (but not on all channels simultaneously) --- End quote --- Stop repeating things that are not true. It doesn't work like that. And even more difference in Bode plot calculations, because of, physics.. It is not Siglent marketing but true. Fun fact is that even Rigol is not even pretending that what are you saying is true.. This is your own misunderstanding..... --- Quote from: Warpspeed on October 01, 2022, 11:28:53 pm ---What you require, really depends on the application and test envioronment. What are you planning to Bode plot ? Things such as frequency range, noise floor and dynamic range are pretty obvious, and many measuring instruments these days have some excellent features. If you are studying just analog type circuits, amplifiers, filters, servo systems etc... that is all pretty straightforward. These days switching power supplies are a significant area of interest, and Bode plots are just about a must have, if you wish to maintain your sanity. Switching supplies are are very Bode plotter unfriendly by being significant producers of wideband noise by the power components. Trying to resolve a sine wave of a couple of millivolts submerged in hundreds of millivolts of spikes and ripple is something very simple equipment is just not capable of doing. Its all very well the software being able to plot a nice smooth gain curve over 100db dynamic range, but unless millivolt or microvolt level signals can be resolved beneath huge levels of noise, the pretty plot on the screen is just not going to happen. Many if not all low end Bode plot systems just use direct analog to digital conversion and some clever number crunching. That works fine for demo purposes by the plotter salesman, but not when trying to make real world measurements on switching power supplies or in really noisy applications. The only way to do it is with a couple of very narrow band swept filters, similar in concept to a spectrum analyser. That can be done either with hardware or very sophisticated software to reject everything but the exact test frequency being run through the equipment under test. All very clever, but it does not come cheap unfortunately. So a simple low end Bode plotter may be all you need, or it may not work for you at all, depending on the test environment. --- End quote --- While in general what you say is true, you seem to not know how it is implemented.. Very narrow band swept filters with sophisticated software and processing synchronized with generator and vari-level sampling and vary-level stimulus is exactly how it IS implemented in Siglent. And it works very well.. |
| nctnico:
--- Quote from: 2N3055 on October 02, 2022, 01:41:54 pm --- --- Quote from: nctnico on October 02, 2022, 01:14:37 pm --- --- Quote from: balnazzar on October 02, 2022, 11:13:18 am --- --- Quote from: nctnico on October 01, 2022, 11:16:03 pm ---No. But depending on your location, a GW Instek GDS1054B could be a good alternative to buy a decent 4 channel oscilloscope (options can be enabled for free using a key generator available on this forum). For example: https://eleshop.eu/gw-instek-gds-1054b.html --- End quote --- Interesting. Mh. How does it compare to the Siglent? Snappier UI? The screen looks smaller than Siglent's, but it's still 7". Probably it's the scope body that's larger.. I'm seeing that people on this forum adapted a 8" screen, but it's far from being straightforward. Tell me, is that Eleshop a reliable vendor? Thanks! --- End quote --- IMHO Eleshop is a reliable vendor. I have bought some test equipment from them (and returned one as well because it didn't meet my expectations). The firmware for the GDS1054B is mature. If you do run into a problem, the service department from GW Instek is responsive and they will fix bugs (if you happen to find one). Personally I find GW Instek's UI easier to use compared to Keysight. The key difference is that GW Instek has a horizontal and vertical row of buttons which makes navigating through the menus much easier. The seperate 'select' button prevents you from turning the rotary encoder while pressing it and selecting a different menu item than the one you wanted to select (which typically happens to me when the rotary encoder and select button are integrated in one). --- End quote --- Little GW Instek 1000 has bode plotting? --- End quote --- No, but it leaves enough room in the budget to buy an analog discovery to do bode plotting with. It could be a more powerfull combo compared to buying a single, more expensive unit. |
| mawyatt:
--- Quote from: Warpspeed on October 01, 2022, 11:28:53 pm --- The only way to do it is with a couple of very narrow band swept filters, similar in concept to a spectrum analyser. That can be done either with hardware or very sophisticated software to reject everything but the exact test frequency being run through the equipment under test. All very clever, but it does not come cheap unfortunately. --- End quote --- Don't think a traditional SA actually "Sweeps" the analog filter, but "Sweeps" the LO of a Mixer to produce a result that fits within a fixed frequency high quality analog filter. Swept analog filters are very difficult to implement, and high quality swept filters like YIG types are large and expensive. So don't think Siglent is doing this but implementing an effective swept filter by means of a digital implementation of something similar to the Synchronous Sampling Technique. For this to work well the DR of the overall ADC conversion needs to be very good as well as the noise floor. With the dynamic scaling of the Ch1 and Ch2 input amplifiers and their low inherent noise this allows Siglent to do a very respectable implementation of the Bode Function, which our own experience confirms!! Best, |
| 2N3055:
--- Quote from: nctnico on October 02, 2022, 03:49:47 pm --- --- Quote from: 2N3055 on October 02, 2022, 01:41:54 pm --- --- Quote from: nctnico on October 02, 2022, 01:14:37 pm --- --- Quote from: balnazzar on October 02, 2022, 11:13:18 am --- --- Quote from: nctnico on October 01, 2022, 11:16:03 pm ---No. But depending on your location, a GW Instek GDS1054B could be a good alternative to buy a decent 4 channel oscilloscope (options can be enabled for free using a key generator available on this forum). For example: https://eleshop.eu/gw-instek-gds-1054b.html --- End quote --- Interesting. Mh. How does it compare to the Siglent? Snappier UI? The screen looks smaller than Siglent's, but it's still 7". Probably it's the scope body that's larger.. I'm seeing that people on this forum adapted a 8" screen, but it's far from being straightforward. Tell me, is that Eleshop a reliable vendor? Thanks! --- End quote --- IMHO Eleshop is a reliable vendor. I have bought some test equipment from them (and returned one as well because it didn't meet my expectations). The firmware for the GDS1054B is mature. If you do run into a problem, the service department from GW Instek is responsive and they will fix bugs (if you happen to find one). Personally I find GW Instek's UI easier to use compared to Keysight. The key difference is that GW Instek has a horizontal and vertical row of buttons which makes navigating through the menus much easier. The seperate 'select' button prevents you from turning the rotary encoder while pressing it and selecting a different menu item than the one you wanted to select (which typically happens to me when the rotary encoder and select button are integrated in one). --- End quote --- Little GW Instek 1000 has bode plotting? --- End quote --- No, but it leaves enough room in the budget to buy an analog discovery to do bode plotting with. It could be a more powerfull combo compared to buying a single, more expensive unit. --- End quote --- Analog Discovery II is 400€.... |
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