| Products > Test Equipment |
| Bode Plot Torture Test |
| << < (5/7) > >> |
| mawyatt:
--- Quote from: Someone on November 09, 2022, 08:42:19 pm --- --- Quote from: mawyatt on November 09, 2022, 01:53:47 pm ---So maybe Siglent is "listening" and will open the "Black Box" and/or allow more user parameter adjustments!! --- End quote --- That's it, you post a generic topic and then push the particular upsides of the Siglent, no possible comparison, no discussion. This would be far better titled... Todays experiment with Siglent bode plot, adding synthetic noise. We get it, you like the built in Siglent app and you find uses for it. But it pushes you to do that in very specific ways and is slow. You haven't pushed its limits or shown how/why/where it fails, so this smells like fanboy/boostering/astroturfing. --- End quote --- I'm sure if we had a Tek, R&S, KS, LeCroy or Rigol DSO we would also find the Bode Function useful, however we have the Siglent DSO, so that's what we use. In your opinion, which BTW really doesn't matter, the title should be changed, maybe you should have started this thread!! Regarding "smells like fanboy/boostering/astroturfing", think you've already done as masterful job on yourself regarding Anti-Aliasing & DSO behavior over here ;) https://www.eevblog.com/forum/testgear/bode-plot-computational-time-for-various-dsos/25/ Anyway, this topic is about DSO built-in Bode Plots and how they may be applied/beneficial in the presence of outside noise like influences/disturbances and not about any specific DSO brand or preference. Personally think there have been some very useful and constructive posts by various folks, so instead of bashing everyone/thing here, if you don't have any useful constructive input then buzz off and go find another thread to distract!! Best, |
| nctnico:
IMHO noise is not the main problem for doing network analysis as most of the suitable algorithms get rid of noise anyway. And in some cases noise is good to get some extra bits from an ADC. The worst noise can do is swamp the DSO input and thus making it impossible to switch to a low enough range to acquire meaningfull data. What is more likely to be a problem are interfering signals (= external signals with a fixed frequency), harmonics and DUT behaviour. It would be interesting to come up with a DUT that really tests the limits of FRA / network analysis. Another thing I have not wrapped my head around entirely is calibration. On my network analyser I do an offset calibration before doing any measurement. Or to be more precise, I can choose from a variety of calibration methods depending on the type of measurement (reflection, pi-network or through). It would be nice to have some kind of zero-calibration in FRA on an oscilloscope as well. At least through would be nice. Then again I don't know how well the vertical (V/div) ranges are calibrated in respect to eachother. The frequency response can certainly differ at higher frequencies so a calibration cycle would need to test every range. OTOH with a typical DC error of 2% at most (say up to 1MHz) the error is less than 0.2dB but it could be much higher when going over -say- 50MHz. |
| mawyatt:
--- Quote from: nctnico on November 10, 2022, 04:10:54 pm ---IMHO noise is not the main problem for doing network analysis as most of the suitable algorithms get rid of noise anyway. And in some cases noise is good to get some extra bits from an ADC. The worst noise can do is swamp the DSO input and thus making it impossible to switch to a low enough range to acquire meaningfull data. What is more likely to be a problem are interfering signals (= external signals with a fixed frequency), harmonics and DUT behaviour. It would be interesting to come up with a DUT that really tests the limits of FRA / network analysis. --- End quote --- Oscillators and SMPS seem like good candidates!! BTW you should consider doing the test that rf-loop performed with your DSO, this revels the Frequency Selective nature of the "Black Box" Bode Functions and helps one understand the effects and limitations imposed by such, same goes for the non-linear effects shown by TopQuark. Maybe others will also perform these on their respective DSOs, may revel the strengths and weaknesses of various implementations which is what this thread was originally intended to show. Best, |
| Someone:
--- Quote from: rf-loop on November 08, 2022, 07:20:30 pm ---How to get this FRA RBW figure. Well it is simple as... Very extremely simple way to do it. There is not DUT at all. Just one fixed signal. During sweep, in this case signal to Ch2 is fixed 350kHz sinewave and amplitude is fixed 2dBm (roughly full scale when 100mV/div) Nice detail is that there can also see signal 2nd harmonic and there in 700kHz FRA RBW is bit more wide. Of course, I have lot of more details about this thing also done with some other ways etc. --- End quote --- This is interesting as it shows the detector being frequency selective, but having zero/no rejection of external signal. Which is the opposite of the example in the first post (external signal rejected). Do you know why this is so different? What options/methods/parameters can a user control to make such a difference? |
| switchabl:
--- Quote from: Someone on November 10, 2022, 10:00:10 pm ---This is interesting as it shows the detector being frequency selective, but having zero/no rejection of external signal. Which is the opposite of the example in the first post (external signal rejected). Do you know why this is so different? What options/methods/parameters can a user control to make such a difference? --- End quote --- Unless I missed something, in the OP the spurious tone is simply added to the input. Its frequency is also conveniently located on a sweep point, where it will basically just increase stimulus power and maybe shift the phase (both of which is accounted for through the reference channel). And the step size is probably larger than the receiver BW, so adjacent points are hardly affected. |
| Navigation |
| Message Index |
| Next page |
| Previous page |