Products > Test Equipment
Most accurate signal generator
loop123:
--- Quote from: nctnico on April 02, 2024, 10:19:09 am ---
--- Quote from: loop123 on April 02, 2024, 10:05:51 am ---
--- Quote from: gf on April 02, 2024, 09:43:04 am ---
--- Quote from: nctnico on April 02, 2024, 08:49:57 am ---Regarding the bottom picture: The noise is there but the sampling frequency and/or bandwidth is too low to make noise appear as jagged edges. Run an FFT on both signals (using equal record lengths and sampling frequencies).
--- End quote ---
It is the same noise in both plots. Therefore the spectrum of the noise floor is the same as well. Flat up to ~1kHz, then rolling off with 12dB/octave. The first plots adds a 50Hz sine wave to the noise, and the 2nd plot adds a 900Hz sine wave to the noise. However, time/div is different in both plots in order to fit 10 signal periods of 50Hz or 900Hz into the screen width.
[ The units of the x-axis are samples, at a sample rate of 48kSa/s, in both plots. ]
--- End quote ---
They have same noises but isnt it the 2nd plot has more clean and more easily resolvable sine waves? doesn this mean it is better to make higher frequency signal to create cleaner sine waves?
Please tell me the software you used so I can play with it.
--- End quote ---
The 2nd plot isn't more clean! It has less samples. If you can dump the samples into a file and read it into an audio processing program (like Audacity which is free), you can do an FFT analysis. But make sure record an equal number of samples for each recording if you want to compare.
--- End quote ---
gf (just wondering if a he or she), can you pls use the same sampling (used at 50Hz) at 900Hz to show the same noise as the 50Hz plot?
gf:
--- Quote from: nctnico on April 02, 2024, 10:19:09 am ---The 2nd plot isn't more clean! It has less samples.
--- End quote ---
Sure, it spans a shorter time interval. But the OP wanted to know what to expect upon zoom-in.
The 2nd plot would look different, of course, if the noise would be white, and not lowpass filtered.
But without filtering, the total noise level (over the full ~20kHz audio bandwidth) would be much higher as well.
ebastler:
--- Quote from: loop123 on April 02, 2024, 10:31:34 am ---gf (just wondering if a he or she), can you pls use the same sampling (used at 50Hz) at 900Hz to show the same noise as the 50Hz plot?
--- End quote ---
If you mean, show the 900 Hz signal over the same 10000 data points as used in the 50 Hz plot: You will not be able to resolve the actual 900 Hz oscillations, and will see a signal trace which is a big fat solid band, filling the plot.
gf:
--- Quote from: loop123 on April 02, 2024, 10:31:34 am ---gf (just wondering if a he or she), can you pls use the same sampling (used at 50Hz) at 900Hz to show the same noise as the 50Hz plot?
--- End quote ---
With the same time scale, 180 periods of the 900Hz signal. would need to fit into the screen width. Even w/o noise, the plot becomes so dense that you hardly can see the waveform any more. You had explicitly asked how it would look if you zoom-in in order to inspect the waveform in detail.
loop123:
--- Quote from: gf on April 02, 2024, 10:45:57 am ---
--- Quote from: loop123 on April 02, 2024, 10:31:34 am ---gf (just wondering if a he or she), can you pls use the same sampling (used at 50Hz) at 900Hz to show the same noise as the 50Hz plot?
--- End quote ---
With the same time scale, 180 periods of the 900Hz signal. would need to fit into the screen width. Even w/o noise, the plot becomes so dense that you hardly can see the waveform any more. You had explicitly asked how it would look if you zoom-in in order to inspect the waveform in detail.
--- End quote ---
I only use and familiar with Audacity which uses time scale in horizonal and not sample format. what other popular software uses samples format so i can try them all? tnx
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version