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).
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. ]
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.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.
The 2nd plot isn't more clean! It has less samples.
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 (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 (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?
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.
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
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
It's really a simple conversion as long as a fixed sample rate is always used. 10,000 samples in 200 ms, 50 samples per ms, 1 sample per 20 µs. I am not sure where your problem with those plots lies?
If you use 40000 samples per 20µs instead of 1 sample. and you zoominto the 900Hz sine wave. You can already see the jagged edge noises, isnt it?
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?
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.
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
It's really a simple conversion as long as a fixed sample rate is always used. 10,000 samples in 200 ms, 50 samples per ms, 1 sample per 20 µs.
It's really a simple conversion as long as a fixed sample rate is always used. 10,000 samples in 200 ms, 50 samples per ms, 1 sample per 20 µs.
Btw, just to clarify: I had calculated my plots at 48kSa/s (which is a commonly used audio sample rate).
1 seconds = 48000 samples, 200ms = 9600 samples, etc.
Unfortunately, I was lazy. I should have labeled the time axis in seconds (instead of samples) to avoid confusion.
Ok. I'm familiar with 48kSA/s since my Audacity uses that audio sample rate too. Let's say the audio sample rate is 2000kSA/s instead of just 48kSA/s then you can already see the jagged edge noise in the 900Hz, right?
Ok. I'm familiar with 48kSA/s since my Audacity uses that audio sample rate too. Let's say the audio sample rate is 2000kSA/s instead of just 48kSA/s then you can already see the jagged edge noise in the 900Hz, right?
No, it is not a matter of the sample rate (48kSa/s is more than enough for this signal), and it's not a matter of sampling.
It is a matter of filtering. Feeding an analog white noise signal though a corresponding analog filter would have the same effect.
Btw, it's not difficult to do the same simulation in Audaity, too. I'm not familiar with this program, still I was able to find all the tools within a couple of minutes. Create one track and fill it with a sine wave. Create a 2nd track and fill it with white noise. Create a 3rd track by mixing the two tracks. Apply lowpass filter to the 3rd track. Done. See attachment.
Ok. I'm familiar with 48kSA/s since my Audacity uses that audio sample rate too. Let's say the audio sample rate is 2000kSA/s instead of just 48kSA/s then you can already see the jagged edge noise in the 900Hz, right?
No, it is not a matter of the sample rate (48kSa/s is more than enough for this signal), and it's not a matter of sampling.
It is a matter of filtering. Feeding an analog white noise signal though a corresponding analog filter would have the same effect.
Btw, it's not difficult to do the same simulation in Audaity, too. I'm not familiar with this program, still I was able to find all the tools within a couple of minutes. Create one track and fill it with a sine wave. Create a 2nd track and fill it with white noise. Create a 3rd track by mixing the two tracks. Apply lowpass filter to the 3rd track. Done. See attachment.
Ok. I'm familiar with 48kSA/s since my Audacity uses that audio sample rate too. Let's say the audio sample rate is 2000kSA/s instead of just 48kSA/s then you can already see the jagged edge noise in the 900Hz, right?
No, it is not a matter of the sample rate (48kSa/s is more than enough for this signal), and it's not a matter of sampling.
It is a matter of filtering. Feeding an analog white noise signal though a corresponding analog filter would have the same effect.
Btw, it's not difficult to do the same simulation in Audaity, too. I'm not familiar with this program, still I was able to find all the tools within a couple of minutes. Create one track and fill it with a sine wave. Create a 2nd track and fill it with white noise. Create a 3rd track by mixing the two tracks. Apply lowpass filter to the 3rd track. Done. See attachment.
Ok I tried Audacity generator and mixing. I first created white noise in 1st track. then apply 1000kHz filter to the white noise. In the first screenshot I added a 50Hz sine wave in 2nd track and mix in 3rd track. There is noise.
(Attachment Link)
In the following image I added a 900Hz sine wave in 2nd track with the same white noise 1000kHz filtered in first track and mix in 3rd track. The jagged edge is not seen.
(Attachment Link)
If the above methods are correct. Can we just say that in the 900Hz. There is simply less noise per sine wave compared to the 50Hz in first image that is why there is no jagged edge in the 3rd track?
Ok. I'm familiar with 48kSA/s since my Audacity uses that audio sample rate too. Let's say the audio sample rate is 2000kSA/s instead of just 48kSA/s then you can already see the jagged edge noise in the 900Hz, right?
No, it is not a matter of the sample rate (48kSa/s is more than enough for this signal), and it's not a matter of sampling.
It is a matter of filtering. Feeding an analog white noise signal though a corresponding analog filter would have the same effect.
Btw, it's not difficult to do the same simulation in Audaity, too. I'm not familiar with this program, still I was able to find all the tools within a couple of minutes. Create one track and fill it with a sine wave. Create a 2nd track and fill it with white noise. Create a 3rd track by mixing the two tracks. Apply lowpass filter to the 3rd track. Done. See attachment.
Ok I tried Audacity generator and mixing. I first created white noise in 1st track. then apply 1000kHz filter to the white noise. In the first screenshot I added a 50Hz sine wave in 2nd track and mix in 3rd track. There is noise.
(Attachment Link)
In the following image I added a 900Hz sine wave in 2nd track with the same white noise 1000kHz filtered in first track and mix in 3rd track. The jagged edge is not seen.
(Attachment Link)
If the above methods are correct. Can we just say that in the 900Hz. There is simply less noise per sine wave compared to the 50Hz in first image that is why there is no jagged edge in the 3rd track?
there is the same amount/magnitude/presence of noise, it just looks different. you can do an FFT to confirm that, then increase the noise amplitude, and do another FFT and see how the noise floor rises equally on both 50 hz and 900 hz if the applied noise is the same
Then is it like the quantum vacuum where no matter how smaller scale you try to sample it, the noise is the same because the quantum vacuum is random and lorentz invariant and background independent?
Ok. I'm familiar with 48kSA/s since my Audacity uses that audio sample rate too. Let's say the audio sample rate is 2000kSA/s instead of just 48kSA/s then you can already see the jagged edge noise in the 900Hz, right?
No, it is not a matter of the sample rate (48kSa/s is more than enough for this signal), and it's not a matter of sampling.
It is a matter of filtering. Feeding an analog white noise signal though a corresponding analog filter would have the same effect.
Btw, it's not difficult to do the same simulation in Audaity, too. I'm not familiar with this program, still I was able to find all the tools within a couple of minutes. Create one track and fill it with a sine wave. Create a 2nd track and fill it with white noise. Create a 3rd track by mixing the two tracks. Apply lowpass filter to the 3rd track. Done. See attachment.
Ok I tried Audacity generator and mixing. I first created white noise in 1st track. then apply 1000kHz filter to the white noise. In the first screenshot I added a 50Hz sine wave in 2nd track and mix in 3rd track. There is noise.
(Attachment Link)
In the following image I added a 900Hz sine wave in 2nd track with the same white noise 1000kHz filtered in first track and mix in 3rd track. The jagged edge is not seen.
(Attachment Link)
If the above methods are correct. Can we just say that in the 900Hz. There is simply less noise per sine wave compared to the 50Hz in first image that is why there is no jagged edge in the 3rd track?
there is the same amount/magnitude/presence of noise, it just looks different. you can do an FFT to confirm that, then increase the noise amplitude, and do another FFT and see how the noise floor rises equally on both 50 hz and 900 hz if the applied noise is the same
There is the same amount of noise given the same time. But one 900Hz sine wave can form superposition with the noise at smaller scale that is why the 900Hz sine wave has no jagged edge. Is this simple interpretation correct?
If wrong. Then is it like the quantum vacuum where no matter how smaller scale you try to sample it, the noise is the same because the quantum vacuum is random and lorentz invariant and background independent?
if your noise contains every frequency between 1 and 1000hz, your low frequency signal has what you call jagged edges because the signal's period is too long compared to most of the noise, so the higher frequency noise will look "jagged" because, let's say the 1khz component of the noise, it goes up and down in a much shorter time than your 50hz signal. at 900hz, the period of the signal is much shorter than that of most of the components of the noise, and very close to that of the higher frequency components of the noise, so as your signal goes up and down, the higher frequency noise goes up and down at about the same rate, so there is a visually different effect if you observe the captured waveform, and the lower frequency noise is also there, but its period is so much longer that it is barely "visible" if you observe a single, or a few periods of your high frequency signal.
do this in audacity, generate a 50hz signal, without noise, and generate a 900hz signal, also without noise, then add them.
if you zoom out, you will see the 50hz signal with the 900hz making it look fuzzy, but if you zoom in, you will see the 900hz signal slowly being offset from the center at a rate of 50hz. both signals are equally present in that sum output, it just looks different depending on how zoomed in or out you look at it.
for your original 200$ budget, i would get an owon HDS242S. it's a very reasonable oscilloscope, multimeter and generator for the price, here's the owon's generator in yellow, vs a keysight 33212a in blue, both set for the same frequency and amplitude of 1.8vpp. you can see the measured Vpp and frequency for both channels to the right of the waveforms.
keep in mind that the output of both generators is going to a high impedance load (the analog discovery's 1Mohm inputs) and will be halved if you connect them to a 50 ohm load. the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads, so if that doesn't work for you, then yeah, this won't work, but within that voltage range, the generator of the owon is pretty reasonable for the frequency range you want, and you also get an oscilloscope and multimeter.
Member "gf" told me not make another thread so I post this question here.
There is another topic that I've been thinking for over a month. Can you share any software that can demonstrate the power of digital filter especially oversampling that can apply lowpass or bandpass filter with brick wall frequency response. My BMA-200 that uses the AMP01 has 2 order Butterworth filter with -12dB/octave response while my gtec USBamp has no amplifier but only ADC that directly maps the microvolt signal at +- 250mV. I'd like to know if it's oversampling (ability to do moving averages) capability can make me see signal that I can't with the BMA (between 1 to 2400Hz), and worth spending $3000 just to get the software to run it. Here is the spec of the USBamp. Pls share sofware to demonstrate the power of oversampling via digital filter. How much can it beat 2 order Butterworth filter with its almost brick wall response?"
Remember that a 2nd order Butterworth filter with less vertical low-pass edge only adds about 7.5% noise compared to the digital brick-wall filter.
So does digital filter oversampling only remove the noise above the cut-off...
https://www.gtec.at/product/gusbamp-research/
"Each of the 16 analog to digital converters operates at 2.4576 MHz. Oversampling 64 times yields the internal sampling rate of 38,400 Hz (per channel and for all channels!). In addition, a powerful floating point Digital Signal Processor performs oversampling and real-time filtering of the biosignal data (between 0 Hz – 2,400 Hz). Therefore, a typical sampling frequency of 256 Hz yields an oversampling rate of 9,600. This results in a very high signal to noise ratio, which is especially critical when recording evoked potentials (EP) in the EEG or identifying small amplitude changes in high-resolution ECG recordings. You are measuring far below the noise-range of conventional amplifiers."
for your original 200$ budget, i would get an owon HDS242S. it's a very reasonable oscilloscope, multimeter and generator for the price, here's the owon's generator in yellow, vs a keysight 33212a in blue, both set for the same frequency and amplitude of 1.8vpp. you can see the measured Vpp and frequency for both channels to the right of the waveforms.
keep in mind that the output of both generators is going to a high impedance load (the analog discovery's 1Mohm inputs) and will be halved if you connect them to a 50 ohm load. the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads, so if that doesn't work for you, then yeah, this won't work, but within that voltage range, the generator of the owon is pretty reasonable for the frequency range you want, and you also get an oscilloscope and multimeter.
You said "the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads". I need the 5vpp voltage bec it would be at least 1.76V rms for the E1DA. How does it calibrate 5vpp for 1Mohm load and 2.5vpp for 50 ohm load? What if my load or amplifier has arbitrary input impedance like 10,000 Megaohm in the case of my BMA-200 (see below) or 640 Ohm for my E1DA ADC? how do you compute the voltage output for those impedances?
what if I will use a 1Mega ohm resistor in parallel to the output of the Owon HDS242S to be sure the load would be 1Mega ohm for unknown input impedance like my USBamp?
Is the Owon HDS242S the best 3 in 1 there is (...) in the $200 price range?
Once I get it. I'll use it for the next 20 years