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FFT and 60 Notch filter software

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loop123:

--- Quote from: gf on March 14, 2024, 11:08:13 am ---
--- Quote from: tggzzz on March 14, 2024, 10:51:46 am ---
--- Quote from: loop123 on March 14, 2024, 10:37:43 am ---Does it mean Audacity 1 to -1 is really 5 Volts? Or does it change depending on your setups? how?

--- End quote ---

Sigh. You really don't understand.

Audacity processes numbers, either floating point or integer. Those numbers have absolutely no defined relationship to any input voltage.

Sometimes those numbers might originate in an ADC. Often they will have been "artificially generated" inside a computer program.

--- End quote ---

Exactly.

ffmpeg -i netech\ 10uv\ 50hz\ bma\ 1000hz\ 50000\ gain.wav
...
Input #0, wav, from 'netech 10uv 50hz bma 1000hz 50000 gain.wav':
  Duration: 00:00:29.94, bitrate: 705 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 1 channels, s16, 705 kb/s

The file contains just a stream of signed 16-bit integer numbers whose full-scale range is mapped by Audacity to a -1...+1 range when it loads the file. Either the creator of the file can tell you the codes per Volt in the file, or you need to find out yourself.

--- End quote ---


If I used the same ADC and amplifier like the BMA + E1DA. The output at Audacity is consistent? For example using my 5V full scale 1 to -1 baseline in my last message. Can you tell what is the approximate voltage level of the following?   



I really thought it was 10uV and displaying right at the 2nd BMA. But half day later. I can't get the same waveforms. So I assumed it was 30uV.    Based on my 5V baseline using the same BMA + E1DA. Do you think it's 10uV or 30uV?

With the AMP01 noise of 5nv/sqrt (Hz). I should be getting 0.158uV rms noise. And using 10uV signal. There should be no wide band noise like the ones I shared previously.

Andy suggested I go far away to test it. But then with no specific frequencies like 60Hz and harmonics. It is not interference, right? You can already tell from the analysis that the wideband noise is not interference but the noise floor already. Or can interference mimic for all intent and purposes the noise floor such that you can't differentiate noise floor from interference? Please elaborate. Thanks.

tggzzz:

--- Quote from: loop123 on March 14, 2024, 12:26:06 pm ---
--- Quote from: gf on March 14, 2024, 11:08:13 am ---
--- Quote from: tggzzz on March 14, 2024, 10:51:46 am ---
--- Quote from: loop123 on March 14, 2024, 10:37:43 am ---Does it mean Audacity 1 to -1 is really 5 Volts? Or does it change depending on your setups? how?

--- End quote ---

Sigh. You really don't understand.

Audacity processes numbers, either floating point or integer. Those numbers have absolutely no defined relationship to any input voltage.

Sometimes those numbers might originate in an ADC. Often they will have been "artificially generated" inside a computer program.

--- End quote ---

Exactly.

ffmpeg -i netech\ 10uv\ 50hz\ bma\ 1000hz\ 50000\ gain.wav
...
Input #0, wav, from 'netech 10uv 50hz bma 1000hz 50000 gain.wav':
  Duration: 00:00:29.94, bitrate: 705 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 1 channels, s16, 705 kb/s

The file contains just a stream of signed 16-bit integer numbers whose full-scale range is mapped by Audacity to a -1...+1 range when it loads the file. Either the creator of the file can tell you the codes per Volt in the file, or you need to find out yourself.

--- End quote ---


If I used the same ADC and amplifier like the BMA + E1DA. The output at Audacity is consistent? For example using my 5V full scale 1 to -1 baseline in my last message. Can you tell what is the approximate voltage level of the following?   

--- End quote ---

Read the preceding two messages in your message. Please. Pretty please. Think about what they say.

If you don't come to understand why we can't tell you the "approximate voltage level", then there's little anybody can do to help you.

Yes that requires hard work on your part. We've had to go through that process, and so will you.

Alternatively, get out your meter and simply measure the bloody input voltage!

loop123:
I have thought and tested a lot what you mentioned. I really can estimate approximate voltage level in my files. Here is why.

In my BMA + E1DA, 5V corresponds to 1 to -1. If I adjusted the amplitudes or the gain, the amplitudes can decrease proportionally. This is also why your audio or music can sound as it is because Audacity can consistently track the amplitudes that is why your wave files don't suddenly have jumping amplitudes that don't corresponds to original recording.

Not only that. But if I save the Audacity file into WAV. And later retrieve. It still shows the same amplitude. Therefore I can estimate approximate voltage level because I know the baseline in my particular equipment. Although you can't estimate the approximate level because you don't know my baseline. Yes. I have from start read gf punchline "The file contains just a stream of signed 16-bit integer numbers whose full-scale range is mapped by Audacity to a -1...+1 range when it loads the file.". I know my full range to be 5V so I can estimate my voltage level. But you can't estimate my voltage level becauase you don't know what voltage corresponds to my full range during the mapping of Audacity of the full range in the stream of signed 16-bit integers as gf put it to 1 to -1. Do you guys agree here? Or do you emphasize even I can't estimate my own voltage level in my own file where I know the full range corresponds to 5V??

nali:
The point being made is that a WAV file has no concept whatever of what a voltage is. It's just a table of numbers. Those numbers are 0 through 2^n-1 e.g. 0-65535; the +/-1 is just Audacity normalising.

The ONLY part of your system that can correlate the information in your WAV file to actual voltages in the real world is your ADC. Fine, if you're 100% confident that your ADC maps to a peak of 5V (is that 5V pk-pk or 5V RMS?) then yes you can use it to work out voltages.

I assume tha ADC is intended for audio. Does it have any form of automatic gain control or clipping protection? If it does you can forget using it for measurements - sell it and buy a scope instead.

loop123:

--- Quote from: nali on March 14, 2024, 09:46:34 pm ---The point being made is that a WAV file has no concept whatever of what a voltage is. It's just a table of numbers. Those numbers are 0 through 2^n-1 e.g. 0-65535; the +/-1 is just Audacity normalising.

The ONLY part of your system that can correlate the information in your WAV file to actual voltages in the real world is your ADC. Fine, if you're 100% confident that your ADC maps to a peak of 5V (is that 5V pk-pk or 5V RMS?) then yes you can use it to work out voltages.

I assume tha ADC is intended for audio. Does it have any form of automatic gain control or clipping protection? If it does you can forget using it for measurements - sell it and buy a scope instead.

--- End quote ---

I'll ask Ivan about the E1DA. So when I told "gf" my full range is 5V, and asked him to estimate the voltage level of a lower amplitude waveform then he should be able to do it since I gave the 5V baseline for the 1 to -1. The reason I need to estimate is because when I used the 2nd backup BMA initially. I got what I thought was a 10uV with BMA 1000Hz switch with no noise. but I couldn't repeat it. Instead I always got the same noise as the one I shared early which some of you made frequency analysis with unknown 78Hz peak. The following is the 5V reference waveform to 1 to -1, the 10uV with 100Hz selected (here I can't duplicate it so gf, Karel, WatchfulEye, please run the Wav file attached and let me know how to duplicate the dancing waveforms).. In the third image is the one I thought was 10uV with 1000Hz bandwidth with no noise, but the amplitude is much larger so I was wondering if it is really 30uV instead of 10uV. Hence asking gf to verify the voltage level with the 1 to -1 referenced to 5 Volts (I am sure) given.







gf. please check if the last image above has the same amplitude as the middle image with confirmed 10uV or is the last image not 10uV? If so, then it is 30uV and the noises in the earlier image I shown which you made frequency analysis is correct. If so, my next goal is figuring out how a AMP01 with excellent 5nV/sqrt (Hz) noise figure turn to 1000nV/sqrt (Hz) noise figure in the BMA and build a virgin AMP01 that can do 10uV with 0.158uV noise.

 

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