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Most accurate signal generator
nctnico:
Filters do not have infinitely steep slopes. Likely the bandwidth filters on your equipment are first or second order at most in order not to create too much phase shifts. The source of the 1kHz signal can be anything (for example an intermodulation product from a noise source, including poor grounding). I'd start with measuring with the inputs of your ADC shorted and go from there.
gf:
--- Quote from: nctnico on March 30, 2024, 10:55:21 am ---I'd start with measuring with the inputs of your ADC shorted and go from there.
--- End quote ---
This was already suggested by a member in the other thread, and loop123 already did this measurement.
I don't know why loop123 starts multiple threads on the same topic, having the consequence that context is lost :-//
loop123:
--- Quote from: nctnico on March 30, 2024, 10:55:21 am ---Filters do not have infinitely steep slopes. Likely the bandwidth filters on your equipment are first or second order at most in order not to create too much phase shifts. The source of the 1kHz signal can be anything (for example an intermodulation product from a noise source, including poor grounding). I'd start with measuring with the inputs of your ADC shorted and go from there.
--- End quote ---
I mean I want to get a signal generator so I can output 10uV and 1kHz to see what the waveforms and noises look like at 1kHz because all I experienced seeing are always 50Hz signal. I havent see what 1kHz signal with noise looks like.
gf:
--- Quote from: loop123 on March 30, 2024, 11:46:23 am ---
--- Quote from: nctnico on March 30, 2024, 10:55:21 am ---Filters do not have infinitely steep slopes. Likely the bandwidth filters on your equipment are first or second order at most in order not to create too much phase shifts. The source of the 1kHz signal can be anything (for example an intermodulation product from a noise source, including poor grounding). I'd start with measuring with the inputs of your ADC shorted and go from there.
--- End quote ---
I mean I want to get a signal generator so I can output 10uV and 1kHz to see what the waveforms and noises look like at 1kHz because all I experienced seeing are always 50Hz signal. I havent see what 1kHz signal with noise looks like.
--- End quote ---
The method I suggested with your FNIRSI generator can also be done at 1 kHz. Only the amplitude calibration (if you don't trust the generator) with the DVM needs to be done at a frequency which is within the spec of your DVM -- thereafter you can also tune the generator to a higher frequency. I would not expect the generator to show a significant amplitude deviation between 50 Hz and 1000 Hz.
To get a first impression what to expect, I would just capture the noise floor with shorted input and add an artificial 1kHz tone (with 3dB lower amplitude to account for the filter) in Audacity.
loop123:
--- Quote from: gf on March 30, 2024, 12:08:51 pm ---
--- Quote from: loop123 on March 30, 2024, 11:46:23 am ---
--- Quote from: nctnico on March 30, 2024, 10:55:21 am ---Filters do not have infinitely steep slopes. Likely the bandwidth filters on your equipment are first or second order at most in order not to create too much phase shifts. The source of the 1kHz signal can be anything (for example an intermodulation product from a noise source, including poor grounding). I'd start with measuring with the inputs of your ADC shorted and go from there.
--- End quote ---
I mean I want to get a signal generator so I can output 10uV and 1kHz to see what the waveforms and noises look like at 1kHz because all I experienced seeing are always 50Hz signal. I havent see what 1kHz signal with noise looks like.
--- End quote ---
The method I suggested with your FNIRSI generator can also be done at 1 kHz. Only the amplitude calibration (if you don't trust the generator) with the DVM needs to be done at a frequency which is within the spec of your DVM -- thereafter you can also tune the generator to a higher frequency. I would not expect the generator to show a significant amplitude deviation between 50 Hz and 1000 Hz.
To get a first impression what to expect, I would just capture the noise floor with shorted input and add an artificial 1kHz tone (with 3dB lower amplitude to account for the filter) in Audacity.
--- End quote ---
What I want to see is noise deviation between 50Hz and 1000Hz with all settings the same like bandwidth switch of 1000Hz selected at amplifier. Before today I was thinking that if there were many noises like in my 50Hz waveform shared in last message, the noises would be same size at higher frequency such that at 100Hz the sine wave become blur as they merge to the noise. But today I was thinking of the possibility the noises size gets smaller with more frequency such that with my amplifier set to 1kHz bandwidth. It would still show 900Hz signal assuming the Netech simulator can output 900Hz instead of just 50Hz?
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