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Most accurate signal generator
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nctnico:

--- Quote from: loop123 on March 29, 2024, 02:11:43 pm ---Guys. Besides needing 1.8V, 3000Hz to calibrate the E1DA ADC. I also need a 10uV signal generator at least 1000Hz with differential output to test my 16 channel USBamp bioamplifier directly in differential inputs. as well as the BMA bioamplifier. I got the following at Audacity. I can't figure out if its due to the Netech EEG simulator output that has noise or those amplifiers. Do you know any 10uV signal generator at 1000Hz (what is the highest possible without noise) that won't produce any noise or at least imperceptible?

--- End quote ---
Simple: get a step attenuator and connect it to the output of a signal generator.
loop123:

--- Quote from: nctnico on March 29, 2024, 04:20:42 pm ---
--- Quote from: loop123 on March 29, 2024, 02:11:43 pm ---Guys. Besides needing 1.8V, 3000Hz to calibrate the E1DA ADC. I also need a 10uV signal generator at least 1000Hz with differential output to test my 16 channel USBamp bioamplifier directly in differential inputs. as well as the BMA bioamplifier. I got the following at Audacity. I can't figure out if its due to the Netech EEG simulator output that has noise or those amplifiers. Do you know any 10uV signal generator at 1000Hz (what is the highest possible without noise) that won't produce any noise or at least imperceptible?

--- End quote ---
Simple: get a step attenuator and connect it to the output of a signal generator.

--- End quote ---

In Op-Amps or INA. Noise characteristics are in the form of nV/Sqrt (Hz). How many about signal generators? Are the noises also in nV/Sqrt (Hz)?

Since my differential input is 10uV (microvolt). The noise peak to peak has to be less than 1uV. So noise should not be more than 1uV peak to peak or in rms  is 1uV/6.6 = 0.00000015 or 0.15uV rms noise. This is at 1000Hz. My Netech ECG simulator even with step attenuator used still has noises. Therefore what 1.8V signal generator  has noise of 0.15uV rms at 1000Hz?  Since I'd be using it not just on the E1DA but directly on the bioamplifier signal input too (just thought of yesterday). My budget is back to $200 from $50. But since I can only buy one $200. Please suggest one with guaranteed noise of at least 0.15uV rms at 1000Hz or below with differential output.

If noises in signal generator are not in nV/Sqrt (Hz), then what they are in? The quantization has to be lesser than 0.15uV rms too (or what its equivalent in quantization error)?


gf:
If your budget is low, why don't you try in the first place what I suggested here:
https://www.eevblog.com/forum/testgear/most-accurate-signal-generator/msg5413988/#msg5413988
That cost's you a few cents for two 1% resistors.
You are asking for a SINAD of ~35dB. That's not really challenging for a signal generator.
I guess that even your FNIRSI toy can reach that, at least at the full scale level of the DAC
(EDIT: and 10µV are then obtained by dividing (say) 1V by 100,000 with a voltage divider, which does not increase SINAD).
The noise floor of your DUT (see your other threads) is significantly higher anyway.

EDIT:
And if I look at the spectrum plots in your other thread, then I cannot see that your ECG simulator did increase the random noise floor significantly. But yes, its signal obviously contains several undesired spurs. Additionally, your setup seems to pick up mains hum (and possibly some other noises) from the environment. I don't know, but I rather don't think this is coming out from your ECG simulator. So also take measures to minimize any pick-up of undesired signals from the environment.
nctnico:
Shielding is everything with these kind of low signal levels; I don't think it is sensible to try and measure low level signals without being inside a shielded room. Also the grounding needs to be good so so you get noise from differences in ground levels.
loop123:

--- Quote from: gf on March 30, 2024, 09:33:17 am ---If your budget is low, why don't you try in the first place what I suggested here:
https://www.eevblog.com/forum/testgear/most-accurate-signal-generator/msg5413988/#msg5413988
That cost's you a few cents for two 1% resistors.
You are asking for a SINAD of ~35dB. That's not really challenging for a signal generator.
I guess that even your FNIRSI toy can reach that, at least at the full scale level of the DAC
(EDIT: and 10µV are then obtained by dividing (say) 1V by 100,000 with a voltage divider, which does not increase SINAD).
The noise floor of your DUT (see your other threads) is significantly higher anyway.

EDIT:
And if I look at the spectrum plots in your other thread, then I cannot see that your ECG simulator did increase the random noise floor significantly. But yes, its signal obviously contains several undesired spurs. Additionally, your setup seems to pick up mains hum (and possibly some other noises) from the environment. I don't know, but I rather don't think this is coming out from your ECG simulator. So also take measures to minimize any pick-up of undesired signals from the environment.

--- End quote ---

My Netech simulator only has frequency choices of 0.1Hz, 2Hz, 5Hz, 50Hz, 60Hz only. I dont know how a frequency of 1000Hz would appear given the amplifier has 1000Hz bandwidth selected and ADC 48kHz in all cases in my setup. Based on the following. Can you describe how 1000Hz version of it would look like instead of just 50Hz.  Again In both cases my amplifier has switch selected to 1000Hz bandwidth. Can the sine wave at say 900Hz still be distinguished with the noises in the following becoming imperceptible or would 900Hz appear like a blur with no sine waves seen?

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