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Most accurate signal generator

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nctnico:
Aha, just do as I wrote before: get an RF step attenuator (like this one from Aliexpress: https://nl.aliexpress.com/item/32905603744.html ) and connect it between the generator output and the ADC. You'll need to terminate the step attenuator with 50 Ohm so you'll need a 50 Ohm feedthrough terminator.

loop123:

--- Quote from: nctnico on March 30, 2024, 12:18:31 pm ---Aha, just do as I wrote before: get an RF step attenuator (like this one from Aliexpress: https://nl.aliexpress.com/item/32905603744.html ) and connect it between the generator output and the ADC. You'll need to terminate the step attenuator with 50 Ohm so you'll need a 50 Ohm feedthrough terminator.

--- End quote ---

Are the inside of the RF step attenuator composed of resistor dividers? I actually did the following before:




I connected 1Mohm in series with 1k ohm. Then when I want to lower the voltage by 0.001. I connect the input to the 1k ohm resistor, so that 1V become 1mV, and 1mV become 1uV. isn't this accurate? I don't use it with my cheap F-Nirst and FG-100 signal generators because I can't tell 1V from 2V and my multimeter is 20 year old and only up to 500Hz. Ok. I'll look and buy the best suggestions made here. Since it would take time for them to arrive. For those with signal generator, RF step attenuator and amplifier. Pls try the following:

Set your amplifier to bandwidth between 1kHz to 5kHz.

Set your signal generator to 10uV, 50Hz  using RF attenuator or resistor divider. Take the screenshot of the noise at 10uV, 50Hz. Now set your signal generator to 10uV, 1000Hz. I want the see noise difference between 50Hz and 1000Hz in the signal generator with the amplifier set to 1kHz in all settings. Please show the waveforms.  I want to see the noise deviation or appearance between 50Hz and 1000Hz. I want to know what to happen to the huge noise seen at 50Hz when signal generator is set to 1000Hz. whether you can still see the noise and to what degree. This is what I couldn't see all these months. Thanks.



Anthocyanina:

--- Quote from: loop123 on March 30, 2024, 01:18:36 pm ---
--- Quote from: nctnico on March 30, 2024, 12:18:31 pm ---Aha, just do as I wrote before: get an RF step attenuator (like this one from Aliexpress: https://nl.aliexpress.com/item/32905603744.html ) and connect it between the generator output and the ADC. You'll need to terminate the step attenuator with 50 Ohm so you'll need a 50 Ohm feedthrough terminator.

--- End quote ---

Are the inside of the RF step attenuator composed of resistor dividers? I actually did the following before:

(Attachment Link)


I connected 1Mohm in series with 1k ohm. Then when I want to lower the voltage by 0.001. I connect the input to the 1k ohm resistor, so that 1V become 1mV, and 1mV become 1uV. isn't this accurate? I don't use it with my cheap F-Nirst and FG-100 signal generators because I can't tell 1V from 2V and my multimeter is 20 year old and only up to 500Hz. Ok. I'll look and buy the best suggestions made here. Since it would take time for them to arrive. For those with signal generator, RF step attenuator and amplifier. Pls try the following:

Set your amplifier to bandwidth between 1kHz to 5kHz.

Set your signal generator to 10uV, 50Hz  using RF attenuator or resistor divider. Take the screenshot of the noise at 10uV, 50Hz. Now set your signal generator to 10uV, 1000Hz. I want the see noise difference between 50Hz and 1000Hz in the signal generator with the amplifier set to 1kHz in all settings. Please show the waveforms.  I want to see the noise deviation or appearance between 50Hz and 1000Hz. I want to know what to happen to the huge noise seen at 50Hz when signal generator is set to 1000Hz. whether you can still see the noise and to what degree. This is what I couldn't see all these months. Thanks.





--- End quote ---

that setup is very likely to pick up enough noise to make the 10uV signal indistinguishable from the background noise. you might have better chances soldering the resistors together, closely, and connecting the generator leads right where the resistor leads meet the resistor bodies

nctnico:
There are resistors inside an RF step attenuator, but these have much lower values (single digit Ohm) as each section needs to maintain a 50 Ohm impedance at in & out. The step attenuator also has internal shielding to avoid signal leakage between sections. The low value resistors alone reduce noise compared to your breadboard setup. For your purpose, the breadboard setup is completely inadequate.

Fungus:

--- Quote from: loop123 on March 30, 2024, 01:18:36 pm ---Are the inside of the RF step attenuator composed of resistor dividers? I actually did the following before:

--- End quote ---

Yes, but to avoid noise you need high current (low impedance), short tracks, and shielding.

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