| Products > Test Equipment |
| Siglent 1104X-E Automatically capture frequency of max voltage of sweep of coil? |
| (1/3) > >> |
| t1d:
Scope Skill Level = Novice. But, I have a rather nice lab and equipment. Goal: I want to find the resonate frequency of a coil. Method: I will inject a frequency sweep and investigate the output’s maximum voltage amplitude. I know that my scope can easily capture the max voltage and tell me what it is. But, can it also automatically tell me at what frequency the max voltage was encountered? If so, what are the scope settings. All of the methods that I have studied have the operator watching the sweep and noting the maximum him/herself, visually. I would think that the scope would have a mathematical function that would make the determination automatically (and more precisely,) but I do not know how to set up my specific scope. The scope setup is what I need help with. Please and thank you. PS: I apologize for this being poorly written, but I am not feeling well. |
| noisyee:
Scopes don't know what max voltage is but we know (or we can predict). So the trick is how to capture what we want. Sorry I don't have a coil to demonstrate, but I have a very high Q crystal filter. Just set trigger level high enough (to where the scope can barely trigger) to capture only the resonate in a sweep, then the scope can easily measure the frequency. If we want observe the whole sweep while measure the resonate frequency, we can use the same trick to set trigger (to “freeze” the sweep to a certain position) and use gate mode to measure certain part of the captured waveform. Or try bode plot to measure the resonate property. >:D |
| t1d:
--- Quote from: noisyee on January 05, 2023, 09:09:20 am ---Scopes don't know what max voltage is but we know (or we can predict). So the trick is how to capture what we want. Sorry I don't have a coil to demonstrate, but I have a very high Q crystal filter. Just set trigger level high enough (to where the scope can barely trigger) to capture only the resonate in a sweep, then the scope can easily measure the frequency. If we want observe the whole sweep while measure the resonate frequency, we can use the same trick to set trigger (to “freeze” the sweep to a certain position) and use gate mode to measure certain part of the captured waveform. Or try bode plot to measure the resonate property. >:D --- End quote --- Thanks, noisyee; that's good information. My scope does have a set of math functions that will find the max/min voltage. I was hopeful that it would have the ability to tell me the frequency at the moment of highest/lowest amplitude. But, your methods are very clever and I do like them. I will try them and add them to my skill set. I have never used the FFT function. I wonder if it might be useful for this application? |
| noisyee:
--- Quote from: t1d on January 06, 2023, 04:48:55 am --- --- Quote from: noisyee on January 05, 2023, 09:09:20 am ---Scopes don't know what max voltage is but we know (or we can predict). So the trick is how to capture what we want. Sorry I don't have a coil to demonstrate, but I have a very high Q crystal filter. Just set trigger level high enough (to where the scope can barely trigger) to capture only the resonate in a sweep, then the scope can easily measure the frequency. If we want observe the whole sweep while measure the resonate frequency, we can use the same trick to set trigger (to “freeze” the sweep to a certain position) and use gate mode to measure certain part of the captured waveform. Or try bode plot to measure the resonate property. >:D --- End quote --- Thanks, noisyee; that's good information. My scope does have a set of math functions that will find the max/min voltage. I was hopeful that it would have the ability to tell me the frequency at the moment of highest/lowest amplitude. But, your methods are very clever and I do like them. I will try them and add them to my skill set. I have never used the FFT function. I wonder if it might be useful for this application? --- End quote --- FFT is a powerful tool, it's also helpful in this application. Use the Max Hold display mode in the FFT while continuous sweeping, we can get frequency response (or to be strict, amplitude response rather than magnitude response) of the DUT. I use this trick all the time. But it require some setting tweak to get better result. e.g, if we want more frequency resolution, we need more FFT points, which increase calculate time and slow down the measurement. |
| t1d:
--- Quote from: noisyee on January 06, 2023, 10:13:07 am ---FFT is a powerful tool, it's also helpful in this application. Use the Max Hold display mode in the FFT while continuous sweeping, we can get frequency response (or to be strict, amplitude response rather than magnitude response) of the DUT. I use this trick all the time. But it require some setting tweak to get better result. e.g, if we want more frequency resolution, we need more FFT points, which increase calculate time and slow down the measurement. --- End quote --- That is a good trick, noisyee, and I will give it a go. I briefly scanned my scope's manual and it looks like I may have a Bode Plot function. But, there may be caveats... 1) The manual clearly states that this function only works if you have a Siglent function generator. Mine is a Rigol. But, there may be a hack to work around this. So, I will need to investigate that. 2) This may be a pay-to-play add on feature and I did not buy any of those. I did try just using manual methods to sweep the frequency. And, yes, that is not a particularly hard thing to do. But, as said, I would like to learn to do it automatically, if my scope is capable of doing that. My results are posted below, in a separate post. There, I will just sharing the fun that I am having. |
| Navigation |
| Message Index |
| Next page |