Search found 49 matches

by dnessett
Thu Jun 13, 2019 10:34 pm
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

Hi Gerry, Thanks for the well-researched and highly readable analysis of the problems I raised. Also thanks for the references you provided, especially the one on Dynamic Signal Analysis Basics. I have added these to my library of tutorials on digital signal analysis and will, no doubt, refer back t...
by dnessett
Fri May 31, 2019 11:02 pm
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

Hi Gerry,

I am getting unexpected results, but I don't think they are due to PicoScope 6 correcting for processing gain when using dBm@50 ohm display. In fact, I don't think they have anything to do with the PicoScope, so no need to reply to my previous message.

Sorry for the bother.

Regards,

Dan
by dnessett
Fri May 31, 2019 5:30 am
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

Hi Gerry, I am getting some unexpected results when analyzing the phase noise of an oscillator. After re-examining the corrections I apply (and they seem correct), it occurred to me that when gathering data at dBm@50 ohms, the PicoScope 6 software may already correct the output for processing gain. ...
by dnessett
Tue May 28, 2019 12:59 am
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

I am sad to say that I have given up on using the Linux version of PicoScope 6 and now use the Windows version. I have switched to dBm@50 ohms measurements and given up trying to convert dBV values into dBm values. The problem is the Linux version is just too crippled (no dBm@50 ohms, problems with ...
by dnessett
Sat May 25, 2019 1:13 am
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

Thanks Gerry, I am now missing only one thing I need to convert windowed data with amplitude correction to windowed data with power correction. The amplitude correction factor for 4-term Blackman-Harris. As this is probably hidden in the library function PicoScope 6 calls, I figured you might not be...
by dnessett
Wed May 22, 2019 10:44 pm
Forum: PicoScope for Linux
Topic: Strange behavior when saving data in csv format
Replies: 9
Views: 412

Re: Strange behavior when saving data in csv format

Hi Gerry, I did what you requested, doing runs with 32 samples and 100 ms/div. I did 5 runs and each showed no problem. The bin size changed, of course. It was 953.7 mHz (I have attached a screenshot of the properties). By the way, I don't know how to tell if the last buffer was complete other than ...
by dnessett
Wed May 22, 2019 9:04 pm
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

Hi Gerry, Thanks for the response. Just to make sure I understand correctly, the adjustment PicoScope 6 makes to the data is to divide by the factor associated with the window, not by this factor times the bin width. So, to back it out, I multiply by that factor. Correct? However, I still lack the n...
by dnessett
Sun May 19, 2019 10:52 pm
Forum: Getting Started
Topic: Corrections for Windowing functions in FFT calculations
Replies: 13
Views: 733

Re: Corrections for Windowing functions in FFT calculations

Hi Gerry, Previously, I decided to ignore the corrections for ENBW associated with a particular window function, since they were small. Consequently, while I read and understood your response to my original question, I did not pursue it further. I have changed my mind and now wish to ensure these co...
by dnessett
Wed May 15, 2019 4:16 pm
Forum: PicoScope for Linux
Topic: Strange behavior when saving data in csv format
Replies: 9
Views: 412

Re: Strange behavior when saving data in csv format

Hi Gerry, Without changing anything, I ran a spectrum capture for the same device connected to my PicoScope 4262. This time the bin width was 4 times 19.02. I have attached the csv file to this message (test2.csv) and uploaded the psdata file to my Google Drive account: https://drive.google.com/file...
by dnessett
Wed May 15, 2019 4:05 pm
Forum: PicoScope for Linux
Topic: Strange behavior when saving data in csv format
Replies: 9
Views: 412

Re: Strange behavior when saving data in csv format

Hi Gerry, I tried attaching the psdata file to a message, but when I previewed the message, the 11 MB file didn't show up as being attached. So I am attaching the csv file (TMJ Faraday Run 2.csv) to this message and have uploaded the file to my Google Drive account. You should be able to download it...
by dnessett
Tue May 14, 2019 8:24 pm
Forum: PicoScope for Linux
Topic: Strange behavior when saving data in csv format
Replies: 9
Views: 412

Re: Strange behavior when saving data in csv format

Hi Gerry, I assume you meant post the csv file. It is ~500 KB compressed. The psdata file is 11 MB (compressed or uncompressed). I have attached the former to this email. I you want the psdata file, let me know. However, it may be too large to attach to a forum message, in which case I can upload it...
by dnessett
Tue May 14, 2019 1:05 am
Forum: PicoScope for Linux
Topic: Strange behavior when saving data in csv format
Replies: 9
Views: 412

Re: Strange behavior when saving data in csv format

I know it is unusual to reply to my first post without intervening comment. But, I thought I would run the experiment again in order to save the psdata file (which I failed to do the first time). Now the csv file has bins 2 times the 19.07 bin width. That is: Frequency,Channel A (kHz),(dBV) 0.000000...
by dnessett
Mon May 13, 2019 11:34 pm
Forum: PicoScope for Linux
Topic: Strange behavior when saving data in csv format
Replies: 9
Views: 412

Strange behavior when saving data in csv format

Hi, I am getting some strange behavior when I save spectrum results in csv format. In particular, sometimes the file entries do not correspond to expected bin widths selected when the spectrum is created. For example, I created a spectrum that should have bin widths of 19.07 mHz. However, when the c...
by dnessett
Wed May 01, 2019 11:00 pm
Forum: Getting Started
Topic: PicoScope 4262 noise floor has significant spurs
Replies: 26
Views: 3973

Re: PicoScope 4262 noise floor has significant spurs

Hi Gerry, ... However, if you are making the measurements w.r.t. 1mW dissipated into a load for dBm, and your load is 50Ω then you need to make the necessary correction to the measurement, in particular, if you want to use a voltage reference then the ref for a 50Ω load will be √(50 * 0.001) = 0.223...
by dnessett
Tue Apr 30, 2019 11:42 pm
Forum: Getting Started
Topic: PicoScope 4262 noise floor has significant spurs
Replies: 26
Views: 3973

Re: PicoScope 4262 noise floor has significant spurs

Hi Gerry, I figured out the problem in my conversion program. I was first converting dBV to millivolts by dividing the dBV value by 20, exponentiating 10 by this value, and then multiplying by 1000. To get power I squared the result and divided by 50. This is obviously incorrect. Power is voltage sq...