PicoScope 7 Software
Available on Windows, Mac and Linux
how to monitor frequency over time
how to monitor frequency over time
Hello. I do not have a PicoScope yet, but am lured by the promise of using the math functions. In particular, the statement on the website that "An example would be to graph the changing ...frequency of your signal over time" is exactly what I want to do. I've downloaded the software and user manual, but still can't figure out how to plot the frequency over time.
I've opened an XY view with time on the x-axis and frequency on the y-axis. What I would like to do is once-per-second, sample the input signal and plot its frequency. It's a sine wave whose amplitude does not concern me. All I care about is its frequency. I just want to monitor frequency over time.
Can someone at least point me to where in the 222 page manual I should be looking. Better yet, if anyone has done this, I'd like to hear about how you did it Thanks.
I've opened an XY view with time on the x-axis and frequency on the y-axis. What I would like to do is once-per-second, sample the input signal and plot its frequency. It's a sine wave whose amplitude does not concern me. All I care about is its frequency. I just want to monitor frequency over time.
Can someone at least point me to where in the 222 page manual I should be looking. Better yet, if anyone has done this, I'd like to hear about how you did it Thanks.
Re: how to monitor frequency over time
No need to use XY plot. With the SIne wave on channel A, with many cycles displayed, go to Tools->MathChannels->Create and click through to the equation editor and either type in
freq(A)
or click on Advanced and select freq button and then Channel A.
Continue in the editor and manually select the frequency range to reflect your expected frequencies. Finish the wizard and select the newly created MathChannel.
Now you should have a nice plot of Frequency on y-axis against Time on x-axis
freq(A)
or click on Advanced and select freq button and then Channel A.
Continue in the editor and manually select the frequency range to reflect your expected frequencies. Finish the wizard and select the newly created MathChannel.
Now you should have a nice plot of Frequency on y-axis against Time on x-axis
Martyn
Technical Support Manager
Technical Support Manager
Re: how to monitor frequency over time
Yes, I tried that first, but there are two problems.
1. The vertical axis is not useful. It goes from 0 to 9.766 MHz for a 1kHz signal. Even with a 10kHz LPF applied, The auto-ranging vertical axis is still up to 9.766 MHz. I wish I could select 0 to 2 kHz, for example, just like I can on a stand-along oscilloscope.
2. The horizontal axis is not useful. I would like the x-axis to be time, from 0 to 600 seconds, so I can monitor the frequency over time as advertised. The x-axis defaults to the same ms scale, which is not useful, even when scaled by the maximum 50x.
1. The vertical axis is not useful. It goes from 0 to 9.766 MHz for a 1kHz signal. Even with a 10kHz LPF applied, The auto-ranging vertical axis is still up to 9.766 MHz. I wish I could select 0 to 2 kHz, for example, just like I can on a stand-along oscilloscope.
2. The horizontal axis is not useful. I would like the x-axis to be time, from 0 to 600 seconds, so I can monitor the frequency over time as advertised. The x-axis defaults to the same ms scale, which is not useful, even when scaled by the maximum 50x.
Re: how to monitor frequency over time
I figured out the vertical axis issue thanks to other forum entries. I edited the freq math function to use fixed min and max for the y-axis. If I allow it to go automatically, it chooses the MHz range.
I still haven't figured out the x-axis issue, though. Any help would be appreciated.
I still haven't figured out the x-axis issue, though. Any help would be appreciated.
Re: how to monitor frequency over time
If you want to see the frequency over a time period of around 600 seconds then you will need to set the collection time accordingly. The possible options would be 50s/div for 500 seconds, or 100s/div for 1000 seconds.
You would also need to set the Number of Samples across the screen to an appropriate value, remember that you can zoom in to see the detail of the signal if you need to, as it is likely to look like a solid block at this slow collection time.
You would also need to set the Number of Samples across the screen to an appropriate value, remember that you can zoom in to see the detail of the signal if you need to, as it is likely to look like a solid block at this slow collection time.
Martyn
Technical Support Manager
Technical Support Manager
Re: how to monitor frequency over time
This doesnt seem to work for me, it graphs dispays 50hz when it should display 60hz which the measurment inadded correctly has 60hz here in the USA measuring from the wall any ideas?
Re: how to monitor frequency over time
Please post a psdata file so we can see what is happening, and how you have the scope set up.
Martyn
Technical Support Manager
Technical Support Manager