We typically recommend the same method Daniel suggested (smallest volt/div setting, AC RMS or std deviation or a vertical histogram) with one addition (which I think Daniel would agree with) - you should really figure it as a percent of full scale as some oscilloscopes have 10 vertical divisions and some only have 8.
how many samples are you actually using for calculation for the 1 GS/s sample rate?
Thanks for doing this! I'm also interested in how you measured noise. We generally use the smallest hardware V/div setting and measure V RMS (NOT Peak-Peak). This makes sure you don't have any issues with the quantity of acquisitions/update rate.I'm wondering if that is the best way of doing it on an oscilloscope which uses decimated data for on-screen measurements. Also the RMS peak measurement may be affected by any DC offset in the signal. Using the actually sampled data and doing a noise spectrum analysis seems like a much better way to me.We typically recommend the same method Daniel suggested (smallest volt/div setting, AC RMS or std deviation or a vertical histogram) with one addition (which I think Daniel would agree with) - you should really figure it as a percent of full scale as some oscilloscopes have 10 vertical divisions and some only have 8. Of course the other key thing to keep in mind when measuring noise using this method is that noise is a function of BW. So you may need to use filters to get an apples to apples compare.
-Rich
Interesting, Daniel. Have you ever seen any manufacturers skew or butcher RMS measurements that could lead to incorrect results?
Everything I learned about measuring scope noise I learned from Rich, back before he went to the dark side
how many samples are you actually using for calculation for the 1 GS/s sample rate?I am using all the samples, about 1M, but I set the linewidth of the FFT to 1 MHz. One can use smaller linewidth, but then the scatter is bigger.
Instek scopes make the best csv files from space point of view. They save only the waveform data in bits, so its typically only a single integer number for shorted input. It compresses down to 147 kB for 1 M data points. The only problem is that the preamble doesn't specify the volts/bit conversion in a very clear way. Its easy enough to scale the y axis and make the x axis.
The easiest way is to send it by Wetransfer or another file sharing service. There is no need to jump through all kinds of hoops to attach a file to a forum message.
can someone tell me and others that don't know, the basics here, whats the graph mean ? whats good/bad ?
Hello,
first measurements of PicoScope 5444A
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I would really appreciate it if somebody could explain this to me, thanks .
With math you can average to lower the noise.
Please someone correct me if I am wrong, but is the noise of the 5444 about five to ten times higher than the noise from the cheap Chinese scopes from the first page?
This makes little sense to me, since it has modes up to 16 bit resolution.
Thanks a lot! I was looking for exactly this data. Please someone correct me if I am wrong, but is the noise of the 5444 about five to ten times higher than the noise from the cheap Chinese scopes from the first page?
This makes little sense to me, since it has modes up to 16 bit resolution.
I would really appreciate it if somebody could explain this to me, thanks .
Thanks a lot! I was looking for exactly this data. Please someone correct me if I am wrong, but is the noise of the 5444 about five to ten times higher than the noise from the cheap Chinese scopes from the first page?
This makes little sense to me, since it has modes up to 16 bit resolution.
I would really appreciate it if somebody could explain this to me, thanks .
The Picoscope details I have seen show an integrated CMOS transimpedance buffer intended for DSOs from TI that by itself has 100 times the noise of a discrete front end at low frequencies. I mean literally 1000nV/SqrtHz where a discrete design could be 10nV/SqrtHz.
So a broadband RMS noise of 125.7uV over 200MHz does not surprise me at all and that is about 5 times worse than my 40+ year old 200MHz analog oscilloscopes.
Very interesting. I really wonder why they made this design decision. In my opinion it looks like this contradics the whole purpose of a high resolution mode.