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Bode Plot Oscilloscopes
Bode Plot Oscilloscopes
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Old 10th February 2019, 05:29 PM   #11
BluesTM is offline BluesTM  United States
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I looked again. I see Digilent sells bundle packages with the connectors. Interesting.

I don't think I'm ready to use it to replace the scope but it could do the Bode function on it's own.
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Old 10th February 2019, 05:54 PM   #12
jan.didden is offline jan.didden  Europe
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They used to have a small $ 20 breakout board that plugged into it with BNCs for the signal i/o.

Edit: here BNC Adapter for Analog Discovery - Digilent

Jan
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Old 10th February 2019, 09:31 PM   #13
BluesTM is offline BluesTM  United States
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That's not too bad.

Thanks.
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Old 11th February 2019, 12:07 AM   #14
Calvin is offline Calvin  Germany
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Hi,

there's also a small breakout board 'Impedance Adapter' and a breadboard adapter, all adapters for <20$/pcs.

jauu
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Old 22nd February 2019, 02:18 AM   #15
BluesTM is offline BluesTM  United States
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I wanted to provide some closure on this thread I started.

I ended up purchasing the Keysight DSOX1102G. After looking at all the online reviews functionally it seemed the best. Hardware wise there's not much difference I can see in the quality of the lower end Chinese built scopes. However as far as operation and execution the Keysight seemed to consistently do what it was intended to do, good or bad. Spec wise it's kind of mediocre for the price but it seemed easiest to live with.

On the Bode Plot or FRA as they call it. When I first ran the plots I was a little disappointed with the displayed results. I'm using it for audio amp testing so I'm mostly plotting below 100KHz. The plot itself will not start below 20Hz (my 35660A was useless that low anyway) and the vertical resolution of the display won't go lower than 5dB per division. Good for filters but nowhere near the resolution of what I had. The plots look nice but not a lot of detail.

Not knowing for sure what it was doing I decided to actually pull the .csv from the tests. So best as I can tell the measurement resolution is much better than I thought.

It's running a stepped sine sweep. From 20Hz tp 100KHz it takes 38 measurements logarithmically along the X axis(my 35660A has 400 points but since they are linear the low frequency spacing reduces the resolution). The vertical resolution in the output is actually 0.01dB so actually pretty fine. So while the displayed results look pretty but not that useful there is some good stuff in the data if you look at it.

It's not really going to replace my HP 35660A but it's really easy to set up and the FRA remembers your setting from last time you used it. So once you get it setup you just connect and start the test.

So if you're looking to use the Keysight DSOX1102 for audio -
+ Scope seems to function exactly as I'd expect.
+ To me 70MHz is enough BW.
+ Bode plot does work with fair resolution in the measured data and being log scale both ways it's more suitable to audio measurements.
+ Display has good contrast on and off axis.

- Bode plot display resolution is low even though the recorded data is OK.
- 150V input limit.
- 7" screen is not that big especially when so much is used for the status bar on the right side.
- WaveGen works OK but sine wave distortion at 1KHz / 1Vrms = 0.2% THD+N.
- FFT is useless at low frequencies, at least so far.

So this is my experience. I realize different people have different expectations. A couple of things could be better but I'm keeping it.
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Old 22nd February 2019, 07:19 AM   #16
jan.didden is offline jan.didden  Europe
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Thanks for the review, useful.

Jan
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Old 28th February 2019, 08:19 PM   #17
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by jan.didden View Post
I think you'd also find the function on many USB scopes. It's all software driven anyway. My TiePie Handyscope 3 has it.

Jan
I designed my own USB scope.
I had trouble finding a bug free FFT C# function for it.
A lot were very noisy or just didn't work.
I eventually found one that did work correctly and it gives very good results.
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Old 28th February 2019, 11:31 PM   #18
trobbins is offline trobbins  Australia
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I would just note for others doing typical audio work, that a suitable 192kHz soundcard and probe and something like REW achieves similar Bode plot performance.
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Old 1st March 2019, 05:56 AM   #19
Calvin is offline Calvin  Germany
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Hi,

not just similar, but rightout better due to the vastly greater resolution and dynamics of a soundcard.

jauu
Calvin
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Old 3rd March 2019, 08:07 PM   #20
BluesTM is offline BluesTM  United States
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So I've been working with the FFT a little bit on this. I retract my earlier statement. It does work well enough to pull some harmonic information out of the noise. A little averaging would help. Resolution is not bad and it has all the standard windows.
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