Hello
I'm looking for some people that have had experience with the Bode Plot function on some of the newer digital oscilloscopes.
I've been using an old HP 35660A to run frequency response plots on amplifiers I've either been repairing or building. It also does a fair job of displaying harmonic distribution in its THD mode. I've had this box for years and I have a pretty good grasp of what it can and can't do. In particular the lowest frequency bins can be very erratic with low resolution unless you really limit the span and stay away from the bottom bins. Frequency response measurements are limited to 51 kHz since it requires both channels.
And to be honest every time it boots up and goes through its self test routine I keep my fingers crossed. So far so good.
So what's happening is that I'm looking to replace my digital scope, a BK 2534. It works fine for most of what I do but the screen resolution is limited and the screen is kind of small and these newer scopes seem to do a lot more. Bandwidth is fine and I've never needed more than two inputs for audio work. Maybe it's scope envy.
As I'm shopping new scopes the Bode Plot function has been listed on a couple of them. After a little research and viewing a few videos it looks kind of cool. Most of the demos I've seen are mainly around RF filter response. I haven't seen one run on an audio amplifier across the band.
So I'm wondering if someone on the forum has used one of these scopes and what they thought. Is it a toy feature or is it really useful? Is the old HP a better tool? What are the limitations?
I've found two scopes close to my price range -
The Siglent SDS2202X-E which requires a Siglent SDG series generator that the scope can control. An SDG 805 or 810 should do it and I'd rather have a stand alone FG.
The other is the Keysight DSOX1102G which comes with a built in generator. I really like this scope but for the price the specs are pretty average.
The Siglent has better specs but I've not used either and the devil is usually in the software and execution.
Anybody tried either of these?
Thanks
I'm looking for some people that have had experience with the Bode Plot function on some of the newer digital oscilloscopes.
I've been using an old HP 35660A to run frequency response plots on amplifiers I've either been repairing or building. It also does a fair job of displaying harmonic distribution in its THD mode. I've had this box for years and I have a pretty good grasp of what it can and can't do. In particular the lowest frequency bins can be very erratic with low resolution unless you really limit the span and stay away from the bottom bins. Frequency response measurements are limited to 51 kHz since it requires both channels.
And to be honest every time it boots up and goes through its self test routine I keep my fingers crossed. So far so good.
So what's happening is that I'm looking to replace my digital scope, a BK 2534. It works fine for most of what I do but the screen resolution is limited and the screen is kind of small and these newer scopes seem to do a lot more. Bandwidth is fine and I've never needed more than two inputs for audio work. Maybe it's scope envy.
As I'm shopping new scopes the Bode Plot function has been listed on a couple of them. After a little research and viewing a few videos it looks kind of cool. Most of the demos I've seen are mainly around RF filter response. I haven't seen one run on an audio amplifier across the band.
So I'm wondering if someone on the forum has used one of these scopes and what they thought. Is it a toy feature or is it really useful? Is the old HP a better tool? What are the limitations?
I've found two scopes close to my price range -
The Siglent SDS2202X-E which requires a Siglent SDG series generator that the scope can control. An SDG 805 or 810 should do it and I'd rather have a stand alone FG.
The other is the Keysight DSOX1102G which comes with a built in generator. I really like this scope but for the price the specs are pretty average.
The Siglent has better specs but I've not used either and the devil is usually in the software and execution.
Anybody tried either of these?
Thanks
R&S RTB200X K36 is a Bode option
Here is another scope to possibly add to your consideration list, the Rohde & Schwarz RTB200X series, because they recently (just a couple of months ago) added "K36" Bode option.
R&S K36 Body option
K36 bode option video (link to a video running the bode option in that post)
I just received my keycode to unlock it 2 days ago.
Haven't had time to mess with it yet though. Looks like the same option is available for the higher end 3000 and 4000 series. (does more stuff, I think, on those).
BTW - welcome to DIY Audio (join date)!
Here is another scope to possibly add to your consideration list, the Rohde & Schwarz RTB200X series, because they recently (just a couple of months ago) added "K36" Bode option.
R&S K36 Body option
K36 bode option video (link to a video running the bode option in that post)
I just received my keycode to unlock it 2 days ago.
Haven't had time to mess with it yet though. Looks like the same option is available for the higher end 3000 and 4000 series. (does more stuff, I think, on those).BTW - welcome to DIY Audio (join date)!
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I have the Keysight DSOX1102G. Love it. It replaced my TEK 2465B (which I still have) as I really needed a storage scope.
I haven't used the bode function yet, but if I recall correctly, the generator goes to 10 MHz, so I'd expect you to be able to sweep from near DC to 10 MHz without issues.
Tom
I haven't used the bode function yet, but if I recall correctly, the generator goes to 10 MHz, so I'd expect you to be able to sweep from near DC to 10 MHz without issues.
Tom
Thanks everyone.
I realize you can probably never have too much scope but that Rhode is more than I was thinking about. I love the touch screen. Looks like a great scope. I've used Rhode gear at work, it's really good stuff.
Thanks Tom, I like the feedback for the Keysight.
I know the USB scopes are out there but so far I'm not feeling the desire for one.
Thanks
I realize you can probably never have too much scope but that Rhode is more than I was thinking about. I love the touch screen. Looks like a great scope. I've used Rhode gear at work, it's really good stuff.
Thanks Tom, I like the feedback for the Keysight.
I know the USB scopes are out there but so far I'm not feeling the desire for one.
Thanks
Hi,
my Siglent SDS1204X-E (and its 100MHz brother SDS1104X-E) are capable of Bode plotting in togetherness with Siglent function generators, SDG2042X for example, or other signal generators using a control script. The 2-channel brother SDS1202X-E can´t do Bode plots (still though a brilliant entry oscilloscope). It seems that the prescision decreases with lower frequencies. The curves certainly look better >10kHz (I won´t exclude that I used a slightly too low signal level ... I almost never use it, since I have dedicated audio analyzers and a AD2). The three Siglents and the function generator are extremely capable ... You won´t find anthing better at the time in their price class. None of the A-brands offers anything close to that below 2k€.
Also Bode plot capable is Digilent´s AnalogDiscovery2 (AD2), a really tiny USB device for ~300-350$ (with flyout boards). Bandwidth is restricted to 30MHz max (some functions even <10MHz), but for Audio it´s more than suffcient. As it is a 14Bit device, the resolution is considerably higher than with the 8Bit benchtop oscilloscopes. Besides a quite good Bode plot functionality it also offers spectrum-, impedance- and network analyzer functions and more. It even features balanced In- and Outputs. A powerful little gadget almost perfect for audio and mobile measurements.
jauu Calvin
my Siglent SDS1204X-E (and its 100MHz brother SDS1104X-E) are capable of Bode plotting in togetherness with Siglent function generators, SDG2042X for example, or other signal generators using a control script. The 2-channel brother SDS1202X-E can´t do Bode plots (still though a brilliant entry oscilloscope). It seems that the prescision decreases with lower frequencies. The curves certainly look better >10kHz (I won´t exclude that I used a slightly too low signal level ... I almost never use it, since I have dedicated audio analyzers and a AD2). The three Siglents and the function generator are extremely capable ... You won´t find anthing better at the time in their price class. None of the A-brands offers anything close to that below 2k€.
Also Bode plot capable is Digilent´s AnalogDiscovery2 (AD2), a really tiny USB device for ~300-350$ (with flyout boards). Bandwidth is restricted to 30MHz max (some functions even <10MHz), but for Audio it´s more than suffcient. As it is a 14Bit device, the resolution is considerably higher than with the 8Bit benchtop oscilloscopes. Besides a quite good Bode plot functionality it also offers spectrum-, impedance- and network analyzer functions and more. It even features balanced In- and Outputs. A powerful little gadget almost perfect for audio and mobile measurements.
jauu Calvin
Forgot about the Digilent, yes great piece of gear. And its successor the ADALM2000. Scope, signal generator, Bode plotter, network analyzer, power supply, logic analyzer. The works. About $ 150.
Jan
Jan
It looks like one vote for the Keysight and one for Siglent.
It sounds like you guys like those scopes but the Bode plot function was not a primary driver for purchasing them. Calvin's experience with the Siglent reminds me of how the 35660 works although it starts to get erratic under 125 Hz or so. Above it's fine and the more signal the more consistent the results.
Because it keeps coming up I did look at the Digilent site. So if you're using the Analog Discovery do you build a separate breakout box for traditional connectors?
Thanks.
It sounds like you guys like those scopes but the Bode plot function was not a primary driver for purchasing them. Calvin's experience with the Siglent reminds me of how the 35660 works although it starts to get erratic under 125 Hz or so. Above it's fine and the more signal the more consistent the results.
Because it keeps coming up I did look at the Digilent site. So if you're using the Analog Discovery do you build a separate breakout box for traditional connectors?
Thanks.
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
Edit: here BNC Adapter for Analog Discovery - Digilent
Jan
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.
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.
Attachments
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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