Could the the noise you see on Ch1 be related to the MCU clock ?
I know there are occasions when a STOP, Single or screenshot displays things that take some understanding
Hi,
I wonder what I am observing here - a bug in the latest stock firmware (7.0.6.1 25R2) or something else. I noticed that every time when I zoom in (change vertical sensitivity) on the recorded signal it looks quite noisy. Eventually I simplified the test to avoid any ambiguity and this is the result:
a) the signal source (MCU) with stable power supply generates 50 pulses. The channel 4 monitors power line. The SDS1204X-E is single trigger mode, 5V/div, the signal is applied to channel 1
b)now lets change the scale to 1V/div - the signal looks quite noisy and I know that this is not true.
c) another recording of the same signal, SDS1204X-E is in single trigger mode, 1V/div, the signal looks as it should be. The only difference a c is the vertical sensitivity.
My question is - what is this wrong with displaying the previously recorded signal when the vertical sensitivity has been changed ?
Thanks!
Before I start tell basic fundamentals how digital oscilloscope works (and what you have meet here) I want you tell me why your first image display 20MSa/s because if you did as you tell, this 20MSa/s with 14Mpts is not possible at all when t/div is 100us/s. Is it possible you have captured it using 50ms/div and after then zoomed in? What other things, if any, you coincidentally forget to tell?
Is it so that everything user do not understand is the manufacturer's fault?
I can give one tip first. ADC is 8bit.
In the main, this is a problem in education, not in the oscilloscope.
Here we can work together to study, shorter and longer courses about basic fundamentals of oscilloscopes.
Before I start tell basic fundamentals how digital oscilloscope works
So I must say that I am very impressed with this scope, especially with the extended bandwidth. Definitely an amazing value for the price.
One thing that I have noticed is that when I am using multiple channels, I would really like to have the channel buttons for each channel being displayed to be lit up, e.g. if I am measuring waveforms with channels 2 and 3, I would like the physical buttons to be lit up for channels 2 and 3. I realize that this might conflict with fact that the active channel is lit up, but perhaps the active channel button could cycle between a bright and dim state to accommodate that feature.While that's not a bad idea, lighting in a workplace present or not could effect the usability of dual illumination of buttons. I suspect it couldn't be done with SW but we'd have to check the front panel HW to know for sure.
So I must say that I am very impressed with this scope, especially with the extended bandwidth. Definitely an amazing value for the price.
One thing that I have noticed is that when I am using multiple channels, I would really like to have the channel buttons for each channel being displayed to be lit up, e.g. if I am measuring waveforms with channels 2 and 3, I would like the physical buttons to be lit up for channels 2 and 3. I realize that this might conflict with fact that the active channel is lit up, but perhaps the active channel button could cycle between a bright and dim state to accommodate that feature.While that's not a bad idea, lighting in a workplace present or not could effect the usability of dual illumination of buttons. I suspect it couldn't be done with SW but we'd have to check the front panel HW to know for sure.
Personally I would be against of such modification, I really like the way the channel button's logic works right now. What would the proposed change give? To indicate what channels are activate? But there are channel indicators on the screen, plus in some situations (depends on the used trigger mode) the visible signals (in different color) immediately give you the idea what channels are enabled. The situation would be different if they have not used multiplexed vertical controls but we have what we have.
[ It is my opinion that it can be easily missed that the channel has been turned on. I have attached a copy of an image demonstrating this scenario in this message.
[ It is my opinion that it can be easily missed that the channel has been turned on. I have attached a copy of an image demonstrating this scenario in this message.
Hi SMB784,
could you please double check if you forgot to attach the aforementioned image?
Thanks!
[ It is my opinion that it can be easily missed that the channel has been turned on. I have attached a copy of an image demonstrating this scenario in this message.
Hi SMB784,
could you please double check if you forgot to attach the aforementioned image?
Thanks!
Yep sorry just attached it!
I realize that after a large number of hours working with this device that this issue may be mitigated by experience
As you wrote earlier:QuoteI realize that after a large number of hours working with this device that this issue may be mitigated by experienceThis is the key here, but not a 'large number of hours', only a little time to look at the display with a little more analytical mind.
Other than the 2 indicators you've mentioned (zero level marker and channel ON box) there's also the zero level indicator in the channel box that when compared with the V/div setting indicates the waveform will obviously be off the display. When you find yourself in this situation a press of the Position control returns the active channel to the 0V position to where you can place it where it suits best.
Much of this is just familiarity with the UI, is it right or wrong or just another way to do the same operations as any other DSO ? They are all different in some way or another.
Compared to the other scope images you've posted I ask which has the most prominent active channel box on the display ?
As you wrote earlier:QuoteI realize that after a large number of hours working with this device that this issue may be mitigated by experienceThis is the key here, but not a 'large number of hours', only a little time to look at the display with a little more analytical mind.
Other than the 2 indicators you've mentioned (zero level marker and channel ON box) there's also the zero level indicator in the channel box that when compared with the V/div setting indicates the waveform will obviously be off the display. When you find yourself in this situation a press of the Position control returns the active channel to the 0V position to where you can place it where it suits best.
Much of this is just familiarity with the UI, is it right or wrong or just another way to do the same operations as any other DSO ? They are all different in some way or another.
Compared to the other scope images you've posted I ask which has the most prominent active channel box on the display ?
I definitely concur that after a few days/weeks of familiarity that one becomes used to looking for active channels in the channel box, however there are a few things that I will point out.
The first and foremost of these is the fact that in a display a little redundancy goes a long way when it comes to ease of use. In this situation, nothing is sacrificed and in order to further emphasize the channels being used in an obvious and unambiguous way.
Secondly, there is the visibility aspect. It is difficult to see the on screen channel indicators from a distance beyond a couple feet. This is especially problematic when you have less than four but more than one channel activated, as it is possible to see that two/three channels are on from the channel box but it's difficult to tell which ones specifically are active. A lighted button for each active channel would make this completely unambiguous at any distance or viewing angle.
Finally, there is the mainstream appeal factor. You sacrifice nothing in opting for this feature and it makes your scope more familiar to those who are used to other competing scopes, which may improve your appeal.
Regardless it's not a huge deal, and I do love the scope, but the OCD in me made me bring it up, especially given that it is a feature that I know and love after having used scopes from just about every manufacturer there is
It's nice to have a discussion where we can explore POV's and I fully get what you're asking here but I'd ask that if all active channels ON/OFF buttons were lit, how could the user know which one was active for the vertical controls ?
Would you have to press one again to set it to the vertical controls ?
This is what 17_29bis was meaning when he said he thought the existing channel management/indication logic was good.
Others ?
I'm a bit confused about the proposed use case: measure a non-active channel that is also off-screen ? Is there a "non" too many ?
Regarding measuring off-screen waveforms, how well does that actually work ? I would expect the scope to set the ADC range to cover mainly the screen, so the measured signal may be clipped or suffer other distortions ? Or does the Siglent let you choose screen position and DC offset independently ?
I'm a bit confused about the proposed use case: measure a non-active channel that is also off-screen ? Is there a "non" too many ?
Regarding measuring off-screen waveforms, how well does that actually work ? I would expect the scope to set the ADC range to cover mainly the screen, so the measured signal may be clipped or suffer other distortions ? Or does the Siglent let you choose screen position and DC offset independently ?
I'm a bit confused about the proposed use case: measure a non-active channel that is also off-screen ? Is there a "non" too many ?
Regarding measuring off-screen waveforms, how well does that actually work ? I would expect the scope to set the ADC range to cover mainly the screen, so the measured signal may be clipped or suffer other distortions ? Or does the Siglent let you choose screen position and DC offset independently ?
Exactly my thought. If my memory serves me well someone (the one who knows the ropes) on this forum already said that if the oscillogram/waveform does not fit the screen then it's most likely / almost guarantied that the measurements on this channel will be incorrect i.e. it has no practical use.
Here these ramp images.
Here these ramp images.
Thanks a lot ! These images show very clearly what I suspected would go wrong when pushing these limits. SMB784's use case may still work, but would require prior characterization of scope performance for the exact set of settings to be used.
By the way, I find it interesting that one can already see a hint of non-linearity in the top and bottom parts of image 178. That shows how narrow the margins really are.
Fun ideas for when someone gets around to writing alternative firmware for a scope:
- add optional warnings when waveforms get clipped, especially if measurements are active that would be directly affected,
- if moving parts of a waveform with high distortion onto the screen, visually indicate that these parts can't be trusted,
- add (optional) auto-ranging of front end configuration to capture entire amplitude,
- allow manual control of ADC of front end configuration, including separate control for DC offset and screen position,
- per-channel intensity control so that one can just hide active channels one doesn't want to look at (i.e., the real issue SMB784 is trying to solve).
Especially the first two could help less experienced users in situations where the scope is doing something that's very different from what they think it should be doing.
rf-loop:
R&S RTB2k (and I assume their higher end siblings) do the first three of these ideas. You get little red arrows on the channel info bar when clipping (pointing up, down or both depending on clipping direction), a hard cut-off edge to the waveform in orange when moving it up/down the screen after capture and measurements will show "clipping+" or "clipping-" when used on a clipped waveform.
Definitely agree about being able to decouple ADC range from 1:1 mapping to screen display range - some scopes allow for the ADC range to cover a smaller portion of the screen so that you can "stack" waveforms for better visibility without reducing the captured resolution, but these scopes seem to be few and far between (I think the new Tek scopes do this, but others have in the past too despite the Tek marketing droids claiming it as revolutionary).
SMB784:
Again comparing to the RTB2k (and also the new Tek scopes) - this does what you want (enabled channels have lit LEDs behind their respective panel buttons), but this scope also has the ability to light up the knobs with the currently selected channel's colour (via RGB LEDs behind the panel). This means that you can tell BOTH which channels are on and which channel is currently selected for adjustment - unfortunately hard to do without the multicoloured LED thing or referring to the screen. Without this it's always going to be a compromise as to how the use the channel button LEDs - it's never going to be right for everyone. Both of my examples are well above the Siglent price point though (and have their own quirks) so I think it's hard to criticise a few compromises and limitations like this!
I'm just using it for a screenshot because I can go to my upstairs computer and capture without fussing around with a USB drive; all my operations were done from the front panel.
The problem with reducing sensitivity is that when I turned down sensitivity on CH3-4 for this test, the Math waveform degraded substantially. IMHO it's using the lower values (post-attenuation) to calculate the waveform and if the amplitude of the source channels displayed is too low, the Math waveform suffers badly from bit truncation. I can post an example of this if it's not clear what I'm describing.
Meanwhile, I found that turning the trace brightness down affects everything except the Math waveform, so that is a workable alternative - again, unless I am overlooking an option.
No, I've tried setting the timebase to extreme values and it doesn't change at all. It really does look like the Math function is working with too little vertical resolution on the source waveforms. At the sensitivity I'm using here they look pretty pixilated as well, though the input signal is fine.