Products > Test Equipment
buy a better oscilloscope than the Siglent SDS1104X-E
uargo:
--- Quote from: Fungus on August 15, 2023, 05:51:45 am ---
--- Quote from: uargo on August 14, 2023, 10:07:09 pm ---I already know it. but people comment that the firmware is still unpolished, that it is logical that all oscilloscopes have many bugs at the beginning and over time they are fixed
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Even so: If it does then things I need very well then I can overlook a few bugs in the CAN bus decoder, or whatever.
eg. The way the stats work and the overall user interface on these new Rigols could save hours per day if that's what you spend your time using.
I expect a big push from Rigol in the next few months when their new 800 series hits the market. I'm already saving up for mine.
--- End quote ---
I also hope to see a review of the new rigol and siglent 1000hd, I'm impatient
uargo:
--- Quote from: 2N3055 on August 15, 2023, 08:26:50 am ---
--- Quote from: Fungus on August 15, 2023, 05:51:45 am ---
--- Quote from: uargo on August 14, 2023, 10:07:09 pm ---I already know it. but people comment that the firmware is still unpolished, that it is logical that all oscilloscopes have many bugs at the beginning and over time they are fixed
--- End quote ---
Even so: If it does then things I need very well then I can overlook a few bugs in the CAN bus decoder, or whatever.
eg. The way the stats work and the overall user interface on these new Rigols could save hours per day if that's what you spend your time using.
I expect a big push from Rigol in the next few months when their new 800 series hits the market. I'm already saving up for mine.
--- End quote ---
Well, other people are different.
For instance I will take simpler device, that is reliable and works well, over a device that was developed by marketing department and has impressive list of "features" in datasheet but none of it works as it should...
And praise how "new Rigols" have "good interface" is fact that they finally made touch screen interface. In fact the were late to the party, it was long due on their part. And state of software is still what other manufacturers would call beta.. They will eventually get there, but their track record is that they do it slow.
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+1 I think like you, even so they are interesting devices to keep track of them
uargo:
--- Quote from: Performa01 on August 15, 2023, 10:01:03 am ---
--- Quote from: uargo on August 14, 2023, 10:12:40 pm ---The Siglent SDS2104X PLUS convinces me more and more, the firmware is more established, if the 10-bit mode works for me to see the noise, it is an oscilloscope that I like
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That's it. Do not believe everything posted here, like claims a DSO being the wrong tool for noise characterization. This might be true for some scopes with noisy frontends and/or lousy FFT implementation, but not for e.g. an SDS2000X Plus. Of course, an SDS2000X HD would be even better.
When analyzing noise, we don't want a single absolute number like from a DMM with its very limited bandwidth; we want to see the entire spectrum with accurate levels for every single frequency component. Such information also helps us to identify the source of the noise (so we might be able to do something about it).
Once again, instead of just claims and speculations, here is a practical demonstration (older measurement, not the latest firmware), where I happened to measure a weak 10 MHz signal and wanted to find out if the 10 bit mode can improve such measurements even though the FFT in itself provides a resolution enhancement already.
I've found a measurement of the -70 dBm level particularly, which is 71 µVrms or 200 µVpp respectively - far below 600 µV (whatever it should be, peak, p-p or rms).
First the measurement in 8 bit mode.
SDS2354X Plus_LVL_10MHz_1mV_-70dBm_8bit
Of course the signal is not visible in the time domain, because at about 600 MHz bandwidth, the oscilloscope's own noise is 76 µVrms or 685 µVpp. Yet the FFT shows the overall noise floor as well as the single signal quite well.
The frequency step is 119,2 Hz and with Flattop window the resulting RBW (Resolution Bandwidth) is ~450 Hz. I did not measure the noise floor back then, but from the graph we can estimate it to be about -124 dBm = 141 nVrms or 399 nVpp for a 450 Hz wide bin. From this, we can calculate the noise density to 141 nVrms / √450 Hz = 6.65 nV/√Hz. From this, we can calculate the total noise for any desired bandwidth.
Hint: The signal source for this particular test did not include noise deliberately, so this measurement shows the limits of the instrument in this particular configuration and setup. It means that external noise has to be stronger than about 10 nV/√Hz in order to be detectable. Still not too bad.
But even more important than the wideband noise floor is the identification and proper measurement of spurious signals, which can give a strong hint on the noise source.
In this example, with just 8 bits, we measured the 10 MHz signal as -69.8 dBm (72 µVrms, 205 µVpp), which results in an error of +0.2 dB or +2.33 % - not too bad for a microvolts signal level at 10 MHz - try that with any DMM!
Now the same measurement in 10 bit mode.
SDS2354X Plus_LVL_10MHz_1mV_-70dBm_10bit
The signal is still not visible in the time domain, even though the input bandwidth is now limited to 100 MHz because of the 10 bit acquisition mode.
The noise floor is now at about -130 dBm = 71 nVrms or 200 nVpp for a 450 Hz wide bin. From this, we can calculate the noise density to 71 nVrms / √450 Hz = 3.34 nV/√Hz. That means, the noise floor has dropped dramatically by 6 dB – we have gained one bit of dynamic range, or in other words: the ENOB has been increased by one bit, just as expected – and up to 100 MHz there should hardly be any noise sources we could not accurately characterize with this.
Again, we can calculate the total noise for any desired bandwidth.
The measurement of the 10 MHz signal is now spot on as well. We can measure it as -70.015 dBm – an error of just -120 nVrms or -350 nVpp, equivalent to -0.015 dB or -0.17 % - no further comment necessary.
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Thank you very much and great collaboration, summarizing an SDS2104X PLUS works, although an SDS2104HD would be better, and the 1000HD would need to see a review to see what background noise they have
uargo:
--- Quote from: nctnico on August 15, 2023, 11:09:45 am ---
--- Quote from: Performa01 on August 15, 2023, 10:01:03 am ---
--- Quote from: uargo on August 14, 2023, 10:12:40 pm ---The Siglent SDS2104X PLUS convinces me more and more, the firmware is more established, if the 10-bit mode works for me to see the noise, it is an oscilloscope that I like
--- End quote ---
That's it. Do not believe everything posted here, like claims a DSO being the wrong tool for noise characterization. This might be true for some scopes with noisy frontends and/or lousy FFT implementation, but not for e.g. an SDS2000X Plus. Of course, an SDS2000X HD would be even better.
When analyzing noise, we don't want a single absolute number like from a DMM with its very limited bandwidth; we want to see the entire spectrum with accurate levels for every single
--- End quote ---
If you look at OP's specific problem then you'll see it is about finding power supply noise in an analog circuit. Unless the OP has totally messed up the power supply decoupling, that means the problem is in the DC to several tens of kHz frequency range. You'd need a filter to make FFT usefull on an oscilloscope to prevent aliasing due to large sub-sampling factor. There are better tools out there compared to a general purpose oscilloscope. As I wrote before, probing also becomes an important factor so a device with floating or differential inputs will help to keep ground induced noise out.
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Thanks, for that, apart from buying the SDM3045X, I wanted to see what oscilloscope could help me with this, and the answer seems to be the SDS2104X PLUS, the SDS2104 HD (out of my budget), and the 1000 HD series from Rigol and Siglent
Performa01:
--- Quote from: uargo on August 15, 2023, 01:33:58 pm ---I also hope to see a review of the new rigol and siglent 1000hd, I'm impatient
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Instead of being impatient, what about contributing to the community and do a thorough review yourself ;)
Seriously though, there are plenty "reviews" out there. They will show you how to unpack the Rigol and some fanboys will praise it to no end, even though they've never touched one, just because it finally has an acceptable noise level and a user interface that doesnt look like a slot machine.
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Just to provide complete information on the SDS2000X Plus: aliasing isn't a problem even at low frequencies on a decent DSO with long FFT. For instance, we can analyze down to 100 Hz and still have 250 MSa/s for the FFT. Together with the 20 MHz bandwidth limiter and the 10 bit mode, which additionally limits the bandwidth at 100 MHz rather steeply, we don't have a problem with aliasing due to subsampling at all.
It is true though that general purpose oscilloscopes have a rather strong rise in noise below some 100 kHz, hence measuring very low noise will not be possible at low frequencies.
600 µVpp would be equivalent to 212 µVrms or -60,46 dBm (I use dBm even though we are talking about voltages here, just because my measurements happen to be in dBm). Consequently, we can analyze noise as long as the FFT plot does not exceed that level. As we can see from the attached graph, even at just 1 kHz, the measured level is still -96 dBm for 450 Hz bandwidth – way below the -60.46 dBm calculated before. Only down at 200 Hz we reach a noise level of 900 µVrms.
But then again: if you need to look just for mains hum and its harmonics – and 600 µV would be a problem for your circuit alrady, then you actually need a dynamic signal analyzer (expensive) or a PicoScope 4262.
SDS2354X Plus_Noise_1M_BW20M_10bit
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