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2 GHz scope: Rigol MSO8000 vs Siglent SDS6000

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tautech:

--- Quote from: Barleyman on December 13, 2024, 06:15:27 pm ---
--- Quote from: tautech on December 13, 2024, 01:51:10 pm ---
--- Quote from: Barleyman on December 12, 2024, 07:01:53 pm ---Unless they're barefaced being dishonest about it, that's exactly what both Rigol and Siglent claim. 1.6pF and low-z 500R for Rigol RP6150A, Siglent RP6150A (note the names..) claims 1.8pF and 500R and gives you a lot more performance data. Presuming they're the same probe except for the spiffy connector for Rigol, Siglent's data probably matches fairly well for Rigol as well.

Rigol:
https://int.rigol.com/Images/RP6150AUserGuideCNEN_tcm7-3146.pdf
Siglent:
https://siglentna.com/product/sp6150a-1-5-ghz-oscilloscope-probe/

There's discussion about Siglent's version here:
https://www.eevblog.com/forum/testgear/new-siglent-sp6150a-passive-1-5-ghz/

--- End quote ---
I have SP6150A here to pair with SDS6204A but not tested it in detail yet.
Also SAP1000 active probe and various signal sources including a nice Leo Bodnar 30ps pulser.


Gets interesting examining probing effects ......endorsing the fact that taking any measurement itself effects the measurement.

We had a nice little thread on this matter..... a couple of posts:
https://www.eevblog.com/forum/testgear/probe-into-probes-whats-up/msg4678768/#msg4678768
https://www.eevblog.com/forum/testgear/probe-into-probes-whats-up/msg4684580/#msg4684580

--- End quote ---

How do you do the HF compensation exactly? I can see from your images that the uncalibrated 500MHz probe is what it is but after calibration it's radically improved. I mean, cheap old probes have this screw you can tweak with a plastic bit to improve them a bit but somehow, I do doubt that's what's going on here. Is this a Siglent scope software feature?

Also WRT to the standard issue 500MHz probe you tested there, these low-z probes are rather different beasts, I'm not quite sure what to expect. USB HS line has theoretical 45R single ended impedance (but let's be realistic here) so feeding that to a ~150R+50R load (at 500MHz) would already drop the voltage by ~20% and at the leading edge it'd be much more significant. Very similar as your uncompensated image shows.

--- End quote ---
Typically the HF compensation requirement is 1 MHz with 1ns risetime.

This is specified in the attachment in this post where I question why one couldn't use a 10 MHz Bodnar pulser:
https://www.eevblog.com/forum/testgear/playing-with-probes-guessing-game/msg4735067/#msg4735067

nctnico:

--- Quote from: AndyC_772 on December 13, 2024, 11:08:13 am ---1.6pF is impressively low, but it's still 66 Ohms at 1.5 GHz.

IMHO any scope 500 MHz or above really needs active probes. It's pointless not to have them because the load from any passive probe dramatically distorts the signal being probed.

--- End quote ---
I disagree. Take the Tektronix P6156 probe as an example of a passive Low-Z probe which has a capacitance of less than 1pf with a bandwidth of 3.5GHz (10x and 20x attenuators). An active probe won't do any better in that respect as the impedance of the input capacitance dominates the load the probe poses to the circuit.

Barleyman:

--- Quote from: tautech on December 13, 2024, 08:08:56 pm ---Typically the HF compensation requirement is 1 MHz with 1ns risetime.

This is specified in the attachment in this post where I question why one couldn't use a 10 MHz Bodnar pulser:
https://www.eevblog.com/forum/testgear/playing-with-probes-guessing-game/msg4735067/#msg4735067

--- End quote ---

Ah, so you are indeed talking about the trimmer caps the probes have. I was imagining some fancier procedure. Sure, yeah, that's fairly basic stuff and easy to do. Often the scopes have a calibration pin with square wave for this very purpose.

In any case, I'll put in (purchase request) order next week, the one thing to find out is if the free "software bundle" Rigol distributor in UK shows is valid. They seem to be rather relaxed about updating their web pages when promotions end.. I could also get the thing from eleshop.eu, but buying "local" is just easier since the brexit thing.

Yes, I'm aware some people on Santa's naughty list have scripts to activate said software package for free. I would never, you cannot prove I did.

points2:
hi,
just an idea :
why no answer vs these basic but nice & straightforward questions from 2N3055 ?

--- Quote from: 2N3055 on October 24, 2022, 06:45:23 pm ---What fast digital signal? (...) What risetimes?

--- End quote ---
If anyone wants a "nice" device to play with (without answering 2N3055's questions) : no brainer ! Go for it guy : many scopes on the market...
But if only result matters => back to basic => if you know the rise-time of the signal => you know what scope you need.

I guess it's all about digital signal thus => it is a repetitive signal => a sampling scope is the right choice, not a RT-scope.

tautech:

--- Quote from: points2 on December 14, 2024, 11:23:38 pm ---hi,
just an idea :
why no answer vs these basic but nice & straightforward questions from 2N3055 ?

--- Quote from: 2N3055 on October 24, 2022, 06:45:23 pm ---What fast digital signal? (...) What risetimes?

--- End quote ---
If anyone wants a "nice" device to play with (without answering 2N3055's questions) : no brainer ! Go for it guy : many scopes on the market...
But if only result matters => back to basic => if you know the rise-time of the signal => you know what scope you need.

I guess it's all about digital signal thus => it is a repetitive signal => a sampling scope is the right choice, not a RT-scope.

--- End quote ---
Fast depends on the mode of use.

In Digital mode the waveform bears little resemblance to the same waveform in analog mode.
What matters most is the probing mechanism used so to impact the waveform in the least possible manner.

Check out the posts I made on this and follow the links.
Without tests on the edge we cannot know how our probes (or scope) will perform when pushed.

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