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Siglent SDS1104X-E In-Depth Review

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Performa01:

--- Quote from: rf-loop on February 21, 2018, 08:43:33 pm ---@Performa01

In sequence mode if I understand right you show average max sapeed. (how much time some amount of segments aka "frames".  But this is not whole truth about speed.  One thing is speed what it can use without missing any trigger.

--- End quote ---

I see your point - this is certainly a good suggestion for yet another test/measurement. If I got you right, it's pretty much equivalent to a guaranteed max. re-arm time, which in turn determines the guaranteed min. event rate (frequency) that can be captured without losing an event.

Before the latest firmware, we could have measured it just by observing the trig-out signal and looking for the widest gap between two trigger events within a sequence (with a sufficiently high input frequency of course). As it is now, we really need to use your suggested method with the burst generator to measure this. I will try to include such a measurement in a future update of the sequence mode review.

EDIT: When looking at your table, I suspect there will not be much difference, as your guaranteed numbers are even a bit higher than my average ones. Most likely because we have used different input signals - mine was a 20MHz sine...

Performa01:
I have noticed some folks might be wondering how good the original Siglent probes are and if some other (maybe also more expensive) probes would provide better results, i.e. more bandwidth, faster rise time etc.

I thought it might be beneficial to compare different probes on the 200MHz SDS1202X-E just to give you an idea what can be expected.

Before I’m going to show the results, I feel inclined to remind you that the LF-adjustment found on every scope probe is not the end of the story. The input impedance of a scope channel is a bit more complex than just 1MOhm in parallel with the input capacitance, and the probe cable has some characteristic impedance that is severely mismatched on both ends and the frequency response would be awful if no counter measures were taken – but these depend on the individual scope input channel and its impedance over frequency. This is why the performance of the probes that ship with a decent scope are usually hard to beat, because they are matched with that particular scope input.

More expensive probes provide a separate HF-adjustment and should be more universal because of this. Certain probes have even more adjustments than that. One such probe with separate HF-adjustment has been included for this comparison – just to see if it can outperform the humble little PP215 that ships with the 200MHz SDS1000X-E entry level scopes.

The contenders are:

1.   Siglent no name (300MHz) that came with the SDS2304
2.   Siglent SP2030A (300MHz) that comes with the SDS2304X
3.   Siglent PP215 (200MHz) that comes with the SDS1202X-E and SDS1204X-E
4.   Siglent PP510 (100MHz) that comes with the SDS1104X-E
5.   Pico Technology TA131 (250MHz) that comes with their 200MHz scopes
6.   TesTec TT-MF312 (250MHz) that has a separate HF-adjustment, so should be pretty universal

First comes the probe adjustment, which is straight forward for all candidates except the TesTec TT-MF312, which has the additional HF-adjustment. The instructions tell us to use a 1MHz square wave and adust the edges for virtually no overshoot (just as usual for this kind of probes). But I suspected that my square wave might have a little overshoot (some 5%), so I’ve adjusted the probe accordingly.

The following table shows the frequency response of the Siglent SDS1202X-E with the various probes:


SDS1202X-E_Probe_Comparison 1

The 2nd graph shows the frequency response of the probe alone, i.e. the frequency response of the scope has been subtracted:


SDS1202X-E_Probe_Comparison 2

As can be seen, the differences are not huge, up to 260MHz the probe-only frequency responses match within 2dB. Yet when we look at the first graph, we can see the best probe would be the Pico Tech. TA131, closely followed by Siglent PP215 and PP510.
The Siglent SP2030A has the worst high frequency response above 210MHz.

Now let’s have a look at the pulse test results:


SDS1202X-E_Probe  Siglent NN


SDS1202X-E_Probe  Siglent SP2030A


SDS1202X-E_Probe  Siglent PP215


SDS1202X-E_Probe  Siglent PP510


SDS1202X-E_Probe  Pico Tech TA131


SDS1202X-E_Probe TesTec TT-MF312


Now that’s quite revealing!

The Siglent NN 300MHz probe is a representative of the bulky type and it’s HF-compensation clearly doesn’t match the SDS1202X-E input channel; the transition times are very slow: 2.72ns rise and 3.39ns fall time. We can also see this by the softly rounded pulse corners. Even though the frequency response didn’t look quite as bad, this probe is clearly not suitable for the 200MHz SDS1000X-E series scopes.

The Siglent SP2030A 300MHz probe is a better match, but now we get soft corners and overshoot at the same time, which comes from the +1.5dB peak in the frequency response at around 40MHz. Transition times are still not fast: 2.50ns rise and 2.57ns fall time. This probe is not for the 200MHz SDS1000X-E series scopes either.

The Siglent PP215 200MHz probe is a near perfect match. The top of the pulse is almost flat without overshoot and the corners are reasonably sharp – after all, we’re not talking about a superfast scope here. Transition times are as good as it gets on a 200MHz scope: 2ns rise and fall. There is a reason why this probe is shipping with the 200MHz SDS1000X-E series scopes!

The Siglent PP510 has been a big surprise when we were looking at the frequency response graph; despite being only rated for 100MHz, it performed very close to the PP215 in this regard. But the pulse test reveals the difference as the pulse top and bottom are no longer flat but slanted. Other than that, we still get nice sharply defined corners and the rise and fall times are only 2ns, just like with the PP215.

The Pico Technology TA131 250MHz probe pulse test result looks similar to the Siglent PP215, but corners are even sharper and we see very slight traces of ringing. Top and bottom of the pulse are almost flat and the transition times are the best by far in this comparison: 1.9ns rise and fall times. This probe would be worth a 2nd thought if someone plans to replace the PP215, but I still wouldn’t do that. The TA131 probe is an old-style bulky one with a wire type hook instead of a blade type. The cable is thicker and less flexible. But performance wise it is clearly a winner.

The TesTec TT-MF312 250MHz probe is mixed bag and rather disappointing overall. The Pulse top is not slanted and the transition times of 1.92ns for rising and 2.0ns for falling edges are even a tad better than the original PP215 (this might be due to the intentional HF-misalignment for 5% overshoot, which has most likely been unjustified after all), but we have to pay a high price for that in shape (literally!) of ugly overshooting, once again due to the +1.5dB peak in the frequency response at 50MHz. At the same time we have a pronounced -1.5dB dip around 175MHz, which makes this probe the worst in the whole contest. There is certainly no reason to use this probe instead of the original one and it’s another “bulky type” on top of that.

rigol52:
Good work Performa01, thanks.

Very informative. Till yet I was aware a little different, namely:

"Buy your scope-probe, at  least 3x bandpass of your scope."

nctnico:
Several remarks:
- Don't try to measure anything over 100MHz with a high-Z probe. You don't know what you are looking at on the screen because the impedances are all screwed up.
- Probe bandwidths are defined using a source with a 25 Ohm output impedance so you should at least use that doing these kind of tests.

Performa01:
Just to make sure no one gets alienated or confused by a couple misleading statements I’d like to assure you that probe manufacturers are no cheats. They don’t sell passive high-Z probes rated up to 500MHz just for fun.

The original PP215 probe deviates by no more than +/- 0.5dB from the direct measurement up to some 260MHz, as can be seen in the 2nd graph (SDS1202X-E_Probe_Comparison 2). That speaks for itself.

I recognize that some context and the reason for this probe test are missing, so here’s the reference:

https://www.eevblog.com/forum/testgear/siglent-sds1204x-e-released-for-domestic-markets-in-china/msg1434294/#msg1434294

The relevant parts:


--- Quote ---The most important (and expensive) part of any scope probe is the cable, that should be low capacitance and needs to have some well defined resistance for the inner conductor (around 200 ohms) in order to damp the resonance effects from the ill-terminated characteristic cable impedance. The optimum cable resistance depends on the circuit details of the scope input and on the SP2030A it quite obviously is just right for the SDS2304X, but a tad too high for the SDS1202X-E.

Some people like to replace their multimeter probes immediately after purchase with “sexier” ones and that is perfectly fine (except that I never did it because I have no use for these impractical probes at all in a lab, be they sexy or not). But for a scope, you should not replace the original probes with random ones without a second thought, just because they look sexier or have a higher bandwidth rating – only inexperienced folks do that. You might end up with an unpleasant surprise if you take the time to actually measure the performance of the probe/scope combination. Of course there’s always a chance that it actually fits well, but you should be able to verify that beforehand.

--- End quote ---


--- Quote ---As can be seen, the circuit already contains the standard test setup: Signal generator with 50 ohms source impedance and 50 ohms through termination directly on its output, resulting in a total source impedance of 25 ohms, as seen by the probe.

--- End quote ---

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