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Using (and living with) Siglent SDS1000X-E Series Oscilloscopes

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SimonM:
The more I look at my scope, the less confident I think I know anything about what it's doing...

I have two cables, one was delivered as RG58 50 ohm and the second is RG59 75 ohm. I bought the RG59 that was described as RG58 - when it arrived, I noticed a difference and checked the identification printed on the cable. The vendor had made a mistake because it is RG 59! I am looking to replace both BNC cables with some better and balanced RG58 50-ohm cables, as buy cheap, buy twice...

I'm looking at the differences using a 15MHz square wave out of SDG1032X set for 50 ohms) on both channels with 2nd channel locked, feeding 50-ohm terminators into the scope. I'm using channels 1 & 3 of the scope and the waveforms are slightly different, with RG58 providing a squarer waveform, especially evident at 30MHz, compared to the RG59.

Both these channels should be in phase - that's a known problem with the scope that the dealer is looking into and using channels 1 & 2 they can be shown to be in phase. Here's a print, where they are out of phase using channels 1 & 3:



As well as being out of phase, I get an interesting effect when I turn on either of the two other channels. The 3rd channel is phase-shifted, see the attached print. At 30MHz this is also particularly noticed, but for the cables, I was using a lower frequency signal.



Channels 2 & 4 aren't connected to anything. Since I'm triggering on channel 1, this stays exactly centred around the trigger point, but channel 3 moves back. Unless I haven't thought it through, I wouldn't expect adding another channel to the display, to make any difference to existing channels. Perhaps it just highlights again that the 2nd ADC isn't (particularly) aligned with anything? I get a similar shift if I trigger on another channel and add either of the other two channels.

Simon

StillTrying:
It shouldn't do that either.

"that's a known problem with the scope that the dealer is looking into"

Have they told you anything such as tested one of their current stock? The scope's own 120ns rise time 1kHz would be enough to see the 29ns error.

All I can think of is reinstall the latest firmware, hopefully tautech will know if that's a worth trying not.

I suspect it will be going back myself.

tautech:

--- Quote from: StillTrying on July 05, 2021, 11:54:42 pm ---It shouldn't do that either.

"that's a known problem with the scope that the dealer is looking into"

Have they told you anything such as tested one of their current stock? The scope's own 120ns rise time 1kHz would be enough to see the 29ns error.

All I can think of is reinstall the latest firmware, hopefully tautech will know if that's a worth trying not.

I suspect it will be going back myself.

--- End quote ---
Yeah I know......been busy....

Problem is most likely with settings in SDG1032X where outputs are not perfectly edge aligned by default so settings must be tweaked to ensure edges are perfectly in phase.

Adjust as follows:
SDG>Utility>P2>Phase Mode = Locked
Utility>P1>Channel Copy Coupling>Track = ON

This SDG1032X requires a Ch2-Ch1 Phase Deviation of -2o

Screenshots below SDS1104X-E where SDG Ch1 always = Ch4 on SDS.
First 2 on each scope ADC and last 2 on same ADC.
The scope is NOT the problem only the phase deviation in the SDG.
It should also be noted that once channel phase differences have been trimmed out that a Power ON =Last setting be made so adjustments to phase differences will be saved.

bdunham7:

--- Quote from: tautech on July 06, 2021, 02:16:04 am ---The scope is NOT the problem only the phase deviation in the SDG.

--- End quote ---

I'm not clear on what you are saying here...

At one point he split a single channel and observed 29ns of difference on the scope.  How could the scope not be the problem?

tautech:

--- Quote from: bdunham7 on July 06, 2021, 02:25:20 am ---
--- Quote from: tautech on July 06, 2021, 02:16:04 am ---The scope is NOT the problem only the phase deviation in the SDG.

--- End quote ---

I'm not clear on what you are saying here...

At one point he split a single channel and observed 29ns of difference on the scope.  How could the scope not be the problem?

--- End quote ---
Where, which post ?

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