Products > Test Equipment

Pocket-Sized 6 GHz 1 TS/s ET Scope

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hpw:

IMHO, the crappy TXCO is here a limitation factor.

As no external connection for any better reference OXCO to connect.  :phew:

As 1Ts/s as 1ps sampling rate, IMHO any 1...5ps deviations will be hard to analyze. Or any live measurements Videos convince.

 my 2 cents

Hp

SJL-Instruments:

--- Quote from: points2 on January 14, 2024, 09:16:04 am ---1.1. Does it mean that the USB link is USB.2 ?

--- End quote ---
The USB communications are USB 2.0 FS (12 Mbaud) but the device requires USB 3.0 power levels (900 mA @ 5V). The actual power draw is around 650 mA @ 5V to allow for a factor of safety (e.g. running over a USB extension cord).
The USB 2.0 spec only allows 500 mA @ 5V, so the device requires a USB 3.0 port. (Many USB 2.0 ports can deliver more power than specified, but don't risk it.)


--- Quote from: points2 on January 14, 2024, 09:16:04 am ---1.2. Did you test the performance of the device with different "power supply" :
for instance
=> the USB link
vs
=> a tweaked USB link that enable to get power from an external PS, for instance a "nice" linear PS (less noisy than the power coming from a hub / PC...)

--- End quote ---
We have seen no observable effect with different USB power supplies. Your standard laptop/desktop/tablet USB power is almost certainly fine.


--- Quote from: points2 on January 14, 2024, 09:16:04 am ---2. Trigger frequency : internal vs external.
I guess this question is valid to any sampling scope... (?)
Is it better to rely on (your advice) =>
2.1. the hardware to find out the trigger frequency & stick to it (timebase + PLL ; given that both have their own jitter)
2.2. OR, using an external clock signal (that match the frequency to trigger) ; for instance, a DIY clock based on a "good" tcxo ? (as I don't deal with >100 different frequencies,   :D , it is cheap to buy a fixed-frequency oscillator from a vendor..., and quite easy to get a rather good stability)

--- End quote ---
Not quite sure what you mean here - there is no PLL in the hardware. The trigger is just an edge trigger, behaving the same as with any other scope.
If you're referring to eye diagrams in particular, you need to do clock data recovery (CDR) to obtain a clock signal that (to some extent) tracks the jitter of the data signal. If you want to do this 'properly,' you'll need to get into some weeds about e.g. choosing PLL bandwidth - lots of reading to do.
Trying to match the data frequency with an independent oscillator is likely to cause headaches. Using a simple edge trigger will force the jitter to "zero" (really, the trigger jitter) on one edge of the pseudo-eye-diagram, and so increase the jitter on the other edge. (It also "looks like" a 01 or 10 serial trigger - you need to look a few eyes down the line.) It can be useful to get a qualitative sense of your signal integrity, but shouldn't be used to quantitatively characterize your signal.


--- Quote from: hpw on January 14, 2024, 11:23:46 am ---IMHO, the crappy TXCO is here a limitation factor.

As no external connection for any better reference OXCO to connect.  :phew:

As 1Ts/s as 1ps sampling rate, IMHO any 1...5ps deviations will be hard to analyze. Or any live measurements Videos convince.

 my 2 cents

Hp

--- End quote ---
A better reference wouldn't help for two reasons. The current typical timebase precision is 15 ppm, which is 1.5 ps at 100 ns. The effective jitter floor (Section 2.3 in manual) at 100 ns delay is ~8 ps RMS. What actually happens in practice is the 1.5 ps deviation "gets absorbed" into the measured effective jitter and increases the value of alpha (technically, only the portion of the phase noise integrated up to the sampling timescale, Section 2.2.2). So decreasing the reference phase noise at 10 kHz and up doesn't do much (since it adds in quadrature, it will still be ~8 ps RMS).

A larger issue is that the timebase is used to continuously calibrate the delay generator, which can only hold 15 ppm precision. In that light, the 2.5 ppm TCXO precision is plenty, and improving the phase noise below 10 kHz wouldn't help either. We think that beating this would require a completely different architecture (e.g. TDC random sampling), and drive up the price a lot.

joeqsmith:
How do I save/recall  the settings?  Is there an option to have the program use the last settings? 

SJL-Instruments:

--- Quote from: joeqsmith on January 15, 2024, 11:40:23 am ---How do I save/recall  the settings?  Is there an option to have the program use the last settings? 

--- End quote ---
The software currently doesn't support this. We'll add this to our queue as well - thanks for the suggestion.
This has been implemented as of v2.5.5 (released 2024-01-21).

joeqsmith:
Your documentation mentions different firmware revisions.  How are you making these available and what tools are in place to upgrade the product in the field?  Or are you requiring that the product is returned to be upgraded?   

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