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| Pocket-Sized 6 GHz 1 TS/s ET Scope |
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| SJL-Instruments:
--- Quote from: joeqsmith on February 04, 2024, 04:32:30 am ---Indeed, at 5.8GHz the required level is different than 1GHz. Is the sensitivity vs frequency defined somewhere? I assume that we can bias that 200mV anywhere as long as we stay within the common mode range (+/-950mV). --- End quote --- We do not have an official spec for sensitivity vs. frequency. To give you a rough idea, generally the GigaWave can trigger off 60 mVpp @ 1 GHz. The trigger level must be centered within the peak-to-peak range. The 200 mVpp edge can have any DC bias within the specified range. --- Quote from: joeqsmith on February 04, 2024, 04:32:30 am ---0.2 X 20 (probe attenuation) or 4V swing which is CMOS. Even if you work reliably at 100mvp-p, or a 2V swing, that rules out most logic? Are you expecting it to work with say LVDS and a 20X resistive probe? The manual doesn't offer any suggestions or guidelines when it comes to probing. --- End quote --- We would not recommend using a 20x resistive probe - even a 0.3 pF input capacitance, which is the lowest we've seen for a 20x commercial resistive probe, presents as ~270 ohm @ 2 GHz. The fastest transition time we've found is ~80 ps for a 20x passive probe, which is twice the 40 ps spec of the GigaWave. At that point, we'd recommend using a 5x probe which has a flat 250 ohm input impedance up to 6 GHz. We have such a design, and plan to include a few as a standard accessory in the future. We are actually considering open-sourcing this design. A 5x probe with LVDS would give a ~70 mVpp swing, which we have found that the GigaWave can trigger on directly @ 2 Gbps. However, we would recommend using an external clock or CDR for generating an eye diagram. --- Quote from: joeqsmith on February 04, 2024, 04:32:30 am --- --- Quote ---The THD will display as invalid if there isn't enough resolution to get an accurate measurement. You should have five full periods (ideally 10) to get a meaningful result. We'll clarify this in the manual. --- End quote --- Is the THD in your software calculated differently than the calibration certification? If the settings are critical as far as replicating what you call out, you may want to define them. --- End quote --- The THD in the calibration certificate is obtained via a time-domain regression, not an FFT. With only a few periods, the THD calculated from the FFT will depend on the windowing method used and the timebase range. The time-domain method is immune to these considerations (and gives statistical uncertainties on the extracted parameters). We will mention this, as well as the exact timebase settings used, in the manual. |
| SJL-Instruments:
As promised, we have released v2.5.7 of the software which adds math channels, histograms, and various other improvements. The accompanying manual has also been updated (revision H7). |
| joeqsmith:
Interesting idea about including probes. 5X is getting down there. I try to keep loading under 10% error and use 10X (500ohms) in many cases. 100 ohm differential termination with another 200 to ground on each leg .... maybe... I guess as long as people understand the limits of the trigger it's fine. Leave it up to them to sort out if it can be used or not. Consider you may be using a delay line with the 5X probe, knocking another 6dB off. A lot to consider. As you said, it's down to price point. After starting the software, set all offsets to 0. Entering 50 for scale on channel 1 will randomly select 50 V/div or 50 mV/div. I would expect it to be predictable and was surprised that 50V would be valid. Seems easy enough to reproduce. I have had the software appear to hang. Basically it was displaying wait, but appeared not to be updating the plots as nothing was being displayed on the graph for all 4 channels. Nothing, meaning a blank screen. I changed the scale to 500mV/div, and it remained blank. Offsets all set to 0. I increased the input voltage to 500mVp-p with no triggers. 10MHz. All I did was exit the software and restart, everything was working as expected. I have not been able to replicate this but I have seen the software hang like this before with an earlier revision. I am curious if you are getting any feedback on the UI. It's easy enough to run but IMO, not very smooth. It's a real pain to hunt down your waveforms with manually setting the offset and scale. Typing in the scales rather than the drop down selection do allow me to set it to what ever I want, but now its a bigger time waste entering all that data. I would like to see this thing have some sort of intelligent mode where is autoscales the vertical, locks the start of acquisition to the left, changing the vertical scale resets or at least causes min/max to track. It's the same with dragging the waveform to change the offset, the min/max doesn't track it. It's a constant close waveforms and recreate. Or if I change the vert scale for channel 1, the scale for the min/max don't track it. Having that start of acquisition time moving all over based on the Base is a pain. I am constantly dragging waveforms. It's very possible that your customers like the UI. Consider I am up there in years and have used a lot of different scopes, it could just be my bias on how they should work. Years ago, I looked at a brand new logic analyzer from HP. That is all I have ever used and for the most part, they all drove the same. Even with the touch screen and single knob. This new thing was like they had fired the entire staff, brought in new management that had no idea what a LA was, and decided to make a product that worked (in their minds) better than the old systems. Or they had no idea how their old products drove. To me it seemed they were trying to target software people for the end user rather than hardware. It was so bad, I gave a simple test to other EEs to see if they could run it. In the end, the software was why I didn't procure it. A few years ago I wanted to buy a better VNA for home hobby use. Get out of the 1970s... I looked at Picotech. Really liked the hardware. Price was high but specs are good. 4-receiver.... Then I tried their software and ditched the idea. I reached out to them last year to make a series of videos on their VNA but no bites. Point being, software for these is IMO, is every bit as important as the hardware. If it drives different than every product out there, it may not get a lot of acceptance. Again, MO. |
| SJL-Instruments:
--- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---Interesting idea about including probes. 5X is getting down there. I try to keep loading under 10% error and use 10X (500ohms) in many cases. 100 ohm differential termination with another 200 to ground on each leg .... maybe... I guess as long as people understand the limits of the trigger it's fine. Leave it up to them to sort out if it can be used or not. Consider you may be using a delay line with the 5X probe, knocking another 6dB off. A lot to consider. As you said, it's down to price point. --- End quote --- Yes, the loading is not ideal. The 5x probe prioritizes flatness over loading. Perhaps we could offer both 5x and 10x probes. At high frequencies, you become limited by the characteristic impedance of the probe tips themselves, which (thought of as a transmission line) are ~200 ohm. This is close enough to 250 ohm that a 5x probe is easy, but a 10x probe is harder to get right. --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---After starting the software, set all offsets to 0. Entering 50 for scale on channel 1 will randomly select 50 V/div or 50 mV/div. I would expect it to be predictable and was surprised that 50V would be valid. Seems easy enough to reproduce. ... It's a real pain to hunt down your waveforms with manually setting the offset and scale. Typing in the scales rather than the drop down selection do allow me to set it to what ever I want, but now its a bigger time waste entering all that data. --- End quote --- Entering "50" will give 50V/div, and entering "50m" will give 50 mV/div. We'll change this back to a dropdown in the next update, with an option to change it to a textbox if you need arbitrary scales. This change was made primarily for compatibility with high-voltage probes. --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---I have had the software appear to hang. Basically it was displaying wait, but appeared not to be updating the plots as nothing was being displayed on the graph for all 4 channels. Nothing, meaning a blank screen. I changed the scale to 500mV/div, and it remained blank. Offsets all set to 0. I increased the input voltage to 500mVp-p with no triggers. 10MHz. All I did was exit the software and restart, everything was working as expected. I have not been able to replicate this but I have seen the software hang like this before with an earlier revision. --- End quote --- That's odd - nothing, as in the axis labels were gone also? Or only the traces? Shortly after v2.5.7 released, we noticed that de-embedding did not work at 128 pts/div (screen would blank), and re-uploaded a patched version. This may or may not be the issue. --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---It's the same with dragging the waveform to change the offset, the min/max doesn't track it. It's a constant close waveforms and recreate. Or if I change the vert scale for channel 1, the scale for the min/max don't track it. --- End quote --- Got it - next update, we will implement the min/max so that it tracks the offset/scale properly. (And waveform persistence as well.) The current way (with math channels) gives more flexibility, but is non-standard. --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---Having that start of acquisition time moving all over based on the Base is a pain. I am constantly dragging waveforms. ... I would like to see this thing have some sort of intelligent mode where is autoscales the vertical, locks the start of acquisition to the left[...] --- End quote --- To clarify: the software currently references the "timebase position" to the center of the screen. Changing the base (or zooming in with the scroll wheel) will zoom in keeping the center of the screen fixed. This lets you put the event of interest in the center of the screen, and zoom in. It was implemented this way by customer request. Are you proposing that changing the timebase scale should instead keep the left side of the screen fixed? Or the T=0 marker fixed? It's easy enough to make this an option. --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---Point being, software for these is IMO, is every bit as important as the hardware. If it drives different than every product out there, it may not get a lot of acceptance. Again, MO. --- End quote --- We agree with this - your feedback so far has been immensely helpful. We want to be as responsive as possible to customer feedback, to push the software in the right direction. |
| joeqsmith:
--- Quote from: SJL-Instruments on February 05, 2024, 05:20:19 pm --- --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---After starting the software, set all offsets to 0. Entering 50 for scale on channel 1 will randomly select 50 V/div or 50 mV/div. I would expect it to be predictable and was surprised that 50V would be valid. Seems easy enough to reproduce. ... It's a real pain to hunt down your waveforms with manually setting the offset and scale. Typing in the scales rather than the drop down selection do allow me to set it to what ever I want, but now its a bigger time waste entering all that data. --- End quote --- Entering "50" will give 50V/div, and entering "50m" will give 50 mV/div. We'll change this back to a dropdown in the next update, with an option to change it to a textbox if you need arbitrary scales. This change was made primarily for compatibility with high-voltage probes. --- End quote --- I guess I wasn't clear. Entering "50" does not always give 50V/div. It will sometimes give 50mV/div. Try setting channel 1 using 50m. You should see 50 mV/div. Now set it to 50. Does it stay at 50 mV/div or does it change to 50 V? Try it a few times. It's not repeatable every time. Appears random. --- Quote from: SJL-Instruments on February 05, 2024, 05:20:19 pm --- --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---I have had the software appear to hang. Basically it was displaying wait, but appeared not to be updating the plots as nothing was being displayed on the graph for all 4 channels. ... --- End quote --- That's odd - nothing, as in the axis labels were gone also? Or only the traces? Shortly after v2.5.7 released, we noticed that de-embedding did not work at 128 pts/div (screen would blank), and re-uploaded a patched version. This may or may not be the issue. --- End quote --- Sorry I did not take a screen capture. It was showing wait. Signal input was more than enough to trigger device. Trigger level set to 0. It was like the internal trigger was not working and it wasn't able to detect a valid trigger. Restart of the software cleared it. --- Quote from: SJL-Instruments on February 05, 2024, 05:20:19 pm ---To clarify: the software currently references the "timebase position" to the center of the screen. Changing the base (or zooming in with the scroll wheel) will zoom in keeping the center of the screen fixed. This lets you put the event of interest in the center of the screen, and zoom in. It was implemented this way by customer request. Are you proposing that changing the timebase scale should instead keep the left side of the screen fixed? Or the T=0 marker fixed? It's easy enough to make this an option. --- End quote --- Exactly. I want to lock the timebase position to the left, center or right. Adjusting anything else in the timebase would not effect its location. I would also like to be able to set the acquisition length rather than the samples per division. I want to start at T0, or 11ns, record for 2ns with a resolution of 1ps. Today, it's not that flexible. --- Quote from: SJL-Instruments on February 05, 2024, 05:20:19 pm --- --- Quote from: joeqsmith on February 05, 2024, 03:03:18 pm ---Point being, software for these is IMO, is every bit as important as the hardware. If it drives different than every product out there, it may not get a lot of acceptance. Again, MO. --- End quote --- We agree with this - your feedback so far has been immensely helpful. We want to be as responsive as possible to customer feedback, to push the software in the right direction. --- End quote --- I downloaded the PicoTech software for their scope and tried it out. --- Quote from: SJL-Instruments on February 04, 2024, 03:42:49 pm --- --- Quote from: joeqsmith on February 04, 2024, 04:32:30 am ---Is the THD in your software calculated differently than the calibration certification? If the settings are critical as far as replicating what you call out, you may want to define them. --- End quote --- The THD in the calibration certificate is obtained via a time-domain regression, not an FFT. With only a few periods, the THD calculated from the FFT will depend on the windowing method used and the timebase range. The time-domain method is immune to these considerations (and gives statistical uncertainties on the extracted parameters). We will mention this, as well as the exact timebase settings used, in the manual. --- End quote --- Is there a reason why you do not implement the same method in your software as what was used to derive the calibration cert? |
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