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Test Equipment / Re: Choosing between entry-level 12-bit DSOs
« Last post by shapirus on Today at 05:03:20 pm »
It sounds a little bit comical indeed when a 200 MHz instrument is demanded to “see” a 500 MHz signal. But yes, if you don’t care for the true amplitude – why not?

For the screenshot below, a 1.6 Vpp signal has been used, i.e. it fills the screen height at lower frequencies such as 100 MHz.
Some conclusions from this screenshot:

- the SDS800X HD can also be modded (provided that the input low-pass filter is a hardware one) to make one of the channels special, dedicated for high-frequency signals;
- the frequency counter does not fail at this out-of-spec frequency, unlike the Rigol's, so such a mod would be more useful than with the Rigol;
- it can perhaps go way above 500 MHz and still show a proper signal (save for the true amplitude, obviously), I would speculate that it can do at least 800 MHz. @Performa01 would you be willing to verify that, if you have a signal source that can go that high?
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Test Equipment / Re: Choosing between entry-level 12-bit DSOs
« Last post by gf on Today at 05:02:05 pm »
Agreed. In addition I'd like to add that sin x / x reconstruction (which is a relatively simple filter to implement) can reconstruct a sine wave little over  fs / 2.5  (0.4 * fs).

Well, there is no such thing as THE sin(x)/x interpolation. In order to make sin(x)/x practically usable, it must be truncated and windowed. And both the truncation length and the window function are still variables which determine the reconstruction limit of the resulting filter. I agree of course that 2.5 can be considered a common value.
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Power/Renewable Energy/EV's / TPS61021A boost regulator can't handle 50mA
« Last post by hlab on Today at 04:59:43 pm »
Hello all,

I'm in need of some pointers for a problem I have with a TPS61021A boost circuit. I've designed a small GPS tracker device that is supposed to run from a single AA battery. The boost circuit is supplies a 3.3V LDO with 3.6V, with a maximum draw of 150mA. Without the GPS unpowered, the entire circuit draws around 25mA, and the boost converter has no problem operating all the way down to 0.5V as the datasheet indicates, with around 80% efficiency at this voltage. But as soon as I connect the GPS module (which is using 25-30mA), the efficiency drops off a cliff. At 2.0V, the input current is 1A. If I decrease the input voltage further to 1.5V, input current quickly rises to 3A (which is the internal current limit) and output voltage falls out of regulation. L1 is BDHE002016101R0MQ1 1uH inductor from Pulse Electronics, with a saturation current of 3.6A. C1, C2, and C3 are CL21A476MQYNNNE, with an effective capacitance of 18.8uF at 3.6V. The output voltage of the boost converter is spot on 3.6V, so I can rule out the resistor divider being incorrect. One point that may or may not be relevant is that when I supply 3.6V on Vout with the the boost converter disabled, I get ~2V at Vin. The datasheet seems to indicate this shouldn't be happening due to the 'True output disconnect' feature.

Troubleshooting I've done so far
  • My first thought was the inductor was saturating for some reason, so I put an identical inductor in parallel with L1, but the efficiency numbers were the same.
  • I forgot to add the feedforward capacitor to the current design, but I haven't experienced any instability issues. Just to rule this out, I've added a 10pF cap in parallel with R2, but I didn't see any difference in efficiency.
  • I tried adding/removing output capacitance, still no effect.
  • At higher input voltages like 3.0V, I'm seeing the expected 2MHz switching frequency on the scope, and nothing stands out as unusual. Tonight I will collect more datapoints with the scope.
  • All of these findings have been replicated on multiple units, so I don't think faulty components are to blame.

At this point, I'm starting to wonder if there's a problem with the layout, given the relatively high switching frequency of 2MHz. The chip's ground pad extends on the same layer to the input and output caps. There's also an uninterrupted ground plane under the whole circuit. I tried to minimize the switching loop size, but maybe there's something I missed.

Any suggestions from power supply gurus out there?

Best Regards,
Caleb

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Test Equipment / Re: Magnova oscilloscope
« Last post by nctnico on Today at 04:58:42 pm »
They said it is passively cooled.
Rotating it 180 probably isn't a problem, 90° probably is.
No. From the description: Therefore a fan is unnecessary in normal operation and the Magnova can run silently. This clearly says the Magnova oscilloscope does have a fan. Just that is may not be on all the time depending on use & environment temperature.
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Test Equipment / Re: SDS800X HD Wanted Features
« Last post by Martin72 on Today at 04:57:29 pm »
As I've written here before, this is a Christmas wish list.
You write all sorts of things on it, in the knowledge that not all of them can and will happen.
Most of the time and for most people. ;)
I really hope that nobody actually believes that the Siglent development team will sit down, leave everything else behind and work through the lists.
For a device with a starting price of 359€.... :-X
If a few things are realized here, then this is a pure service to the customer, a goodwill in the truest sense of the word and we can then be happy about it, because these are free enrichments.
But I've also had to read here before, yes, a lot should be done in 6-12 months.
You don't know what to say about that either...
Super cheap, super quality, must be able to do everything and have everything.


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Repair / Re: Laser Level Charger PCB ID
« Last post by Shaky on Today at 04:50:33 pm »
You could have a battery pack with "memory", meaning  they could show some voltage  but wont charge if everything is okay ...

I didn't realise Li-ion suffered from the memory effect ! Thought that was just NiCd + NiMH, you learn summat new everyday - cheers.  ;)
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Test Equipment / Re: Choosing between entry-level 12-bit DSOs
« Last post by Antonio90 on Today at 04:48:48 pm »
You guys are making me jealous
Gotta grab the dremel and drill my new Ryzen. I might be able to measure 5GHz somewhere around the die with my brand new passive probes.
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This is how I do that.

The base drive voltage together with the emitter resistor form a current sink. (Udrive-0.7V)/ R1

Select R2 such that the voltage across R2 never exceeds the maximum gate source voltage for M1.

You can adjust the turn on speed with C1 (Miller integrator) to prevent high current surges if the load is capacitive.

You can add a diode in series with C1 if only the turn on speed should be adjusted.
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Security / Re: Microsoft repackages apps with a telemetry .NET wrapper
« Last post by tooki on Today at 04:46:50 pm »
Your reasoning is detached from the outcome.
That’s a rather lofty accusation.

I worked in the software industry for years, and at a usability agency. I have relevant, real-world experience with this, and am not the deluded simpleton you essentially accuse me of being.

I'm not making an accusation. I'm just stating that the data and the intent do not always end in the conclusion that people think that they do. That is mostly because people don't know how to do a proper analysis of anything really. This is not specific to this but the claims of a tangible outcome are vastly overstated.
You didn’t say “people”, you said me, so it’s hard to not see this as you basically calling me incompetent or stupid.

I would suggest that the "usability agency" is a considerable bias as well based on my other comment. Literally there is no business if you tell the client not to touch something, so the default state is that a change must be made otherwise there is no report to make.
That’s on you. If a client wants to test the existing state, an agency will do it. If you weren’t getting this, it’s because you neglected to ask for it — or more likely didn’t want to pay for it when offered.

The reason that we stopped hiring agencies to run user studies for us is that at no point did anyone run a baseline analysis against a null hypothesis i.e. no change. I got into a hefty argument with a consultant over this who said that a change is 100% necessary, without providing any evidence and before the study was run. That is a complete lack of objectivity, intellectual and professional integrity in the industry.
Then you were dealing with a REALLY shitty agency. The one I worked at absolutely did not work like that.

Many of our projects began with testing the status quo to figure out where the problems are. (One memorable example was a health insurance company’s enrollment forms: an old lady was doing the test and got to the question “have you consumed cannabis products within the past 60 days?” to which she said out loud “no, but I could use some right about now!” 😂)

Don’t extrapolate to the entire industry; there ARE honest players. Just avoid the ones in any way affiliated with big management consulting companies! :P

I will also add that a LOT of the usability experience I got was at the software company, where it was all being done for the benefit of our own end users.

Personally I think that's a shitty feature because it doesn't work like anything else in the rest of the OS or any other software. It's literally an edge case coded into the office UI runtime.
Jeez Louise you’re rigid!

TONS of software uses custom controls to do useful things. Done well — like here — they are unobtrusive and doesn’t interfere with existing workflows.

On Windows, the basic UI widgets are MUCH dumber than those on macOS, so Windows developers are more or less forced to use custom widget extensions or third-party widget libraries to get more advanced behavior.

Compare to "Paste and Match Style" on macOS which is system wide.
Yep, it’s a great feature. But it can’t work everywhere. The document object models of the Office apps are WAY more complex than even macOS’s basic widgets. macOS and windows both use RTF as their basic formatted text format. Word, for example, does not. It’s a stylesheet-based system with nested stylesheets which apply to different levels of document structure, so merging them requires intimate knowledge of said structure. An OS-level command can’t do that.

I don’t disagree in principle with that statement, but maybe I’m just not quite as jaded as you.

It's not really jaded, but experienced.
I’m experienced, too.

You’re jaded from negative experiences. You accuse me of having bias, but so do you. I’m sorry you had very bad experiences with agencies, but not all are like that. Some are comprised of good, honest people who do good work that truly benefits their clients.

FWIW one reason I left the computer and usability industry entirely is because I got jaded — about clients. Too many times, after properly studying the problem, we’d design and test a really good solution, but the client would then not implement it as designed (often because they didn’t want to put in the effort on their backend systems to actually support the interaction design they’d been seeking). The half-baked implementation then would introduce new problems, which the client would tolerate for a few years before undertaking another website redesign, throwing out all prior work and starting over again rather than improving the implementation. So as a usability engineer, I rarely got to see my actual designs implemented, just pale, unsatisfying ghosts of them.

Put it this way, who's the last person you go to for financial advice? Actually a financial advisor. Why? Well it turns out that they have two principal objectives (a) earning commission and (b) reaching sales targets. That gets you a mediocre outcome. What gets you the best outcome is developing an understanding of the domain and the problem and that comes from a proper study and analysis, not witchcraft and hope for a fixed price.
Well what you’re describing isn’t a financial advisor, it’s a broker or salesperson, who at a big financial firm may well have the title of “financial advisor”.  But there exist independent financial advisors, and their advice, as I understand it, can be quite good precisely because they aren’t selling you any of the products they advise you to buy (or not). The flip side is that their services aren’t free.

You get what you pay for: a free financial analysis or free usability review is basically a way to get you in the door so money can be made on you some other way. It sounds to me like you may not have a good feel for this.
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Test Equipment / Re: Choosing between entry-level 12-bit DSOs
« Last post by Performa01 on Today at 04:45:33 pm »
Difference is that "the other" scope actually does work as 4ch 200MHz BW scope.
At all times, no special conditions..
The argument that it's not that hard to disable 3 of the channels on the Rigol to get higher bandwidth is comical, not professional.
comical or not, professional or not, sds800x cannot see 400-500MHz even on one channel active, prove me wrong.

It sounds a little bit comical indeed when a 200 MHz instrument is demanded to “see” a 500 MHz signal. But yes, if you don’t care for the true amplitude – why not?

For the screenshot below, a 1.6 Vpp signal has been used, i.e. it fills the screen height at lower frequencies such as 100 MHz.


SDS824X HD_Sine_500MHz_Meas
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