Recent Posts

1

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by Kleinstein on Today at 08:47:04 am »

The run-up modulation with a 4/60 or 60/4 modulation has a usefull part of 60-4 = 56 cycles that are actually modulated. It is not just the 4 cycles that are effectively lost, but also the 4 the other polarity.
Depending on the integrator hardware 4 cycles (500 ns) for the shortest pulses and settling looks about right.
This gives the residual charge a range of about +-60 cycles range. depending on the delay between reading the comparator and the start of the feedback the range may get a little larger than just 1 feedback step. This way the run-down part could get a little larger than just -31 to + 30 counts. The range is more approximate than accurately calculted through.

A big question is how good the jitter is and if one needs / wants external synchronization to a more stable clock. Chances are the clock from the RP pico is not good enough and would at least need an external oscillator. It is not so much jitter, modulation of the crystal frequency depending on how neighboring pins are set or how much current is drawn. At the very least the pins for the ref. modulation should be away from the clock.

2

Security / Re: Microsoft repackages apps with a telemetry .NET wrapper

« Last post by bd139 on Today at 08:46:28 am »

Of course corporations want to make believe that their spyware (ahem, "telemetry") is the equivalent of a usability study, but it plainly is nothing of the kind. Collecting statistics—on which buttons are clicked most often—doesn't yield any useful information if there is no experimental control. Data without a control is just worthless junk (see most papers in econ and nutrition for examples).

The UI changes that they justify on the basis of this worthless junk are also, you guessed it, worthless. But everybody already knew that if they are remotely familiar with user interfaces in the pre-2005, and compare to what dreck is pushed out these days. There are other reasons for the widespread UI failure ("responsiveness" and touchscreens are a large component) but reliance on uncontrolled UX data collection is surely a major factor.

That's mostly because the user studies are invalid.

What is considered:

1. If we do change X then outcome Y happens.
2. If we do change P then outcome Q happens.

What should have been considered but is never done is a control option:

1. Leave my shit alone and stop pissing around with it.

This is normally isolated from user studies because people don't consider that as a valuable outcome because it does not generate work and people value work more than leaving shit alone and stop pissing around with it.

3

General Technical Chat / Re: The strange case of phase angles

« Last post by strawberry on Today at 08:44:45 am »

simulate in Qspice

4

Security / Re: Microsoft repackages apps with a telemetry .NET wrapper

« Last post by bd139 on Today at 08:44:35 am »

Regarding my comment about telemetry being fine, yes it is fine. But if it is constrained properly and the user consents to it.

If someone does a proper analysis then it is a powerful tool for making decisions. That requires some formal framework, proper collection methodology, thinking and statistical analysis around it. And that requires people who are formally qualified to do an analysis in that space (consider RSS / IMA members)

BUT the general approach of the technology industry is to collect everything, hope there is something useful in it and fabricate some official looking outcome from it without publishing your methodology. At the same time, creating a privacy violating dragnet and covering that with marketing. That is NOT ok. And that is Microsoft's approach. In fact their approach seems to be measuring what a completely helpless and powerless set of users will put up with.

It's important to distinguish the two. No absolutes are good for anyone.

5

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Fungus on Today at 08:44:28 am »

Somebody just added a full screen mode to the Rigol... 

charming indeed but... the hidden complication is "not signed" app meaning no access to system file, cannot do screen capture. thats why be careful making post like this in beginner section.

Screen capture over network still works even on an unsigned app.

6

Test Equipment / Re: Hacking the Rigol DHO800/900 Scope

« Last post by ebastler on Today at 08:38:10 am »

If they used GPL code, then they must release the source code of the entire project, and can't restrict the use of the code.

That depends on how they included potential GPL code (or libraries), and what the specific licenses require. If I recall correctly, there is an Open Source Acknowledgement built right into the firmware, so Rigol are not ignorant of their obligations. And I don't think that Acknowledgement states that the whole firmware is open source.

7

Altium Designer / Re: Altium V15 - Dup designators that won't fix on board level annotate

« Last post by Psi on Today at 08:37:33 am »

I also get some odd errors like  "Duplicate net names wire NetF5_2"

This is for a wire that I have not give a manual net name, its giving its own internal net name to that net and for some reason its giving two nets the same name then complaining about it.

8

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by tggzzz on Today at 08:36:58 am »

Since we are so far off topic, I guess it's okay for me to ask an incidental question. While all this conversation is quite interesting and instructive, I'm curious how many people actually use or need bandwidth or sampling beyond 100 MHz and 312.5 S/s? Presumably, anyone working in comms, but who else? My thought process when buying the DHO800 was that even with 4 channels operating, I still have enough sampling to adequately cover the 100 MHz capability of the scope with the included 150 MHz probes being well clear of having any attenuation effect at 100 MHz.

For example, here are some waveforms from a buck convertor I designed and built this week running at 100 kHz. (Note the oscillations on switching are mostly due to using the clip-on scope probes...when I use the spring and tip, the yellow gate drive signal is clean and the overshoots on the cyan and magenta traces halve.)

My question is....for the kind of work I'm doing (hobbyist audio and SMPS in the 100 W to 5 kW range), what would be the benefits, if any, in me having a more capable scope? (Please excuse my ignorance, as my professional background is 50 Hz HV & EHV transmission)

Back in the late 70s and early 80s 100MHz was suitable for TTL and LSTTL logic. Since then logic speeds have increased "a bit", so the required bandwidth has increased "a bit".

Note that the inputs/outputs of logic gates are analogue signals that are interpreted by the receiver as digital signals. In order for the interpretation to be correct, the analogue waveforms have to meet the specifications, e.g. min/max voltages and over/undershoots, timing (the hold time, t_H, is particularly tight), clock edge rates and monotonicity, etc. Ensuring all that is in order is called "signal itegrity", and the required bandwidth depends only on the transition time; a clock/signal period is completely irrelevant.

As others have noted, at such speeds the probes become an integral part of the circuit and measurement. Start by working out the input impedance of a typical 10Mohm/15pF probe at  100MHz; rather than 10000kohms, it is more like 0.1kohms Then add the inductance of a 6"/150mm ground lead, and calculate the resonant frequency with the 15pF tip capacitance.

Nowadays jellybean logic has edge rates of 1ns, and faster. That translates to 350MHz, and higher.

9

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tszaboo on Today at 08:35:26 am »

they are superior materials but they are difficult to make and expensive, some require a long heat treat process (72 hours glowing)

You do realize that this is just a resistor without the resistance coating? Albeit, a specific Al nitride one.
All the processes that you describe are already solved for high quantities.

10

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Sham73 on Today at 08:31:49 am »

But you shouldn't exaggerate, it's not a high precision device. 

Do you mean FY3224s... or DSO2512G?