Recent Posts

1

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.

2

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.

3

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?

4

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

« Last post by Mechatrommer on Today at 08:30:56 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. i know there's post about deactivating signing but i dont want to dig deeper until they finalize it. its still in R&D stage.

What was the topic again?
Question for a friend...

discussion about nyquist, that lead to proper Sinc reconstruction reveals siglent DHO800X can do it properly unlike Rigol, this can also can help user make decision whether this is important or not. this discussion can also make newbie aware of some technical and theory informations. for me Sinc reconstruction is important when signals contains spectral near Sr / 2, let alone if more than that.

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?

you never know what lie ahead of you. not so long ago, i deal with opamp circuit that experience oscillation beyond nyquist limit, granted BW limited siglent may suppressed this signal, but with rigol, i saw some nasty oscillation, but with betterer Sinc reconstruction, it may help distinguish some of signal near nyquist limit. if you can limit yourself to arduino circuit, you may not be aware of this and you are safe with rigol. but if you dont have enough belt color, unaware probing 250MHz spectral at 312.5MSps may bite you. ymmv.

5

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

« Last post by Psi on Today at 08:30:39 am »

So I have a schematic that uses many device sheets, some device sheets use other device sheets.

The issue I'm having is in trying to get the designators all unique using board level annotate.
The process does not seem to work right, once its done there are still many dups that it creates.

Have tried "reset schematic designers" and reapplying them, no change.

I have tried resetting unique identifiers, there were some dups that got fixed.

Any ideas?

6

RF, Microwave, Ham Radio / Re: Transistor tester

« Last post by Solder_Junkie on Today at 08:28:55 am »

The DCA-75 is a very nice unit. One of the Peak USA distributors has the DCA-75 in stock, http://www.alltronics.com/

I have the more basic DCA-55 which is currently in stock at Digikey.

SJ

7

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

« Last post by ebastler on Today at 08:27:53 am »

Or you may want to take a look at the DHO1000/4000 GUI. With its larger screen, it shows four separate Math boxes in the bottom status bar, which show details about each Math function when it's activated. (Also a bit like the Siglents. )

The font is a bit smaller in your modified UI, right? Do you still find it comfortably readable on the built-in screen, or do you mostly use an external monitor?

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Projects, Designs, and Technical Stuff / Re: Connectors for Breadboard and PCB: GPS module EM-506

« Last post by Ian.M on Today at 08:17:55 am »

Does the GPS end of that cable unplug?
If so, either get a cable to fit and mod it with duPont pins to suit breadboarding, or get something like this: https://www.sparkfun.com/products/18081

If not, you need the matching male pin header + one of these: http://www.proto-advantage.com/store/product_info.php?products_id=3800003 and a six pin strip of 0.1" SIL pin headers.

9

Test Equipment / Re: Siglent SDS1000X HD 12bit DSO's

« Last post by tautech on Today at 08:12:46 am »

Dave does a teardown, finds some surprises and seems confused about other stuff that is clearly stated in the datasheet.


Added to OP.

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

« Last post by shapirus on Today at 08:09:20 am »

Let's see whether they are brave enough to distribute this hack (and other related ones). The DHO1000 hacking took a similar approach of decompiling and patching the executables, back in December. I keenly followed that effort, since I had a DHO1074 at the time and was hoping to see the 50 Ohm inputs and 400 MHz bandwidth enabled.

Back then, the developer(s) never made their modifications available to others and eventually pulled the plug on that effort -- due to legal concerns in my understanding. Rigol does explicitly forbid reverse engineering and decompiling in their license terms. Of course we have not seen them act on this, but who is willing to run the experiment?

Distributing patches, at least, should be legally clean. Don't quote me on this, though. Besides, there was a point about GPLed code being used in the apk. I don't know if it is so, but there seem to be a lot of standard android stuff included. Not sure what license it has.