Recent Posts

1

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

« Last post by shapirus on Today at 09:34:37 am »

I'd like to see a frequency sweep.

I second this.

@KungFuJosh can you please set the scope to 500 Msa/s, low waveform acquisition rate (to make the TinySA's glitches less visible), low persistence, and record a video of a 30 seconds long frequency sweep from, say, 110 MHz to 270 MHz?

Coax connection with a 50 Ohm feed-through terminator, if possible, to make the test conditions the same as in my test.

It will be interesting to see at what frequencies (and at what ratio relative to the sampling rate) it will become first wobbly and then AM-like (if it will), to compare that to Rigol.

2

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

« Last post by ebastler on Today at 09:32:24 am »

The Rigol is applying the theory correctly

When was THAT proven? 

Rigol have repeatedly cut corners in their signal processing. The sampling rate vs. bandwidth mismatch has been discussed at length here; the very generous inter-channel skew spec, wobbly AC trigger, wonky FFT "resolution bandwidth", incorrect flat-top window function come to mind as well. I would not be surprised at all if they had not gotten the Sinc interpolation quite right.

3

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

« Last post by shapirus on Today at 09:28:41 am »

BTW, speaking of signal integrity, the (unlocked) Rigol can more or less properly show signals at up to 500 MHz at 1.25 Gsa/s (the 2.5x ratio again btw), albeit with a greatly reduced amplitude, apparently because of the hardware low-pass filter on the input.

While not suitable for measurements, it will at least allow to see qualitatively if there are any unwanted oscillations up to 500 Mhz. The frequency counter fails by that time (maybe because of the reduced amplitude), but the waveform looks all right and proper frequency if you measure it using cursors.

I think it may make sense, as was suggested by several people, to mod the input filter on one of the channels (say ch4) and reserve it for the cases when a higher bandwidth input is required. Of course, that, as usual, requires to understand the limitations, knowing how to probe at those frequencies, etc.

4

Beginners / Re: Convert US standard 115V to International 230V

« Last post by soldar on Today at 09:28:29 am »

This thread makes me want to bang my head against the wall. Besides all the noise and useless arguing, there is something that bothers me and it is that I believe the OP is just not qualified or certified and should not be making this type of decisions. It is one thing to ask in a forum for personal things or for professional things if one has the appropriate knowledge and background, but this, to me, screams like a bad idea.

There are too many unknown variables and the OP is, clearly, not qualified. A medical device sold professionally and for export and this is how it is being designed?  In America? Really? Nobody thinks there is something wrong in this scenario? Really?

My response would be that you need to hire a qualified engineer who does not need to ask this type of questions and who is responsible for their work.

Some months ago a friend asked me if I could repair an automatic watering system box device which had not lasted long. Proudly designed and made in the USA ... and complete crap. The power supply part was designed by someone totally unqualified for the job.  Among other things it had a resistor making lots of heat right next to components which could not take the heat and all enclosed in a weather-proof box with no ventilation. It was crap and there was really no good repair except to replace the unit with something else. ... probably designed and made in China with better design and quality.

I am all for helping people learn and develop their own projects but for commercial, professional products you need a pro.

Just the way I see it.

5

FPGA / Re: Help on translate schematics to Verilog.

« Last post by Wiljan on Today at 09:23:58 am »

(well, I use Quartus schematics for now...)?

If you use Quartus and have made a schematic, then while the schematic are selected you can click "File"/"Create/Update"/"Create HDL Design File from current file" (the schematic)  select verilog, give it a name, quartus will then make a verilog version of your schematic.

6

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

« Last post by Fungus on Today at 09:22:14 am »

In reply #465, 2N3055 showed stable reconstruction of a 220 MHz sine which was sampled at 500 MSa/s. So the SDS800X HD can still resonstruct properly at a sampling rate of less than 2.5x of the signal frequency, while the Rigol started to show wobbles at 3x or so.

I'd like to see a frequency sweep.

The Rigol is applying the theory correctly and the Siglent can't possibly be doing an infinitely wide reconstruction, so... 

7

Beginners / Re: What function generator, that does a bit more than just a simple signal

« Last post by Doctorandus_P on Today at 09:15:14 am »

I read about the FY6900, that there are a few issues (hardware/software) and it seems a bit pricey to me. Is it really that much worth?

So what do you think it costs or is worth?

I bought the JDS6600 myself, which is quite similar to the FY6900, but I bought the "low frequency" variant ("Only" up to 15MHz). It's plenty for my needs and paid around EUR80 for it.

And these things use DDS, and can do much more then sine waves. In the end the limitations are with memory depth and the software to generate a waveform. But I agree with johansen. It may be better to combine the outputs from multiple devices. From your description, it looks like you want to do some signal modification mostly based on logic levels, and that is probably best done with a microcontroller.

8

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

« Last post by Fungus on Today at 09:14:12 am »

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

Yep. If you're really into "logic" then a Rigol MSO5000 is the way to go.

9

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

« Last post by Aldo22 on Today at 09:13:17 am »

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

Do you mean FY3224s... or DSO2512G?

Both of course. 
Both are pretty much the cheapest usable representatives of their kind.
FY3224s has quite good precision (frequency response) up to 10MHz / 10V, but is not very accurate, i.e. the multimeter shows slightly different values in certain voltage ranges from what is set on the FY3224s.
Normal oscilloscopes are rarely very accurate. 2%-5% voltage is normal.
That's OK, just don't overdo the calibration, it won't be like a multimeter.

https://en.wikipedia.org/wiki/Accuracy_and_precision

10

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

« Last post by Fungus on Today at 09:12:25 am »

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

not everybody like to connect to network for a mere screen capture, i do it with usb stick. my ethernet cable is super long and its quite a mess trying to run it to my dso, at my lab setup, connecting to usb cable is much easier. and that luckily i have ethernet cable at all so i can do some adb hack albeit a bit inconvenience. ymmv.

Cable? My WiFi adapter cost me $7...