#861

[@jj74qformerlyjailbreak3]

I absolutely love these little breakout pcbs. I did the same thing with 2 WS2812b chip Leds. Most things i find to use the pcbs with, also become my favorite tools

[@ericksonengineering7011]

Great video, thanks. For 'truth' you could use a 50 ohm coax and the scope in 50 ohm mode. Or a 50 ohm 10x or 20x probe. Or a homemade 950 ohm resistor + 50 ohm coax to give a 20x fast probe. Either will give

[@SpinStar1956]

I think the greatest value of this video is confirming that we don't have to worry that much about the scope-probe as long as we're not buying absolute junk--thanks for doing it! Also, in my experience, if I am going to have a circuit that generates fast waveforms, I solder one of those coaxial-connectors to the PCB that allows the probe-tip to just plug in; if you have one, you might try that as the ground wire-clips are problematic. A long time ago, I had an HP 1-GHz vacuum-tube sampling oscilloscope (it was GIGANTIC!). So they did make much faster probes. I might should have kept the probe when I sold the scope, as it would have made a great reference probe. I also think it was a 50 Ohm system...

[@IMSAIGuy]

Yes if you stand the low impedance then skip using a probe.

[@SpinStar1956]

@@IMSAIGuy Well you just stirred up a question! Since you have yourself a very fast square wave generator, does the RIGOL scope have a 50 ohm input selection where you could just run coax to check the ultimate response of the scope?

[@IMSAIGuy]

@@SpinStar1956 yes, I should do that someday. Rigol does not have 50 ohms but I can put a load on the input

[@SpinStar1956]

@@IMSAIGuy That’s good, because it would be nice just to run straight-coax so that you have less fixturing for this particular type of test. Also it would be interesting to actually look at those loads that you spoke of on a VNA just to see how clean they really are.

[@dilbertnewton6864]

Just had thought, can you use the tiny vna to verify prob's?

[@BryanByTheSea]

I wonder if your results would have been even better with a dead bug or full PCB style setup vs the addition of a breadboard. Wonder if the breadboard causes some issues.

[@TheChipburner]

Hi. Can you measure reflection of the scope's inputs using nanovna, that is connected to that ports directly w/o cable?

[@IMSAIGuy]

why, that makes no sense

[@TheChipburner]

@@IMSAIGuy Low frequency scopes have 25pF capacitor at the input. Obviously, that does not work at 500MHz. So, it is interesting how Rigol did it.

[@IMSAIGuy]

@@TheChipburner 1megohm 17pf 350mhz bw

[@TheChipburner]

@@IMSAIGuy 17pF has impedance of 27Ohm at 350Mhz, that is too low.

[@IMSAIGuy]

@@TheChipburner sorry, the scope works just fine. kzbin.info/www/bejne/m5LSeYyNjrGFjJI

[@ChrisSmith-tc4df]

If you're ever interested in a handy upgrade, I'd steer you towards the TI LMK61E2EVM that has a USB programmable frequency and a rise/fall time

[@IMSAIGuy]

Thanks, looks like a nice part

[@mr1enrollment]

If you are not sick of updating this topic I have some suggestions: 1) Could mention the old Tek estimate of bandwidth from rise time,... Bandwidth x rise time = 0.35 2) Could compare to the scope calibrator edge. 3) Could mention effect of probe 'calibration' and how that compensates. Which may effect the ringing etc. (Although the 'modern' probes don't always have that little screw) Otherwise good video as always.

[@jdmccorful]

Ditto, think its a good idea for additional topics. Thanks for the look.

[@LazyTurtle1988]

Hi. I wish you had tested them in 1x ratio too(if possible of course), and maybe build a probe with coax and test it too?

[@IMSAIGuy]

1x probe will be very slow. yes I should do a no-probe measurement, that would be the fastest

[@humidbeing]

Your scope doesn't have the bandwidth to do this. You need 10x the square wave freq, so 1GHz min. It's obvious just looking at the wave on the screen.

[@tseckwr3783]

did you compensate each probe on the rigol prior to the test session?

[@IMSAIGuy]

yes

[@robertmontgomery3892]

Why did you buy the Rigol instead of the Siglent scope?

[@IMSAIGuy]

I was familiar with Rigol and knew about the software hack. I believe hacking the siglent was harder. The Rigol is not perfect. I have been attracted by the Siglent spectrum analyzers. Both brands are on pretty equal footings I believe. did you watch my first video: kzbin.info/www/bejne/m5LSeYyNjrGFjJI

[@jsdutky]

I don't understand how you are supposed to measure a sub-400 ns rise time on that Rigol scope. A 400 ns edge implies a bandwidth of at least 875 MHz, and your scope won't have more than 350 MHz (if you've upgraded or hacked it).

[@IMSAIGuy]

kzbin.info/www/bejne/Y6DXlIOme5anjM0si=KelDdBQWJZ-CZ5If

[@mavamQ]

You never showed the hook up of the probe tip. Are you using a 6" lead for the ground connection? I think you have mentioned the Curly Q. A very short ground that has a ring for the tip ground and a smaller ring for the tip to slide into. I just saw a part where you should the 6" ground wire. Get rid of that. Here is a poor picture of a PCB that has two Curly Q's, The angle is bad so you can't see the holes where the scope probe inserts, but I think this will help.

[@IMSAIGuy]

yes I did that, read the description for an update on the measurements

[@mavamQ]

@@IMSAIGuy OK.