EEVblog
Vložit
- čas přidán 19. 03. 2014
- Fundamentals Friday
Dave explains what the ripple and noise specifications on a power supply is and how to measure it using different methods on both analog and digital oscilloscopes. From bad techniques through to good, showing the effect of each one. Traps for young players aplenty in this one.
How do you detect common mode noise issues and ensure that the signal you are measuring is really coming from your device under test?
Single ended & differential measurement, DIY coax solutions, termination, analog vs digital oscilloscopes, bandwidth limiting, and even oscilloscope probe coax construction issues. It's all here.
Mysteries of X1 oscilloscope probes revealed:
• EEVblog #453 - Mysteri...
How to track down common mode noise:
• EEVblog #441 - How To ...
Opamp Noise voltage tutorial:
• EEVblog #528 - Opamp I...
Forum: www.eevblog.com/forum/blog/eev...
EEVblog Main Web Site:
www.eevblog.com
EEVblog Amazon Store:
astore.amazon.com/eevblogstore-20
Donations:
www.eevblog.com/donations/
Projects:
www.eevblog.com/projects/
Electronics Info Wiki:
www.eevblog.com/wiki/ - Věda a technologie
Ignore anyone complaining about content being to long. youtube is littered with videos that dont' actually explain anything in any useful detail. You rock! I am a software guy for 30 years, between you, Mike, Bruce Simpson, Jeri Ellsworth and the young guys like Kevin Darrah and Jeremy Blum I am actually understanding the hardware that powers what I have been doing for a living since the 80's!
Dave, you may think 20MHz is an arbitrary frequency, but it is also the point where poor probing methods with long inductive probe ground leads start to cause extra ringing on fast logic causing measurement errors.
So for clarity 20MHz is for convenience when risetime induces false ringing from poor probing skills and gets a better textbook looking trace.
For ideal trace remove probe tip and ground clip and only use tip and probe ring to a pair of test pins or wires of similar spacing for convenience or use the coiled ground spring accessory . This gives the best results using a 10:1 probe.
Generally signals much less than 30MHz are used for this mode but logic rise times faster than 100ns ( most are) will get an overshoot proportional to the ground probe length and transition frequency resulting in ringing..
Tony EE since 1975
6 years on and your 'deep dive' stuff is still pure gold, I wonder if the UNI's around the world use this in their curriculum..they should..cheers.
8 years later, came here to say this. Evergreen content for sure!
9 years later and the sentiment is still the same! Rock on! 🎉
Thanks for doing the fundamentals. These are my favorite videos.
Excellent video. Instrumentation and measurement and understanding the limits of your equipment and sources of errors are very important and often a poorly understood area. Nothing like a real demonstration to highlight the concepts and pitfalls. Good stuff Dave.
Dave, I really like your channel. Outstanding quality topics, content, judgement and sharing of your understanding and tricks. Thank you for sharing your excellence and passion.
Totally agree with Jens Andree. These kind of videos actually makes a difference in the world for a lot of people. Thx Dave....more of this stuff :)
Thanks Dave, keep up the Fundamentals videos. I can't wait to get out to my lab and try this with my own scope..
no book could have given such memorable clarity on these pitfalls.... excellent video Dave and the best part is its a free video )))
Dave, really awesome. Well worth the time. Thanks for going through this one. I can't tell you how much the EEVBlog comes up here at work lately. Too many geeks with not enough to do? ;) ... Love it.
It's everyday friday here! thanks Dave for your lessons!
Thank you, thank you, thank you! Starting out in electronics and your video's help so much!
This is exactly what I needed, thanks for explaining Dave!
You, Sir, are a gift from heaven!
An awesome video that I have been watching since years again and again! Thanks Dave! :)
Excellent, informative, and eye and mind opening!!! Thank You!!!
Those measurement tips and tricks were sooooooooooooo informative. Thanks for sharing this content!
Excellent because it shows the tips&tricks of ripple and noise measurement.
Really insightful. Thank you Dave!
Very helpful Dave, just what I need right now!
Hugely instructive as usual Dave! Cheers!
Wohoo! :D
I have waited for these videos :)
Thanks Dave!
Awesome explanation of all the concepts!
Great vid Dave. Thanks
Amazing video! Learning a lot... much more than at school!
I've been wondering for months what a CRO probe was. True, I didn't look it up, but still wondered. Cathode Ray Oscilloscope (CRO) probe.
Brilliant!
Brilliant video. So useful. Perhaps I shouldn't be so disappointed with my digital scope after all! Thank you.
Found this to be enormously helpful- thanks!!
this was amazingly informative. another ripper dave this has been really useful. great scientific reasoning
great video ! helped me a lot. got here because of exactly the kind of spikes seen in this video from a dual rail power supply i built.
Another great video, thanks Dave!
Great Dave! I have learned a lot with this video. Thanks
For me one of the best videos from the EEVBlog series. Cannot really understand why two guys gave a thumbs down...
actually they are four by now....i presume they do not give a damn on noise as they only play music *loud* ;)
There is a lot of good info here. I got that exact ds2202 and I'll have to check some of the linear PS i have. I will certainly learn something, most likely the probing. Great video.
good video, I didn't understand it all, I'm a repair tech not an engineer, but I did learn a lot. thx Dave
Love your documentary its very professional, thank you
Wonder if you could do a video on ground loops? Thanks great channel!
czcams.com/video/wopmEyZKnYo/video.html
this video is extremely informative! thanks much!!
Terrific video, Dave. I went into this thinking I would not learn a thing. I was wrong.
Love the tuts Dave.
I really liked this one! Thumbs up and more of this please.
Thanks for sharing, Dave
Top notch and informative video, thanks
Great lectures. Definitely talented instructor.
But how do you get rid of noise??
Great explanation well done
Great great video Dave!!!! Many thanks!!!
nice video. it would be interesting if you discuss about power supply transient response as well in your next video
Many thanks Dave
These videos are great. You would have a blast at the Dayton Hamvention.
Great video this one. Good work!
Dave... just great! Keep going please!!
thanks a lot,I watch your video and learn so much
Follow up this video from Afrotechmods 's DC-DC Buck Converter. And keep following up Dave and your videos are awesome! I can learn EE start just my a little knowledge of EE in high school (in Thailand) to starting some basic of Reverse Engineering! Well you're rock, Dave.
Hi, I haven't gone through all your videos. But I wish you could make some videos on different kinds of sensors and motors or even robotics control. That would be an interesting topic.
Dave Jones, the EE Professor
Hey nice video. Though one more way to get rid of high frequency noise is to use a 0.1 micro farad disc cap on the probe tip. Infact you can solder it onto the probe tip and then leave a little bit of lead say 3mm extra to act as the points to probe the power supply. This is one of the standard methods
Hey Dave! Thanks for this amazing, content filled video! I has one question, what do the 50 ohm terminators do exactly?
That was heavy (but fun). I have found if an auditing Piezo sounds 'normal', were golden. If the screech is too Bjork or Yoko then I find a Dave.
Fundamentals Friday FTW!
Nice one! So we learned something new today too! :) Great - thanks!
Wow! That was low tech but for me that was very interesting. I have that same Rigol scope and power supply. I also have that DC programmable load. I had no idea that load could put that noise on the there. Very interesting. I know my equipment a lot better now. Thumbs up!
I got some Lambda LQ/LQD series linear bench PSUs recently, circa 1983 (warranty seals were unbroken haha!).. their ripple + noise specs are 0.15mV RMS, 1mV pkpk. Temp coeff. is ±(0.005% + 10μV) /°C. Line/load regulation is 0.005% + 0.5mV. Current regulation is 1mA/2.5mA (line/load), at full voltage range. Just fantastic. I verified those figures with my scope, still fully within specs. Zero overshoot with maximum load. They employ a custom Lambda branded IC for V/I regulation. I've sourced a replacement for one from China, gonna see if the specs change after I put it in.. I suspect it's not an original part from 31 years ago. :P
traps explained, loved the vid!
Absolutely excellent tutorial. I am going to have to troubleshoot the power supply of my VTVM, and my thinking is to make the probes you demonstrated for my Tek 475 scope. I have another option that I wanted to ask you about, however. It happens that I have an old Tek 545b scope with a differential plug-in. My question is, what is the best way to hook it to the power supply, or am I just as well off to use your adaptors and the later model 475 scope.
Thanks,
Bob
I miss Dave's videos like this
Very good thank you Dave.
Woo Dave 666 videos on your main channel!
Keep up the great work!
Dave, excellent tutorials, can you explain how to measure the any oscilloscope noise floor ?
That HP calculator induced memories. Highschool programming, iterating math & stuff.
You make a good lecturer
Hey Dave, where can you buy the probe BNC adaptor for the rigol scope. Do you have a part number. Cheers
Measuring the ripple is so much easier using a True RMS multimeter. Set it to AC voltage, read the result, done. However, using a scope is more fun.
Great shirt! Got one just like it;)
Very nice video Dave, thanks.
hi nice video dave. Though in my company which made power supply for defense institutions and special custom built power supply. The way we would measure ripple is to use a single probe but solder a 104 disc cap on the tip ( 0.1 micro farad) on the tip. off course no use the ground lead that is serious a big ******* antenna.
Thanks Dave that was great.
Awesome Dave! I learned a lot from this video! More like this please!
There is another aspect of power supply noise that is little thought of. I was involved with a huge project at a large computer site in 2010 that had to have the power supplies replaced on 5000 installed servers. The switching power supplies also generate noise back onto the ac feed line. When you had 5000 servers with no isolation, all generating noise, the electrical noice would shut down the site UPS systems. The replacement power supplies,all 10,000 of them fresh in from China,now had toroid coils on the ac line. Guess the server vendor didn't save 20 cents per server after all ?
Hi Dave,
Can't you set the oscilloscope in 1MOhm resistance and measure it using two probe technique, without attenuation?
Any recommendations for the Caps on the Homebrew probes? Will just a small value ceramic do the job??
What value do you used for the AC-coupling capacitors in your last schematic. If you choose it to big, all noise was filtered away...
Great Video.
I was hoping you would test the power supply you designed to see how it compares to the Rigol.
Brilliant, thankyou!
Thumbs up, Cant you dave use. BNC video cable from an end to another?
Like video cables, they are way less impedance and can deliver higher quality signal?... and specially for this purpose?
spectrum analyser is a great way to see what noise looks like. since i am poor i use my audio interface with software doing fourier transform. can see all the harmonic lovelies
Why the 50ohm terminators made so much diference?
Yes Mr Johns. Make a short video explaning about 50 ohm termination. Pliiiiiizzzz , with sugar on . Please ?
In this example it gave the signals a reference since the PSU is a floating supply.
It also acted as a voltage divider because the probes have about 300 ohms of resistance
Because without it the PSU output is at a high impedance.
It has to do with the coax usually having 50 Om impedance as well. Basically, the coax is a tramission line, and when you trasmit a signal over coax, it is vitally important to have it terminated with a matching impedance load. Otherwise, you get the signal all messed up.
Can you measure this using a bench DMM using maths or AC setup ? That would be a useful video. Is it really as easy as RMS AC ?
I got a whole lecture on noise and distortion when i studied EE, we did a huge amount of mathematical theory and a lot of fourier transform, 3rd order interseption points and stuff like that back than, but we did *not* measure a thing even at the coresponding laboratory lecture...sad...sad.
Something I notice is that using buck converters that let me regulate current, such as battery chargers (XL4015), I had way more noise when I demanded a current near to the limit I put on. Lets say I set my power supply to deliver up to 1.2A, when I put a load that demanded 1A y had some noise, but if I limit the current up to 2A with the same load, at the same conditions, the noise was smaller than before ._.
How do we talk you into doing more Fundamental Fridays? I absolutely love these segments.
"How do we talk you into doing more Fundamental Fridays?"
Make more Fridays. TGIF. If everyone thanks god for Fridays, how come there's only 1 Friday per week?
ionyou I wasn't aware that Dave put out a "Fundamentals Friday" video every Friday. When did this happen?
That kind of educative videos makes me want to drop out and become an electrical engineer... damnit :P
How do I know if my ripple capacitors can handle the ripple current? I have some surplus caps that I am using for ripple suppression, they are rather large and I am scared they will blow up if I have too much ripple current. It's on a 110vAC 60hz input with rectified ripple of 4-6v p/p. The Current load is 150amp for a DC motor load. Caps are 250v 2000uF each but that's about all the specs I have on them.
what would be an appropriate test setup, to see if the noise is making it onto the output of my rf amplifier? Spec An? Oscope?
Thank you
very good vid!
you don't need 400uV vertical sensitivity, you need a good pre-amplifier, and you can measure down to microvolts; that's how Linear does it
if im checking a crown amp ps.with both b+ and b- rail voltage is it best I use the diff measurement method?
Dave you have saved my ass many times! :P thanks a ton! :)
You should try the noise testing with an old DECT phone next to it.