How to Select the Right Probe Bandwidth - Probing Pitfalls
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- čas přidán 11. 07. 2024
- What bandwidth oscilloscope probe do you need?
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If you don’t have enough bandwidth in your probe, you won’t be able to see your true signal. Therefore, any of the measurements you make could be false, leading to errors and poor engineering decisions.
In this episode of Probing Pitfalls, Erin explains the dangers of choosing a probe with the wrong bandwidth and walks you through what bandwidth is, how much you need, and the consequences of choosing the wrong bandwidth.
She explains:
• How the 3dB point determines bandwidth specs
• How rise time of your signal determines how much bandwidth you need
• Why harmonics determine the bandwidth needed for square waves
• Why system bandwidth is the ultimate restriction on your test bandwidth
Stay tuned for future Probing Pitfalls episodes covering common probing mistakes and how to avoid them. You’ll be on your way to making more accurate measurements.
Ask Erin questions on Instagram: @keysightoscilloscopes
Learn more about using oscilloscopes: oscilloscopelearningcenter.com
Check out the EEs Talk Tech electrical engineering podcast: eestalktech.com
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Probing Pitfalls is hosted by Erin East and Melissa Spencer. The video series covers common oscilloscope probe pitfalls, the impact they have on your designs and measurements, and how avoiding them can improve your test results. You’ll learn proper probing practices that will save you time in validating and debugging your designs, plus improve your overall knowledge and skill in the test lab.
#oscilloscope #oscilloscopes #bandwidth #bandwidthproblems #probing #oscilloscopeprobeing #probe #oscilloscopeprobes - Věda a technologie
There seems to be an error in your video at 1:15. The amplitude of the signal is reduced to 0.707 not by 0.707
I thought probes cost an arm and a leg, but apparently it's just an arm. :P
As always ... great video! Thank you you all Keysight Labs team.
Amazing and simultaneously so simple and understood explanation! Thanks a lot!
Very good and informative videos; the explanations too are clear and concise.
Informative. Good job 👍😁
Erin was great! 💖 I learned stuff!
Lovely. Very informative.
It seems that I’m not the only one reacting violently when someone tries to steal my probes! :-)
Really useful video! I think I need to cross out and write a new bandwidth figure on my scopes and then tell myself anything higher than that and I have to do maths!
I have the idea of design a isolated high voltage probe, with this video have a lot of nice concepts to take into account, thanks
Well Done!
Keysight Awsome.. Thanks for your 'KEY👌 info..Appreciated.
06:25 I'm sorry to hear about your cast. good luck and I'll pray for your recovery
Nice video, quite interesting. Hope that arm heals soon.
As always, another great video! If possible, could someone describe how the 0.34/tr is derived or point to an article that explains how this was determined? I'd like to better understand where this rule of thumb came from :) Thanks!
You can check out the Wikipedia page about Rise Time:
en.wikipedia.org/wiki/Rise_time#cite_note-Orwp30-17
Note that the .34 is for Gaussian-responding filters.
I like this series, but also here, circuit designers are not the only professional users of a scope (and other testgear) . I'm a repairtech ( measurement and calibration gear, and some industrial and automotive stuff, many are kinda problem cases) I use a scopes every day (most times 2 at the same time, but I have more) and many special probes (current, diff, HV, 10x, 100x, active etc) and there are many people like me, maybe even more as designers here in Europe) But scopes, app notes etc seems to be only designed with the electronic designing EE in mind. And then is it a bit strange that most app-notes etc are more or less at a beginner level. Some one who can design complex circuits should know this kinda things. Maybe an idea, many users do not know the max voltage decreases with frequency. And that counts for a probe too. I had a dead scopemeter from a customer who blew up the front end. To measure ignition (automotive) he set the probe setting at 1000x and used a 1x probe. And he was surprised he blew up both channels after each other :-)
Your video's are a step in the right direction because these things are very scope specific. I would like to see more about more advanced triggering, optimal use of settings or aquisition modes, zooming, memory use etc
Fred
Great feedback, thank you!
You might be interested in our 2-Minute Guru series, it starts basic but covers a lot of scope topics: czcams.com/play/PLzHyxysSubUkc5nurngzgkd2ZxJsHdJAb.html
There are also a few webcasts that go into some more depth: czcams.com/play/PLzHyxysSubUlKfrZIcXfXhJwhRwLVnKq1.html
Nicely done, as always. 6:03 - "having too little bandwidth means that you won't be able to see a true representation of your signal" Thanks for the knowledge, now I know that I have to have a 72 hz monitor instead of a casual one, which is able to operate at 60 hz... just to see a true representation of that 24 cinematic FPS CZcams video, which will never be snown in a cinema :) What is the reason to use 24 FPS for CZcams content instead of 30?
FPS is editor's choice :)
Yeah, and editor is not an engineer... Thanks for the answer BTW
Fun video! It really helped me memorizing more stuff.
Rule of thumb when dealing with reasonable fast signals:
3dB - Half Watt (vv)
6dB - Half Volt (v) - Quarter Watt
ω - omega - angular frequency - Analog signal
v - down/up - Digital signal
==> Analog signals - 3 times W(h)att prober req.
==> Digital signals - 6 times (Bw)over
Sorry, but I couldn't resist a comment on Erins current situation:
BtW - It seems that thieves gets cast for PR(is)ON @Keysight
- PowerRobbers gets over/under SHOT on the O'scope at five.00 - and no work... comp ;.)
Get well soon, and keep making great equipment and videos!
Good stuff for revision. Even better when you're too tired to explain it to someone - just refer to this video 🤧
So having a higher bandwidth means that more harmonics of the signal will be captured. This is why having higher bandwidth probe helps and ultimately there is a relationship between the signal rise time and the minimum bandwidth of the probe required to measure it.
Surely specifying the bandwidths at a .5dB point instead of a 3 dB point would eliminate confusion around the actual bandwidth ? I bet if you look at the 0.5dB point of the SYSTEM on a 500MHz scope (as mentioned) it would be close to the 350MHz point, I think the real issue is the effectively false bandwidth claims being made, which seems to be accepted by everyone as normal.
Well, that's a tricky discussion. The -3 dB point has been a standard for this type of equipment for about as long as it has existed. It's also a very common filter descriptor, so it makes sense in this context. It's really one of those industry standards that we are stuck with - for better or for worse.
I can recommand this video(" Why -3dB? (An alternate approach to explaining dBs)") from KainkaLabs. Its explaines why the 3dB point is used. Video link: czcams.com/video/Tn97U1HVtpo/video.html
I believe we call it "Marketing" same thing with Gbps (GigaBits Per second) vs Ghz (GigaHertz)
5:06 "a clean squarewave"???
If i want to measure a filter circuit, will probing change its bandwidth? And if it will any way to minimize it?
It could, you have to also factor in your probe's loading impedance. More on that here: czcams.com/video/kbr9XyD1vlw/video.html
The link should be something like this: czcams.com/video/kbr9XyD1vlw/video.html :)
@Jonas, thanks! I've fixed it.
The last common pitfall at 05:15 with system bandwidth is the worst of all.
What makes a 100MHz probe different from a 500MHz probe? I mean how probe bandwidth is determined ? is probe bandwidth controlled in manufacturing or by any RC components ?
Good question! The bandwidth is determined by the frequency that it can measure (up to it's -3dB point), and is dictated by it's circuitry. I cover bandwidth in more detail here: czcams.com/video/T56XDhUyY2g/video.html
The engineers rule is rather simple: the higher the better. I love "my" 40GSPS, 2.5GHz 4 channel oscilloscope and I will miss it.
It's not true, sometimes you would actually like to do a bandwidth limited measurement.
@@1366solar , and compared with this setup... boy oh boy will you save a bundle
I'm thinking Ca, Mg and Zn along with Vit D, C, E, B-Complex and maybe even K2 MK7 balance for that optimal healing... whether supplements or from your diet. Thanks for the equations too.
Why not always use a high bandwidth probe for everything? You made clear the problems with using a probe with too low of a bandwidth for a given measurement, but why not make some high bandwidth probes and not even bother with something lower?
I don't know if I'm being clear.. all I'm saying is if I buy a scope, why not just buy the highest bandwidth probes with it? Why have a selection?
There are a couple downsides of higher bandwidth. They pick up higher bandwidth noise, cost more, can be more fragile, and can have different input range capabilities. Most engineers have a bit of a "quiver" of probes. Too much bandwidth is better than too little, though.
Erin what happened to your hand? Get well soon!
6:21
Can I have a free oscilloscope? Im poor
How about some free oscilloscope videos?
and yet you can afford the internet bills ;) or even the device you use atm to browse it ;) I don`t own a proffesional osciloscope myself but if I would REALLY need one I could`ve save some money on the side for like a year or two and buy one if I would REALLY need it. The thing I want to say here is that ppl that need them , already have them ;)
Horus Horus I get free internet because I'm a student
@@rockyrivermushrooms529 Don't you technically pay for the internet even as a student...
A non contact probing system is desired. It shall not be affected by system noise. It shall have a bandwidth of DC to "anything".
It shall not contribute it's own noise to its output. It shall not be influenced by ambient noise. Design that, Keysight, and you can earn the $29,000 you charge for probes for your highest bandwidth instruments.
It may be time to design products and instruments immune from the vagaries of diminishing returns from higher speeds and increased memory capacities. Do you think you can afford me, Keysight?
Optical Pockels cell probe. Use a silicon based polarized laser and a crystal with a minimal copper probe contact surface. Bandwidth to terahertz possibly. Photon Dynamics built a test system back in the '80's very expensive. But will eventually solve this problem.
What happened to your hand. Get a health soon 🙏
All healed up!