Learn Oscilloscope Basics with an Arduino Uno and RTM3004 | AddOhms #28 

Thank you so much for the excellent lessons! By the way, your videos are premium quality indeed. May I know the set up for your recording please!

Thanks for the sub!

Just curious, are you using version 6 or 7 of the PicoScope software?

I always intended to program a powder coat mode into the controller. But ... I haven’t had a need ... yet.

@john doe Siglent is also a good one. is you have a better budget, Keysight and Tektronix.

@john doe yes, costs, because Keysight and Tektronix are much better than Rigol and Siglent.

The USB-Scope (PicoScope) I held up at the beginning is less than half the $300 target and it offers every feature I showed. It’s tradeoff, relative to what I showed, is bandwidth.

@@AddOhms sweet, although for those of us that learned "the hard way" it can take a $1000 PC down with it. I am delighted that for this kind of money today we can have gear that was only dreamed of 10-15 years ago.

Additionally, I was trying to get people to not fixate on the $3000 scope and lament not having the features. Grab a salae clone logic analyzer and you can do all the spi/i2c/UART decoding for free. Don't let money stop you from measuring. But if I could only have one tool it would be a scope. Any scope. Even a "bad" scope is useful.

I agree with that statement. I've said in other videos, I use my scope(s) more than my DMM.

You’re welcome and thank you!

There isn’t much to explain on how one works. In transmission current going through it radiates an electromagnetic wave. In reception an electromagnetic wave causes current flow. The design is a different story. I’m not experienced enough to address that.

I'm not sure I follow your concern. Both the scope and laptop reference the same earth potential. Also on low-voltage circuits such as an Arduino, I would expect a number of other protections to trip before a user was exposed to mains voltage. Now in cases where you are not referenced to the same mains circuit or dealing with higher potentials, then yes, there is a concern about referencing. But that would take an entire video to adequately explain.

Thanks Seon. This one was a long time coming. I was glad to finally get to it.

"Any" scope is better than "no" scope. I do think there is value in a "real" scope at some point. But it doesn't have to be a benchtop. There are some really good USB/PC based scopes that are very affordable.

Less than 10 Hz on most scopes. Less than 5 on this one. For the vast majority of power measurements, this isn’t a range of concern. For ones where it is a concern, active rail probes provide extreme offset. Also, you are confusing accuracy with precision. A DC blocking cap affects the accuracy of the measurement, not the precision.

In general, I avoid “accuracy” and “precision” discussions because measurement technique almost always swamps the limitations of an instrument. For example, how many scope tutorials spend forever on how to “calibrate” the RC network in a passive probe, then, clip the probe onto a long piece of wire. The accuracy of the measurement system doesn’t matter in that case. Measurements on a scope are something I’d like to cover in depth. My experience is that most people do not understand what the scope is doing. Again, getting into precision doesn’t matter to me. Understanding which measurements use 10-90 thresholds (and when to change them) or how to tell if interpolated points are being used is FAR more important that proving out the precision of the timebase. Or another one people like to fixate on is ADC resolution, while having waveforms only use a quarter of the dynamic range.

@@AddOhms I understand, this was just the stuff I'm trying to tackle on my own without a proper academic degree. When watching/reading content explaining scopes, I usually get lost when the subject is addressed from the perspective of using a scope to explain a scope. (Like "let's talk Chinese about FFT"... button...button... Chinese... button... button... ..now for the math on paper.. ...Greek... -hopeless) I clicked on this video to see what I might pick up because you are addressing scopes through something relatable with the Ardy1 (much appreciated). Literally everything I wrote before is me just trying to understand the abstract difference between tuning a crystal with what I have versus getting a cheap commercial frequency counter on eBay versus what is possible with a frequency counter w/disciplined oscillator, ...while dreading what I'll need to do to get better tools. I don't need you to fix my issue here. I was simply trying to bring up something relatable as an entry level type of problem. IMO people like Dave Jones and others seem to take on subjects like metrology from a similar outlook to what I imagine they had in school when they began to learn about these things. As a hobbyist I think the learning curve is much different. I need more intuitive grounding with an explanation. I think that's where a lot of us get lost, or at least, that's why I get lost. Heck I still have a disproportionate fear of "blowing up my scope" because of Dave's old video about the subject, and I am reasonably confident in my understanding of circuit isolation. I'm confident enough to wind a few transformers and build a few SMPS designs, but I'm still hesitant to use my scope on anything with isolated mains power bc of watching Dave's video years ago. It's really silly, but oh well... I think people also get lost when a tutorial has a short explanation of some concept followed directly by pushing buttons on a device. I need to understand the various real world circumstances/applications for a technique, especially the how and why of a technique. Then I need to understand what I'm looking for on almost any device in order to use said technique, feature, or function. Most explanations seem like someone using big words/concepts quickly followed by magic buttons...but hey...that's a great way to sell people magic buttons :-) It's kinda sad to break things down to that kind of level here, but if we're brutally honest, I think that's a pretty solid assessment of what people do in general in these situations. "I need to buy that box of magic buttons (person) explained to me so I can do (thing) I barely understand." *buys scope. I don't mean this in any negative sense, it's actually more observational and somewhat reflective of my own past experiences. I'm just sharing to try to help make the path a little straighter for anyone learning on their own under similar circumstances. I've got no problem admitting some of the dumb stuff I've done ;) That's just my $0.002 adsense. -Jake

It is connecting to a non-grounded laptop.

Thank you.

Ideally no. But in general, I advocate NOT changing connections (including probes) while a device is powered, especially when a ground loop might happen.

That might be cool to do on a livestream. Not something I’d do a full video on, but would be fun to play with.

Yes, the Picoscope is a USB scope. It is the one I would recommend. Their software is fantastic for the price. I did a full review here: www.element14.com/community/roadTestReviews/2530/l/picoscope-2204a-usb-oscilloscope-review

Hi there. I've been doing live streams the past few years, but I don't publish them to the channel's feed. Also, I have a bunch of element14 Presents videos (since this one): ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gBqTG9FcvZU.html

First, you should never isolate the scope from Earth ground. That is dangerous and reckless. You should either isolate the device under test or use an isolated measurement method. (e.g. an isolated probe.) The reason for the isolation is that if there is a fault in the device under test, the scope's chassis (and its ground) is now referenced at some higher voltage. One alternative method is to use a battery powered scope since it isn't connected to mains. Even then, you want a scope that has isolated inputs (or isolated probes.)

@@AddOhms Thank you for your answer. So let's suppose I wouldn't use any isolation could this potentially damage my scope or would I just trip my breaker?

Earth connection is a safety mechanism. In normal operation, there should be no current flowing. If it does, a fault has occurred. So ideally a breaker would be tripped. Best case, the scope would take damage. Worst case, you would be electrocuted. Which is why floating the scope is so reckless. It is far more likely the device under test has a fault than your instrument. So if you float one, float the suspicious device under test. If it puts your scope chassis at 200Vac, you’re going to have a bad time. ;)

@@AddOhms Got it! Thanks again :)

The ground wire on the scope lead ties to the ground wire in the outlet, further more at the electrical panel 95%of the time the neutral is tied to the ground. Alot of home owners and even electricians have switched the Hot and neutral on outlets or the device has a non-polarized plug meaning the plug can go in the outlet both ways. If any of the above happens and you attach the ground on your scope the probe and scope will most likely be destroyed. Always use a meter to make sure. You can also be hurt pr killed besides losing your scope. Hope that helps you out.

Logic analyzers let you see when signals transition. Oscilloscopes let you see how they transition. If there is noise on the signal, it might show up as random transitions on a logic analyzer. On the scope, not only can you see what causes the noise, you might be able to correlate it to what causes it. For well validated systems, a logic analyzer is sufficient. But if the signal's analog performance hasn't been validated, a scope might be necessary. You might want to watch this Workbench Wednesdays episode on Logic Analyzers as a contrast: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u1DYs2I-_lU.html

Connect the scope probes to the sensor's output.

@@AddOhms Thank you.

Don’t tell scope companies that. They’ll use it as a bullet point to sell “deep memory!” j/k

In general, use them as an X10 probe.

For your application, doesn't really matter. X10 probe give you higher bandwidth and lower circuit loading, the downside is that it attenuates you signal by factor of 10.

If you have a 1/10x probe it means that in the 1x setting there is a 1M ohm resistor in series with the probe. In the 10x setting a 9M ohm resistor is added so the total resistance is now 10M ohm. This resistance (impedance) is a load that’s applied to the circuit you are measuring. For many circuits adding a 1M resistor may not have any effect on its operation. However if measuring circuits that have low signal levels or are high speed a 1M ohm load may affect the signal you are trying to measure. Switching to 10x will increase the input impedance to the point where it should not impact the signal. You need to make sure your scope is set to match the probe setting so the measured voltage is correct. For reference, most DMMs have a 10M ohm input impedance. This is so they don’t load the circuit under test.

10 MHz to 70 MHz is a good starting point.

The probe is a high impedance input. It measures stray EM fields. It is the same reason a floating input pin randomly switches between a high or low. The signal will usually be 50 or 60 Hz, depending on your AC mains frequency. You can see an example of it in my pull-up resistor tutorial: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-wxjerCHCEMg.html

@@AddOhms Ty, I watched the video and am surprised that it picks up rf. Great videos and hope to see more on oscilloscopes and them in actual use.

It isn't really RF. Radio Frequency (RF) depends on the frequency. It starts in the kilohertz range and goes past the gigahertz range. Signals in the 50 to 60 Hz range are just electromagnetic waves. All RF are EM, but not all EM are RF.

Real engineers can do that one in their head.

This question makes zero sense.

analogWrite on an Uno ranges from 0 to 255.

@@AddOhms I see, thank you. I am doing some reading on it and it seems there is no actual unit for the 255, it just is.

@@freddyrosenberg9288 2 to the power of 8 ie 8 bit byte. I think this guy has a thing for pobes.

@@andrewtaylor9615 I see. Although it should be 256 then, I was wondering how they got the 255, I could not find an obvious answer. Thank you.

256 states. 0 through 255 = 256.