Very Basic Oscilloscope Questions

[HoracioDos]

Hello!

I'm a noob in electronics without any technical background. I'm starting to learn the basics and build some circuits and gadgets, so my posts will have many conceptual errors. I apologize for them in advance.

I think about circuits as arrangements of components that do something in particular and can be used as lego blocks to build bigger things. First I try to understand them in a very high level and then try to go deep to lower levels, so almost all of my projects have been built based on copy & paste, a little theory and a lot of trial and error and experimentation.

I was able to buy a dso (rigol ds1054z) this year and I have with some vary basic questions.

1) I find quite hard to get a signal manually. It's like the dso is unresponsive and have to use the AUTO feature too often. (If trigger is on MANUAL and I set vertical and horizontal scale and position, I guess I should find the signal easily). Is it a begginer problem? Is the dso defective? As I don't have any previous experience, I don't know what the expected behaviour should be. How can I check if it's OK?

2) Many times the 10X probes are over compensated and I have to calibrate them. User manual doesn't say if they should be calibrated so many times. Is it normal?

3) My house is about 130 years old and I have improved the electric circuits over the years but I don't have earth. Big appliances are grounded to water pipes or to their own electric boxes. Should I plug the dso in the same way?

By watching Dave's video #279 - How NOT To Blow Up Your Oscilloscope, I always connect the probe ground to the circuit ground. But, can the oscilloscope and the breadboard circuit be connected both without earth?

Also, the laundry room is next to my office, so I plug the oscilloscope to a surge protector to keep it safe from electric peaks. I can see how the signal changes when the cellar or the washing machine starts and affects the test circuit. How can I protect the oscilloscope without a mayor electrical rework?

In other posts I'll ask a little bit more complex questions related to a project that I'm building.

Thanks in advance!

[ataradov]

1) I find quite hard to get a signal manually. It's like the dso is unresponsive and have to use the AUTO feature too often.

It is hard to tell without having a visual. I would assume that scope is fine, and some of the settings are incorrect. For example, check your memory depth.

Generally you know what signal to expect, so you don't really "search" for it.

Also, responsiveness is a very subjective thing.

2) Many times the 10X probes are over compensated and I have to calibrate them. User manual doesn't say if they should be calibrated so many times. Is it normal?

Each individual probe needs to be compensated once for each individual scope (or even a channel). Do you need to do that more often?

3) My house is about 130 years old and I have improved the electric circuits over the years but I don't have earth. Big appliances are grounded to water pipes or to their own electric boxes. Should I plug the dso in the same way?

  Having a good ground connection is a huge plus, but is not totally necessary. Some safety standards may disagree, but ANSI requires you to wear safety glasses when using multimeters, so safety standards are overly paranoid sometimes.

By watching Dave's video #279 - How NOT To Blow Up Your Oscilloscope, I always connect the probe ground to the circuit ground. But, can the oscilloscope and the breadboard circuit be connected both without earth?

You need to clarify this question.

I can see how the signal changes when the cellar or the washing machine starts and affects the test circuit.

Well, it is possible that device under test is affected by the washing machine, so your scope shows what actually happens.

The scope itself has a switching power supply, so it is very tolerant to input voltage variations, and power supply should never affect the measurement.

[w2aew]

Difficulty getting a trace on a scope is usually related to not having the trigger setup properly. It is perfectly ok to use the AUTO Trigger function.  Contrary to the name, it does NOT setup the trigger automatically for you! The AUTO trigger function is like a timeout feature - if a trigger event isn't detected within a certain period of time (50-100ms typ), then the scope self-generates a trigger. This is done to ensure that there's always a trace/waveform being produced so that you can more easily setup the vertical settings, horizontal settings, and trigger level / mode to stabilize the waveform. One of the first rules with a scope is that you should already have some idea of the waveform that you're expecting so that you can get in the ballpark with your setting before even attaching the probe.

You may want to view the sticky thread on the basics of oscilloscopes that appears near the top of this sub-section.

To give you a better idea on AUTO Trigger, here's my video on that:

[Howardlong]

The way I read it was that the OP was using the Auto setup (Autoset on Tek) feature rather than just Auto trigger, but I may be wrong.

I agree with ataradov, usually you have a reasonable idea of what you're looking for ahead of time, and set appropriately. However having "the knack" is definitely something you learn over time.

Also I agree regarding the probe cal. I recommend using the coloured collars on the probe set to make sure you keep the right probe on the right channel. If you're the only one who uses the scope then it's easy to control, and you should rarely need to do cal a probe other than the very first time you use it on a given channel. If others use it, then all bets are off, and I would do a probe check/cal every time I used the scope. Shared scopes tend not to have the same love and care that your own might have.

[alsetalokin4017]

The way I read it was that the OP was using the Auto setup (Autoset on Tek) feature rather than just Auto trigger, but I may be wrong.

I agree with ataradov, usually you have a reasonable idea of what you're looking for ahead of time, and set appropriately. However having "the knack" is definitely something you learn over time.

But you'll probably learn this "knack" much faster if you don't rely on the Auto setting mode! That "Auto" button is a crutch, useful at times but should probably be relied upon less and less as you use the scope more and more. You should be forced to put a quarter in a jar every time you use it.   

Also I agree regarding the probe cal. I recommend using the coloured collars on the probe set to make sure you keep the right probe on the right channel. If you're the only one who uses the scope then it's easy to control, and you should rarely need to do cal a probe other than the very first time you use it on a given channel. If others use it, then all bets are off, and I would do a probe check/cal every time I used the scope. Shared scopes tend not to have the same love and care that your own might have.

This ^^.  If you are using the same probe(s) on the same channel(s), and you are the only user of the scope, you should only need to adjust probe compensation _once_, period. However it doesn't hurt to check and re-compensate as necessary. On switchable 1x-10x probes, do the compensation on the 10x setting. If your probe compensation drifts, there is probably something wrong somewhere, either with the probe itself, your hookup to the scope or, heaven forbid, something inside the scope, like a dead cockroach bridging a trace or something. 

[Howardlong]

The way I read it was that the OP was using the Auto setup (Autoset on Tek) feature rather than just Auto trigger, but I may be wrong.

I agree with ataradov, usually you have a reasonable idea of what you're looking for ahead of time, and set appropriately. However having "the knack" is definitely something you learn over time.

But you'll probably learn this "knack" much faster if you don't rely on the Auto setting mode! That "Auto" button is a crutch, useful at times but should probably be relied upon less and less as you use the scope more and more. You should be forced to put a quarter in a jar every time you use it.   

Ain't going to disagree with that!

[HoracioDos]

Hello!

Difficulty getting a trace on a scope is usually related to not having the trigger setup properly. It is perfectly ok to use the AUTO Trigger function.  Contrary to the name, it does NOT setup the trigger automatically for you! The AUTO trigger function is like a timeout feature - if a trigger event isn't detected within a certain period of time (50-100ms typ), then the scope self-generates a trigger. This is done to ensure that there's always a trace/waveform being produced so that you can more easily setup the vertical settings, horizontal settings, and trigger level / mode to stabilize the waveform. One of the first rules with a scope is that you should already have some idea of the waveform that you're expecting so that you can get in the ballpark with your setting before even attaching the probe.

Nice tip.

You may want to view the sticky thread on the basics of oscilloscopes that appears near the top of this sub-section.

I have already started to watch them since day 1.  I found this video very useful:
(English)
(Same video in Spanish)

To give you a better idea on AUTO Trigger, here's my video on that:

Thank you for your video. I want to become proficient using the DSO.

[HoracioDos]

Hello!!

The way I read it was that the OP was using the Auto setup (Autoset on Tek) feature rather than just Auto trigger, but I may be wrong.

Yes, I'm using the auto setup, not the auto trigger. Manual says " the scope will automatically adjust the vertical scale, horizontal time base and trigger mode according to the input signal to realize optimum waveform display.

I agree with ataradov, usually you have a reasonable idea of what you're looking for ahead of time, and set appropriately. However having "the knack" is definitely something you learn over time.

I usually know what I'm looking for. Also before turning off the scope I always try to get the reference signal manually to get experience and many times without success.

Also I agree regarding the probe cal. I recommend using the coloured collars on the probe set to make sure you keep the right probe on the right channel. If you're the only one who uses the scope then it's easy to control, and you should rarely need to do cal a probe other than the very first time you use it on a given channel. If others use it, then all bets are off, and I would do a probe check/cal every time I used the scope. Shared scopes tend not to have the same love and care that your own might have.

I don't share the scope. I set the coloured collars in all probes the first day and never removed them. The probes are 1x-10x and I have to calibrate CH1 probe when I use it (10X) almost every time I turn on the scope. I think there is something wrong there.

[HoracioDos]

Hello!

But you'll probably learn this "knack" much faster if you don't rely on the Auto setting mode! That "Auto" button is a crutch, useful at times but should probably be relied upon less and less as you use the scope more and more. You should be forced to put a quarter in a jar every time you use it.   

I agree with that I don't want to be AUTO dependant.

This ^^.  If you are using the same probe(s) on the same channel(s), and you are the only user of the scope, you should only need to adjust probe compensation _once_, period. However it doesn't hurt to check and re-compensate as necessary. On switchable 1x-10x probes, do the compensation on the 10x setting. If your probe compensation drifts, there is probably something wrong somewhere, either with the probe itself, your hookup to the scope or, heaven forbid, something inside the scope, like a dead cockroach bridging a trace or something.

I thought the same. It could be a problem with the probe or the scope.

[HoracioDos]

Hello!

Generally you know what signal to expect, so you don't really "search" for it.

Also, responsiveness is a very subjective thing.

I usually know what I'm looking for but many times I turn the knobs (vertical-horizontal scale and position and-trigger) from top to bottom and nothing happens.  Then I use the Auto setup.

Each individual probe needs to be compensated once for each individual scope (or even a channel). Do you need to do that more often?

Yes, I do it almost every time when I turn on the scope if the probe is 10X.

Having a good ground connection is a huge plus, but is not totally necessary. Some safety standards may disagree, but ANSI requires you to wear safety glasses when using multimeters, so safety standards are overly paranoid sometimes.

Lol!! I have only one eye that works. This recommendation makes sense to me!

You need to clarify this question.

I don't know if the terms are correct in english. Please correct me if I'm wrong.
Power mains is (phase or active, neutral and earth) as the house doesn't have an earth there is no way to discharge current if something goes wrong.

So I want to know if I should plug the scope in the same way that the fridge or the washing machine is pluged.

The scope itself has a switching power supply, so it is very tolerant to input voltage variations, and power supply should never affect the measurement.

Excellent!

[HoracioDos]

To give you a better idea on AUTO Trigger, here's my video on that:

LOL!! I knew your profile was familiar to me. I'm a subscriber since I watched your #75: Basics of Opamp circuits video. I love the explains in paper. It's just like Dave's cad.
Also #238: Oscilloscope Vertical Position and Offset explained was already in my watching list.

[ataradov]

I usually know what I'm looking for but many times I turn the knobs (vertical-horizontal scale and position and-trigger) from top to bottom and nothing happens.  Then I use the Auto setup.

Maybe a short video of this? There are many details that affect perceived responsiveness of the scope.

Yes, I do it almost every time when I turn on the scope if the probe is 10X.

Again, video or screenshots of what exactly happens.

So I want to know if I should plug the scope in the same way that the fridge or the washing machine is pluged.

Well, again, it is better to have a real ground connections, but you will be fine without it. Too many things need to happen at once for things to go wrong.

[rstofer]

Engineers and programmers got paid good money to add the AUTO button to the scope.  There is a manufacturing cost incurred as a result of having added it and you paid for it.  It's there for a reason so use it!

I'm getting old (ok, I AM old) and I seldom remember what condition I left the scope in and the AUTO button is often the fastest way to get a trace on the screen.  Heck, old analog scopes had a Beam Finder button so you could get a baseline just in case your signal was way off screen.  Another crutch?  Not really!

Scope probe compensation should be a one-and-done thing as long as it is used on the same channel.  If that isn't working out, buy better probes.

Trigger mode should be AUTO unless you are trying to take a SINGLE sweep.  NORMAL doesn't bring much to the dance, in my view.  I would rather see a signal improperly triggered than a blank screen which makes me wonder if there even is a signal.

Work out your own process.  If AUTO works for you, by all means use it!  You paid for it!

[ataradov]

I'm getting old (ok, I AM old) and I seldom remember what condition I left the scope in

The reason I don't like AUTO button is that I do remember the condition, and AUTO messes up more things than I like it to.

[HoracioDos]

Maybe a short video of this? There are many details that affect perceived responsiveness of the scope.

I'll keep it in mind and will do one as soon as I have a good example. Thanks for your concern.

[HoracioDos]

Engineers and programmers got paid good money to add the AUTO button to the scope.  There is a manufacturing cost incurred as a result of having added it and you paid for it.  It's there for a reason so use it!

LOL! It crossed my mind but I was afraid to ask. Why there's an Auto setup button if It's so bad to use it?

[ataradov]

Why there's an Auto setup button if It's so bad to use it?

Because sometimes you are in the lab, where you have to use shared scopes, and it is easier to restore a scope to some known state and start from there.

If you know exactly how your scope is set up, then there should be no need for auto button, unless you are absolutely confused.

On my own equipment, AUTO button disorients me, and after using it I have to go back and check all the settings again, since it is very unpredictable what exactly will be changed as a result.

[rstofer]

Why there's an Auto setup button if It's so bad to use it?

Because sometimes you are in the lab, where you have to use shared scopes, and it is easier to restore a scope to some known state and start from there.

If you know exactly how your scope is set up, then there should be no need for auto button, unless you are absolutely confused.

On my own equipment, AUTO button disorients me, and after using it I have to go back and check all the settings again, since it is very unpredictable what exactly will be changed as a result.

But you will have wiggles on the screen!  This alone is worth the cost of admission.

Yes, AUTO will mess up settings and even enable all the channels when I only have one signal but once I get wiggles, the rest is easy.

I don't use my scope every day or even every week.  My last project could have been just about anything.  Getting to a known state, even one with warts, seems pretty useful.

But I can see where folks who use their scope frequently and have yet to completely fry their brains on Margaritas could get along without it.  Just wait!  You'll be old one of these days and that AUTO button just might become your best friend.

[HoracioDos]

I'll try both ways. I hope I'll identify the situations in which I should use AUTO or MANUAL.

Lessons learned:
Auto setup and Manual are not excluding of each other.
Auto Trigger: something to learn about.

I'll wait more time to take the DSO to repair service to check it.

[Howardlong]

I would add that the x1/x10 switch on those probes is notoriously easy to accidentally nudge, such as when storing them away, or even just in normal use, and it's not easy to read the positions on the probe itself.

Not sure of this has anything to do with the compensation problem or not: I tried it this evening on a channel and the compensation seemed fine on x1 and x10 on tthe same probe, but that was a straw poll of one.

I very very rarely use x1, but depending on your use case you may need it more.

[HoracioDos]

I would add that the x1/x10 switch on those probes is notoriously easy to accidentally nudge, such as when storing them away, or even just in normal use, and it's not easy to read the positions on the probe itself.

Not sure of this has anything to do with the compensation problem or not: I tried it this evening on a channel and the compensation seemed fine on x1 and x10 on tthe same probe, but that was a straw poll of one.

I very very rarely use x1, but depending on your use case you may need it more.

The first weeks after buying the scope I set the probes to 1X and everything was fine, later I began to set them to 10X and that's when this strange drift appeared. I will provide screenshots with their datetime to check if it's a normal behaviour.

By the way, please could someone tell me if I can remove the pronoun "I" in every sentence. I feel I'm writing like a child.

[Howardlong]

Until you mentioned it I hadn't noticed, and I don't think it sounds wrong or something I wouldn't say.

It would seem that in English, it's all about me!

[JiggyNinja]

By the way, please could someone tell me if I can remove the pronoun "I" in every sentence. I feel I'm writing like a child.

English doesn't drop pronouns based on context like other languages do, I'm guessing that your native language would be Spanish. While it might seem tedious to someone that is used to not using them, everything you've written so far (pronouns and all) is completely normal English.

With regards to your problem, how much do you know about the settings in the Trigger menu? Scopes have varying levels of sophistication, but these are the most important ones:

Mode: Auto, Normal, and Single
In Single mode, the scope only stores one waveform the first time it is triggered. You need to manually reset it for it to capture another one. This is a very useful mode to capture infrequent, transient signals and take your time analyzing them.

In Normal mode, the trigger resets automatically after each capture. This is the best mode for viewing a periodic waveform, because it will stay stable on the screen.

Auto is almost the same as normal, but if there is no trigger event without a period of time the scope will trigger anyway and capture a waveform. This can help guarantee that something is drawn on the screen, even if your trigger settings are screwed up. It can also be used to view things that might be difficult to know what to trigger off of at first, like a DC signal.

For most uses, you'll probably want Normal mode.

Type:
This defines what condition the scope looks for to cause a trigger. More expensive scopes can have very sophisticated triggering options, but every scope should be capable of Rising Edge or Falling Edge triggering. For viewing simple waveforms, make sure your trigger is set to one of those options and not something exotic.

Source:
I suspect that this might be your issue. Most scopes can only be set to trigger off of one channel at a time. You should be able to set it to any one of the input channels or External. Make sure it's set to the channel you're currently using, and not a channel that's currently unconnected.

[HoracioDos]

With regards to your problem, how much do you know about the settings in the Trigger menu? Scopes have varying levels of sophistication, but these are the most important ones:

Thanks! Super clear explanation.

[HoracioDos]

This is an example about the probe drifting

I first turned on the dso for 30 minutes on 2017-01-27
I took the first pic, calibrated the probe on CH1, took a second pic, turned off the scope and didn't use it any more.
I turn on the dso for for 30 minutes today and took a pic on CH1.
I took a fourth pic and turned off the scope.

Is it normal? Should I send it to the repair service?

[ataradov]

This is most definitely not normal. But it may be a bit too early for the repair service.

1. Can you note what adjustments you need to make for calibration? Like approximate portion of a turn if the cap in the probe and what direction? Does it just go back and forth between power cycles to stay calibrated?
2. Can you connect the output of the test signal generator directly to the input of the scope without a probe?

[HoracioDos]

I forgot to tell I never changed the probe. It's always the same.

1. Can you note what adjustments you need to make for calibration? Like approximate portion of a turn if the cap in the probe and what direction? Does it just go back and forth between power cycles to stay calibrated?

OK, I'll take more detailed notes. I never remember if I turn left or right but It's always less than a quarter of a turn. I have to calibrate it every time I turn on the dso if the probe is 10X. I have 1x-10x default probes. Once in a while it seems that it starts to drift if it was turned on for many hours.

2. Can you connect the output of the test signal generator directly to the input of the scope without a probe?

Yes I could. I should buy a BNC adapter and I think I have a little piece of RG58 somewhere.

[ataradov]

Yes I could. I should buy a BNC adapter and I think I have a little piece of RG58 somewhere.

Do this and observe if signal changes at all over some time. I'm basically trying to eliminate faulty probes.

[alsetalokin4017]

This may be a bit silly... but are you quite sure the spring grabber tips are completely in place on your probes? For the stock probes that come with the DS1054z, these tips need quite a push before they click solidly in place. And even then, they may not make good contact without rotating them a bit. A poor connection to the grabber tip might cause the kind of thing you are seeing.
You could try pulling the grabber off the probe and just using the sharp tip, to see if that makes any difference in the compensation drift.

[ProBang2]

Hmmm...

Seems like totally normal behavior to me. (At least, mine does the same...)

The direct (with BNC to croc-clip cable) connected calibration signal shows a perfect rectangular 3V_PP wave.
All four probes have the same drift after calibration. (Not immediatly. After some time.)

Possible explanation:
The wiper of the calibration trimpot in the probe is made of a cheap metal (maybe aluminium).
This metal is oxidizing when in contact with air. It builts up a layer of oxid on the surface.
This layer prevents the inner part of the metal from further oxidising.
If the wiper is moving while a calibration, then some oxid is scratched of the surface.
After calibration it begins to oxidising again, until the surface is complete covered.

Possible remedy:
Apply some contact-spray or much more simple, a little amount of oil to the trimpot(s).
This covers the metal surface, avoiding the contact between metal and air and thereby the oxidation.
Then there is no more ongoing oxidation, hence the electrical parameters of the trimpot should be stable.

[metrologist]

Why there's an Auto setup button if It's so bad to use it?

Because sometimes you are in the lab, where you have to use shared scopes, and it is easier to restore a scope to some known state and start from there.

If you know exactly how your scope is set up, then there should be no need for auto button, unless you are absolutely confused.

On my own equipment, AUTO button disorients me, and after using it I have to go back and check all the settings again, since it is very unpredictable what exactly will be changed as a result.

I would like to remap the Auto set button to the Default button. I can't remember what I was doing last time, and with this scope it's just easier to remove measurements and some configurations by going full default.

[metrologist]

The probe compensation on mine will drift too. I worked the trim pot full sweeps a few times. I also noticed touching that switch impact the cal. I think the probes are the issue with cheap trim pot and that silly switch. The probes otherwise seem OK, or usable anyway.

[HoracioDos]

This may be a bit silly... but are you quite sure the spring grabber tips are completely in place on your probes? For the stock probes that come with the DS1054z, these tips need quite a push before they click solidly in place. And even then, they may not make good contact without rotating them a bit. A poor connection to the grabber tip might cause the kind of thing you are seeing.
You could try pulling the grabber off the probe and just using the sharp tip, to see if that makes any difference in the compensation drift.

I love this kind of solutions. I'm testing the probe again.

[HoracioDos]

Yes I could. I should buy a BNC adapter and I think I have a little piece of RG58 somewhere.

Do this and observe if signal changes at all over some time. I'm basically trying to eliminate faulty probes.

I've just bought the BNC adapter. I hate to solder these things! I'll try it tonight.

[StillTrying]

Is there any change over time at all in the 1khz when the probes are on X1.

Have you tried a different square wave source, it doesn't have to be exactly 1khz nor exactly 3v.

Do you remove the probes before doing its self-calibration.

[AG6QR]

I don't use the "AUTO" button to fully set everything.  I didn't have an "AUTO" button when I first learned to use a scope, and old habits die hard.  The way I learned was the following:

• Set the trigger mode to Auto.  This guarantees that the beam will sweep the screen periodically.
• Turn the vertical scale knob to zoom out.  That is, toward the largest volts per division available.  You don't necessarily need to go all the way -- you can stop when you see both the top and bottom of the trace.
• If zooming out all the way didn't already give you a trace, click on the "position" knob, and if needed, rotate it a bit.
• Once you see a trace, use the scale and position knobs to zoom in on it so that it covers a reasonable portion of the vertical extents of the screen.  Don't worry about triggering just yet.
• Adjust the horizontal scale as desired.
  
• Now set the trigger level to somewhere in the middle of the waveform to get a stable trace.
• Fine tune things as desired

With just a bit of practice, these adjustments become second nature, and you can do them very quickly.  You may not do them precisely in this order every time.  But the basic idea is, zoom out, find the trace, then zoom in on it.

[tautech]

Probes
It is unnessary to compensate probes on 1:1 setting, only do so on 10:1 settings.