Author Topic: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div  (Read 9022 times)

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Offline NeverDie

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How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« on: August 10, 2015, 08:17:48 AM »
According to the specsheet, "Vertical Scale 1 mV/div to 10 V/div."  Yet, it won't let me set it to less than 10mv/div.  If I try setting it lower, it says "Parameter limited", whatever that means.

What's worse, if I connect the ground clip to the probe tip, instead of getting a nice narrow flat line as I would have expected, I get a fat line instead (see attached screen shot).  Is this scope just not capable of 1mv/div?

I'm sorry, but 10mv/div just isn't terribly useful when working with arduinos.


« Last Edit: August 10, 2015, 08:23:30 AM by NeverDie »
 

Offline Lightages

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #1 on: August 10, 2015, 08:23:05 AM »
Is your probe setting at 10X?
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Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #2 on: August 10, 2015, 08:33:34 AM »
Is your probe setting at 10X?

It was.  Yet if I flip it to 1X, nothing seems to change.  I still get a fat line, and it still won't let me do 1mv/div.  Isn't that rather weird?  Is there some probe setting I need to toggle somewhere to inform it which way the probe is set or something?  Sorry for the bonehead question, but I'm a noob and I barely have any idea what I'm doing.
« Last Edit: August 10, 2015, 08:36:29 AM by NeverDie »
 

Offline dom0

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #3 on: August 10, 2015, 08:35:27 AM »
You need to adjust the probe attenuation setting in the scope as well, or it will not show the correct vertical scale.
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Offline rs20

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #4 on: August 10, 2015, 08:42:05 AM »
Yes. Press "CH1" and there should be a probe ratio setting there.

Why is 10mV/div insufficient for Arduinos? Normal Arduinos work would be at 5V or 3.3V peak to peak, so 500mV/div or 1V/div seems far more typical.

Also, I recommend you watch the EEVBlog video about 1x probes - the frequency response is terrible. You should be sticking to 10x unless your doing work that is both low voltage and low frequency.
 

Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #5 on: August 10, 2015, 08:55:01 AM »
Yes. Press "CH1" and there should be a probe ratio setting there.

Why is 10mV/div insufficient for Arduinos? Normal Arduinos work would be at 5V or 3.3V peak to peak, so 500mV/div or 1V/div seems far more typical.

Also, I recommend you watch the EEVBlog video about 1x probes - the frequency response is terrible. You should be sticking to 10x unless your doing work that is both low voltage and low frequency.

Thanks!  I set the probe itself to 1X and then I set it there at 1x as well.  Now it let's me do 1mv/div.

In answer to your question, I'm trying to measure the transmitter current through an NRF24L01+ module (an inexpensive 2.4Ghz radio module with, allegedly, a Nordic Semiconductor chip on it with that model number) driven by an arduino.  Using a 1 ohm sense resister, with the previous settings I was getting the results below (see attached), and the lines were rather thick, making interpretation difficult (well, difficult  to these noob eyes).
« Last Edit: August 10, 2015, 09:00:40 AM by NeverDie »
 

Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #6 on: August 10, 2015, 08:59:19 AM »
Attached is the test rig with DS1054Z probe attached.
 

Offline T3sl4co1l

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #7 on: August 10, 2015, 09:00:06 AM »
What about Arduinos makes 10mV/div insufficient?  Logic level is 500 divs.  If you're doing sensitive DAQ, you're probably better off testing it at larger signals (where distortion will be more exaggerated) and assuming it's fine at lower levels, using the DAQ itself to provide the data for analysis to confirm this (which will probably be easier than measuring it on the scope -- you can do the analysis on the MCU directly, or prepare and copy an array via serial and process a .CSV or what have you).

Residual noise (noisy signal chain, switching supplies..?) might still be of interest, but this can at least be measured by the same methods, if not so easily tracked and troubleshooted.

To get practical 1mV/div use, you can get a 1x or switchable probe (however: mind the limited bandwidth -- read the spec sheet for that gotcha!), a preamp or probe extender, or connect coax directly to the circuit (assuming it doesn't mind the capacitive load and reflection, or the extra loading if 50 ohm terminated), or using a buffer (to keep the gain but eliminate the loading).  Speaking of noise, be mindful that such levels are very sensitive to ambient and conducted radiation (nearby radio stations can peak over 1mV in unlucky situations), so pay very close attention to grounding, shielding and lead dress.

Also mind the limitations of bandwidth: typically a scope of that bandwidth will have maybe 0.2mV RMS baseline, mostly from the noise of a 50 ohm source.  I believe Rigols aren't usually that good, and have some excess noise beyond that.  A preamp in front (even with a low noise factor) will magnify the source noise, only making it worse (though not necessarily worse than the excess noise of the scope already).

You can discard a lot of noise by narrowing the bandwidth (lower bandwidth setting, or "hi res" or averaging modes, or analog filtering the signal before the scope), but this may discard useful signal information as well.  If your signal is periodic, you should trigger or sync from a much stronger related signal, then use averaging to remove noise unrelated to the signal (this correlates the signal, "pulling it out of" the noise).

This is also helpful on older scopes that used software magnification for the lowest ranges (HP 54600B comes to mind).  Quantization noise remains, but averaging can remove that noise (just as it works with any other noise source), getting a smooth signal back out.  If you were hard pressed for resolution, you probably can't do this on the Rigol itself, but could save a CSV and do the math in a spreadsheet or MATLAB/Octave for the absolute finest resolution.  (The latter also has the benefit of quickly and easily doing spectral and statistical studies, like autocorrelation.)

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Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #8 on: August 10, 2015, 09:45:23 AM »
So, with the 1X settings, I'm now able to get a better picture and can hopefully measure better.  Looks like maybe I can go to a smaller ohm resistor  and go from 5mv/div down to 1mv/div to get an even better measurement, if that makes any sense.
« Last Edit: August 10, 2015, 10:24:58 AM by NeverDie »
 

Offline dadler

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #9 on: August 10, 2015, 09:50:57 AM »
In 10x mode you also better protecting the front end of your scope, by dividing down any transients.

Most higher end scopes only come with 10x probes, as 1x use is rarely necessary--in addition to the downsides listed above.

Here is Dave's video:

 

Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #10 on: August 10, 2015, 10:41:21 AM »
Thanks, I'll watch that tonight.

Speaking of noise, I was thinking of hooking the o-scope up to my computer via USB, and then I thought "Nah, that'll probably just inject even *more* noise into a situation where I want *less* noise."  Is that likely to be true?  I see that the USB cord that came with the Rigol  appears to have big ferrite cores at both ends, so I'm thinking maybe there is a concern there, and that's the cheap way of (partially?) addressing it.  Would a USB isolator also be worthwhile?  If so, would it need to support USB 2.0 "high speed", or would USB 2.0 "full speed" be enough?  Anyone know what speed is actually being used between the scope and a computer?  It seems that most isolators use the same chip (the ADUM4160), and it doesn't support USB 2.0 in "high speed"mode.

Or would the ethernet connection be preferable (or actually worse?)  if noise is a concern?  I have no idea.

Also, would somehow running this scope off battery power rather plugging it into the wall help reduce noise at all?  Or would it actually make it worse?  Again, no clue, but you gents seem pretty smart and I bet somebody here  would probably know.
« Last Edit: August 10, 2015, 10:54:42 AM by NeverDie »
 

Offline rs20

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #11 on: August 10, 2015, 10:51:41 AM »
Thanks, I'll watch that tonight.

Speaking of noise, I was thinking of hooking the o-scope up to my computer via USB, and then I thought "Nah, that'll probably just inject even *more* noise into a situation where I want *less* noise."  Is that likely to be true?  I see that the USB cord that came with the Rigol  appears to have big ferrite cores at both ends, so I'm thinking maybe there is a concern there, and that's the cheap way of (partially?) addressing it.  Would a USB isolator also be worthwhile?  If so, would it need to support USB 2.0 "high speed", or would USB 2.0 "full speed" be enough?  Anyone know what speed is actually being used between the scope and a computer?  It seems that most isolators use the same chip (the ADUM4160), and it doesn't support USB 2.0 in "high speed"mode.

Or would the ethernet connection be preferable (or actually worse?)  if noise is a concern?  I have no idea.

Not to be blunt, but these seem to be questions that you can easily investigate yourself through experimentation. Plug a USB cable in... see if the noise increases.

Having said that, one would expect ethernet to be a more "noise-free" connection because any ethernet connection is galvanically isolated at both ends, eliminating the possibility of the creation of ground loops. But if you can't see the noise from a USB connection, then there's practically no noise from a USB connection either, end of story.
 

Offline EEVblog

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #12 on: August 10, 2015, 11:40:16 AM »
What's worse, if I connect the ground clip to the probe tip, instead of getting a nice narrow flat line as I would have expected, I get a fat line instead (see attached screen shot).  Is this scope just not capable of 1mv/div?

 

Online Fungus

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #13 on: August 10, 2015, 12:09:12 PM »
In answer to your question, I'm trying to measure the transmitter current through an NRF24L01+ module (an inexpensive 2.4Ghz radio module
The datasheet has a very detailed chapter on power consumption.
 

Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #14 on: August 10, 2015, 01:45:09 PM »
In answer to your question, I'm trying to measure the transmitter current through an NRF24L01+ module (an inexpensive 2.4Ghz radio module
The datasheet has a very detailed chapter on power consumption.

True, but it turns out to be very hard to know if you actually have a genuine Nordic Semiconductor NRF24L01+ chip on your module or instead have one of many different counterfeit chips that are being passed off as genuine, when they're not.  In some circles there's growing consensus that if you purchased your modules on Ebay or through AliExpress or similar, you very likely received counterfeit chips--and generally you can't tell by their appearance alone which are fake and which are not:
http://hackaday.com/2015/02/23/nordic-nrf24l01-real-vs-fake/

In a perfect world, though, you're right: I wouldn't need to do this measurement, I could just look at the datasheet.  I'll grant you that.
« Last Edit: August 10, 2015, 01:58:17 PM by NeverDie »
 

Offline T3sl4co1l

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #15 on: August 10, 2015, 01:46:23 PM »
So, with the 1X settings, I'm now able to get a better picture and can hopefully measure better.  Looks like maybe I can go to a smaller ohm resistor  and go from 5mv/div down to 1mv/div to get an even better measurement, if that makes any sense.

Better in what sense?  You're trading signal strength (volts for a given current flow) for noise (noise floor of the scope, stray noise from the radio, other circuits and surroundings), and for no advantage:

For a given change in supply voltage deltaV, the change in power draw will almost certainly be less than deltaI = 2*deltaV*Io.

Which for VCC = 5V and Io = 100mA (just WAGs here), means your ~50mV signal shown above is making a 1% difference in supply, and maybe a 1% difference in current, or out of 500mW load, 2% or 10mW.  Which is a tiny amount, probably less than your combined resistor tolerance plus measurement error.

You always want to use the largest shunt you can get away with, given limitations on peak current demand, desired accuracy, acceptable power dissipation and so on.

Tim
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Offline EEVblog

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #16 on: August 10, 2015, 05:00:36 PM »
I just did a video answering this question, as I see it a lot. Rendering now.
 

Offline vk6zgo

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #17 on: August 10, 2015, 08:11:17 PM »
Once upon a time,Oscilloscopes did not have any way of changing the volts/div setting to match a probe,so if you used a "X10" probe.the displayed voltage would be a tenth of that which the user might expect.

At that time,however,Engineers & Technicians were equipped with a very useful accessory,called "a functioning brain".
Using this amazing device,they were able to multiply the reading by 10 in their heads,& had very little difficulty in using X1,X10,or even X100 probes.

This was obviously an unsatisfactory state of affairs,so 'scope manufacurers devised probes which told the Oscilloscope to multiply the reading so the user didn't need to!

This brought about confusion,as people persisted in using the old style probes,& having switched off their brain,started to get confused,as they expected the Oscilloscope to do their thinking for them! ;D ;D
 

Offline EEVblog

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #18 on: August 10, 2015, 08:32:53 PM »
At that time,however,Engineers & Technicians were equipped with a very useful accessory,called "a functioning brain".

*snort*
 

Offline tautech

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #19 on: August 10, 2015, 09:03:53 PM »
Once upon a time,Oscilloscopes did not have any way of changing the volts/div setting to match a probe,so if you used a "X10" probe.the displayed voltage would be a tenth of that which the user might expect.

At that time,however,Engineers & Technicians were equipped with a very useful accessory,called "a functioning brain".
Using this amazing device,they were able to multiply the reading by 10 in their heads,& had very little difficulty in using X1,X10,or even X100 probes.

This was obviously an unsatisfactory state of affairs,so 'scope manufacurers devised probes which told the Oscilloscope to multiply the reading so the user didn't need to!

This brought about confusion,as people persisted in using the old style probes,& having switched off their brain,started to get confused,as they expected the Oscilloscope to do their thinking for them! ;D ;D
+1

And many that acquire CRO's as their first scope quickly learn this is the case and many threads here attest to this fact. That some also have this affliction with a DSO that does all the work for them I also find amusing.

But we have all done it ourselves in our early days, those that haven't are liars or have bad memory.  :-DD

I still find myself counting graticules and portions of.  :palm: A reminant of times past I guess.  :phew:
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Offline mcinque

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #20 on: August 10, 2015, 09:19:51 PM »
If I try setting it lower, it says "Parameter limited", whatever that means.
Is this scope just not capable of 1mv/div?
Don't be offended, but it seems like you're never touched the manual of the scope you've bought. Not even with a 6ft pole.

As a suggestion, it's always good to read carefully every manual of every instrument you own. This not to avoid asking advices, but to really understand your instruments and what you can do (and most important what you can not do) with them. I'm talking about safety for example.

I'm sorry, but 10mv/div just isn't terribly useful when working with arduinos.
Hmmm... why? If you're working with arduinos, I guess you debug logic levels (TTL, I2C, PWM etc), so why you should need 1mV/div?

I'm basically still a rookie and because of this, even though the best of intentions, I often say bullshit, so never mind.
 

Online mikeselectricstuff

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #21 on: August 10, 2015, 10:10:03 PM »
Yes. Press "CH1" and there should be a probe ratio setting there.

Why is 10mV/div insufficient for Arduinos? Normal Arduinos work would be at 5V or 3.3V peak to peak, so 500mV/div or 1V/div seems far more typical.

Also, I recommend you watch the EEVBlog video about 1x probes - the frequency response is terrible. You should be sticking to 10x unless your doing work that is both low voltage and low frequency.

Thanks!  I set the probe itself to 1X and then I set it there at 1x as well.  Now it let's me do 1mv/div.

In answer to your question, I'm trying to measure the transmitter current through an NRF24L01+ module (an inexpensive 2.4Ghz radio module with, allegedly, a Nordic Semiconductor chip on it with that model number) driven by an arduino.  Using a 1 ohm sense resister, with the previous settings I was getting the results below (see attached), and the lines were rather thick, making interpretation difficult (well, difficult  to these noob eyes).
For this sort of thing, use avaraging or high-res acquisition mode, whatever it's called on your scope - on lower rate timebase settings it avarages multiple samples to produce each sample point. (not trace-to-trace avaraging, though for regular waveforms this can also sometimes be useful)
 Also use bandwidth limiting on the input.
Bear in mind that at high sensitivites, the length of the probe ground wire can be a major issue, so you need to ground at the tip ring, or just use a length of coax with short ends soldered across the resistor instead of the probe
« Last Edit: August 10, 2015, 10:11:49 PM by mikeselectricstuff »
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Offline NeverDie

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #22 on: August 11, 2015, 12:42:29 AM »
I just did a video answering this question, as I see it a lot. Rendering now.

 I just now saw the new video you made.  Fantastic! A+  Thanks!
 

Offline Howardlong

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #23 on: August 11, 2015, 12:51:37 AM »
At that time,however,Engineers & Technicians were equipped with a very useful accessory,called "a functioning brain".
Using this amazing device,they were able to multiply the reading by 10 in their heads,& had very little difficulty in using X1,X10,or even X100 probes.

+10. (or is it +1 or maybe it's +100, not sure, I need to refer to some online help).

Pretty sure many old farts like me still regularly still do so when using non-readout probes on older scopes, or indeed scopes without any probe readout facility or probe correction. Pretty sure they sent men to the moon without much in the way of probe correction too.
 

Offline dom0

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Re: How do I get 1mv/div on the 1054Z? I'm only getting 10mv/div
« Reply #24 on: August 11, 2015, 02:24:44 AM »
At that time,however,Engineers & Technicians were equipped with a very useful accessory,called "a functioning brain".
Using this amazing device,they were able to multiply the reading by 10 in their heads,& had very little difficulty in using X1,X10,or even X100 probes.

+10. (or is it +1 or maybe it's +100, not sure, I need to refer to some online help).

Depends on the appreciation attenuation factor.
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