New Rigol DS1054Z oscilloscope

[Assafl]

Even the Per Vrms (RMS per period) has over a 5% difference between RMS readings.

Of the 4 channels some are closer than others.

[Assafl]

Vrms changes a lot more tha Per Vrms. I never understood what VRMS was without cursors. What segment of the trace does it really include in calculation? Obviously between Ch1 and Ch2 it isn't the same segment...

[Fungus]

Would you at least concede that two channels connected to the exact same signal should report the same RMS value for that signal?

Both CH1 and CH2 connected to the probe calibrator output:

What happens when you swap the trigger to the other channel?

This.   

[Assafl]

Would you at least concede that two channels connected to the exact same signal should report the same RMS value for that signal?

Both CH1 and CH2 connected to the probe calibrator output:

What happens when you swap the trigger to the other channel?

This.   

This indeed. One would expect the scope to measure RMS for both traces in an identical window. Obviously it doesn't and neither does it mark where the calculation window for each channel actually occurs. Which makes comparing two signals using Vrms quite dicey. I guess this is as designed but may get noobs in trouble.

Quite unlike the predictable PerVrms.

[JPortici]

To me, the pulses/pluses update is nearly meaningless. I know what they mean. I don't use an oscilloscope for a language lesson. I want measurements.

So the phantom CH2-4 Vrms bug is the kind of thing that irks me. I don't have enough money or accurate enough secondary equipment to know if some values are wrong, or have high statistical (or in this case, systematic) error. I mean, I know that there shouldn't be a reading without a probe in, but once you get into the realm of plausibility, I will have to accept the results the scope gives me.

I am hopeful that this community will make progress unpacking/decoding the firmware and we'll being to take more control over it ourselves.

Again, it's not THAT important but it is (to me) a sign that they are not taking things seriously, i can understand a spelling error, nobody's perfect, i can't understand not solving it because it is really so simple to fix.. and they are still not fixing or rather "fixing" other bugs and nuisances 'on the side'
so, i can't trust them just as i always resort to triple check the signal waveform with an old tek greenie i know i can give my trust to.
but i told myself i wouldn't argue anymore about this subject. i just want to sell this scope in the moment i can, as i stopped hoping for them to really fix anything

[bitseeker]

Again, it's not THAT important but it is (to me) a sign that they are not taking things seriously, i can understand a spelling error, nobody's perfect, i can't understand not solving it because it is really so simple to fix.. and they are still not fixing or rather "fixing" other bugs and nuisances 'on the side'
so, i can't trust them...

+1. This is the issue exactly, and is not brand-specific. It's a matter of being able to have a reasonable amount of trust in the equipment. The manufacturer's failure to address little things makes you wonder what more important problems are being overlooked or ignored.

[technogeeky]

Again, it's not THAT important but it is (to me) a sign that they are not taking things seriously, i can understand a spelling error, nobody's perfect, i can't understand not solving it because it is really so simple to fix.. and they are still not fixing or rather "fixing" other bugs and nuisances 'on the side'
so, i can't trust them...

+1. This is the issue exactly, and is not brand-specific. It's a matter of being able to have a reasonable amount of trust in the equipment. The manufacturer's failure to address little things makes you wonder what more important problems are being overlooked or ignored.

I do fully appreciate that aspect of the argument against Rigol in this case. (And, as you say, other manufacturers.) However, I have some trust in the ability of Chinese engineers (and laypeople) to add, subtract, multiply, and divide -- and do these things correctly. Thus, I would be perfectly happy to put up with many more spelling errors in the firmware if it meant that all of the calculation, MATH, and measurement errors were gone. That is the way to enhance my trust in the device.

[bitseeker]

Certainly. And, hopefully, the calc, measurement, etc. errors have been taken care of with this update. I'm still observing the reports as they come in, since things haven't always gotten better with firmware updates.

[alsetalokin4017]

I'm waiting for test reports too. I'd like to know about two specific bugs: The Measurements Fail bug and the 500 ns/div Math horizontal error bug.

Measurements Fail:


Math horizontal error at 500 ns/div, see attached screenshot:

[alsetalokin4017]

Would you at least concede that two channels connected to the exact same signal should report the same RMS value for that signal?

Both CH1 and CH2 connected to the probe calibrator output:

What happens when you swap the trigger to the other channel?

This.   

This:

[JPortici]

* audience hold their breaths *

[JohnPen]

I have upgraded my scope to the latest 2016 f/w and so far I can confirm that the 'lockups' appear to be fixed.  The  Maths offset  using *4017  set up but with a 1Mhz square wave shows no delay offset for A+B, AxB etc.  Also I have been unable to reproduce the Stats/Pluses' count lockup despite running for a number of hours.  I haven't noticed any slowing of response to controls in comparison with the previous build but one does adapt quickly and forget easily! 

John

[Fungus]

What happens when you swap the trigger to the other channel?

This.   

This:

Exactly as I suspected - nothing happens!.

OTOH the horizontal timebase does make a big difference. Less waves on screen gives less accuracy. More waves on screen gives more accuracy.





This is also to be expected - we know Rigols work from "on-screen" data.

[Fungus]

Scrolling the data left/right also gives different values (again, no real surprises...)





Even one pixel can make a difference.

Channel 2 does seem to be consistently higher than channel 1 though, even if you swap the probes around.

I wonder if that's an individual 'scope thing or if it's the same on everybody's 'scope. I guess we need more people to try it.

[Fungus]

Turning on AC coupling gives completely different numbers.



nb. The correct RMS for a 3V square wave should be 2.12V  (3/sqrt(2))

[Fungus]

At the end of the day though: You get a few waves on screen and it's pretty close to 2.12.

The periodic RMS seems more accurate. This makes sense (it will look for a complete wave so it's less dependent on horizontal scroll position).

Anything else is interesting...  but nitpicking. Oscilloscopes are for looking at the shapes of things, not precise voltage measurements. Between 8-bit DACs and background noise you're never going to achieve more than about 10% accuracy.

Calculating from on-screen data is probably a DS100Z hardware limitation, nothing to be done. What RMS values do other 'scopes give? How does scrolling around affect them when there's not much on screen to work with?

[Fungus]

Looking at my screenshots: There seems to be more noise at the top of the yellow trace and more noise at the bottom of the blue trace. I wonder if that's what's skewing the numbers and making them bigger on channel 2.

[wraper]

The periodic RMS seems more accurate. This makes sense (it will look for a complete wave so it's less dependent on horizontal scroll position).

Anything else is interesting...  but nitpicking. Oscilloscopes are for looking at the shapes of things, not precise voltage measurements. Between 8-bit DACs and background noise you're never going to achieve more than about 10% accuracy.

So almost 50% higher RMS reading on second channel on your own screenshot is nitpicking? Someone (who that might be?) a while ago told that for some guys these are bad news about new firmware coming out.

[Fungus]

So almost 50% higher RMS reading on second channel on your own screenshot is nitpicking?

It's not 50% when you get a reasonable number of pulses on screen

It's never 50% on the "Per.VRMS" reading.

[wraper]

So almost 50% higher RMS reading on second channel on your own screenshot is nitpicking?

It's not 50% when you get a reasonable number of pulses on screen

It's never 50% on the "Per.VRMS" reading.

Does it tell you how many pulses are reasonable enough so you can trust it?

[Assafl]

So almost 50% higher RMS reading on second channel on your own screenshot is nitpicking?

It's not 50% when you get a reasonable number of pulses on screen

It's never 50% on the "Per.VRMS" reading.

Does it tell you how many pulses are reasonable enough so you can trust it?

Reminds me of EE101 lab. First year in undergrad the lab supervisor made sure we would never trust a scope (or any other T&M) ever again. Simply spoken - until you understand exactly what the scope does everything it shows is meaningless. Everything. (This was mid 80's so this was Tek and HP scope days - none of this Rigol stuff).

In this specific instance I would assume an easy way to know if your RMS reading has stabilized is to add more cycles (change Timebase). At some point the VRMS would stabilize.

[Fungus]

Does it tell you how many pulses are reasonable enough so you can trust it?

No, but.... ummm... I can just twist the knob so there's loads of them on screen. 

(or use the Per.VRMS mode - it's better!)

[Fungus]

Reminds me of EE101 lab. First year in undergrad the lab supervisor made sure we would never trust a scope (or any other T&M) ever again. Simply spoken - until you understand exactly what the scope does everything it shows is meaningless. Everything. (This was mid 80's so this was Tek and HP scope days - none of this Rigol stuff).

Yep. We've just learned something new about how to use oscilloscopes properly.

(I assume this problem applies to other 'scopes as well - does anybody have a GoodWill DS1000B to try the same test...)

In this specific instance I would assume an easy way to know if your RMS reading has stabilized is to add more cycles (change Timebase). At some point the VRMS would stabilize.

It's not rocket science.

[Assafl]

Again, it's not THAT important but it is (to me) a sign that they are not taking things seriously, i can understand a spelling error, nobody's perfect, i can't understand not solving it because it is really so simple to fix.. and they are still not fixing or rather "fixing" other bugs and nuisances 'on the side'
so, i can't trust them...

+1. This is the issue exactly, and is not brand-specific. It's a matter of being able to have a reasonable amount of trust in the equipment. The manufacturer's failure to address little things makes you wonder what more important problems are being overlooked or ignored.

This sub-discussion about a spelling error is actually very good lesson to show non-English speakers about how the English speaking market treats spelling errors.
In countries where a spelling bee is a cultural icon, spelling is one of the fundamentals of trust. This lack of trust will continue to contaminate whatever Rigol is or will be doing right - until they resolve it.

The Japanese were able to resolve these issues only after creating USA marketing organizations that took over much of product management and the entirety of product marketing. Perhaps that is the next step in the evolution of Chinese T&M industry?

[wraper]

So almost 50% higher RMS reading on second channel on your own screenshot is nitpicking?

It's not 50% when you get a reasonable number of pulses on screen

It's never 50% on the "Per.VRMS" reading.

Does it tell you how many pulses are reasonable enough so you can trust it?

Reminds me of EE101 lab. First year in undergrad the lab supervisor made sure we would never trust a scope (or any other T&M) ever again. Simply spoken - until you understand exactly what the scope does everything it shows is meaningless. Everything.

And in this case it IS meaningless, because:

until you understand exactly what the scope does everything it shows is meaningless.

And you certainly don't know the mechanism how it gets it's RMS reading wrong.