New Rigol DS1054Z oscilloscope

[2N3055]

Well, I don't know if this was mentioned before  but found out few new clues...

First, when you disable channels, measurement is still visible for the channel that is trigger source... you change trigger source, it follows enabling measurement for that chn, even with no trace on screen..

Second, I'm definitely seeing something else weird..
If I put vertical to highest sensitivity (10mV/div with 10x probe) and enable only CH2 or CH3, they have an offset of 3-4 mV on that scale (0,3-0,4 of div)..
If I enable channels next to it, offset goes AWAY.. but if I enable CH2 and CH4, I can still see offset on CH2 , unless ... I move trigger source from CH1 to CH4 and then it works in differnet channel configs...
Basically , I guess measurement errors are connected with these offset errors..
It's a combination of enabled channels and trigger sources...

I think this should be enough info for Rigol to know where to look for in the code... And they definitely should...

[hammy]

... they have an offset of 3-4 mV on that scale (0,3-0,4 of div) ...

Well, an Oscilloscope isn't made to measure voltages. It's made to show you voltage characteristics.

Cheers
hammy

[2N3055]

... they have an offset of 3-4 mV on that scale (0,3-0,4 of div) ...

Well, an Oscilloscope isn't made to measure voltages. It's made to show you voltage characteristics.

Cheers
hammy

Hammy, thanks for you trying to help, but let me explain: you probably didn't understand me properly...

So let me explain it further:

1. Hardware offset on channels is actually very low - on the level of 200 uV on my scope ... and is very consistent on ALL channels..
2. What I was referring to was artificial software induced offset on both trace and measurements that happens when enabling weird combinations of channels...
3. Since trace display offset happens in a similar patterns as measurements bugs, I propose there could be a link between those two anomalies.. Especially when we know measurements are taking data from screen data...

I would like that Rigol finds a bug and fixes it.. It's a stupid software annoyance on a otherwise solid and very good instrument...

Anyways nice to hear from you.   For the record, I'we been tinkering with soldering iron since elementary school.. and that was some 40 years ago  ..
I know how to use scope for quite some time, and I do measure voltage with my 6.5 digit voltmeter when I need precision..
But you don't know that so I thank you for you just being friendly and trying to teach me..
Please correct me any time if I don't make sense in the future too....

All the best,
Sinisa

[hammy]

I know how to use scope for quite some time, and I do measure voltage with my 6.5 digit voltmeter when I need precision..
But you don't know that so I thank you for you just being friendly and trying to teach me..
Please correct me any time if I don't make sense in the future too....

No offense intended! 
I see your point ...

[2N3055]

I know how to use scope for quite some time, and I do measure voltage with my 6.5 digit voltmeter when I need precision..
But you don't know that so I thank you for you just being friendly and trying to teach me..
Please correct me any time if I don't make sense in the future too....

No offense intended! 
I see your point ...

Nice to meet you... Take care Hammy!!

[alsetalokin4017]

You did it correctly. When you "delete" number 3, it's just grayed out. If you add the same one again, it's just re-enabled in the same location. If, instead, a new one is enabled, then the others shift to replace the grayed out ones and the new one is added at the end. I guess you could call the behaviors enable/disable/replace -- no delete.

Don't forget about the "Sel. Item" (select item) in Measure. This adds a bit more flexibility in what Measurements are displayed. But they still act like kind of a 'shift register' where new ones are added on the right and once you have 5, then the next (6th) one pushes the first one off to the left, and so on, so you always have the last five measurements chosen, but you can select from the last 5 items chosen in Sel. Item. Then when you are using Large or ExtraLarge fonts, you can display only three or two of the last 5 chosen, as selected in Sel. Item.

[Assafl]

... they have an offset of 3-4 mV on that scale (0,3-0,4 of div) ...

Well, an Oscilloscope isn't made to measure voltages. It's made to show you voltage characteristics.

Cheers
hammy

An Oscilloscope measures voltage vs. time. So an oscilloscope BY IT'S DEFINITION is made to measure voltage.

Perhaps you mean "an oscilloscope isn't meant to measure voltage (nor time, FWIW) to a high degree of accuracy, precision and resolution."; That, I think, few will argue.

But here is a screenshot I sent to Rigol (and got no reply ) . All three channels are connected to the compensation terminal, are all identical probes, etc. The only difference is V/div. This is more than a 400% mistake. Does that fall under the definition of "precision" or "accuracy"? I don't think so. I call this a Bug.

 

[Gabri74]

How do I completely clear a measurement? I was trying to set my scope to duplicate some of the setups here and if I pressed the wrong measurement, I can't figure out how to make it go away completely. If I delete it, it stays grayed out and a new measurement will just be added.

Long-pressing the 'Measure' button clears all the measures :-)

[2N3055]

Long-pressing the 'Measure' button clears all the measures :-)

LOL as soon I get to lab I'm gonna try it... Epic...

[metrologist]

But here is a screenshot I sent to Rigol (and got no reply ) . All three channels are connected to the compensation terminal, are all identical probes, etc. The only difference is V/div. This is more than a 400% mistake. Does that fall under the definition of "precision" or "accuracy"? I don't think so. I call this a Bug.

The scope specs are rated full scale. If I had a 160V full scale panel meter and fed it 3V, how much absolute error would you expect on that voltage reading? Then it's digital 8 bit with a resolution of 1 bit and consider there is real analog noise, what voltage range are we talking now? Now take that figure and perform some floating point math and see where we are.

I'm not saying the scope is right, but I also think we should keep some things in perspective.

I'm not saying I'm an expert either, but is anything in my screenshot out of spec?

[metrologist]

Long-pressing the 'Measure' button clears all the measures :-)

LOL as soon I get to lab I'm gonna try it... Epic...

I read that in the manual now, press and hold measure to clear all measurements. But if you enable one (I enabled the last one), they all come back grayed out, except the last one enabled. The same thing if I use the All Items Delete button. So how do I get rid of them all and just enable only one again, without excess grayed out clutter coming back?

[MarkF]

Long-pressing the 'Measure' button clears all the measures :-)

LOL as soon I get to lab I'm gonna try it... Epic...

I read that in the manual now, press and hold measure to clear all measurements. But if you enable one (I enabled the last one), they all come back grayed out, except the last one enabled. The same thing if I use the All Items Delete button. So how do I get rid of them all and just enable only one again, without excess grayed out clutter coming back?

It's even worse if you select the Large or Extra Large text.  It will only display the first 4 or 2 respectively.  I find there is no way to get one of the off screen measurements to display in the larger text.  Even if measurement is grayed and deleted.

[metrologist]

I found two options, default the scope, or turn them off and cycle power.

BTW, this signal has some jitter and the voltage spikes you see are real. Vrms seems off. 

[David Hess]

But here is a screenshot I sent to Rigol (and got no reply ) . All three channels are connected to the compensation terminal, are all identical probes, etc. The only difference is V/div. This is more than a 400% mistake. Does that fall under the definition of "precision" or "accuracy"? I don't think so. I call this a Bug.

It is a bug but more serious than the related measurement bugs.  But I would consider the ground coupling display a bug (or a lie) also.

The way I remember it, these Rigol DSOs make their measurements on the display record instead of the acquisition record leading to some odd behaviors like the measurements changing depending on the position control or magnification.  Using the display record sort of makes sense when multiple acquisition records are processed to produce it since this allows high record acquisition rates but it does not surprise me that this creates problems.

Does changing the positioning or magnification have any effect?  What about the record length?

[Fungus]

BTW, this signal has some jitter and the voltage spikes you see are real. Vrms seems off. 

What happens if you look at "Per.RMS" instead or put a decent number of waveforms on screen?

[metrologist]

BTW, this signal has some jitter and the voltage spikes you see are real. Vrms seems off. 

What happens if you look at "Per.RMS" instead or put a decent number of waveforms on screen?

I'll try per. RMS, but increasing waveforms had little effect. I used this screenshot so the voltage spikes could be seen.

[TurboTom]

It seems your test signal has pretty much DC offset so the RMS value could very well be correct.

You may try to use AC input coupling for comparison.

[JPortici]

But here is a screenshot I sent to Rigol (and got no reply ) . All three channels are connected to the compensation terminal, are all identical probes, etc. The only difference is V/div. This is more than a 400% mistake. Does that fall under the definition of "precision" or "accuracy"? I don't think so. I call this a Bug.

The scope specs are rated full scale. If I had a 160V full scale panel meter and fed it 3V, how much absolute error would you expect on that voltage reading? Then it's digital 8 bit with a resolution of 1 bit and consider there is real analog noise, what voltage range are we talking now? Now take that figure and perform some floating point math and see where we are.

I'm not saying the scope is right, but I also think we should keep some things in perspective.

I'm not saying I'm an expert either, but is anything in my screenshot out of spec?

If you didn't notice, CH2 and CH3 are set to the same V/div.. CH3 also seems to have a slightly higher offset and yet CH2 reading is 4-5 times higher

[Assafl]

In my post both channels 2 & 3 had the same scale and same input (and settings). Yet one showed 12v RMS and one showed around 2v RMS.

I could do the same with channels 3. & 4 by triggering on channel 2. All channels seem to measure and even calculate correctly. Except if the trigger is set to the preceding channel.

Reeks of a SW bug. Easy to get around as well by just using every other channel (eg ch 1 and 3).

[metrologist]

I understand what you folks are saying, but is the number outside the specification? I showed that the same measurement set up more reasonably is within spec. It's the same signal and same measurement.

If you take your trusty high accuracy DVMs and feed them 0.01 volts and have it set to a 100+V range, are you going to complain if one meter says 0.01 and another is 400% off (0.04)?

I totally understand that it is a software bug and could be fixed, but if both channels were closer in value yet still just as far off, then what? It's in spec! (I think anyway...)

[bitseeker]

Almost sounds like someone started counting from 0 in one part of the code and from 1 in another. Wouldn't be the first time I've seen or heard of that happening.

[2N3055]

I understand what you folks are saying, but is the number outside the specification? I showed that the same measurement set up more reasonably is within spec. It's the same signal and same measurement.

If you take your trusty high accuracy DVMs and feed them 0.01 volts and have it set to a 100+V range, are you going to complain if one meter says 0.01 and another is 400% off (0.04)?

I totally understand that it is a software bug and could be fixed, but if both channels were closer in value yet still just as far off, then what? It's in spec! (I think anyway...)

I think you're missing the point... I'l try to explain, because his example is too elaborate and confusing..

Try this:

(This is with 10X probes and channels set for them)

1. Set timebase to 100 uSec/div..
2. Enable CH1 and CH2, DC coupling, and trigger on CH1, setup trigger to 1.5V to have a stable trace..
3. Set VRMS measurement on both CH1 and CH2..
4. Plug in the probe ONLY to CH1 and connect it to CAL. DO not connect anything to CH2..
5. Set CH1 to 1V/div..
6. Set CH2 to20V/div..

On CH1 I get  2.07 VRms and on CH2 that has NOTHING connected I read 37. 9V VRms 
It gets even better... now disable CH1... it is still the same... Grounding the coupling or disconnecting the cable will make it go away...


This proves there is a spillover of data from CH1 to CH2 for VRMS... It measures about 10% less than CH1 in raw data, and multiplies that with vertical amplifier ratio.

This is not about how accurate is RMS algorithm and details like such... 
It is about the fact that CH2 is showing you data form ANOTHER channel while you don't have anything connected to it ... 

Another thing, Per Vrms is good only for periodic signals... You need this broken RMS for noise, DC and such...  So yeah I need this fixed...

Regards..

[metrologist]

I said I understood it was a bug, but what real world measurement fails for you, that is my point? It's a nice anecdote; however, if you were really measuring low-level DC or noise in the low mv range, who would be setting the scale to 160V?

Of course, I could be wrong and this is certainly a nuisance, but I've found it's best to use equipment in ways that enhance its performance rather than in ways magnify its weaknesses. That is true for anything.

BTW, I think in single channel mode, the performance of the scope is outstanding, and that is why I think this bug is nuisance, because it certainly need not be this way.

[Assafl]

I understand what you folks are saying, but is the number outside the specification? I showed that the same measurement set up more reasonably is within spec. It's the same signal and same measurement.

If you take your trusty high accuracy DVMs and feed them 0.01 volts and have it set to a 100+V range, are you going to complain if one meter says 0.01 and another is 400% off (0.04)?

I totally understand that it is a software bug and could be fixed, but if both channels were closer in value yet still just as far off, then what? It's in spec! (I think anyway...)

+4 digits Can be within spec on a DMM - especially a 4-5-6 digits one. That's least significant digit.

My example was 1 extra digit. But it was most significant digit. And channel 3 set up the same was perfect.

Also, in your example, DMM 1 would usually read higher than DMM 2 but still in spec. In the example channel 2 adds 10 most significant digits only because of CH1. In the same example setting CH1 to GND will get CH2 reading to go from 12 to 2 V RMS.

So no - it has nothing to do with ranges.

[2N3055]

I said I understood it was a bug, but what real world measurement fails for you, that is my point? It's a nice anecdote; however, if you were really measuring low-level DC or noise in the low mv range, who would be setting the scale to 160V?

Of course, I could be wrong and this is certainly a nuisance, but I've found it's best to use equipment in ways that enhance its performance rather than in ways magnify its weaknesses. That is true for anything.

BTW, I think in single channel mode, the performance of the scope is outstanding, and that is why I think this bug is nuisance, because it certainly need not be this way.

I don't know if you for some reason refuse to read what I wrote or you're making fun of me...

NO milivolts... Read again.. CH1 AND CH2 on 1V/DIV , probe connected only to CH1

NOTHING on CH2, disconnected, no probe connected...

RMS on CH1 2.07V, RMS on CH2 1.9V !!!

With nothing connected to the CH2 BNC.

CH2 with NOTHING connected to it measures cca 80%  of whatever you are measuring on CH1 ( not flecking micro-volts, but 80 %  of data from CH1.....)

That fails EVERY real world measurement criteria for that channel and particular RMS measurement.....

If I have NOTHING connected to CH2(no probe, BNC is empty), I can't have spillover from CH1  to CH2 of 1.9V RMS... That is 2 DIVs

But is a serious thing if you need RMS... I can just measure on CH2 and CH3 as a workaround but it is a serous flaw anyways.. And I didn't buy 4CH scope to use it as a 1CH...
I could have gone with 2CH DS2000 series with just a little more money but I needed 4CH for the  things I do...
So I want all channels to work normally.. Of course I will make do with it for the time being.. But it should be fixed eventually..

I don't want this to become an argument of a sorts. I'm persistent because you seem not to understand the problem, and despite your good will to help, you are talking about unconnected things..
I just want to untangle misunderstanding..

All the best..