Author Topic: DS1054z Issue  (Read 10694 times)

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Offline blabla

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DS1054z Issue
« on: March 04, 2016, 06:28:44 PM »
Hello,

Long time lurker, first time poster. It's because of this place I got a ds1054z some time back and have just got around to start using it.

I'm trying to measure my 120v, 60hz mains. Yes, I'm aware of the safety risks involved. I'm using a probe with the ground pigtail removed since the scope's grounded. Probe and scope set to 10x

I have all 4 channels set to 50v/div and zero'd to the center of the screen. Vrms displayed below on all channels. With no inputs, 1/2 show ~2.8v and 3/4 show ~1.4v. I understand this is normal... sounds like its picking up 1-2 ADC counts noise. So far so good.

When I apply the probe to channel 1 (with the tip at hot/live wire) The vrms indicates (in order channel 1/2/3/4) 122/63/1.4/1.4.

When I move the probe to channel 2, I see 2.8/122/63/1.4. Channel 3 - 2.8/2.8/122/64. Channel 4 - 2.8/2.8/1.4/122

If I put two different probes in 1 and 2 (3/4 empty) both tied to the same hot, I get 122/138/64/1.4

I will say this - the "phantom" voltage is only shown on the vrms indicator. The waveforms are as they should be, flatline when theres no input, and ~340vpp sine when there is input. Is this some kind of side effect of measuring the same mains I'm powering the scope from, or is this a bug I've stumbled on? I'm leaning towards bug because the waveform  doesn't match the vrms indicator.
 

Offline blabla

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Re: DS1054z Issue
« Reply #1 on: March 04, 2016, 06:30:14 PM »
Oh, and I'm running what I believe to be the latest firmware through the rigol link I found on here, 00.04.03.sp2.
 

Offline Karel

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Re: DS1054z Issue
« Reply #2 on: March 04, 2016, 06:36:24 PM »
I'm trying to measure my 120v, 60hz mains.

Don't do that without a special isolation transformer.

Yes, I'm aware of the safety risks involved.

Apparently you aren't.

If you want to measure mains voltage in a safe, reliable and repeatable way, use something like this:

http://www.yuanxing.net/1-2-1.asp

The difference between theory and practice is less in theory than
the difference between theory and practice in practice.
Expensive tools cannot compensate for lack of experience.
 

Offline tautech

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Re: DS1054z Issue
« Reply #3 on: March 04, 2016, 07:26:09 PM »
So it would appear that you've got all channels active while you're doing this, right?

Channel crosstalk would be the suspect in my book.
Check the manufacturers specs, there should be a spec for this.
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Offline blabla

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Re: DS1054z Issue
« Reply #4 on: March 04, 2016, 07:39:40 PM »
When I first noticed this, I was just using channels 3/4. 1/2 were not active. I only activated all at the same time after attempting to narrow things down and moving the probe bnc connector around.

Crosstalk... hmm, that would happen at the analog / input stage right? If so I imagine that would effect both the picture waveform and the numeric vrms indicator, not just the indicator.
 

Offline tautech

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Re: DS1054z Issue
« Reply #5 on: March 04, 2016, 07:51:03 PM »
When I first noticed this, I was just using channels 3/4. 1/2 were not active. I only activated all at the same time after attempting to narrow things down and moving the probe bnc connector around.
What do you mean by this? ^^^  :-//

Quote
Crosstalk... hmm, that would happen at the analog / input stage right? If so I imagine that would effect both the picture waveform and the numeric vrms indicator, not just the indicator.

Technically crosstalk can affect any adjacent signal path.
Where it might or might not originate from is really immaterial.

Again, check the specs, or don't Rigol publish them?
Avid Rabid Hobbyist & NZ Siglent Distributor
 

Offline Performa01

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Re: DS1054z Issue
« Reply #6 on: March 04, 2016, 08:17:03 PM »
No need to speculate about crosstalk in this case. It never can be nearly that bad, particularly not at low frequencies.

The obvious bug is the mismatch between waveform display and automatic measurement. maybe you could provide a screenshot or two to illustrate the issue?

What about lower voltages? Is the behavior the same or is it just an issue with the highest attenuator setting (50V/div)?

If a bug like this actually exists in this scope, then I really wonder how it can be that nobody has stumbled across it yet...
 

Online ebastler

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Re: DS1054z Issue
« Reply #7 on: March 04, 2016, 08:53:12 PM »
No need to speculate about crosstalk in this case. It never can be nearly that bad, particularly not at low frequencies.

The obvious bug is the mismatch between waveform display and automatic measurement. maybe you could provide a screenshot or two to illustrate the issue?

What about lower voltages? Is the behavior the same or is it just an issue with the highest attenuator setting (50V/div)?

If a bug like this actually exists in this scope, then I really wonder how it can be that nobody has stumbled across it yet...

Agree, the decribed mismatch between the curve display and the measurement (Vrms) is the real issue here. Very surprising too -- so far, I was convinced that the measurements are derived from the screen memory, and should hence be consistent. I would love to see a screenshot illustrating the issue!
 

Offline blabla

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Re: DS1054z Issue
« Reply #8 on: March 05, 2016, 01:13:54 PM »
Here we are. I moved the zero of each channel so you can see them easier. I tried getting the vrms indicators to show up in order but I couldn't, so just note they are in order of 1/3/4/2 but the channels are in order of 1/2/3/4 top to bottom. This is with the probe plugged into channel 1, 2/3/4 have nothing connected.
« Last Edit: March 05, 2016, 01:16:41 PM by blabla »
 

Offline blabla

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Re: DS1054z Issue
« Reply #9 on: March 05, 2016, 01:23:22 PM »
Here's two more. This time there is a probe in both 1 and 2, measuring the same mains at same point. First image is with channels in same position as inital screenshot. Second is with 1 and 2 at same zero point. Notice the curves overlap as you would expect, but vrms is different.
 

Offline markone

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Re: DS1054z Issue
« Reply #10 on: March 05, 2016, 01:36:15 PM »
Here we are. I moved the zero of each channel so you can see them easier. I tried getting the vrms indicators to show up in order but I couldn't, so just note they are in order of 1/3/4/2 but the channels are in order of 1/2/3/4 top to bottom. This is with the probe plugged into channel 1, 2/3/4 have nothing connected.

Could you confirm you are not a troll ? ( no offense intended ;) )
Sorry ... but i have to ask, what are you showing seems weird to say the least.

Anyway, for what is worth, have you tried to "short tap" the unused channels ?
 

Offline blabla

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Re: DS1054z Issue
« Reply #11 on: March 05, 2016, 01:47:43 PM »
Lol. No troll here. Although I'm troll-like, short and hairy. Does that count?  :P

What does short-tap mean? Tie the probe tip to ground? If so, it leads to the same result. I tied probe1 to mains, shorted probe 2, and screenshot looks same as first.

I also noticed just now.. With only channel 1 on mains, if all the v/div are set to 50, you see what you do in the screenshots. If I set channel 1 to 20, channel 2 reads 231vrms. If I set it to 100, it reads 64vrms.
 

Offline markone

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Re: DS1054z Issue
« Reply #12 on: March 05, 2016, 02:13:41 PM »
What does short-tap mean? Tie the probe tip to ground?

Yep, but setting them to 1:1 .

Of course you know that if your scope miss earth ground connection with this kind of connections the whole experience could become "unpleasant" ;)
 

Offline alsetalokin4017

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Re: DS1054z Issue
« Reply #13 on: March 05, 2016, 02:43:07 PM »
Wow. These 64vrms readings on channels that aren't even supposed to be getting a signal -- that's disturbing all right.

I'm unwilling to try to replicate this one on my scope because... well, because of the safety issue for one thing but also because I'm afraid of what I might see.

The easiest person to fool is yourself. -- Richard Feynman
 

Offline Mechatrommer

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Re: DS1054z Issue
« Reply #14 on: March 05, 2016, 02:52:13 PM »
Here we are.
report it to rigol its a software bug. signal shows nothing but measurement says something... that "software crosstalk" is weird.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline alsetalokin4017

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Re: DS1054z Issue
« Reply #15 on: March 05, 2016, 03:13:40 PM »
Well... this is as far as I'm willing to go. 60Hz in from my cheapo DDSFG cranked up all the way. Signal in to CH1, CH2, CH3 and CH4 in succession. Channels set to 10x even though I'm making a direct connection from the FG, so the displayed voltages are higher than the actual 15 v p-p being supplied.

So this bug is definitely here on my scope too. The next channel in sequence shows about 1/2 the RMS value of the actual channel receiving the signal, except when signal is in to CH4. And it's not necessary to use the mains as input to reproduce this bug.

With slower timebase settings the value of the "wrong" channel rms voltage goes up (5th screenshot below).
 
Selecting "GND" for the "wrong" channel input coupling has no effect on the spurious RMS voltage indication, it's still there. (Not shown in my shots but you get the idea.)

Yes, this is definitely one to report to Rigol. Does anyone have the earlier (SP1) software, to check if this bug is present there too?



The easiest person to fool is yourself. -- Richard Feynman
 

Offline blabla

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Re: DS1054z Issue
« Reply #16 on: March 05, 2016, 03:19:42 PM »
Sweet! Thankyou for your efforts alsetalokin4017. Does Dave read this? I bet if he can get his Rigol contacts to look at it that would get a faster result.
 

Offline alsetalokin4017

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Re: DS1054z Issue
« Reply #17 on: March 05, 2016, 03:28:00 PM »
You're welcome. I've been having lots of fun discovering and documenting bugs on this great little scope. (It truly is, but the bugs can be annoying...putting it mildly.)

The problem exists at different frequencies, voltage settings, and waveforms, and even when the "wrong" channel is set to GND input coupling.

The easiest person to fool is yourself. -- Richard Feynman
 

Offline blabla

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Re: DS1054z Issue
« Reply #18 on: March 05, 2016, 03:32:25 PM »
Good to know. It seems whatever algorithm they use to calculate the vrms references (channel-1) variable instead of its own variable. From what I've fooled with it seems to only do it on vrms, not the other measurements.
 

Online TheSteve

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Re: DS1054z Issue
« Reply #19 on: March 05, 2016, 04:15:18 PM »
I don't believe I am able to replicate this on my DS1074Z-S.

I am running one rev back from the newest firmware - 00.04.03.01.05

When was the last time you performed a self calibration?

edit - in my original pic I don't have channels 2/3/4 grounded. I redid it with them set to ground and you can see a slightly elevated voltage on ch2 - but it is pretty minor. If I need to try different parameters just let me know.
« Last Edit: March 05, 2016, 04:20:04 PM by TheSteve »
VE7FM
 

Online vk6zgo

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Re: DS1054z Issue
« Reply #20 on: March 05, 2016, 04:23:47 PM »
I'm trying to measure my 120v, 60hz mains.

Don't do that without a special isolation transformer.

Yes, I'm aware of the safety risks involved.

Apparently you aren't.

If you want to measure mains voltage in a safe, reliable and repeatable way, use something like this:

http://www.yuanxing.net/1-2-1.asp

The OP  is not connecting the probe ground clip to anything,& is in fact,removing the ground lead entirely,relying upon the Oscilloscope's earthing via its power cord to provide the return path.

This method is quite safe,providing certain sensible precautions are taken,

(1) Clip the probe onto the Active connection with the power at the socket off,step away from the connection,then turn the power on.
In countries which don't have switches,read this as plugging the power cord in----in any case,it is a good idea to  leave the power lead unplugged,until you are ready.

(2)Following your test,switch off, the Mains supply to the point your probe is clipped to,before touching anything.


Experienced Techs working on linear power supplies in equipment,often "have a look" at the incoming Mains to the device,just  to check it is there.

One side of the transformer primary should show 120v/230v w.r.t earth,the other side.maybe a few volts.

If both sides show 120/230v,the Neutral connection is broken,if they both say "a few volts" the Active is broken.

If both say "zero" both sides of the Mains are missing.
 

Offline _Wim_

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Re: DS1054z Issue
« Reply #21 on: March 05, 2016, 06:05:18 PM »
Hi,

I had a try on mine, and cannot reproduce this (still running of SP1). I connected my Rigol DG1032Z to the DS1054Z, one time grounded (with bnc cable, see screenshot 1), and one time floating (with red clip only of a bnc to clip cable, see screenshot 3).
 

Offline blabla

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Re: DS1054z Issue
« Reply #22 on: March 05, 2016, 06:13:52 PM »
Wim, do you still have the sp1 firmware file? If so, please post. I'd like to try older version to see if bug follows it.

TheSteve - does the -S series use the same firmware as the non-S series? If not, then it may not be effected.
 

Online ebastler

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Re: DS1054z Issue
« Reply #23 on: March 05, 2016, 06:19:30 PM »
Unfortunately Rigol prevents "downgrading" the firmware to an older version. There has been a thread about this on the forum. It seemed to be possible to downgrade with a very early bootloader version in early models of the DS1074Z, but not with any of the more recent bootloader versions.
 

Offline blabla

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Re: DS1054z Issue
« Reply #24 on: March 05, 2016, 06:23:48 PM »
Thanks for the heads up. I'd still like to have the file to fiddle with.
 


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