Author Topic: EEVblog #933 - Keysight U1272A EMC Issue  (Read 146435 times)

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Offline dentaku

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #50 on: October 13, 2016, 02:07:39 pm »
Hmmm... A little unknown "EEVBlog blue" meter in the background?

It's not a secret anymore. Dave has posted quite some info in supporter's lounge section. You can buy membership or donate to his patreon to get access, or posting more than 1000 posts automatically gets you into that section.

He's talked about it more on the Amphour too. It looks nice and small.
 

Offline t-17

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #51 on: October 13, 2016, 02:33:50 pm »
Is there any reply from Keysight yet? I'm kind of dissapointed after buying one of these. Apparently I was wrong when I thought, "this Keysight multimeter will do the job and will have reliable readings".

I build, test and troubleshoot amateur radio stuff and now I don't know when and if I can reliably measure something with the meter anymore. That's unacceptable.

Thank you so much for bringing this to my attention! Looking forward to that explanation from Keysight.
 

Offline saturation

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #52 on: October 13, 2016, 04:32:54 pm »
Confirmed on both my 1272A.  You can worsen it by putting your hand on top of the dial.

No effect on Fluke 87V, 85III, 85, Agilent 1252A.

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Offline D3f1ant

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #53 on: October 13, 2016, 08:12:06 pm »
Enabling the lpf seems to reduce the effect considerably but not enough that I would have any practical faith in the current range anywhere other than a controlled environment.
« Last Edit: October 14, 2016, 01:29:44 am by D3f1ant »
 

Offline hdj80r

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #54 on: October 13, 2016, 08:49:57 pm »
I have a U1194A DC Clamp meter, and it also if affected on DC Amps.

It also gets affected when I transmit on a 0.5W hand held UHF CB radio anywhere near it. 
 

Offline EEVblog

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #55 on: October 13, 2016, 11:21:20 pm »
Is there any reply from Keysight yet?

Just that it's been passed onto R&D.
 
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Offline Brumby

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #56 on: October 14, 2016, 02:30:59 am »
Is there any reply from Keysight yet?

Just that it's been passed onto R&D.

Run & Duck?

Seems to be somewhat of an embarrassment and while some might discount the circumstances in which the issue is found, let's not forget that they aren't particularly bizarre or exceptional and they do have the ability to quite significantly affect readings - even when properly connected for current measurement.  Even if the readings given appear to be accurate, there's still going to be that niggling suspicion.
 

Offline blueskull

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #57 on: October 14, 2016, 02:40:46 am »
Run & Duck?

Seems to be somewhat of an embarrassment and while some might discount the circumstances in which the issue is found, let's not forget that they aren't particularly bizarre or exceptional and they do have the ability to quite significantly affect readings - even when properly connected for current measurement.  Even if the readings given appear to be accurate, there's still going to be that niggling suspicion.

Shit happens, but at least they did what they are supposed to do. Assuming they are really bad at crisis handling, they would have sent Dave a C&D letter or a $100k check. That's called really bad crisis handling.
« Last Edit: October 14, 2016, 03:05:12 am by blueskull »
 

Offline Brumby

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #58 on: October 14, 2016, 03:02:44 am »
A business like Keysight doesn't get to live long and prosper by accident.  They certainly would have a good handle on crisis management - but I wouldn't put this issue quite at that level.  Not yet, at least.

As for them taking the correct action, there are still some stages to go before that call can be made - but, certainly, their initial response is what would be expected.


I might go so far as to say that Keysight might actually be happy with the disclosure - especially here - as it provides an objective and open discussion from a relevant cross section of their end-users.  Clarity of the issue through informed reports and discussion means the topic is less likely to spiral off into journalistic sensationalism.

From what has been posted already, I see there are at least three other benefits for having members here report on their experiences....
1. The issue is consistent across many units
2. Different models have been identified as having the problem, so a common design element between them is a likely candidate for review.
3. Other models from Keysight have been shown to NOT have the problem - which means that Keysight's multimeter range has been demonstrably shown to have the problem in a limited number of models.  So, if you're using one of their meters that is not on the naughty list, you can continue using it with confidence.
 

Offline Faith

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #59 on: October 14, 2016, 03:04:08 am »
Haha. These kind of issues do take a little bit of time to investigate.

I think it's more worthwhile to wait a while longer for a definite answer, solution and remedial action plan, than for some half-baked pie which could turn our tummies upside-down.

This issue has after all been around for almost five years, what's another week or two >,<"...

Still though, a quick "repo successful, we are investigating now" would be nice!

/wave Keysight
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Offline omgfire

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #60 on: October 14, 2016, 09:18:17 am »
After Keysight released new U1282A, the old U1272A become not so great. Good timing. Reminds me of some other company though.
 

Offline EEVblog

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #61 on: October 14, 2016, 09:53:15 am »
As for them taking the correct action, there are still some stages to go before that call can be made - but, certainly, their initial response is what would be expected.

If I was the R&D engineer at Keysight that got passed this, I'd say I'd need at least a few days to look into it before giving initial comments. In fact I'd be hesitant to even comment back to management at all until I'd found the problem. How long that takes depends on Murphy and how many blind alleys you follow first.
Not that anything R&D says ever makes it to the public, there are many layers of filtering.
This isn't like the soldering incident where there was a clear production manufacturing issue they could respond publicly instantly with "Yep, that's a problem, we'll investigate it."
 

Offline aromring

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #62 on: October 14, 2016, 02:47:38 pm »
Dave, put this spooky meter next to the spooky radio from Mailbag #922 and you'll get one heck of a Halloween episode! ;)
Great minds discuss ideas.
Average minds discuss events.
Small minds discuss people.
 

Offline Brumby

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #63 on: October 14, 2016, 03:44:57 pm »
Not that anything R&D says ever makes it to the public, there are many layers of filtering.

A fundamental principle in play here.

Once the problem is identified, the action to be taken will be considered by those 'layers of filtering'.  This will include the formal announcement (or not) and any recall or repair campaigns.  Expect a lot of internal discussion - very little of which, if any, will ever see the light of day.

Like any business, managing the spin on anything is important to preserve the reputation of the organisation as much as possible while (hopefully) addressing the problem to the satisfaction of those affected.


Hopefully an answer will come - but patience will be required.
 

Offline f4eru

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #64 on: October 14, 2016, 05:55:53 pm »
Worthless? How do the readings look when you're actually measuring something, with and without the artificial presence of an antagonising signal?
Yes, an instrument you can't trust is worthless. Loss of time and money.
 

Offline Owen

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #65 on: October 14, 2016, 08:49:27 pm »
I can reproduce this on U1242C but only when sig gen is connected. Couldn't find any orientation where radiated emi would mess with the current measurements.

Using 5 MHz, 10 Vpp meter shows -24 mA on mA range and -90 mA on A range.  :-\

+1 on both U1272A with firmware 2.04. However it shows Daves behaviour when current AC+DC mode is selected. There's a safety service note for the u1272a when using ac+dc mode on DC voltage that dates back to november 2013: http://literature.cdn.keysight.com/litweb/pdf/U1272A-03-S.pdf ... They may have tweeked the current readings as well because the LPF mode is activated as standard as well.
 

Offline Richard Head

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #66 on: October 15, 2016, 08:29:36 pm »
One strategically placed bypass cap or a small RF shield I expect will solve the problem.
 

Offline alouko

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #67 on: October 16, 2016, 07:33:58 am »
I get exactly the same phenomenon with Dave's uCurrent.  5MHz square wave to either current input posts and there is full negative DC reading in the voltage output!  So I think it is a chopper opamp in U127x, too.  Possibly MAX4239 in that or a similar one.
 
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Offline FrankT

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #68 on: October 16, 2016, 08:00:04 am »
I had to check mine to see if this problem was going to effect me.  I set up a test measuring my 1mA reference, then ran a cable carrying a 10Mhz under the meter, (typical of my messy work space) and the reading changed.

That's really disappointing.  The U1272A is my only piece of "quality" test gear (all the rest is relatively cheap), and I've already had to return mine once after a recall.
 

Offline FrankBuss

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #69 on: October 16, 2016, 06:16:16 pm »
As you note the lower limit for radiated immunity is 80MHz (and applied from a distance). This test in the video is more like the conducted immunity test which might? be appropriate for the inputs of a meter, but would be applied with them in use not the synthetic case here. So its possible a solid compliance was found to the EN61326-1 but as this test falls outside of it the particular problem was missed. Standards don't cover everything!
As Dave shows in the video from 12:15, the main problem is not the conducted immunity, the meter has the problem even when the signal generator wires are only near it. Someone should send flodins a unit to test it according to the standard, would be interesting. And maybe someone should do the mobile phone test  :-DMM

The wire on top of the meter is already quite a strong field: much of the field should be in the few cm to the meter. So this is more like 1000 V/m compared to the 3 or 10 V/m test requirements. Still even the lower field showed some influence.
Right, 1000 V/m would be a lot, so probably within the standard. Still, all other meters Dave tested don't have this problem.
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Offline Dr.Trinity

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #70 on: October 16, 2016, 07:13:50 pm »
This is a very disturbing problem about these Keysight meters. It was confirmed on a few of our lab meters.
Thank you for making this evidence public.

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Offline TheAmmoniacal

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #71 on: October 16, 2016, 08:38:07 pm »
The problem is confirmed on my U1272A too, and it's pretty bad  :-[ that finally explains the times it's been acting up.
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Offline Dwaine

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #72 on: October 17, 2016, 06:50:20 am »
I have a U1194A DC Clamp meter, and it also if affected on DC Amps.

It also gets affected when I transmit on a 0.5W hand held UHF CB radio anywhere near it.

There is one test that I have not been able to reproduce with my U1272a unit.  I have three radios running 24/7.  One at 144.350mhz, 144.390mhz and 10.147.60 @ 50watts, 65watts and 100watts.  Readings are rock solid, no jumping.  Which is strange, I was expecting it to have a problem. 

Like my DC power supply 3005D, which shuts down when the 144.3xxmhz radios transmit.   :palm:

Maybe that's one area Dave could add more of in his videos.  Some addition RF interference testing of products.  :popcorn:
 

Offline Dwaine

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #73 on: October 17, 2016, 06:54:35 am »
Just adding to the list of affected devices.  My device has the latest firmware of 03.03 and has the LPF on by default.
 

Offline Mr_X

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Re: EEVblog #933 - Keysight U1272A EMC Issue
« Reply #74 on: October 17, 2016, 03:37:45 pm »
Hi,

I have tested this today on my U1273A and I saw the following when using a test signal being a 10 MHz
sine wave at 10 Vpp connected single ended to the amps jack.

-14 amps error when holding the palm of the hand on the dial with the fingers wrapped around the right side
of the instrument. There is definitely some antenna like behaviour going on!

 


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