EEVblog #933 - Keysight U1272A EMC Issue

[jashugan]

Also, if you watch at minute 3.15 more ore less, one Keysight multimeter is influenced by the common mode noise conducted on ANOTHER Keysight multimeter: Dave plug the banana jack on one multimeter, and the instrument on the left is influenced as well... It seems as a big common mode immunity issue..

[bernroth]

I wasn't expecting this issue being so huge 

[Faith]

I got word that Keysight are furiously working on this, but don't want to make a public statement until it's thoroughly investigated and the public response is vetted by their legal department 

/legal/PR

[Zbig]

Checking if my U1273A also has this issue is not a valid reason to get a signal generator.
Checking if my U1273A also has this issue is not a valid reason to get a signal generator.
Checking if my U1273A also has this issue is NOT a valid reason to get a signal generator.

I'm sorry, please ignore me...

[Berni]

Checking if my U1273A also has this issue is not a valid reason to get a signal generator.
Checking if my U1273A also has this issue is not a valid reason to get a signal generator.
Checking if my U1273A also has this issue is NOT a valid reason to get a signal generator.

I'm sorry, please ignore me...

We all know you are just saying that. I tested mine on a HP 8082A Pulse generator that goes up to 250 MHz square wave with 800ps rise times that i bought for 70 bucks on ebay(Sold as does not turn on but it just needed a new fuse).

[drussell]

Checking if my U1273A also has this issue is not a valid reason to get a signal generator.
Checking if my U1273A also has this issue is not a valid reason to get a signal generator.
Checking if my U1273A also has this issue is NOT a valid reason to get a signal generator.

LOL...  Well, a signal generator can certainly be a useful instrument to have but I'm sure you could cobble together a simple oscillator circuit that is suitable enough to use for this test.  Likely with parts from your junk box. 

[Zbig]

LOL...  Well, a signal generator can certainly be a useful instrument to have but I'm sure you could cobble together a simple oscillator circuit that is suitable enough to use for this test.  Likely with parts from your junk box. 

You mean actually building an electronic circuit as a part of this hobby? I don't know, seems strange... Just kidding, of course you're right

[nidlaX]

I would love to see a "Repair" video on this. 

[Neilm]

Depends what the pass/fail criteria are, performance criteria "C" requiring user interaction is considered a worse failure than "B" which is self recovering (Dave puts his preference the other way around in the video) and both are less desirable than performance criteria "A" where the device functions within specifications during the test. And we're not sure how the intensities dave shows in the video compare to the commercial immunities claimed in the U1272A manual.

The performance criteria for radiated and conducted immunity in IEC661326 is criteria A - perform within spec. I don't think there is a length limit on test leads for conducted tests. I know you don't need to do fast transients if the leads are less than 3m

[Keysight Technologies Rep]

Thanks to those on this thread for pointing out a potential EMC issue on the U1272A family of handheld multimeters. We have our best EMC technical experts at Keysight doing a deep dive to replicate the problem and determine its root cause. We expect them to complete the investigation within the week, and we’ll get back to the community on what we’ve found and any follow-up actions we may decide to take.

[tgetec]

Just to mention, my U1282A measures around 7Amps when fed with 16MHz square(almost) wave signal on the amps input with open ground. 
U1252B shows "0" in this test setup...like other branded DMMs.

[WackyGerman]

got the same issue with my Agilent U 1241B . When feeding 20 Vpp 10MHz Squarewave with Duty Cycle of 34 % it measures roundabout -9 A and when my hand is close to the multimeter it measures -11 A with open ground . The same issue when I feed the COM Jack . I should change my nickname to VoodooGerman perhaps 

[Keysight Technologies Rep]

Thanks again to the EEVblog and those on this thread who pointed out the EMC-related finding with Keysight’s U1272A family of digital multi-meters. Your input is very helpful and we value it. 
 
As mentioned in our earlier post, we asked our EMC technical experts to look into this – and they were able to replicate the symptom. Keysight engineers found the majority of U1272A measurement modes and ranges meet published specifications in the presence of an RF field, but the product is susceptible to RF fields in certain measurement modes.

You can significantly improve the immunity performance by using the U1272A’s low pass filter, especially during DC measurements. Based on the insight you provided, we are characterizing the accuracy of the U1272A’s performance in the presence of an RF field, and will revise the product’s data sheets accordingly. We will let you know via this blog when we have posted the revised datasheets on Keysight’s website.

For those of you who use a U1272A, please be aware that since we released firmware version 2.04 in 2013, you can independently configure the low pass filter for DC and DCAC measurement modes. You can refer to pages 131 through 133 in the U1272A product user guide for instructions and filter options.
 
And if you haven’t done so already, you can download the latest U1272A product firmware, Version 3.03, which was released in 2015. All firmware released since version 2.04 has the DC low pass filter turned “on” by default. To get the latest product updates as soon as they are available, sign up at myKeysight.
 
Again, we thank the EEVblog and everyone on this thread who have been involved in this productive conversation. This exchange reinforces Keysight’s belief in the important role your feedback and social media plays in improving product quality and increasing customer satisfaction.

[alouko]

You can significantly improve the immunity performance by using the U1272A’s low pass filter, especially during DC measurements. Based on the insight you provided, we are characterizing the accuracy of the U1272A’s performance in the presence of an RF field, and will revise the product’s data sheets accordingly. We will let you know via this blog when we have posted the revised datasheets on Keysight’s website.

Again, we thank the EEVblog and everyone on this thread who have been involved in this productive conversation. This exchange reinforces Keysight’s belief in the important role your feedback and social media plays in improving product quality and increasing customer satisfaction.

Please clarify, does this mean that:

• You are not fixing this, instead just documenting what crap your DMMs are?
• You think it is enough just to "improve the immunity performance" and still get faulty readings?
• Your other DMMs are really ok? 1281 and 1241 are affected, too.  Especially all 127Xs
• Remember, no other brands of DMMs, even cheap Chinese but yours were affected

Personally, I expect to get my U1273A fixed or replaced with a working DMM with similar features, not having to think and wonder whether it gives correct readings.

And, as you don't supply USB cables with these, how are we going to upgrade the FW?

[madires]

Yeah, a tad disappointing. You've bought a professional DMM with specific specs, some measurement modes are screwed in a RF environment and the response of the vendor is to down-spec the DMM. The low pass filter mitigates the issue. It's not a complete disaster and you can work around the issue, since you're aware if it. Still, this will nag me the next times I have to select the vendor for T&M devices.

[bernroth]

My U1272A with which I discovered the issue had the latest firmware 3.03. I did not modify the settings for the low-pass filter.

I expect the Keysight professionals to track down the problem and propose either a fix in software or hardware.
Modifying the specs is not an option. This must be a joke.....   

BTW: Why did you introduce the default LPF with a firmware update on that meter? Did you possibly had some issues with noise or incorrect readings when the LPF is turned off?

Currently Keysight meters are a NO-GO for me. Last week I bought a new Fluke 117 for one of my employees.

 

[dr.diesel]

Wow that is a very disappointing response.

[HighVoltage]

This Keysight reply is like a joke to me as well, that I would not have expected at all from Keysight.

If your experts have found the problem, why not explaining it here in detail.
May be there are some people here that would fix their own DMM hardware, if possible and if you explain how.
I think you should try again!
 

[FrankBuss]

This Keysight reply is like a joke to me as well, that I would not have expected at all from Keysight.

If your experts have found the problem, why not explaining it here in detail.

Where did he/she wrote that they found the problem? They "were able to replicate the symptom" and it "meets the published specifications". The only thing missing is the recommendation from the rep to buy a Fluke if you want a better DMM

[Neilm]

As mentioned in our earlier post, we asked our EMC technical experts to look into this – and they were able to replicate the symptom. Keysight engineers found the majority of U1272A measurement modes and ranges meet published specifications in the presence of an RF field, but the product is susceptible to RF fields in certain measurement modes.

Sounds like the meter wasn't tested correctly in the first place. I suppose it is possible a supposedly minor change could have had unforeseen consequences.

If I were them, I would be getting the original EMCed instrument out and testing to find if that is compliant.

You can significantly improve the immunity performance by using the U1272A’s low pass filter, especially during DC measurements. Based on the insight you provided, we are characterizing the accuracy of the U1272A’s performance in the presence of an RF field, and will revise the product’s data sheets accordingly. We will let you know via this blog when we have posted the revised datasheets on Keysight’s website.

If they want to still sell it in Europe, they will really have to almost destroy the specifications. For multi-meters to be CE marked, they have to meet IEC61326. The pass criteria is A - instrument remains within published specification. If it does not then they are not compliant and it should be withdrawn.

[FrankBuss]

If they want to still sell it in Europe, they will really have to almost destroy the specifications. For multi-meters to be CE marked, they have to meet IEC61326. The pass criteria is A - instrument remains within published specification. If it does not then they are not compliant and it should be withdrawn.

It probably meets all published specifications. The problem is that the electric field might be much stronger with the test Dave did, so only other brands and cheap Chinese multimeters can withstand it.

[TheSteve]

As someone with a significant amount of HP/Agilent/Keysight gear this is a pretty disappointing response to the problem.

[PA0PBZ]

It probably meets all published specifications.

Keysight engineers found the majority of U1272A measurement modes and ranges meet published specifications in the presence of an RF field...
...
...and will revise the product’s data sheets accordingly.

Volkswagon anyone?

[madires]

Keysight engineers found the majority of U1272A measurement modes and ranges meet published specifications in the presence of an RF field...
...
...and will revise the product’s data sheets accordingly.

Volkswagon anyone?

VW cheated on purpose. Keysight didn't, I'd assume.

[FrankBuss]

Right, I meant it probably meets the requirements of the RF field immunity test standards for all modes and ranges. I might be wrong, but if you read it carefully, what Keysight said was just that it doesn't always work in the presence of an RF field (I guess a strong field as tested by Dave was meant). So the meter sucks sometimes, but technically there is nothing wrong, no need to fix it. The datasheet gets an additional note that it doesn't work with very strong external electrical fields, case closed.

Dave, can you confirm that the Keysight Rep account is genuine? I have Keysight gear, too, a very nice DSO oscilloscope and wouldn't have expected such a solution. Or maybe Keysight could publish the analysis and the datasheet solution on their webpage.