EEVblog #933 - Keysight U1272A EMC Issue

[Kas.Lewis]

My scope is not IP67 rated, my DMM is... And for the record Keysight conceded that this was enough of an issue that they would take the unit back to do a thorough cleaning and recalibration.

Kas

[eliocor]

ever heard of Triboelectric effect? https://en.wikipedia.org/wiki/Triboelectric_effect or electrostatic charge?

[aXit]

Got my replacement today. Never had a tracking number sent to me, just the initial 'we will process your request' email 2 weeks ago.

I chose the new u1272a, there wasn't a USB adaptor in the box. I'd forgotten how bright the orange was on these meters, especially compared to the 5 years of grime on the other one. 

[HighVoltage]

I chose the new u1272a, there wasn't a USB adaptor in the box.

The USB adapter is only part of the U128xA series and when I got my U1282A replacement, it came with one.
 

[matkar]

Ask Keysight about the USB adapter. I believe they said they will provide one to everyone.
I also unexpectedly received my shipment yesterday after they have sent me the processing note about two weeks ago. I've chosen U1282A.

[wraper]

Ask Keysight about the USB adapter. I believe they said they will provide one to everyone.

That adapter was a separate shipment only for those who opted for U1272A before fixed version became available, so they can update the firmware to somewhat reduce the problem before fixed meter arrives. U1282A comes with adapter as a standard package.

[bambadoo]

Asked for u1272a.. Got a response tonight.
They are sending me a u1280 ??
Also thought the USB converter would be shipped at first.
27 April:

Thank you for your response and for choosing the option to a U1270 series handheld digital multimeter. We will process your request based on the information you provided as listed below.

15 May:

We are pleased to informed that we had sent you a U1280 handheld digital multimeter from factory. This multimeter includes an enhancement for DC current measurement at noisy environment to help you achieve better results.

EDIT: But an u1272a arrived today 

[128er]

Asked for u1272a.. Got a response tonight.
They are sending me a u1280 ??
Also thought the USB converter would be shipped at first.
27 April:

Thank you for your response and for choosing the option to a U1270 series handheld digital multimeter. We will process your request based on the information you provided as listed below.

15 May:

We are pleased to informed that we had sent you a U1280 handheld digital multimeter from factory. This multimeter includes an enhancement for DC current measurement at noisy environment to help you achieve better results.

EDIT: But an u1272a arrived today 

You got what you asked for, right? 

Maybe they messed up the message from may 15th.

[komet]

I also received a U1282A today via DHL. Thumbs up to Keysight!

[rsjsouza]

I received a U1282A directly from Malaysia and it is certainly larger when compared to my U1273A. Overall it is a great meter, however I found it slower on the ohms autorange and it seems that it has a smaller current for the diode testing.

[agmbass]

I also received the U1282A  . Thanks Keysight !

[Electro Detective]

I complained and bitched so hard about all these bugs,     
demanding a meter for all seasons that actually worked, sick and tired of being someone's Beta Test Whipping Boy!!!   

Finally they got back to me, sending yet another new 'fixed' meter with a waiver form to sign upon delivery,
that the 'matter is now officially closed upon acceptance',
arriving in the mail soon.   

Apparently this time it's a Fluke.. 

[Zbig]

I complained and bitched so hard about all these bugs,     
demanding a meter for all seasons that actually worked, sick and tired of being someone's Beta Test Whipping Boy!!!   

Finally they got back to me, sending yet another new 'fixed' meter with a waiver form to sign upon delivery,
that the 'matter is now officially closed upon acceptance',
arriving in the mail soon.   

Apparently this time it's a Fluke.. 

There sure is quite a bit of emotion Could you please calmly elaborate what the actual issues you keep having are?

[Electro Detective]

I complained and bitched so hard about all these bugs,     
demanding a meter for all seasons that actually worked, sick and tired of being someone's Beta Test Whipping Boy!!!   

Finally they got back to me, sending yet another new 'fixed' meter with a waiver form to sign upon delivery,
that the 'matter is now officially closed upon acceptance',
arriving in the mail soon.   

Apparently this time it's a Fluke.. 

There sure is quite a bit of emotion Could you please calmly elaborate what the actual issues you keep having are?

No more orange meter issues, the Fluke is working fine 

[lowimpedance]

 



So a change of color did the trick ?.



 

[Electro Detective]

yes, it was a LEMON masquerading as an orange 

[HighVoltage]

I had one more U1273A that I had forgotten about and just today I received the replacement unit.
Thanks so much Keysight!

[lowimpedance]

yes, it was a LEMON masquerading as an orange 

If you would care to elaborate more on the 'bugs' you have found (apart from those already covered here) I'm sure many "lemon" owners would be most interested and indeed could perhaps be considered a safety issue and doing us a favor in sharing.
 I am actually curious what further issues remain, as so far in my lab situation at least I have not had any measurement issues yet but of course I have not used all the functional capabilities thus far either.

[Electro Detective]

I can't elaborate anything more than the same bugs as "those already covered here"

which was more than enough to test my patience, and run back to my eye candy challenged Fluke meters,

begging for forgiveness    

[bambadoo]

Anyone got a "tax and customs" bill from DHL when getting a new item from Keysight?
I got one at about 60USD.
Keysight tells me not to pay and they will fix it but payment due is tomorrow and I really dont like being late

Best Regards

[Sbampato12]

Anyone got a "tax and customs" bill from DHL when getting a new item from Keysight?
I got one at about 60USD.
Keysight tells me not to pay and they will fix it but payment due is tomorrow and I really dont like being late

Best Regards

I've paid for the USB cable. After paying I send an email, and they told me that if that happens again, to not pay until emailing them. But it doesn't happened again to me.

[HighVoltage]

I have received two instruments through DHL Express and never was bothered by the customs service, although this would be very typically in Germany.

[Mr. Scram]

Original Agilent mods complete , for now!.
Indeed it would have been interesting to know the design choice for the original specified parts, but I think that will be only speculated on. What we do have is what changes have been considered necessary to harden the spec for  EMI resistance.

 Out of curiosity I changed only BD4 and 5 first to a resistor value of 0.2 as per what values bernoth used and tested the EMI immunity with the result being now only a few milliamps indication on the display was shown when a 10Mhz 100mV signal was applied to the Amp terminal and this reading did not seem to change with activation of the LPF. So a considerable improvement in de sensitizing the current mode to external EMI but not quite there.
 So next was to change BD7 and R55 to both 2K4 . And now testing this complete mod shows no obvious EMI effect at the applied RF signal (or any stray effects when a hand is placed around and on the meter). Now its quite possible that more signal amplitude or different frequency may have a different outcome but for my uses I'm more than happy to leave it there with now two 1272's.
 I did test the ohms ranges and noted the CAL was still good with an input short. Both meters showed identical behavior when presented with a short in the ohms mode. I did note that the LSD on the old Agilent '72' in Current mode was sitting between 2 and 3 counts so perhaps a RE CAL of that function may be needed. Looking at the CAL. procedure it looks as if it maybe possible to do an individual function as opposed to the whole meter. Perhaps I'll give it a go sometime if I get motivated enough and will post here whether successful or not!.

Just to get this right: replacing two sets of resistors should fix the problem on afflicted multimeters? Has this affected the calibration in any noticeable way?

[lowimpedance]

There does appear to be some change in the ohms zero, and maybe a few digits in dc mA range. After testing on a Fluke 5500a calibrator the only function to be notably affected by the mod's would be the ohms.
I have done the ohms cal on the 'modded' meter and now the zero is indeed zero with a direct input short. Not entirely sure if the rest of the ranges needed cal as well besides the input short test, but I did them anyway.
 Need to test the replacement from Keysight under the same conditions to see what ohms reading it has with an Input short etc.
Pictures of testing and zero ohms input short after adjustment. (was 0.05 or thereabouts prior!).

edit : forgot to note the 3458a was for cross reference of the calibrators ohms output, to be sure you know  .

[Mr. Scram]

There does appear to be some change in the ohms zero, and maybe a few digits in dc mA range. After testing on a Fluke 5500a calibrator the only function to be notably affected by the mod's would be the ohms.
I have done the ohms cal on the 'modded' meter and now the zero is indeed zero with a direct input short. Not entirely sure if the rest of the ranges needed cal as well besides the input short test, but I did them anyway.
 Need to test the replacement from Keysight under the same conditions to see what ohms reading it has with an Input short etc.
Pictures of testing and zero ohms input short after adjustment. (was 0.015 or thereabouts prior!).

edit : forgot to note the 3458a was for cross reference of the calibrators ohms output, to be sure you know  .

Thanks! Just a few more questions, as it seems I might attempt a repair. Did you ever figure out whether you can calibrate just the ohms range? And if you replace the four resistors, might it be important to match the pairs somehow?