EEVblog #133 - Dodgy Digikey Components

[alm]

Some were off by more than 1% IIRC, so I wouldn't put much trust in the markings. They aren't 10ohm, 0.1%, that's fairly certain. No one (except possibly Bourns) knows what they really are, so I would assume the worst, and not simply 10.13ohm 0.1% (or whatever the measured value was). Tempco can be anything, they could even be high TC resistors designed for TC compensation (if they make those in these sizes and values).

[Icchan]

This just shows how important testing can be even in small batches of components/products. But what I really liked in this episode was that this one had a real problem and to solve that, Dave showed many basic techniques for finding, measuring and solving the problem. An inportant lesson for any  EE out there

[E.L.Brown]

This is exactly why i check every single part with a tolerance rating below 1% when it arrives at my place 

If you want 0.1% or better , you want it for a reason . . .

Trust me - the extra 10 minutes are worth it !

[Psi]

This is exactly why i check every single part with a tolerance rating below 1% when it arrives at my place 

So you're trying to avoid the following...

Unbelievable that this little piece of junk could be such a big problem.

[EEVblog]

I ordered the same part from Digikey to build my own uCurrent, P/N: CRT0805-BY-10R0ELFCD-ND, date on my packaging is 16-Nov-2010.  I measured a couple of resistors in my batch using my Agilent U1253A and they were 10.12 and 10.13, so I suspect that the parts I have are from the same reel.

I haven't contacted Digikey, but will be interested to know the outcome of Dave's investigation.

Thanks for the confirmation. Yes, likely the exact same reel.

I now have the replacements and will measure when I get home.
They are the exact same type and part number, but Digikey have assured me they have tested them and they are within spec.

Bourns have also requested one of my uCurrent's so they can analyze further in their Taiwan facility, and the left-over parts I have too.
How that is going to help them is beyond me, they have a whole bloody reel of parts, and my uCurrent is irrelevant!

Dave.

[Jimmy]

How that is going to help them is beyond me

Maybe they will copy it and put it on the market

[Fraser]

Bourns have also requested one of my uCurrent's so they can analyze further in their Taiwan facility, and the left-over parts I have too.
How that is going to help them is beyond me, they have a whole bloody reel of parts, and my uCurrent is irrelevant!

Dave.

May be they want to fully understand the implications of their 'out of tolerance' component on your design and the work required to correct it.... Financial Compensation assessment  ? Canon had a major reliability problem with some Sony CCD chips that they used. They repaired my Camcorder when it was over 5 years old....Sony had to pick up all associated costs for all such repairs including postage and labour.

[allanw]

How that is going to help them is beyond me

Maybe they will copy it and put it on the market

Haha, that's easy enough to do already considering Dave has published full schematics and layout and even described the entire design process in a video.

[mikeselectricstuff]

Bourns have also requested one of my uCurrent's so they can analyze further in their Taiwan facility, and the left-over parts I have too.
How that is going to help them is beyond me, they have a whole bloody reel of parts, and my uCurrent is irrelevant!

Dave.

My guess is that it's standard procedure to look at the customer's design to eliminate the possibility that the  application is not causing problems running parts out of spec. Current-sensing R's can be subject to all kinds of abuse, and users won't necessarily understand the limitations of the parts they are using.
 They probably haven't looked at the ucurrent design in any detail.

As regards testing, for a test instrument like this, I'd suggest that the minimum production test really should check zero and full-scale accuracy on all 3 ranges, as apart from the unlikely chance of bad parts, more common things like bad solder joints, PCB faults and wrong components can easily happen.
A full functional test pretty much eliminates the need for testing parts, as any part issues will surface.

[EEVblog]

My guess is that it's standard procedure to look at the customer's design to eliminate the possibility that the  application is not causing problems running parts out of spec. Current-sensing R's can be subject to all kinds of abuse, and users won't necessarily understand the limitations of the parts they are using.

No need for that when Digikey have confirmed they have found reels that are out of spec.

As regards testing, for a test instrument like this, I'd suggest that the minimum production test really should check zero and full-scale accuracy on all 3 ranges, as apart from the unlikely chance of bad parts, more common things like bad solder joints, PCB faults and wrong components can easily happen.
A full functional test pretty much eliminates the need for testing parts, as any part issues will surface.

That's exactly what I do.

Dave.

[Neilm]

My guess is that it's standard procedure to look at the customer's design to eliminate the possibility that the  application is not causing problems running parts out of spec. Current-sensing R's can be subject to all kinds of abuse, and users won't necessarily understand the limitations of the parts they are using.

They will also check that the customers process has not caused any of the problems - for instance the soldering might have been done at too high a temperature, or been held at that temperature too long. I once had a problem with an IR transever - they would work in the factory but fail prematurely. After sending off the boards from both failed units and boards just assembled, the supply came back with the conclusion that the unit was being damaged by the assembly process, but for some reason some were fine, other were not. It turned out that the failed boards had been reworked to fix minor faults. When that happened a soldering iron was held above the transever - it focused the energy onto the detector and damaged it. The fix - ensure they were covered up prior to any rework.

As regards testing, for a test instrument like this, I'd suggest that the minimum production test really should check zero and full-scale accuracy on all 3 ranges, as apart from the unlikely chance of bad parts, more common things like bad solder joints, PCB faults and wrong components can easily happen.
A full functional test pretty much eliminates the need for testing parts, as any part issues will surface.

Assuming that it doesn't have a wierd error curve that puts it out mid range.

Neil

[mikeselectricstuff]

Assuming that it doesn't have a wierd error curve that puts it out mid range.
Neil

True, but assuming the design itself works OK, a manufacturing fault causing mid-point errors is pretty unlikely. Except possibly  a stability issue, e.g. oscillating under certain conditions. 

[Bored@Work]

When you give them the left-overs they have the evidence and you have nothing any more. And then suddenly the evidence disappears.

[Neilm]

When you give them the left-overs they have the evidence and you have nothing any more. And then suddenly the evidence disappears.

When I sent off the IR transceivers I got back a whole series of X-ray pictures showing the receiving circuit of the various devices. It was that which allowed us to work out what had happened – instances of boards that had not been reworked were substantially less than non-reworked.

Neil

[Mechatrommer]

sorry for bumping this. but i got reminded when eetimes emailed me. here the link to bulk resistivity test (but i'm not sure what they mean by bulk), i thought how to measure massive amount of resistors, but turned out not be like that. but might useful to others (might not), check the linked pdf, adios:

http://www.eetimes.com/design/test-and-measurement/4212791/Measuring-the-resistivity-of-bulk-materials?cid=NL_TestMeasurement&Ecosystem=test-and-measurement

[MBY]

Sorry to bump this thread once more. But I tried to watch episode 133 again but something has happened.  The #132 and #134 works, but it seems that the file for episode #133 is missing?

[EEVblog]

Wow, so it is, no idea why.
Fixed.

Dave.

[MBY]

Great! Good episodes is always worth watching at least twice!

[pascal_sweden]

Maybe that company has to change their name into Dodgykey