Counterfeit LM34 temperature sensors.

[lmester]

I just got some LM34 temp. sensors from EBay. I tried them and got no output. Using a multimeter I found two junctions both with about .6v drop. What common component has two diode junctions in a three terminal device? I plugged it into my transistor tester. Yes, it's an NPN transistor with a gain of 150.

Looks like I got my first counterfeit part from china. Maybe counterfeit is not the right word. It's not a clone or copy of a legitimate part. It's a cheap transistor labeled as a more expensive LM34.

The good news is that I got a refund from the seller. The bad news is that they are still listing the part. Actually a search shows a number of different sellers offering it. Same photo in the listing but from different sellers.

After wasting a few weeks waiting for my parts I'll now order them again from a U.S. seller.

Attached are two pictures. The part with 38RB is the fake one. 521SP is a real one.

[dannyf]

I plugged it into my transistor tester. Yes, it's an NPN transistor with a gain of 150.

What would the transistor tester say if you plug in a real LM34?

don't put too much stock in the transistor tester.

[lmester]

I plugged it into my transistor tester. Yes, it's an NPN transistor with a gain of 150.

What would the transistor tester say if you plug in a real LM34?

don't put too much stock in the transistor tester.

The tester is one of those microcontroller based component testers. It identifies the component and shows the pinout. I'm not sure if I'd want to risk plugging in a real LM34.  At least not until I get some spares. The tester is current limited and shouldn't kill the lm34. When I get more I'll plug one in and see what it says.

Also, I did the same manual tests on a real LM34. I was using the diode test function on a multimeter. I saw more than just two junctions in the device. Various voltage drops between pins depending on which two pins and the polarity.

[Tomorokoshi]

Actually a search shows a number of different sellers offering it. Same photo in the listing but from different sellers.

That's a good flag that parts are counterfeit.

[uncle_bob]

Hi

There is a major industry out there re-labling parts. In some cases they do a really good job of it. In other cases ...not so much. The main targets are things that are a bit more complex (and rare / expensive) than a LM34.

Bob

[dannyf]

The tester is one of those microcontroller based component testers. It identifies the component and shows the pinout.

So?

The tester is current limited and shouldn't kill the lm34.

then nothing to worry about.

[wraper]

The tester is one of those microcontroller based component testers. It identifies the component and shows the pinout.

So?

The tester is current limited and shouldn't kill the lm34.

then nothing to worry about.

But what for? That part is obvious fake which does not work. They didn't even manage to properly make National semiconductor logo.

[wraper]

Looks like I got my first counterfeit part from china.

If you have bought operational amplifiers, voltage regulators, transistors, logic ICs  or electrolytic capacitors, very likely it's not first. Usually counterfeits work, just good enough to not spot it right away. I buy from China only those parts which are very hard to counterfeit like MCUs or parts which are unique enough that something else cannot be put inside and seem to work. Or those which are impossible to get by other means and then inspect/test them thoroughly.

[uncle_bob]

The tester is one of those microcontroller based component testers. It identifies the component and shows the pinout.

So?

The tester is current limited and shouldn't kill the lm34.

then nothing to worry about.

But what for? That part is obvious fake which does not work. They didn't even manage to properly make National semiconductor logo.

Hi

If you paid more for the fake, they would do a better job on the logo

I am amazed that there is enough money in a crime like this to make it worth doing.

Bob

[Tomorokoshi]

I am amazed that there is enough money in a crime like this to make it worth doing.

Bob

Here's something even more amazing:
http://www.asq.org/asd/2009/03/compliance/counterfeit-parts.pdf

See page 32!

[uncle_bob]

I am amazed that there is enough money in a crime like this to make it worth doing.

Bob

Here's something even more amazing:
http://www.asq.org/asd/2009/03/compliance/counterfeit-parts.pdf

See page 32!

Hi

With 0402's there likely is no "scrub and re-mark" involved. They just reel them up and send them out marked as 0.01 uf bypass caps. The sad part is that probably >80% of the parts actually are close enough to or greater than  0.01 uf. People put them on a board with lots of caps in parallel and don't even spot the problem after they have used them. The fact that they blow up in reflow *might* be a clue though ....Parts on the reel with six different color dielectrics in a row could also be a bit of a giveaway.

Crazy Stuff

Bob

[PartialDischarge]

I am amazed that there is enough money in a crime like this to make it worth doing.

Bob

Here's something even more amazing:
http://www.asq.org/asd/2009/03/compliance/counterfeit-parts.pdf

See page 32!

interesting link, did know about the counterfeit problem but wasnt aware of its magnitude... lately I just source everything from mouser.....except Linear Technology items which arent sold there!

[uncle_bob]

Hi

Even through very legit distributors, you can see fake stuff pop up. It's rare, but it does happen. *So far* everything that we've seen has been caught with quick / simple visual inspection. If these LM34s had come in from a major distributor ... we would not have caught them.  The pile of 0402 caps re-reeled ... yup we catch those.

Bob

[lmester]

The tester is one of those microcontroller based component testers. It identifies the component and shows the pinout.

So?

I guess you need a little more information. This tester is not the nearly worthless tester that you find on some multimeters. I've found that it does a good job of identifying components. It's intended to be used with simple two terminal parts like passive components or, three terminal devices like bipolar transistors triacs mosfets etc.  When you plug in something unusual it commonly shows it as an unknown or failed part. Sometimes it will identify it as a combination part like a BJT with a flyback diode across the collector and emitter. It's a useful test instrument. Very useful to me since I have a load of old no number or house numbered parts.  It's nice to be able to plug in a bunch of unknown transistors and quickly find their polarity and gain.

Also, there is a thread for this tester on the eevblog board.

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/

The tester is current limited and shouldn't kill the lm34.

then nothing to worry about.

I've been working with electronics for over 30 years. I've learned when to be cautious. I'm very cautious when I have no spares for a needed component.

I'm currently finishing the code for a  PIC 12F683 based temperature controller.  I'm at the point where I'm tweaking up the thermal response of the system. Without a working LM34 my tweaking will be on hold.  With my last LM34 on the breadboard, I'm being really careful with it.  I debated even testing the LM34 with my multimeter diode check function. Since I know that the multimeter diode check is limited to 1mA current and 3.5V open circuit voltage I decided that this was fairly safe.

Plugging my last LM34 into my transistor tester is an unknown.  I know that the tester has current limiting. No idea how much current or the open circuit voltage.

I should have some more LM34's in a day or so.  I'll then plug one into the tester and post the results.




Finally, back to the main point of this thread. The fake LM34.

As others have said, I'm also surprised that the Chinese would bother to make fake parts that sell for about $1.

Maybe low price fake parts are just a way to sneak past the EBay checks.  If you sell a few $500 fake parts every buyer will be complaining to EBay. With cheap parts normally bought by hobbyists, the buyer might just assume that they made a mistake and destroyed the part. The buyer also might not bother to get a refund or return for something that only cost a few dollars.

With a bunch of EBay sales like this you could make good money even on parts that only sell for a dollar!

[dannyf]

'I guess you need a little more information'

I was simply trying to tell you such testers are fallable, especially on more complex devices. The fact they misidentify your device, by itself, isn't sure sign of it being fake. For example you can try a tl431 or mk484 at the tester and see what I mean.

A better but still not 100 pct fool proof way is to compare it vs. A genuine lm34.

As to buying parts from places like eBay, you should assume them being fake unless proven otherwise.

[kandrey89]

Don't understand why you guys buy parts from ebay, that's like going to a flea market to buy refrigerators, microwaves, electronics, and furniture for a brand new house, the quality is questionable and there is no warranty of performance.

[uncle_bob]

Don't understand why you guys buy parts from ebay, that's like going to a flea market to buy refrigerators, microwaves, electronics, and furniture for a brand new house, the quality is questionable and there is no warranty of performance.

Hi

Maybe because the price (fully delivered) is <1% of what it is elsewhere ....

Bob

[chris_leyson]

Don't understand why you guys buy parts from ebay, that's like going to a flea market to buy refrigerators, microwaves, electronics, and furniture for a brand new house, the quality is questionable and there is no warranty of performance.

Exactly ! You can can buy the real part from Farnell, RS, Digikey, Mouser etc. At the end of the day it's just piss poor product design buying cheap shit from an unknown source with no traceability. And how many of these things are you building, one or two for hobby use or thousands. You got your fingers burnt, learn from your mistakes, don't buy cheap shit.

[uncle_bob]

Don't understand why you guys buy parts from ebay, that's like going to a flea market to buy refrigerators, microwaves, electronics, and furniture for a brand new house, the quality is questionable and there is no warranty of performance.

Exactly ! You can can buy the real part from Farnell, RS, Digikey, Mouser etc. At the end of the day it's just piss poor product design buying cheap shit from an unknown source with no traceability. And how many of these things are you building, one or two for hobby use or thousands. You got your fingers burnt, learn from your mistakes, don't buy cheap shit.

Hi

Ok, so when I can buy it new for $150,000 that should be the *only* approach I would consider. Buying something used for $150 should *never ever* be considered ...sorry, it just does not work that way on the planet I live on. There *always* is a cost consideration that trades off against the risk and the reward.

Bob

[Seekonk]

There are almost no real Chinese sellers on ebay.  They are mostly surrogates that lend their name to a seller with hopes that they will get a little cut.  Enough negatives they get kicked off ebay.  There are millions more to take their place.  That is why you can't ask a question, they have never seen the products they sell.  Many times I have been asked to close a case on ebay so they can correct the problem.  I am sure there is a good percentage of people that fall for that.  I don't have many problems with ebay.  The parts I buy are dirt cheap enough that they aren't worth faking.

[dannyf]

There are almost no real Chinese sellers on ebay.  They are mostly surrogates that lend their name to a seller with hopes that they will get a little cut.

The two don't seem to be mutually exclusive. For example, those surrogates can certainly be real Chinese sellers.

[dannyf]

I measured a bunch of voltage reference / regulators, all genuine.

TL431: as npn, hFE=0.
78L15: some as mosfet and some as unknown.
LD33: unknown.
AMS1117: mostly unknown. the low voltage ones came out as npn.

So basing your assessment of ICs on the tester isn't a terribly reliable way.

[M4trix]

My OCD gets worse when I open threads about counterfeits. Who can you trust these days ? 

[uncle_bob]

My OCD gets worse when I open threads about counterfeits. Who can you trust these days ? 

Hi

You need to do some level of visual inspection on your reels of parts. We have seen bad stuff come in from authorized distributors who only come up with :

Mumble ... mumble ... mumble ...

as a corrective action. It's rare with them, but it still does happen.

Bob

[wraper]

Hi

You need to do some level of visual inspection on your reels of parts. We have seen bad stuff come in from authorized distributors who only come up with :

Mumble ... mumble ... mumble ...

as a corrective action. It's rare with them, but it still does happen.

Bob

As you said you would not spot this one bot spot supposedly fake capacitors IMO there could be something wrong with your criteria. Because if I see such LM34 for a moment, I will suspect a fake right away (wrong case, wrong marking). What particular capacitors (manufacturer) you suspected to be fake and what particularly was wrong with them?