Counterfeit LM34 temperature sensors. - Page 1
Forum section: electronics / general

author: lmester
author_rank: Regular Contributor
timestamp: June 17, 2016, 10:45:48 am
content: 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.

author: dannyf
author_rank: Super Contributor
timestamp: June 17, 2016, 11:15:05 am
content: QuoteWhat would the transistor tester say if you plug in a real LM34?don't put too much stock in the transistor tester.

author: lmester
author_rank: Regular Contributor
timestamp: June 17, 2016, 11:34:44 am
content: Quote from: dannyf on June 17, 2016, 11:15:05 amThe 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.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: June 17, 2016, 12:21:46 pm
content: Quote from: lmester on June 17, 2016, 10:45:48 amThat's a good flag that parts are counterfeit.

author: uncle_bob
author_rank: Unknown
timestamp: June 17, 2016, 12:54:00 pm
content: HiThere 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

author: dannyf
author_rank: Super Contributor
timestamp: June 17, 2016, 12:54:50 pm
content: QuoteSo?Quotethen nothing to worry about.

author: wraper
author_rank: Unknown
timestamp: June 17, 2016, 01:03:14 pm
content: Quote from: dannyf on June 17, 2016, 12:54:50 pmBut what for? That part is obvious fake which does not work. They didn't even manage to properly make National semiconductor logo.

author: wraper
author_rank: Unknown
timestamp: June 17, 2016, 01:12:46 pm
content: Quote from: lmester on June 17, 2016, 10:45:48 amIf 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.

author: uncle_bob
author_rank: Unknown
timestamp: June 17, 2016, 01:13:48 pm
content: Quote from: wraper on June 17, 2016, 01:03:14 pmHiIf you paid more for the fake, they would do a better job on the logoI am amazed that there is enough money in a crime like this to make it worth doing.Bob

author: Tomorokoshi
author_rank: Super Contributor
timestamp: June 17, 2016, 01:22:58 pm
content: Quote from: uncle_bob on June 17, 2016, 01:13:48 pmHere's something even more amazing:http://www.asq.org/asd/2009/03/compliance/counterfeit-parts.pdfSee page 32!

author: uncle_bob
author_rank: Unknown
timestamp: June 17, 2016, 01:39:19 pm
content: Quote from: Tomorokoshi on June 17, 2016, 01:22:58 pmHiWith 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 StuffBob

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 17, 2016, 02:33:21 pm
content: Quote from: Tomorokoshi on June 17, 2016, 01:22:58 pminteresting 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!

author: uncle_bob
author_rank: Unknown
timestamp: June 17, 2016, 02:37:48 pm
content: HiEven 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

author: lmester
author_rank: Regular Contributor
timestamp: June 18, 2016, 06:53:06 am
content: Quote from: dannyf on June 17, 2016, 12:54:50 pmI'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!

author: dannyf
author_rank: Super Contributor
timestamp: June 18, 2016, 11:17:18 am
content: '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.

author: kandrey89
author_rank: Contributor
timestamp: June 18, 2016, 05:04:37 pm
content: 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.

author: uncle_bob
author_rank: Unknown
timestamp: June 18, 2016, 05:06:16 pm
content: Quote from: kandrey89 on June 18, 2016, 05:04:37 pmHiMaybe because the price (fully delivered) is <1% of what it is elsewhere ....Bob

author: chris_leyson
author_rank: Super Contributor
timestamp: June 18, 2016, 05:40:14 pm
content: QuoteExactly ! 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.

author: uncle_bob
author_rank: Unknown
timestamp: June 18, 2016, 06:17:03 pm
content: Quote from: chris_leyson on June 18, 2016, 05:40:14 pmHiOk, 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

author: Seekonk
author_rank: Super Contributor
timestamp: June 18, 2016, 07:28:13 pm
content: 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.

author: dannyf
author_rank: Super Contributor
timestamp: June 18, 2016, 07:37:46 pm
content: QuoteThe two don't seem to be mutually exclusive. For example, those surrogates can certainly be real Chinese sellers.

author: dannyf
author_rank: Super Contributor
timestamp: June 18, 2016, 08:02:04 pm
content: 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.

author: M4trix
author_rank: Frequent Contributor
timestamp: June 18, 2016, 08:05:07 pm
content: My OCD gets worse when I open threads about counterfeits. Who can you trust these days ?

author: uncle_bob
author_rank: Unknown
timestamp: June 18, 2016, 08:48:47 pm
content: Quote from: M4trix on June 18, 2016, 08:05:07 pmHiYou 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

author: wraper
author_rank: Unknown
timestamp: June 18, 2016, 09:05:50 pm
content: Quote from: uncle_bob on June 18, 2016, 08:48:47 pmAs 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?

author: uncle_bob
author_rank: Unknown
timestamp: June 18, 2016, 10:03:29 pm
content: Quote from: wraper on June 18, 2016, 09:05:50 pmHiSpecifically we have received:Reels of tantalum SMT caps that were fake rather than real. They were spotted by variations in the body shape.Reels of chip caps that were fake / wrong value. They were spotted as I have described by the variation in dielectric color between chips on the reel.Various reels that somehow got marked with the more expensive part number when they (from the part's marking) contained legitimate lower grade parts.The first two categories are most certainly counterfeits. They were verified as such by the vendors on each of the various batches that have come in. The third category does not seem to get quite as accurate a reply. The vendor says "yes they are our parts". There is then a finger pointing exercise about the labels.Lots of fun.Bob

author: M4trix
author_rank: Frequent Contributor
timestamp: June 18, 2016, 10:34:42 pm
content: Btw, @lmester, please link the ebay seller that sold those fake LM34 ! Those kinds of sellers should be exposed.

author: Rerouter
author_rank: Super Contributor
timestamp: June 18, 2016, 10:35:17 pm
content: Also from the original image there is spur left on the plastic casing, I have never seen such on a genuine part.

author: chris_leyson
author_rank: Super Contributor
timestamp: June 18, 2016, 10:55:28 pm
content: Hi BobAll I was saying was sort out your supply chain, maybe I was a bit harsh on the OP, but he learned, got his fingers burnt. It costs more to buy from the big suppliers but at the end of the day it saves money, how much would reworking a hundred PCBs cost compared to the saving when buying "bargain parts". These days you have to pay for peace of mind.

author: uncle_bob
author_rank: Unknown
timestamp: June 18, 2016, 11:04:26 pm
content: Quote from: chris_leyson on June 18, 2016, 10:55:28 pmHiGo to Mr Google and ask him for a list of the top 8 distributors by volume in the US. We've seen "stuff" from 4 of the 8 on the list. We don't do enough business with two of them to notice.Bob

author: JoeN
author_rank: Frequent Contributor
timestamp: June 19, 2016, 03:46:40 am
content: An interesting old story related to this topic:https://www.sparkfun.com/news/350https://www.sparkfun.com/news/395

author: wraper
author_rank: Unknown
timestamp: June 19, 2016, 06:36:48 am
content: Quote from: Rerouter on June 18, 2016, 10:35:17 pmDon't know about LM34 particularly. But is not something very uncommon to see on genuine parts. BTW that was some genuine transistor which got relabeled, it's not like they manufactured the part itself.

author: lmester
author_rank: Regular Contributor
timestamp: June 20, 2016, 07:02:11 am
content: Quote from: dannyf on June 18, 2016, 08:02:04 pmI'm sorry, now I see what you're talking about. I've used the tester to identify the parts that it was intended to test, transistors diodes caps etc...I tested a bunch of complex IC components including some old 7400 series IC's from my junk box. Testing various combinations of three pins of a 7411 AND gate gave some interesting results. Most combinations listed it as an unknown component. One gave a result as a pair of diodes.You now had me wondering if this fake part is really an NPN transistor. I decided to do some more tests. My curve tracer would be a good choice. Unfortunately, I've not used it for years. Don't even remember where I stored it. So, I just breadboarded a simple class A amplifier using one of the fake LM34's. It amplified the input signal. Gain was appropriate. It's probably a transistor.I guess I was somewhat lucky. I got a counterfeit part. It was at least a functional transistor.Also, I got my order for more LM34's from Digikey. Now that I have spares, I plugged some LM34's into the tester. They all show as a PNP with a flyback diode across the collector and emitter. A crappy PNP with an hFE of only 13. Also, the LM34's were not damaged by the tester.Now to reply to some more posts. I don't often post to MB's. I check my mail only once or twice a day. I'm not one of those millennials that takes their phone to bed with them! I'm getting way behind on this EEVBlog thread.

author: lmester
author_rank: Regular Contributor
timestamp: June 20, 2016, 07:37:43 am
content: QuoteI'm building this for my own use. I'm a cheapskate but, for anything critical I won't use EBay. Certainly not a Chinese EBay seller. If this project is ever sold commercially I'll then have another problem. The cheapest way to get a product produced is to send the design to China. They send back the finished product. No reliable way to know if legit or crappy fake components were used in it.

author: lmester
author_rank: Regular Contributor
timestamp: June 20, 2016, 08:01:22 am
content: Quote from: M4trix on June 18, 2016, 10:34:42 pmThe EBay seller ID is wikita* Listings for that LM34 are still up.I sent a refund request to them stating that the item was counterfeit. They promptly sent a refund with no requirement to send back the parts.I also flagged the listing as a counterfeit with EBay. Probably about as effective as trying to bail out the ocean with a teaspoonThis seller has a load of components for sale. No way to know if they are in the business of selling counterfeit parts or that they just got burned by a supplier. I'll be safe and not buy from them again.

author: uncle_bob
author_rank: Unknown
timestamp: June 20, 2016, 02:42:20 pm
content: Quote from: lmester on June 20, 2016, 08:01:22 amHiAs mentioned much earlier, many of these outfits on eBay have absolutely no idea about anything they sell. They put up pictures and take orders. When an order comes in, they pick up whatever it is from somebody else. Who knows who they get it from or anything about it. They keep their rating clean by doing quick no hassle refunds. Low markup on each transaction, shipping subsidized by the government. Not much income, but enough.Bob