Bought some cheap Chinese crap on ebay... - Page 1
Forum section: electronics / testgear

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: April 29, 2014, 03:31:45 am
content: got some cheap Chinese crap! Of course, not to suggest that all things Chinese are cheap crap! But these guys definitely count.I needed to get some 50 ohm pass through terminations since none of my scopes have 50ohm input coupling and I had an experiment in mind. But alas, they're worth their weight in gold and even used go for $15 a pop on ebay.Turns out, I probably should have spent it. Instead, I got a bunch of T couplers and 50 ohm end terminations (which are somehow wildly cheaper).Well, the terminators are ABSOLUTE crap. Not so much the values on the picture below, they're not precision. But the bayonets BLOW. Like, so bad I'd never let them touch a connector I spent real money on. Initially I was testing them with a BNC to Banana adapter and I think only one out of the ten of them actually fit. The rest would go with AGGRESSIVE force, more than I was about to use. Tried them on some other fittings, same deal. The bayonets are covered in burrs, the phenolic (if that's what it is?) just grabs and won't let go, it's awful. Luckily, SOME combinations of the T couplings and terminators seem to work alright.The couplings are much better mechanical quality, but alas, 3 of the 10 are dead shorts. Glad I only need 4!I think I paid $20 for the couplers and $8 for the terminators. Lesson to take away: spend more than I did.

author: echen1024
author_rank: Super Contributor
timestamp: April 29, 2014, 04:12:43 am
content: I got lucky on this autction:eBay auction: #231146874191$0.99 for everything. Some still NIB.

author: David Hess
author_rank: Super Contributor
timestamp: April 29, 2014, 08:57:59 am
content: It took me months to get a good but inexpensive feedthrough on Ebay but I bought one of these and it is not bad at least up to 300 MHz which is as high as I can reliably test but they never have them in stock anymore. Whoever made it OEMs it for several companies so someone out there probably has them at a reasonable price.http://www.mpja.com/50-Ohm-Feed-Through-Terminator/productinfo/16549%20TE/

author: GreyWoolfe
author_rank: Unknown
timestamp: April 29, 2014, 01:50:16 pm
content: Echen, that's stepping into a steaming pile of doggy doo and coming out smelling like a rose. I need to prowl eBay more.

author: rdl
author_rank: Super Contributor
timestamp: April 29, 2014, 01:53:42 pm
content: Why are the feedthrough type so much more expensive than the end cap type? I found a decend brand end cap at Mouser for about $3, I can't find a feedthrough for anywhere close to that, a Pomona for almost $50 seems excessive.

author: linux-works
author_rank: Super Contributor
timestamp: April 29, 2014, 02:00:57 pm
content: I've also had to pay close to $20 for a used 50ohm insertion term.if you want precision gear, you pay for it. you will NOT get precision from ebay/china. we all hope to get reasonable gear from ebay/china but time and time again, we get disappointed.I stop even trying unless I know my application can live with absolute worst quality parts. for test gear or things I need to count on, it won't be china, that's for sure!

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 02:02:51 pm
content: QuoteThose manufacturers can survive people there is a demand for crappy parts. So blame the buyers for that.

author: linux-works
author_rank: Super Contributor
timestamp: April 29, 2014, 02:19:04 pm
content: no, do not blame the buyers. what kind of thinking is that??ALWAYS blame the maker if the product is crap. even in an upside down world, I cannot fathom how you can blame consumers for the poor quality of vendors!!

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 29, 2014, 02:21:08 pm
content: I am also guilty of this , but as a reminder .If we want jobs , quality , service etc. , don't send your dollars to those that are undermining us / U.S.The problem is corporate greed - trickles down - they do not want the costs involved in manufacturing , just the profits .Then that trickles down to us getting use to buying cheap chineeze crap and then wondering why it doesn't work

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 29, 2014, 02:25:10 pm
content: Quote from: linux-works on April 29, 2014, 02:19:04 pmMaybe you should increase the depth of your fathoming , if we buy it then they sell it .If we don't , they won't .There is never just one answer , all issue's have a range of responses .

author: linux-works
author_rank: Super Contributor
timestamp: April 29, 2014, 02:30:43 pm
content: I just can't blame buyers for wanting to get the cheapest price for goods. the problem is, many have no idea what they are giving up when 'saving money' from poorly made china stuff.lets talk about fakes: its pretty much a given that if you buy a 'kit' board from ebay/china, the caps and chips and silicon will be fakes. but they never say so and they will deny it if you ask. the consumer probably would not buy if he knew the truth about the components but he's never given the truth; the most you'll hear is 're-used regulators' and its apparent when you get the kit that they were unsoldered and reused from a previous product.things can be made cheaply but they don't have to be made POORLY. china tends to put things at the lowest possible price to the point where cheap == poor. it does not have to be that way ('made in japan' used to be cheap AND good quality; so this proves that being lower priced does not always force you to cut corners to the point of being unsafe.again, I'm ok with reducing cost up to a limit. but we disagree where those limits are and should be, I guess. china does not seem to care and keeps trying to lower that bar each year and this is the worrisome trend.

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 03:32:48 pm
content: QuoteYour 1st sentence tells how to not blame the buyers; and your 2nd sentence proceeded to blame the buyers. :0QuoteWhenever someone tells me to believe in concensus or conventional wisdom or something is a "given", my alarm bells go off,QuoteI thought for a period of time, "It's a Sony" used to be quite derogatory. As was "It's a Toyota" or "It's a Datsun".QuoteI think we are in perfect agreement - you just haven't realized it.QuoteWhy should it? If there are plenty of fools rushing to give you their hard-earned money, they deserved to be rip'd off.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: April 29, 2014, 03:35:55 pm
content: There's absolutely a place for ultra-cheap. In this case, if the auction had said "these terminators will chew and marr whatever you plug them into" I'd probably have paid 2x for some that didn't.

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 03:43:14 pm
content: QuoteI actually agree. There should be a market for low-quality parts, just as there are BMWs and there are Chevys: BMWs are not for everyone, not are Chevys. More choices and diversity in quality / price points are always better.QuoteFor the sellers to be able to do that, don't they need you to send your plugs to them?I think you are accepting their low prices, but not the low quality / lack of services such low prices demand. It's like you are demanding BMW quality at a Chevy dealership. If you have paid for a Chevy, expect Chevy quality and Chevy services.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: April 29, 2014, 03:47:50 pm
content: I mean you're probable right, but having no frame of reference for what terminators SHOULD cost, I can't know. Are those $50 Pomona pass through terminators expensive because manufacturing is actually super hard or because the market doesn't really care about cost and they can extract large margins? I'd guess more the latter than the former.

author: linux-works
author_rank: Super Contributor
timestamp: April 29, 2014, 03:53:53 pm
content: test gear is not usually marketed toward home users who are cost-concious. business can afford higher prices and so the market set it that way. I don't honestly think that making a 50ohm term in a bnc should cost $50 or anything near that, but they get away with it because business has deep pockets.its only the semi-new lower end test gear market that china is addressing. I still see 2 polarities here: very very low end stuff and the very high end stuff. the middle end is what we buy, that used to be high end years ago and is now 'too old' for corps to feel good about using or supporting.parts on a mercedes cost more than hondas. they are NOT made better, but the buyer can usually pay more since they are buying a prestige model and they expect to pay more. same for test gear.

author: TVman
author_rank: Frequent Contributor
timestamp: April 29, 2014, 04:02:56 pm
content: Quote from: linux-works on April 29, 2014, 02:00:57 pmI thought A fluke was made in china.

author: linux-works
author_rank: Super Contributor
timestamp: April 29, 2014, 04:08:50 pm
content: ok, you force me to explain what should be obvious. ok, I'll do that.when people generally say 'china made' we are talking about indies and not big international companies that care about their rep.example: I have an olympus e3 pro (arguably, but...) photo body. its made in china but its pretty high quality and the fact that its built in china does not mean much; olympus watches over all essential processes. its no longer a 'china item' in common forum talk.no one is saying that goods FROM china can't be decent quality, but if we just say 'china good' we usually are not talking about the big brands that send their work overseas; we are talking about the rogue companies who don't want to play by international (safety, certification, etc) rules. we are talking about things that essentially have no warranty, no support and no care at all for end users. return sales never matter to the lower end china no-name makers.this is not at all the same as a fluke, tek or olympus (just to pick 3 random names) that is made in china.you have to read the context of what people are writing about. comprehension matters here.

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 04:21:36 pm
content: QuoteOr they provide better services, as in faster shipping, better returns, more availability, longer warranty, ...?The point I was trying to make is that no one gets up everyday thinking about how to make crappy products. The only reason there is supply of anything is that there is demand for that.If you don't want to see crappy products being sold, don't buy crappy products.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: April 29, 2014, 04:23:02 pm
content: Quote from: linux-works on April 29, 2014, 03:53:53 pmIn many cases this isn't exactly the case: luxury car parts are rarely expensive on the grounds that they can make large margin there. Often, the luxury car part is more expensive than than the economy car part simply because it's substantially more complex. For example, most water pumps are super simple mechanical devices consisting of a bearing, a pulley, an impeller, and half a housing that bolts onto a cutaway in the engine block. Overall, maybe $50 or $100 retail. On the other hand, BMW uses electric water pumps, which by virtue of being a fully self-contained unit including motor, housing, impeller, fasteners, etc, is much more expensive ($350-400). Of course, there are advantages: the pump can run when the engine is off, it can circulate at a rate independent of engine RPM, and because the bearing isn't side-loaded by a belt under lots of tension, it's theoretically not a wear item and most of them in the field last the life of the engine. Of course, when it DOES go bad, you pay much more.Luxury vehicle profit margin isn't in parts, it's in service. The dealer will charge you $1k to put in that water pump instead of $100 for the economy pump, and THAT'S mostly because they can.

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 04:27:58 pm
content: QuoteAgreed.QuoteOr unfavorable economy of scale? or newer technology? or branding / marketing? or a lack of competition? ... No simple answers here.

author: madires
author_rank: Super Contributor
timestamp: April 29, 2014, 05:09:50 pm
content: Hmm, that means that I could sell my old 10-Base2 stuff and become rich :-) The issue with the old 50 Ohms terminators for 10-Base2 is the limited bandwidth, they just need to work properly up to 10MHz. You should get pass-through terminators which exceed the bandwidth of your scope. I'd go for a 1 or 2 GHz type for hobbyist use.

author: Jarrod Roberson
author_rank: Regular Contributor
timestamp: April 29, 2014, 05:10:55 pm
content: I think you have your automotive brands mixed up!2014 Chevrolet Impala is the highest scoring sedan in Consumer Reports ratingsRead more:http://www.nydailynews.com/autos/consumer-reports-aglow-2014-chevrolet-impala-article-1.1408811#ixzz30IQWQoaaGM is winning best in class awards in pretty much every division and category the last few years.

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 05:20:06 pm
content: QuoteAbsolutely true. That's why so many people forgo BMWs / MBs / Ferraris (and whatever other luxury brands you may use) for Chevys and Buicks, ....

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: April 29, 2014, 05:26:51 pm
content: Quote from: Jarrod Roberson on April 29, 2014, 05:10:55 pmHaha! This is funny. Quoting Consumer Rpts. as an unbiased authority. They are really horribly biased and much worse. A product that I was very knowedgable of was reviewed against some in the same class/category and it was astounding what they wrote. They never did the tests they claimed to have done. They lied. It's yellow journalism (if anyone even knows what that is anymore) probably owned by Hearst Corp.

author: London Lad
author_rank: Regular Contributor
timestamp: April 29, 2014, 05:35:39 pm
content: Quote from: Jarrod Roberson on April 29, 2014, 05:10:55 pmSorry but that is total biased rubbish (the article, not your post)

author: miguelvp
author_rank: Super Contributor
timestamp: April 29, 2014, 05:44:00 pm
content: I have 2 50 ohm terminators that I've been using for a long time, they were originally made for networking when networking used rg-58 coax. I also have somewhere around a digital equipment one, but it's just too bulcky so I lost track of it because I never used it for my scope when using the function gen.The scope (Rigol) aparently has one inside that is software switchable via a PC. But I won't be using that in case I forget to change it back, I rather use a physical one.My point is, why does the price matter if they will last you over a decade?

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: April 29, 2014, 05:50:24 pm
content: Quote from: miguelvp on April 29, 2014, 05:44:00 pmBecause I don't actually NEED them for any practical purpose. Same reason I wouldn't spend $400 retail on a Fluke. Want it, don't need it. If it was a need, I'd have no problem.

author: dannyf
author_rank: Super Contributor
timestamp: April 29, 2014, 06:08:02 pm
content: QuoteYou don't always need high quality (thus having to pay high prices), the same reason someone may opt to buy Chevys not BMWs. "Constrained optimization", in econ terms.

author: David Hess
author_rank: Super Contributor
timestamp: April 29, 2014, 11:45:24 pm
content: Quote from: miguelvp on April 29, 2014, 05:44:00 pmQuote from: madires on April 29, 2014, 05:09:50 pmI just measured it and using a BNC-T and a normal but good coaxial termination is only good up to about 70 MHz. At about that point, the stub length of the BNC-T starts to cause visible errors. Ethernet terminators actually need to operate considerably above 10 MHz because the harmonics from the Manchester coding are part of the signal as well.The price would matter if you wanted good feedthrough terminator for performance above about 70 MHz.

author: David Hess
author_rank: Super Contributor
timestamp: April 30, 2014, 12:05:59 am
content: Quote from: rdl on April 29, 2014, 01:53:42 pmQuote from: linux-works on April 29, 2014, 03:53:53 pmQuote from: alexwhittemore on April 29, 2014, 03:47:50 pmHigh performance feedthrough terminators (and attenuators) use a coaxial resistive element, either a disk or a cylinder or some other special shape, as part of the coaxial assembly itself so producing them is practically a vertical type of manufacturing. You cannot just buy the element and connector and put it together. Note that the unterminated stub length of a feedthrough connector limits performance no matter how good the coaxial termination is so 1 GHz is pretty good and higher performance implementations have a custom coaxial output connector that is application dependent.The cheap ones which can be good to at least 1 GHz like the example I linked use planar transmission line construction and surface mount parts so they are a lot cheaper but you can build one like that if desperate and expect pretty good performance. Good connectors will still push the cost of just the parts into the $10+ range though.In inflation adjusted dollars, I would expect a good one to cost $75 ($20 in 1977) so the Pomona price is pretty reasonable. The cheap Chinese 1 GHz ones are an excellent bargain if you can find them.

author: gregariz
author_rank: Frequent Contributor
timestamp: April 30, 2014, 12:32:58 am
content: Quote from: David Hess on April 30, 2014, 12:05:59 amI bought some Chinese SMA's-BNC adapters at a hamfest and they wouldn't even mate to a SMA jack. They hadn't been machined properly as the wall thickness was too wide. Another common problem with Chinese RF connectors is that they have metricised many of the older american connectors like the PL-259/SO-239. As a result after some use the threads grind. This has been a problem that various Ham Rig makers found the hard way.I visited a contract maker about 18 months ago. I was a bit surprised to see in the PCB fab chemicals just laying on the floor, people walking through it and no protections in place. Most I was told were on 50-75c an hour. I think in this day an age that's as close to slavery as it gets. I'm not sure if we should be buying this stuff or not really.$50 seems to be a fair price I would think if its made out of brass/copper and is machined properly.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: April 30, 2014, 12:45:33 am
content: Quote from: David Hess on April 29, 2014, 11:45:24 pmThat's super interesting! What was your test setup? I'd love to try to replicate it for funsies.

author: David Hess
author_rank: Super Contributor
timestamp: April 30, 2014, 01:23:51 am
content: Quote from: alexwhittemore on April 30, 2014, 12:45:33 amI just compared the signal levels from my 50 ohm leveled signal generator between using my relatively good feedthrough attenuator (tested to 300 MHz but it is better than that) and a BNC-T with attenuator attached so the only variable that changed was the feedthrough attenuator itself. They started to visibly differ at about 70 MHz on the oscilloscope I used.I have some slower but higher power feedthrough attenuators which are rated to 100 MHz but up to 300 MHz they perform identically to my better one. Someone was OEMing them at one point and many companies remarked and sold them including Tektronix and Probe Master.

author: echen1024
author_rank: Super Contributor
timestamp: April 30, 2014, 01:40:34 am
content: Quote from: GreyWoolfe on April 29, 2014, 01:50:16 pmI think I just stumbled onto that auction. I was looking for "BNC Terminator" and saw the usual Chinese Crap, and saw this one. Surprisingly, no one had bid yet, so I decided to wait, and at the last minute, put down a $10. $5.99 and 2 days later, I get a little USPS priority box bursting at the seams. Quite a deal

author: miguelvp
author_rank: Super Contributor
timestamp: April 30, 2014, 02:13:05 am
content: I measured one of mine with the T and a 6 feet RG-58A coax and I get 51 Ohms, can't find my 2nd terminator at the moment.By itself it reads 50.6

author: David Hess
author_rank: Super Contributor
timestamp: April 30, 2014, 05:01:09 am
content: Quote from: gregariz on April 30, 2014, 12:32:58 amI had the same problem with one of the few Chinese BNC connector buys I made. The clamp nut and barrel required metric wrenches, which still did not fit, and the clamp nut inside diameter was completely wrong for RG-58. They sent replacements but the metric issue still remains.

author: rdl
author_rank: Super Contributor
timestamp: May 03, 2014, 03:50:25 pm
content: Is this the right thing for 50 ohms on a DS1052E? Price is reasonable.http://www.mouser.com/ProductDetail/Amphenol-Connex/112667/?qs=sGAEpiMZZMvKcUa6gL0RXBE73v2MC6IOG%2fEt3OdsDt0%3d

author: David Hess
author_rank: Super Contributor
timestamp: May 03, 2014, 04:19:12 pm
content: It is not a feedthrough terminator. As far as I can tell, Amphenol does not make any.

author: Skimask
author_rank: Super Contributor
timestamp: May 03, 2014, 04:26:50 pm
content: Quote from: Jarrod Roberson on April 29, 2014, 05:10:55 pmAnd you might also notice that this particular rating is in "initial quality". Doesn't say squat about what the POS is going to be like in a year or two.

author: rdl
author_rank: Super Contributor
timestamp: May 03, 2014, 05:36:03 pm
content: I guess Mouser just doesn't have them, or I'm just searching wrong. If I search for terminators, that's what I get, the kind that caps the connection, not feed thru. If I search feed thru all I get is attenuators and bulkhead fittings. Ah well.

author: David Hess
author_rank: Super Contributor
timestamp: May 03, 2014, 07:22:20 pm
content: Mouser has the Pomona one that was mentioned for $42.60:http://www.mouser.com/ProductDetail/Pomona-Electronics/4119-50/?qs=sGAEpiMZZMt9sB5fRq%2fLmybXVExKLavAj7ddmtdXsQc%3dCal Test electronics has one for $30:http://www.amazon.com/Cal-Test-Electronics-CT2944-Terminator/dp/B009QBL2T2http://www.caltestelectronics.com/ctitem/72-coaxial-terminators/CT2944I bought one of these and it works well. I wanted three at the time but they only had one in stock and I have never seen them in sock since:http://www.mpja.com/50-Ohm-Feed-Through-Terminator/productinfo/16549%20TE/Which I believe is the same one Pico Technology sells for $15.67:http://www.picotech.com/oscilloscope-accessories.html#TA050

author: rdl
author_rank: Super Contributor
timestamp: May 03, 2014, 09:00:36 pm
content: Yeah, that was the Pomona I found. That's just too much money for something I probably can get by without. I did find this, but still a bit too expensive for mehttp://www.myflukestore.com/p18968/fluke-trm50-50-ohm-feed-through-terminator-bnc

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: June 02, 2014, 07:22:33 am
content: Small update: Not that I particularly care, but I couldn't leave false positive feedback for the BNC Tee purchase, and I didn't want to leave negative feedback without giving the seller a chance, so I asked for three replacement tees for the shorted ones. The seller responded quickly to resolve the issue by sending replacements, so if you're in the market for cheap Shenzen RF stuff, I can definitely recommend that ebay seller connekt (http://www.ebay.com/usr/connekt) has good customer service!

author: IanJ
author_rank: Unknown
timestamp: June 02, 2014, 10:48:00 am
content: Hi all,Had to laught at the title of this thread......it sooooo hit home with me recently.I bought a bag of 100 pcb mounting male Molex connectors (ok, they were ripoffs) and when I got them I was well impressed, perfect sized, perfect spacing and appeared to mate correctly with the female counterpart.................but when I went to solder them to the pcb the weak tinning/plating fell off and the solder wouldn't flow on the pin that was left. In fact the pins started to corrode within days. I binned the lot.Do I still buy from China..............hell yeah!Ian.

author: idpromnut
author_rank: Unknown
timestamp: June 02, 2014, 11:35:32 am
content: Quote from: alexwhittemore on June 02, 2014, 07:22:33 amAh, I have bought a few things from this seller, and I too recommend them (but yes, their BNC stuff is hit-or-miss as to the fitting, as is their N connectors. The SMAs however are quite reasonable).

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: June 03, 2014, 10:20:28 pm
content: Quote from: idpromnut on June 02, 2014, 11:35:32 amActually, FWIW, the terminators where the ones with awful rip-your-face-off BNCs (male), and those came from a different seller. The connector quality on the tees certainly isn't pomona or amphenol, but a layman wouldn't notice any problems.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 04, 2014, 04:08:42 am
content: Quote from: alexwhittemore on April 30, 2014, 12:45:33 amAs a wavelength at 70MHz is around 4.3m,it seems a bit doubtful!Looks more like a problem with the termination,itself.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: June 04, 2014, 04:22:02 am
content: Quote from: vk6zgo on June 04, 2014, 04:08:42 amNot in coax it isn't. I measured a propagation speed on my own coax of roughly 5ns/meter, which is roughly 1/3C or a velocity factor of 33%. That works out to a wavelength at 70MHz of 1.28m, or in other words the stub length starts to look something like around 1% of one wavelength. While we're ballparking, it seems to me that that's a reasonable point one might start to notice signal aberration.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 04, 2014, 06:51:18 am
content: Funny coax--most coax is around 0.66 to 0.8.I% is still pretty small----- not many people can cut coax lengths to a tolerance that close when they are making VHF stubs,etc.Anyway,the velocity factor of the coax doesn't much matter,the legs of the "TEE" are what is involved,& they will most likely have a velocity factor in the same range as common coax types.If you are using 70MHz sinewaves,it will be hard to notice any signal aberrations.If they are 70MHzsquarewaves,all bets are off,due to their high harmonic content.

author: PE1RKI
author_rank: Regular Contributor
timestamp: June 04, 2014, 08:16:36 am
content: velocity factor of 0.33 means your cables dielectric constant is 9sapphire and aluminium oxide have an e of 9

author: David Hess
author_rank: Super Contributor
timestamp: June 04, 2014, 05:02:41 pm
content: Quote from: vk6zgo on June 04, 2014, 04:08:42 amI used the same feedthrough attenuator as either a feedthrough or on one leg of the BNC-T. The attenuator itself is specified to work to 1 GHz but I myself have only tested it to 300+ MHz where it performs identically to the 50 ohm internal termination on my 300 MHz oscilloscope.I looked for an easily perceptible difference in level between the feedthrough configuration and BNC-T configuration.Quote from: vk6zgo on June 04, 2014, 06:51:18 amI used the output from an SG503 leveled sine wave generator with at least one stage of attenuation switched in so any mismatch would not affect the leveling circuit.Square waves would be tricky to test with because transition time and not frequency would be the important criteria making measurements difficult to corroborate with others.