Seriously, what is the value of a $30 thing that is unreliable? - Page 1
Forum section: electronics / testgear

author: watchmaker
author_rank: Unknown
timestamp: August 28, 2024, 12:16:42 pm
content: I get that many of these things are great for initial ID of components. I have a couple (the TC3 is my go to) and even use a $25 two channel USB scope for the display on my Thaikit Curve Tracer.But what is the point of trying toselectcomponents with a measurement system that yields unreliable results.Not even talking about calibration, just consistency and documented approaches to the calculations?When is "good enough" a path to failure and frustration?Because of this forum, I have learned the importance of verifying every component. I am just an amateur doing things to amuse myself, so time is not an issue.Capacitors in particular are more complex than they first appear (at least to me) in their behavior both in and out of circuit. It would seem to me that using these $30 things for their selection can lead to much frustration. Long gone are the days when the choice was ceramic or big electrolytics.OTOH, I get the challenge of working to improve these devices. That provides many with a great deal of fun as evidenced by 300 plus page threads.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 28, 2024, 12:44:22 pm
content: mmm i would say follow the huge threads and see remarks and feedback's and fw evolution'sfor sure an 20-30$ gimmick has some usefulness, and i would say precise 80-90% of the time, unless you have some difficult parts like scr's and some mosfets, they help to basically diagnose stuffsand sure in some cases if you try to test on pcb's, you'll be greatly limittedsame for users who tests caps with an dmm, it's time constant based not a real cap tests with esr dsr z q etc ...you would need lcr meters with serial or parallel functions dc / bias etc...always a compromise between real equipment and gizmos and learning their limitsmy 2 cents

author: watchmaker
author_rank: Unknown
timestamp: August 28, 2024, 02:16:22 pm
content: Quote from: coromonadalix on August 28, 2024, 12:44:22 pm

author: Kean
author_rank: Unknown
timestamp: August 28, 2024, 03:24:16 pm
content: Quote from: coromonadalix on August 28, 2024, 12:44:22 pmThis also applies between two different models/brands of "real equipment" - there are always compromises!It is important to understand the limits of any test equipment, even if you don't fully understand how it works.

author: BeBuLamar
author_rank: Super Contributor
timestamp: August 28, 2024, 03:36:08 pm
content: What $30 thing? I don't understand.

author: Kean
author_rank: Unknown
timestamp: August 28, 2024, 03:43:54 pm
content: Quote from: BeBuLamar on August 28, 2024, 03:36:08 pmThe cheap LCR/transistor/component testers.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 28, 2024, 03:51:06 pm
content: The only value is in what they're good at, and they're usually good at transistor testing. And usually repeatable in that specific case.I would never use them to test basic components that a DMM or real LCR is better suited for.

author: madires
author_rank: Super Contributor
timestamp: August 28, 2024, 04:07:02 pm
content: The Transistortester can measure R, C and L within some limits, but it's not an LCR meter. Unfortunately, many sellers tell nonsense. And the manufacturers of the tester clones cause another issue by poorly porting and modifying the OSHW firmwares to alternative (cheaper) MCUs. The OSHW firmwares are optimized for ATmegas and porting them to other MCUs will take a huge effort. My advise is to buy only Transistortester clones with a genuine ATmega. This way you can also upgrade your tester to one of the two OSHW firmwares.

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 28, 2024, 04:11:16 pm
content: Cited very very freely from Werner Heisenberg: There is no measurement without compromise. Know yourself, know your equipment and know the limits.Knowing the limits I often can also live with cheap equipment. If I have a €7-Transistortester and a bunch of caps that are expected to be equal I can test them and if they all show the same value then it´s an indication that all parts are okay.If I have a €2000 LCR meter then I can test them for absolute values and directly send them back to the supplier if the test fails.But neither of both devices can tell me if a cap is leaky at 400V. For this test I need specialized equipment that I can quite easily build on demand.From my point of view we are living in amazing times because even super cheap test equipment can give you so much information. But no instrument can release you from cleverly interpreting its results. Not even the most expensive one.

author: temperance
author_rank: Super Contributor
timestamp: August 28, 2024, 04:18:12 pm
content: I wonder why you need to verify component with curve tracers and transistor testers?

author: madires
author_rank: Super Contributor
timestamp: August 28, 2024, 04:39:23 pm
content: Because the n-ch JFETs you buy via eBay or AliExpress often turn out to be jellybean NPNs. Or you wonder why the replacement MOSFETs for the SMPSU you're repairing blow up the second time (they are counterfeits).

author: axantas
author_rank: Regular Contributor
timestamp: August 28, 2024, 04:40:00 pm
content: Quote from: temperance on August 28, 2024, 04:18:12 pmBecause we can and we have a collection of these "things", which is to be used

author: AVGresponding
author_rank: Super Contributor
timestamp: August 28, 2024, 04:40:50 pm
content: Quote from: temperance on August 28, 2024, 04:18:12 pmYou don't always, it's entirely dependent on your use case.If you want a couple of transistors to turn on some relays, all you need to know is if they can handle the voltage and current in general terms.If you want a couple of transistors for matched input stages (for anything that might need such things) you're probably going to want to check very carefully that they match in a number of characteristics, in which case a curve trace becomes useful.The point about caps being tested for leakage current at 400V is again, use case oriented. You only really need to do this if you're going to be using them at that voltage.

author: temperance
author_rank: Super Contributor
timestamp: August 28, 2024, 05:57:19 pm
content: QuoteInteresting. So you spend $30 on some test equipment to verify to cheap junk you obtain from whichever place.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 28, 2024, 06:11:21 pm
content: Quote from: temperance on August 28, 2024, 05:57:19 pmAs opposed to what? The exceptionally expensive test equipment we also use to very the expensive components we also purchase?I use the transistor testers to make sure the parts I get from Mouser are functional, and sometimes I check to see if values are close for matching. If the test results are repeatable, that's usually useful.If you know of a significantly better transistor tester that doesn't cost $50,000 and isn't the size of a 1980s computer, I'd love to check it out. 🤷

author: temperance
author_rank: Super Contributor
timestamp: August 28, 2024, 07:36:22 pm
content: A company where I sometimes work places between 300 and 500 K components / hour. After assembly all components are tested with a flying probe tester. 0.0000001 or even less of all rejects are actually defective components. Alter all this, all assemblies are tested by means of an in circuit tester measuring voltages and currents by means of test points on each PCB trace. Here the same applies. Almost each failure is usually caused by assembly problems and not defective components.Of course we do have defective components. But defective components failures are usually failures of a different kind. Those components fail after a short period of use. And even then, some of those defects were engineering mistakes like operating components outside their maximum ratings under startup conditions for example.In my own experience I never received a bad component from a reputable distributor. (On average 400 K components on the shelf for small production runs) If something didn't work it was usually my own error.-Matching BJT's or MOSFET's: with a bread board and a DMM. (But matched pairs are not that expensive anymore)-You will need an RLC meter for special cases and for very special cases you probably have to invent your test equipment. (measuring the saturation behavior of inductors for example up 20 A and higher)-Finding broken semiconductors is easily done with a DMM. If leakage due to aging is a problem I measure some voltages and gently apply some heat to see how things drift around. (I think it is easier than putting every suspect candidate in an dedicated transistor tester.) By doing so you also know if there is anything else wrong in the circuit. (Calculate on the fly which voltages you are supposed to find in there. A rough calculation is good enough to start)-How to put SMD components into such a test device? DMM or scope probes can probe almost any SMD component or a nearby available solder joint.I'm just someone failing to see the value of those test devices and prefer poking around in the circuit itself.

author: shabaz
author_rank: Frequent Contributor
timestamp: August 28, 2024, 08:11:37 pm
content: There is value for hobbyists. I have a cheap $20 or so LCR meter, I used it when I didn't have anything better, for seeing if my inductors were in the right ballpark, despite knowing that the test is not applying a known frequency signal; that's not the way those low-cost meters work. I still have it, and still occasionally use it, despite having access to better instruments. I sometimes (very often!) do not want a precise measurement, nor might I care that there's no specified accuracy for a $30 instrument. Often with uncertainty, I can live with it, it's part of normal life.You can learn a lot by observing the change in value as you compress the inductor, or applying different materials close to it. You also can visually observe drift as the instrument warms up, learn your requirements for a better instrument, and notice the need for calibration, or zeroing, and observing the amount of change that occurs when the test wires are moved.I don't think many engineers would use it to 'select' a component as the OP asked, and there is often no need either, since many circuits can be 'tuned' through voltages or other adjustments. But a $30 meter for observing some quite interesting behaviour for a beginner, and providing results that you may indeed need to verify in other ways (e.g. in-circuit running the end application and seeing if it works) for non-critical work, sounds like a very acceptable thing to do.

author: thm_w
author_rank: Super Contributor
timestamp: August 28, 2024, 10:33:37 pm
content: Quote from: KungFuJosh on August 28, 2024, 06:11:21 pmThere is no need to do this though.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 28, 2024, 10:42:21 pm
content: Quote from: thm_w on August 28, 2024, 10:33:37 pmYou're joking? I build some complex enough products and I don't want to guess if there's an issue. Every single component gets tested before install. Every single time. And yes, I have found failures that saved me a lot of frustration. Sometimes thanks to a DMM or LCR, and sometimes thanks to these cheap transistor testers.

author: temperance
author_rank: Super Contributor
timestamp: August 28, 2024, 11:02:42 pm
content: QuoteI find it hard to believe you will be using a $30 transistor tester powered with two AA batteries to verify component performance. Because that's what this topic is about.I do know that some companies building industrial kW power supplies tested all power transistors before installing them. The same for a company building kW audio amplifiers in de USA. Unfortunately the switching power supplies they developed later on to replace kW transformers were not of the reliable kind and the brand evaporated over night.Edit:I do verify what I receive from suppliers after being burned a few time. Getting 27 mOhm resistors instead of 100 mOhm for example. Instant smoke... But I don't test all components. That would be about 90 K components this month.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 28, 2024, 11:16:34 pm
content: Quote from: temperance on August 28, 2024, 11:02:42 pmBelieve whatever you like, but I only check transistors with the devices this thread is about. I don't go through 90k parts a month, so it's not a big deal for me. What I do is on a smaller scale, so failures are a larger problem.

author: thm_w
author_rank: Super Contributor
timestamp: August 29, 2024, 12:24:50 am
content: Quote from: KungFuJosh on August 28, 2024, 10:42:21 pmSo you've had multiple failed transistors from a major distributor? Not something I've ever heard of before.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 29, 2024, 12:37:52 am
content: Quote from: thm_w on August 29, 2024, 12:24:50 amI've been in business for 30 years. Yes, I've had multiple failed transistors over the years. I'm surprised anybody is surprised by this. I'm in the guitar business, even the bigger distributors aren't always that big, and who knows where they get their inventory from. Probably more relevant is that some devices call for vintage transistors, and that should speak for itself when it comes to testing before using.

author: porter
author_rank: Regular Contributor
timestamp: August 29, 2024, 02:25:54 am
content: Markus Frejek, the inventor (I think) of these types of devices introduced the tester this way:QuoteIs this an entirely new type of instrument?

author: Fungus
author_rank: Super Contributor
timestamp: August 29, 2024, 02:43:26 am
content: Their original purpose of these was a componentidentifier.The fact that they have to do a few basic tests on a component to figure out what it is was secondary.Now people expect a $30 gadget to do the job of an LCR meter and curve tracer?

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 29, 2024, 03:32:27 am
content: Quote from: watchmaker on August 28, 2024, 12:16:42 pmI wouldn't use my TC1 to select components. I use it as a quick check for pinout and go-no-go kind of testing. Or just a quick sanity check to confirm the ID of a component.If I really want to fully test transistors, diodes, zeners, etc, I'll use a curve tracer.For capacitors and inductors, I'll use a LCR meter with leakage test and ringer functions if it's critical.

author: Irilia
author_rank: Regular Contributor
timestamp: August 29, 2024, 04:01:04 am
content: The best is to test in the PCB with a DMM 👀

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 29, 2024, 04:19:06 am
content: @Temperance: In a production environment you are absolutely right. No one can afford to test the components coming out of the tape except it is indisputably necessary to do a pre-selection. And this is usually done with highly specialized equipment, process time is money - and yes it´s often about fractions of seconds.@KungFuJosh: As soon as you combine manual handling with vintage components things get absolutely different. I suppose you follow basic ESD-rules but anyhow each manual step is a risk for sensitive parts - and that step does not necessarily be on your side. I´m quite sure if you buy single components at mouser in antistatic bags then their failure rate is higher than if you buy a reel that´s directly passed on to you from the manufacturer. OEM packaging also has a limited shelf-life in the range of several months. This is mostly neglected as soon as parts are singular and it should affect solderability much more than function of the parts - anyhow it´s a good reason to do more tests when manually handling components.And as soon as you go from a well equipped lab to some home or beginners workbench or also to some aliexpress seller: There probably most of the parts are somehow pre-damaged. An AVR-tester is a really easy way to sort out the really dead ones.

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 29, 2024, 09:34:55 am
content: I've used my DMM and an LCR-T4 to ensure I haven't goofed with my component storage, or when I accidentally spill similar components on top of my ESD mat when preparing for a build. I even got the Aneng tweezers for my AN8008 just so that when I happen to have multiple resistors or capacitors of the same size, I can quickly verify I didn't misplace them in the wrong tray.I like the idea of these LCR tweezers, for the same purposes: identification. Both Fnirsi LCR-ST1 and Zoyi ZT-MD1 seem suitable for this, but I'd like to see a comparison; right now, I could buy either one for about 28€ (including shipping and VAT).