Alan B wrote: ↑
Dec 03, 2017 9:12 am
That's an ESR meter. Designed to measure series resistance of capacitors. Seems to have a resolution of 0.001. Not very adequate resolution for measuring a value of 0.0032 vs 0.0035.
You have no idea what controller companies are doing. You assume they are doing nothing, just slamming parts out of tubes into PC boards. The better manufacturers will do what it takes to have a reliable product, and if that means 100% testing of the FETs before they go into the PCB, they will have an automated test setup that will do exactly that. If the parts are as bad as you claim, they would definitely be doing that. They could choose to test the boards after assembly instead, but if the failure rate was very high the scrap or rework rate would be too much if the parts consistency was that poor.
They will also use good ESD practices, and if they find that the FETs are good enough right out of the tubes they will not need to test each one. If the failure rates are low enough of the final product, why test for something that isn't a problem?
On one project we made elaborate test setups to measure many thousands of FETs for extremely low noise characteristics, something that was really beyond their specs, to find the lower noise units required for physics experiments with tens of thousands of channels. You determine what is important to the project, and you do that. Not every part needs that scrutiny, just the critical ones.
That's why companies employ engineers and even scientists in many cases to determine what needs to be done to make a reliable product.
THat ESR meter does measure low resistances. I get that it was designed for measuring internal resistance of caps. I did read the description. So why does that matter specifically? If I put a shunt across it's 2 leads, will it measure the resistance of the shunt? My suspicion is that it will. So then, it ought to measure the junction resistance of a mosfet as well. Just because something was designed for a specific purpose doesn't mean using it for some other purpose is bad. I recognize it has limited resolution. I'm not expecting much out of a $40 tool, but if it's adequate for my purposes...so be it! Worst case...as I've already said...I send it back...no big deal. AND as I already said, I am fully aware that it isn't a 4 wire tester. Where's the problem here? I recognize what I'm doing and have readily admitted as much. There's really nothing more to say here regarding this meter. Besides, it's a $40 meter. If I toss it in the trash, that's my $40 to throw away...it could happen, but I doubt it.
Am I ignorant and stupid or am I making deliberate and knowing choices? I'm an experimenter and I enjoy modding things and I like learning...so I have to say that I'm making deliberate and knowing choices and not out of stupidity.
I'm reading everything that people write. I do take it to heart! I don't need to be right or wrong. If I'm wrong I'll just say I am. If I find out that the ESR meter I bought is crap and flat out won't work...I'll post that it won't work. Same for the Chinese component tester I bought. BUT!!! IF they do work, well I'm going to post that too!!! Your opinions and criticism about my choices have been noted, but I'm still willing to find out if other options will work.
Questions about static electricity and grounding has come up several times. I don't have a meter or ever bothered trying to detect static charge beyond seeing the tiny arc come off my finger. I do use a grounded Hakko soldering station and work at a grounded desk and generally use grounded test equipment where it is applicable. I discharge myself to my desk pretty often, but I don't wear a ground strap since I'm AT my desk and touching it's bare metal frequently. I do have a ground strap, but haven't used it in a very long time since grounding to my desk has been adequate as far as I can tell. There's not much opportunity for me to build up any static charge in this environment. Sitting at my desk and touching the desk pretty much won't allow any static build-up. If I get up from my desk and walk around my house and then return to my desk, it happens that there will be a spark, when I touch my grounded desk. Static DOES happen and I am aware that it is there. If I roll my chair a few feet, static build up can be significant enough that I will get a spark when I touch my desk. There's not a question of it's existence...hence the grounded desk.
I'm going to be UBER careful with the IXYS mosfets, touch the grounded desk a lot, discharge the ESD bag or tube to the desk before opening it and removing the mosfets, etc. I won't even pull them from the tube or ESD bag until I have the new component tester in my hands and have tried it out on several other mosfets. Just to be sure it really works I'll also compare it's results to my other 2 component testers. If everything matches up for the same mosfet on all 3 component testers...great! I'll also test those same mosfets via this test method...just like I've already said I would do! The results will be the results! THEN, I will pull out a few IXYS mosfets and do the same tests. The test results will be the test results! I will also try out that ESR meter and see if it can do what I hope it can do. If not, oh well. Again...the results will be the results...whatever they are.
I think I'll abuse some mosfets and see what happens when they are exposed to static. Yes I know static is bad for electronics and specifically more so for CMOS components. That's the point! I will take some mosfets (I have lots of them that don't meet manufacturer specs) and test 10 of them. I have AOT290's, IRF4110's and a few others that are all new. All I care about is finding out what they actually test to. I can record that information before the test begins. Each mosfet can be uniquely labeled to eliminate confusion and to keep them straight for later testing. Then I'll take 5 of those mosfets and put them on a piece of wire. I can walk around my house with them in my pocket, wash the dishes, do laundry with them strapped to my wrist and so on. Just expose them to the natural household environment. I'll take another 5 and tie them together on a wire and toss them in with the cloths so that they get dried and thoroughly abused by static in there! Finally, I'll test all 10 mosfets again. Did they suffer harm? Do some of them no longer work at all? Do they now test differently than before? My expectation is that they will suffer some damage, but the proof is in the test results.
I just got an email from Mouser. My IXFP180N10T2 mosfets have been shipped. I also bought $150 of XHP70.2 and XP-L2 LED's from digiKey. The XP-L2's will go in a flashlight that currently has 18 Chinese XML's in it. They are both the same sized die so this will work well. I'll probably need to upgrade the driver board too. The current 18 XML's in it are dimmer than a single legit XHP70. Everything is running at manufacturer spec'd voltage and current. 18 XP-L2's should make it far brighter than the XHP70. The XHP70.2 LED's will go in some Chinese aluminum bike lights for my EV's. A friend suggested using an RC BEC as an LED driver. I'll have to give that a try.
You guys are going to have to try harder! If I bought the cheapest 4 wire tester, that would get criticized. If I bought a mid-range 4 wire tester, that would get criticized. If I bought the best unit on the planet and then tested exactly like "industry" supposedly does, still something would get criticized. YAWN! Do real testing!
How about posting real test results because you spent the time and money to do it? I'd really love it if someone else would do actual testing
. Feel free to use any method you want. I'd LOVE to see refuting or corroborating results based on actual testing. Have I said essentially "do real testing" enough yet?
Madin...you have a 4 wire resistance tester. PLEASE post your results for the AOT290's you just bought. Test other mosfets please. Put your AOT's in your component tester and post the results you get. Let's compare what you get with what I get.
Alan...you've tested mosfets before to find the least noisy of the batch. Test some more and look to see if they meet the manufacturer specs. Post your results! I don't know what you have on hand for parts, get some AOT290's and IRF4110's and XFP180N10T2 mosfets. Back your opinions about manufacturer practices with your own test results.
If Addy is still reading this thread...test mosfets and post your results.
Do actual testing guys!!! Quit looking for fault in what I'm doing. Actually prove that you get different or similar results by TESTING!!!
Lets work together rather than against each other. The results will be the results. I'm going to post my results regardless of what anyone says. Put your money and time where your mouth is. That's all I'm doing! This whole thing started with me stating that I was looking for another mosfet option because my tests on AOT290's were showing that they are inconsistent and diverged from manufacturer specs by a lot.
No one except me to date has even expressed that they are taking up this challenge...not ever....not even to the point of buying a $30 component tester! However, since this whole discussion started, I've not only bought more mosfets, but I've bought test tools too!
What have you done besides criticize and tried to find fault?