Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: "Don" Newsgroups: sci.electronics.design Subject: Re: Predictive failures Date: Wed, 17 Apr 2024 03:46:02 -0000 (UTC) Organization: A noiseless patient Spider Lines: 61 Message-ID: <20240416d@crcomp.net> References: <20240416a@crcomp.net> <20240416c@crcomp.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Wed, 17 Apr 2024 05:46:02 +0200 (CEST) Injection-Info: dont-email.me; posting-host="67bd8e3130374e1c0bb2fce27a54733f"; logging-data="1481953"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19mJBgg7f71E879L7K9M8lY" Cancel-Lock: sha1:+SvSMacV72gBUbMEfM3bENWXKI8= Bytes: 3540 John Larkin wrote: > Don wrote: >>john larkin wrote: >>> Don wrote: >>>>Don Y wrote: >>>>> Is there a general rule of thumb for signalling the likelihood of >>>>> an "imminent" (for some value of "imminent") hardware failure? >>>>> >>>>> I suspect most would involve *relative* changes that would be >>>>> suggestive of changing conditions in the components (and not >>>>> directly related to environmental influences). >>>>> >>>>> So, perhaps, a good strategy is to just "watch" everything and >>>>> notice the sorts of changes you "typically" encounter in the hope >>>>> that something of greater magnitude would be a harbinger... >>>> >>>>A singular speculative spitball - the capacitive marker: >>>> >>>> In-situ Prognostic Method of Power MOSFET Based on Miller Effect >>>> >>>> ... This paper presents a new in-situ prognosis method for >>>> MOSFET based on miller effect. According to the theory >>>> analysis, simulation and experiment results, the miller >>>> platform voltage is identified as a new degradation >>>> precursor ... >>>> >>>> (10.1109/PHM.2017.8079139) >>> >>> Sounds like they are really measuring gate threshold, or gate transfer >>> curve, drift with time. That happens and is usually no big deal, in >>> moderation. Ions and charges drift around. We don't build opamp >>> front-ends from power mosfets. >>> >>> This doesn't sound very useful for "in-situ" diagnostics. >>> >>> GaN fets can have a lot of gate threshold and leakage change over time >>> too. Drive them hard and it doesn't matter. >> >>Threshold voltage measurement is indeed one of two parameters. The >>second parameter is Miller platform voltage measurement. >> The Miller plateau is directly related to the gate-drain >>capacitance, Cgd. It's why "capacitive marker" appears in my >>original followup. >> Long story short, the Miller Plateau length provides a metric >>principle to measure Tj without a sensor. Some may find this useful. > > When we want to measure actual junction temperature of a mosfet, we > use the substrate diode. Or get lazy and thermal image the top of the > package. My son asked me to explain how Government works. So I told him. They hire a guy, give him a FLIR, and bundle both with their product as an in-situ prognostic solution. Danke, -- Don, KB7RPU, https://www.qsl.net/kb7rpu There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on the previous night.