Path: ...!news.misty.com!weretis.net!feeder6.news.weretis.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!feeder.usenetexpress.com!tr2.iad1.usenetexpress.com!69.80.99.23.MISMATCH!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Tue, 09 Apr 2024 17:17:26 +0000 From: john larkin Newsgroups: sci.electronics.design Subject: Re: Inductance meter for BIST Date: Tue, 09 Apr 2024 10:17:26 -0700 Message-ID: References: User-Agent: ForteAgent/8.00.32.1272 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 58 X-Trace: sv3-C7fdmucaBmpPpbxle26VphFNgW6Maj9MQ+hbBACrrkdUHJaW5dgzLBQ0toTVaN+NDrrWdIj9DnVCtEZ!7svG0ArFJcRtfShg4naP0eBPCQNzuK9mZIDQiz9HuHM+rcaO573riafzgkX/AQIfK1+0XFmKo/dW!Vif4Hw== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 3464 On Tue, 9 Apr 2024 17:36:28 +0200, Jeroen Belleman wrote: >On 4/9/24 16:19, John Larkin wrote: >> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin wrote: >> >>> I can build this into my new programmable inductor module, for >>> self-test. With a 1% cap, it should be plenty good. L range will be >>> 750 mH down to maybe 10 mH, part of simulating solenoids and torque >>> motors and such. >>> >>> If I add a switch to open R3 and run some current through R1, it can >>> measure series resistance too. >>> >>> https://www.dropbox.com/scl/fi/tn8lpk38677ioylhdkget/P955_L-meter.jpg?rlkey=xynqyzfc2x020llr3a945c0td&raw=1 >>> >>> https://www.dropbox.com/scl/fi/gojlqxj23r4m57ke9jhui/Ind_Meter_1.asc?rlkey=if40kmtiz49gp62bacfvju3uv&dl=0 >> >> Most L-meters, the AADE sort, lie or don't work with big Ls. >> >> This is better: >> >> https://www.dropbox.com/scl/fi/9tex1slpnaqz4n2cbxp3n/Ind_Meter_Apr_9.jpg?rlkey=52vbyylc5ax48w54qdxm9r9cq&raw=1 >> >> Given a small uP, like the Rasp Pi thing, it could measure L and Rl >> pretty easily. One could get compusive and math out the small >> inductance measuring error from the inductor copper resistance. >> >> I need repeatability more than accuracy, and don't have time to >> explore this very deep, but it's interesting. >> >> I've been buying shaftless torque motors off ebay, to understand them >> electrically. We need to simulate a torque motor. >> >> > >What's R1 (1G to +5) for? It can be switched in, and R2 switched out, to make an ohmmeter. Then the opamp is a DC amplifier into an ADC. > >Are torque motors actually predominantly inductive? Just >because it has coils doesn't necessarily mean it is so. One case is used in some jet engines, for controlling fuel flow I think. 750 mH and maybe 200 ohms.. Unlike steppers, they seem to have no detent torque and I suspect L doesn't change much with angular position. Gotta machine a test setup and verify that. If the brushes short windings sometimes, it could get weird. > >Jeroen Belleman