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 <jl@650pot.com>
Newsgroups: sci.electronics.design
Subject: Re: Inductance meter for BIST
Date: Tue, 09 Apr 2024 10:17:26 -0700
Message-ID: <qkta1j1d6rssgifim5vldca5c72ofcgstc@4ax.com>
References: <go191jli8laisgsbhrrp3fmn113fi5p578@4ax.com> <jnia1j1t40g4ldpk5tkbj6ori2ej13d9ls@4ax.com> <uv3na4$a5pd$1@dont-email.me>
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
<jeroen@nospam.please> wrote:

>On 4/9/24 16:19, John Larkin wrote:
>> On Mon, 08 Apr 2024 17:17:15 -0700, john larkin <jl@650pot.com> 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