On 02/02/2024 17:08, John Larkin wrote:
> On Fri, 2 Feb 2024 16:17:45 +0000, Clive Arthur
> <clive@nowaytoday.co.uk> wrote:
>
>> On 30/01/2024 16:13, Peter wrote:
>>
>> <snip>
>>
>>> A toroid would have less stray flux, and again there is a vast choice.
>>> I have a bag of these from many years ago
>>> https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
>>> which with 83 turns would achieve 8mH.
>>
>> ...but nowhere near enough current. Ferroxcube have (or had) a free
>> downloadable calculator.
>>
>> As you have already some cores, you could stack several into a tube
>> shape. I've done this where the available space made it the only game
>> in town. Tricky to wind but fun, FSVO 'fun'.
>
> An LVDT is not likely to need a lot of excitation current.

Probably, but the OP didn't specify the application. LVDTs can be
*very* long - the materials testing machines I worked on often used
short stroke LVDTs for test coupon strain measurement and long stroke -
0.5m - for clamp positioning, but in some applications much longer
devices can be used.

I'm assuming the OP has tried an 8mH inductor, is happy with the result,
and doesn't want any more complication.

--
Cheers
Clive

On Fri, 2 Feb 2024 23:00:29 +0000, Clive Arthur
<clive@nowaytoday.co.uk> wrote:

>On 02/02/2024 17:08, John Larkin wrote:
>> On Fri, 2 Feb 2024 16:17:45 +0000, Clive Arthur
>> <clive@nowaytoday.co.uk> wrote:
>>
>>> On 30/01/2024 16:13, Peter wrote:
>>>
>>> <snip>
>>>
>>>> A toroid would have less stray flux, and again there is a vast choice.
>>>> I have a bag of these from many years ago
>>>> https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
>>>> which with 83 turns would achieve 8mH.
>>>
>>> ...but nowhere near enough current. Ferroxcube have (or had) a free
>>> downloadable calculator.
>>>
>>> As you have already some cores, you could stack several into a tube
>>> shape. I've done this where the available space made it the only game
>>> in town. Tricky to wind but fun, FSVO 'fun'.
>>
>> An LVDT is not likely to need a lot of excitation current.
>
>Probably, but the OP didn't specify the application. LVDTs can be
>*very* long - the materials testing machines I worked on often used
>short stroke LVDTs for test coupon strain measurement and long stroke -
>0.5m - for clamp positioning, but in some applications much longer
>devices can be used.
>
>I'm assuming the OP has tried an 8mH inductor, is happy with the result,
>and doesn't want any more complication.

Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
current.

On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
<legg@nospam.magma.ca> wrote in <ga1qrit5bgm4if71la3j653qoff41ijibe@4ax.com>:

>On Thu, 01 Feb 2024 15:37:48 +0000, Peter
><occassionally-confused@nospam.co.uk> wrote:
>
>>
>> legg <legg@nospam.magma.ca> wrote:
>>
>>>>It is unusual to run a square wave into an LVDT. If the source is a
>>>>too-big square wave, a simple circuit would shape it into the
>>>>appropriate amplitude sine. Two or three parts.
>>>
>>>I see no reference to an LVDT application in the Peter's posting.
>>
>>It is an instrument which contains an LVDT bent into a half circle, to
>>return an angle.
>>
>>It is excited with 500Hz, and it is pretty well a square wave. I
>>didn't design that bit :) And the output is too high, for reasons too
>>complex to explain. So I need to reduce the output somehow.
>
>About LVDTs, I know nada.

Same here,
but reducing he output of a square wave is simple by adding some series diodes..

On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrote:
> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
> ><occassional...@nospam.co.uk> wrote:
> >
> >>
> >> legg <le...@nospam.magma.ca> wrote:
> >>
> >>>>It is unusual to run a square wave into an LVDT. If the source is a
> >>>>too-big square wave, a simple circuit would shape it into the
> >>>>appropriate amplitude sine. Two or three parts.
> >>>
> >>>I see no reference to an LVDT application in the Peter's posting.
> >>
> >>It is an instrument which contains an LVDT bent into a half circle, to
> >>return an angle.
> >>
> >>It is excited with 500Hz, and it is pretty well a square wave. I
> >>didn't design that bit :) And the output is too high, for reasons too
> >>complex to explain. So I need to reduce the output somehow.
> >
> >About LVDTs, I know nada.
> Same here,
> but reducing he output of a square wave is simple by adding some series diodes..

Not so! That's an inductor being driven, the diodes will cause flyback voltage excursions unless you're
doing them in back-to-back antiparallel pairs.

On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
<whit3rd@gmail.com> wrote in
<be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:

>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>e:
>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>> ><occassional...@nospam.co.uk> wrote:
>> >
>> >>
>> >> legg <le...@nospam.magma.ca> wrote:
>> >>
>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>
>> >>>>too-big square wave, a simple circuit would shape it into the
>> >>>>appropriate amplitude sine. Two or three parts.
>> >>>
>> >>>I see no reference to an LVDT application in the Peter's posting.
>> >>
>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>
>> >>return an angle.
>> >>
>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>> >>didn't design that bit :) And the output is too high, for reasons too=
>
>> >>complex to explain. So I need to reduce the output somehow.
>> >
>> >About LVDTs, I know nada.
>> Same here,
>> but reducing he output of a square wave is simple by adding some series d=
>iodes..
>
>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>ltage excursions unless you're
>doing them in back-to-back antiparallel pairs.

Yes of course 2 anti parallel.

On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
<alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:

>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
><whit3rd@gmail.com> wrote in
><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>
>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>e:
>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>> ><occassional...@nospam.co.uk> wrote:
>>> >
>>> >>
>>> >> legg <le...@nospam.magma.ca> wrote:
>>> >>
>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>
>>> >>>>too-big square wave, a simple circuit would shape it into the
>>> >>>>appropriate amplitude sine. Two or three parts.
>>> >>>
>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>> >>
>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>
>>> >>return an angle.
>>> >>
>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>
>>> >>complex to explain. So I need to reduce the output somehow.
>>> >
>>> >About LVDTs, I know nada.
>>> Same here,
>>> but reducing he output of a square wave is simple by adding some series d=
>>iodes..
>>
>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>ltage excursions unless you're
>>doing them in back-to-back antiparallel pairs.
>
>Yes of course 2 anti parallel.

But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor.
Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.

On a sunny day (Sat, 03 Feb 2024 11:02:39 GMT) it happened Jan Panteltje
<alien@comet.invalid> wrote in <upl6gg$1akff$1@solani.org>:

>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>
>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>><whit3rd@gmail.com> wrote in
>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>
>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>e:
>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>> ><occassional...@nospam.co.uk> wrote:
>>>> >
>>>> >>
>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>> >>
>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>
>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>> >>>
>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>> >>
>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>
>>>> >>return an angle.
>>>> >>
>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>
>>>> >>complex to explain. So I need to reduce the output somehow.
>>>> >
>>>> >About LVDTs, I know nada.
>>>> Same here,
>>>> but reducing he output of a square wave is simple by adding some series d=
>>>iodes..
>>>
>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>ltage excursions unless you're
>>>doing them in back-to-back antiparallel pairs.
>>
>>Yes of course 2 anti parallel.
>
>But only if on the primary driving the inductor.
>The output square wave can just be dropped by diodes
>or even a resistor divider
>You could even use a bridge recifier and use the DC level in a capacitor.
>Or does that setop look for phase?
>Then you can still use the zero crossings!
>One transistor input into base via resistor,
>s diode to protect against reverse Vbe..
>We need to know more about the setup.

PS
you could use a simple bridge rectifier in series with the drive coil
short the + and - output and use the AC input terminals.
One or more bridges in series like that too.

On 4/02/2024 4:38 pm, Jan Panteltje wrote:
> On a sunny day (Sat, 03 Feb 2024 11:02:39 GMT) it happened Jan Panteltje
> <alien@comet.invalid> wrote in <upl6gg$1akff$1@solani.org>:
>
>> On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
>> <alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>>
>>> On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>>> <whit3rd@gmail.com> wrote in
>>> <be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>>
>>>> On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>> e:
>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>>>> On Thu, 01 Feb 2024 15:37:48 +0000, Peter <occassional...@nospam.co.uk> wrote:
>>>>>>> legg <le...@nospam.magma.ca> wrote:

> you could use a simple bridge rectifier in series with the drive coil
> short the + and - output and use the AC input terminals.
> One or more bridges in series like that too.

It's not a good idea to excite an LVDT with a square wave.
The OP should set up a circuit to provide a stable sine wave of the
right amplitude, rather than waste time trying to cut down the amplitude
of the square wave with temperature dependent voltage drops through diodes.

--
Bill Sloman, Sydney

On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>
>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>><whit3rd@gmail.com> wrote in
>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>
>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>e:
>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>> ><occassional...@nospam.co.uk> wrote:
>>>> >
>>>> >>
>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>> >>
>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>
>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>> >>>
>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>> >>
>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>
>>>> >>return an angle.
>>>> >>
>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>
>>>> >>complex to explain. So I need to reduce the output somehow.
>>>> >
>>>> >About LVDTs, I know nada.
>>>> Same here,
>>>> but reducing he output of a square wave is simple by adding some series d=
>>>iodes..
>>>
>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>ltage excursions unless you're
>>>doing them in back-to-back antiparallel pairs.
>>
>>Yes of course 2 anti parallel.
>
>But only if on the primary driving the inductor.
>The output square wave can just be dropped by diodes
>or even a resistor divider
>You could even use a bridge recifier and use the DC level in a capacitor.
>Or does that setop look for phase?
>Then you can still use the zero crossings!
>One transistor input into base via resistor,
>s diode to protect against reverse Vbe..
>We need to know more about the setup.
>
>
>

LVDTs usually use sine wave excitation and a phase-sensitive detector
to convert the signal output into a signed position. The output of an
LVDT is typically zero at the center position. We do most of that
digitally.

There are various LVDT types, too.

One of my manuals has some examples:

http://www.highlandtechnology.com/DSS/P545DS.shtml

On Saturday, February 3, 2024 at 10:28:58 PM UTC-8, Bill Sloman wrote:

> It's not a good idea to excite an LVDT with a square wave.
> The OP should set up a circuit to provide a stable sine wave of the
> right amplitude, rather than waste time trying to cut down the amplitude
> of the square wave with temperature dependent voltage drops through diodes.

Just to elaborate: an ideal drive for an LVDT would include a transformer coupling
with a grounded center-tap. You want inductive coupling, any capacitive effect
is distortion, so low voltage/high current is best, and the high harmonics
of a square wave put more current through a capacitor than the fundamental.

In the old days, an IF strip (three inductor/capacitor cans) was a good
and convenient sort of square-to-sine filter. Those aren't easy to
buy this week. If 450 kHz works, there's some ceramic filters
still on the market.

On Sun, 4 Feb 2024 08:36:12 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

>On Saturday, February 3, 2024 at 10:28:58?PM UTC-8, Bill Sloman wrote:
>
>> It's not a good idea to excite an LVDT with a square wave.
>> The OP should set up a circuit to provide a stable sine wave of the
>> right amplitude, rather than waste time trying to cut down the amplitude
>> of the square wave with temperature dependent voltage drops through diodes.
>
>Just to elaborate: an ideal drive for an LVDT would include a transformer coupling
>with a grounded center-tap. You want inductive coupling, any capacitive effect
>is distortion, so low voltage/high current is best, and the high harmonics
>of a square wave put more current through a capacitor than the fundamental.
>
>In the old days, an IF strip (three inductor/capacitor cans) was a good
>and convenient sort of square-to-sine filter. Those aren't easy to
>buy this week. If 450 kHz works, there's some ceramic filters
>still on the market.

LVDTs most always work in the audio range. Aircraft types might run at
a KHz or two, and the ones used on machine tools at 10K maybe.

LVDTs are high impedance sources and cable capacitance can be a
serious problem. So long runs encourage low frequencies.

On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin
<jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:

>On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>>
>>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>>><whit3rd@gmail.com> wrote in
>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>>
>>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>>e:
>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>>> ><occassional...@nospam.co.uk> wrote:
>>>>> >
>>>>> >>
>>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>>> >>
>>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>>
>>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>>> >>>
>>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>>> >>
>>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>>
>>>>> >>return an angle.
>>>>> >>
>>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>>
>>>>> >>complex to explain. So I need to reduce the output somehow.
>>>>> >
>>>>> >About LVDTs, I know nada.
>>>>> Same here,
>>>>> but reducing he output of a square wave is simple by adding some series d=
>>>>iodes..
>>>>
>>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>>ltage excursions unless you're
>>>>doing them in back-to-back antiparallel pairs.
>>>
>>>Yes of course 2 anti parallel.
>>
>>But only if on the primary driving the inductor.
>>The output square wave can just be dropped by diodes
>>or even a resistor divider
>>You could even use a bridge recifier and use the DC level in a capacitor.
>>Or does that setop look for phase?
>>Then you can still use the zero crossings!
>>One transistor input into base via resistor,
>>s diode to protect against reverse Vbe..
>>We need to know more about the setup.
>>
>>
>>
>
>LVDTs usually use sine wave excitation and a phase-sensitive detector
>to convert the signal output into a signed position. The output of an
>LVDT is typically zero at the center position. We do most of that
>digitally.
>
>There are various LVDT types, too.
>
>One of my manuals has some examples:
>
>http://www.highlandtechnology.com/DSS/P545DS.shtml

Thank you, manual wants a login with pasword though.

>
>

On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin
><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:
>
>>On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
>>wrote:
>>
>>>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>>>
>>>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>>>><whit3rd@gmail.com> wrote in
>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>>>
>>>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>>>e:
>>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>>>> ><occassional...@nospam.co.uk> wrote:
>>>>>> >
>>>>>> >>
>>>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>>>> >>
>>>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>>>
>>>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>>>> >>>
>>>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>>>> >>
>>>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>>>
>>>>>> >>return an angle.
>>>>>> >>
>>>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>>>
>>>>>> >>complex to explain. So I need to reduce the output somehow.
>>>>>> >
>>>>>> >About LVDTs, I know nada.
>>>>>> Same here,
>>>>>> but reducing he output of a square wave is simple by adding some series d=
>>>>>iodes..
>>>>>
>>>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>>>ltage excursions unless you're
>>>>>doing them in back-to-back antiparallel pairs.
>>>>
>>>>Yes of course 2 anti parallel.
>>>
>>>But only if on the primary driving the inductor.
>>>The output square wave can just be dropped by diodes
>>>or even a resistor divider
>>>You could even use a bridge recifier and use the DC level in a capacitor.
>>>Or does that setop look for phase?
>>>Then you can still use the zero crossings!
>>>One transistor input into base via resistor,
>>>s diode to protect against reverse Vbe..
>>>We need to know more about the setup.
>>>
>>>
>>>
>>
>>LVDTs usually use sine wave excitation and a phase-sensitive detector
>>to convert the signal output into a signed position. The output of an
>>LVDT is typically zero at the center position. We do most of that
>>digitally.
>>
>>There are various LVDT types, too.
>>
>>One of my manuals has some examples:
>>
>>http://www.highlandtechnology.com/DSS/P545DS.shtml
>
>Thank you, manual wants a login with pasword though.
>
>>
>>

They want you to register. You might get a newsletter about once a
year.

On a sunny day (Mon, 05 Feb 2024 07:08:16 -0800) it happened John Larkin
<jl@997PotHill.com> wrote in <vbu1sihfc7dtubu0v0mjs8hgb67t8g0k36@4ax.com>:

>On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin
>><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:
>>
>>>On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
>>>wrote:
>>>
>>>>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
>>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>>>>
>>>>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>>>>><whit3rd@gmail.com> wrote in
>>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>>>>
>>>>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>>>>e:
>>>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>>>>> ><occassional...@nospam.co.uk> wrote:
>>>>>>> >
>>>>>>> >>
>>>>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>>>>> >>
>>>>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>>>>
>>>>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>>>>> >>>
>>>>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>>>>> >>
>>>>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>>>>
>>>>>>> >>return an angle.
>>>>>>> >>
>>>>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>>>>
>>>>>>> >>complex to explain. So I need to reduce the output somehow.
>>>>>>> >
>>>>>>> >About LVDTs, I know nada.
>>>>>>> Same here,
>>>>>>> but reducing he output of a square wave is simple by adding some series d=
>>>>>>iodes..
>>>>>>
>>>>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>>>>ltage excursions unless you're
>>>>>>doing them in back-to-back antiparallel pairs.
>>>>>
>>>>>Yes of course 2 anti parallel.
>>>>
>>>>But only if on the primary driving the inductor.
>>>>The output square wave can just be dropped by diodes
>>>>or even a resistor divider
>>>>You could even use a bridge recifier and use the DC level in a capacitor.
>>>>Or does that setop look for phase?
>>>>Then you can still use the zero crossings!
>>>>One transistor input into base via resistor,
>>>>s diode to protect against reverse Vbe..
>>>>We need to know more about the setup.
>>>>
>>>>
>>>>
>>>
>>>LVDTs usually use sine wave excitation and a phase-sensitive detector
>>>to convert the signal output into a signed position. The output of an
>>>LVDT is typically zero at the center position. We do most of that
>>>digitally.
>>>
>>>There are various LVDT types, too.
>>>
>>>One of my manuals has some examples:
>>>
>>>http://www.highlandtechnology.com/DSS/P545DS.shtml
>>
>>Thank you, manual wants a login with pasword though.
>>
>>>
>>>
>
>They want you to register. You might get a newsletter about once a
>year.

Yea, I was thinking adding genocide@whitehouse.gov as email with password biden
but do not want to spam anybody.

On Tue, 06 Feb 2024 05:04:35 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Mon, 05 Feb 2024 07:08:16 -0800) it happened John Larkin
><jl@997PotHill.com> wrote in <vbu1sihfc7dtubu0v0mjs8hgb67t8g0k36@4ax.com>:
>
>>On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid>
>>wrote:
>>
>>>On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin
>>><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:
>>>
>>>>On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
>>>>wrote:
>>>>
>>>>>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
>>>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>>>>>
>>>>>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>>>>>><whit3rd@gmail.com> wrote in
>>>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>>>>>
>>>>>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>>>>>e:
>>>>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>>>>>> ><occassional...@nospam.co.uk> wrote:
>>>>>>>> >
>>>>>>>> >>
>>>>>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>>>>>> >>
>>>>>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>>>>>
>>>>>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>>>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>>>>>> >>>
>>>>>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>>>>>> >>
>>>>>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>>>>>
>>>>>>>> >>return an angle.
>>>>>>>> >>
>>>>>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>>>>>
>>>>>>>> >>complex to explain. So I need to reduce the output somehow.
>>>>>>>> >
>>>>>>>> >About LVDTs, I know nada.
>>>>>>>> Same here,
>>>>>>>> but reducing he output of a square wave is simple by adding some series d=
>>>>>>>iodes..
>>>>>>>
>>>>>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>>>>>ltage excursions unless you're
>>>>>>>doing them in back-to-back antiparallel pairs.
>>>>>>
>>>>>>Yes of course 2 anti parallel.
>>>>>
>>>>>But only if on the primary driving the inductor.
>>>>>The output square wave can just be dropped by diodes
>>>>>or even a resistor divider
>>>>>You could even use a bridge recifier and use the DC level in a capacitor.
>>>>>Or does that setop look for phase?
>>>>>Then you can still use the zero crossings!
>>>>>One transistor input into base via resistor,
>>>>>s diode to protect against reverse Vbe..
>>>>>We need to know more about the setup.
>>>>>
>>>>>
>>>>>
>>>>
>>>>LVDTs usually use sine wave excitation and a phase-sensitive detector
>>>>to convert the signal output into a signed position. The output of an
>>>>LVDT is typically zero at the center position. We do most of that
>>>>digitally.
>>>>
>>>>There are various LVDT types, too.
>>>>
>>>>One of my manuals has some examples:
>>>>
>>>>http://www.highlandtechnology.com/DSS/P545DS.shtml
>>>
>>>Thank you, manual wants a login with pasword though.
>>>
>>>>
>>>>
>>
>>They want you to register. You might get a newsletter about once a
>>year.
>
>Yea, I was thinking adding genocide@whitehouse.gov as email with password biden
>but do not want to spam anybody.

The next tme that Russia or France or Germany wants to invade your
tiny damp country, we'll sit it out.

On Wednesday, February 7, 2024 at 8:00:05 AM UTC+11, john larkin wrote:
> On Tue, 06 Feb 2024 05:04:35 GMT, Jan Panteltje <al...@comet.invalid> wrote:
> >On a sunny day (Mon, 05 Feb 2024 07:08:16 -0800) it happened John Larkin <j...@997PotHill.com> wrote in <vbu1sihfc7dtubu0v...@4ax.com>:
> >>On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <al...@comet.invalid> wrote:
> >>>On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin <j...@997PotHill.com> wrote in <f7evri511ku1p9f31...@4ax.com>:
> >>>>On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <al...@comet.invalid> wrote:
> >>>>>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje <al...@comet.invalid> wrote in <upl5fv$19m8g$1...@solani.org>:
> >>>>>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd <whi...@gmail.com> wrote in <be0e988c-ecb5-4ee8...@googlegroups.com>:
> >>>>>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrote:
> >>>>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
> >>>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter <occassional...@nospam.co.uk> wrote:
> >>>>>>>> >> legg <le...@nospam.magma.ca> wrote:

<snip>

> >Yea, I was thinking adding geno...@whitehouse.gov as email with password biden
> >but do not want to spam anybody.
>
> The next time that Russia or France or Germany wants to invade your tiny damp country, we'll sit it out.

Jan lives in the Netherlands. It doesn't have a common border with France or Russia.

The last time Germany invaded the Netherlands was on the 10th May 1940. They'd completed the job by the 17th May 1940. The USA did sit that one out - they didn't enter WW2 until the 7th December 1941 surprise attack on Pearl Harbor by Japanese forces.

The Netherlands was eventually liberated by US and English forces late in1944 and early in 1945. but mainly in the process of gearing up to invade Germany.

My house in Nijmegen was a Canadian battalion headquarters in the last months of 1944. The convent across the road became a field hospital and the house next door was built - after the war - on land that had been used as a temporary cemetery.

--
Bill Sloman, Sydney

On a sunny day (Tue, 06 Feb 2024 12:59:43 -0800) it happened john larkin
<jl@650pot.com> wrote in <ta75silh3b6qrcegtlstqeqbn4lm7le3vc@4ax.com>:

>On Tue, 06 Feb 2024 05:04:35 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Mon, 05 Feb 2024 07:08:16 -0800) it happened John Larkin
>><jl@997PotHill.com> wrote in <vbu1sihfc7dtubu0v0mjs8hgb67t8g0k36@4ax.com>:
>>
>>>On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid>
>>>wrote:
>>>
>>>>On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin
>>>><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:
>>>>
>>>>>On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
>>>>>wrote:
>>>>>
>>>>>>On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
>>>>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
>>>>>>
>>>>>>>On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
>>>>>>><whit3rd@gmail.com> wrote in
>>>>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
>>>>>>>
>>>>>>>>On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
>>>>>>>>e:
>>>>>>>>> On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
>>>>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
>>>>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peter
>>>>>>>>> ><occassional...@nospam.co.uk> wrote:
>>>>>>>>> >
>>>>>>>>> >>
>>>>>>>>> >> legg <le...@nospam.magma.ca> wrote:
>>>>>>>>> >>
>>>>>>>>> >>>>It is unusual to run a square wave into an LVDT. If the source is a=
>>>>>>>>
>>>>>>>>> >>>>too-big square wave, a simple circuit would shape it into the
>>>>>>>>> >>>>appropriate amplitude sine. Two or three parts.
>>>>>>>>> >>>
>>>>>>>>> >>>I see no reference to an LVDT application in the Peter's posting.
>>>>>>>>> >>
>>>>>>>>> >>It is an instrument which contains an LVDT bent into a half circle, to=
>>>>>>>>
>>>>>>>>> >>return an angle.
>>>>>>>>> >>
>>>>>>>>> >>It is excited with 500Hz, and it is pretty well a square wave. I
>>>>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
>>>>>>>>
>>>>>>>>> >>complex to explain. So I need to reduce the output somehow.
>>>>>>>>> >
>>>>>>>>> >About LVDTs, I know nada.
>>>>>>>>> Same here,
>>>>>>>>> but reducing he output of a square wave is simple by adding some series d=
>>>>>>>>iodes..
>>>>>>>>
>>>>>>>>Not so! That's an inductor being driven, the diodes will cause flyback vo=
>>>>>>>>ltage excursions unless you're
>>>>>>>>doing them in back-to-back antiparallel pairs.
>>>>>>>
>>>>>>>Yes of course 2 anti parallel.
>>>>>>
>>>>>>But only if on the primary driving the inductor.
>>>>>>The output square wave can just be dropped by diodes
>>>>>>or even a resistor divider
>>>>>>You could even use a bridge recifier and use the DC level in a capacitor.
>>>>>>Or does that setop look for phase?
>>>>>>Then you can still use the zero crossings!
>>>>>>One transistor input into base via resistor,
>>>>>>s diode to protect against reverse Vbe..
>>>>>>We need to know more about the setup.
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>LVDTs usually use sine wave excitation and a phase-sensitive detector
>>>>>to convert the signal output into a signed position. The output of an
>>>>>LVDT is typically zero at the center position. We do most of that
>>>>>digitally.
>>>>>
>>>>>There are various LVDT types, too.
>>>>>
>>>>>One of my manuals has some examples:
>>>>>
>>>>>http://www.highlandtechnology.com/DSS/P545DS.shtml
>>>>
>>>>Thank you, manual wants a login with pasword though.
>>>>
>>>>>
>>>>>
>>>
>>>They want you to register. You might get a newsletter about once a
>>>year.
>>
>>Yea, I was thinking adding genocide@whitehouse.gov as email with password biden
>>but do not want to spam anybody.
>
>The next tme that Russia or France or Germany wants to invade your
>tiny damp country, we'll sit it out.

Next time? Russia never invaded here.
On the contrary, it helped - in a big way - defeat the Germans in WW2
Freed many people from German concentration camps.

I have the impression US is falling apart, like the Roman empire did a while after
Nero played the fiddle, just like Trump played twitter (now X).

If you think about 'democracy' lemme give the Musk and Twitter case as example:
Musk asked Twitter users to vote if he should take it over.
Majority said 'yes'.
So that did cost him dearly!
If you held a vote on the next transistor model for your new design, all over the country,
do you think it would work for a majority?
You need decision making done by experts, not by some half senile populist creep like biden.
Playing the masses to power your business.. Like biden's war mongering
to burn his people in wars and grab and increase their taxes by producing and giving away weapons
used for creating unrest all over the globe.
Look at what the creep did, like that other demoncrate named Clignon, make war in Europe
cut Russian pipelines to Europe so as to sell your own oil
then put sanctions on our chip export etc etc (our chip tech is way ahead of the US!)
And the masses will be burned in the next war like your people were burned in Vietnam,
in Iraq (no weapons of mass destruction, just war 'business'), in Afghanistan,
WTF do you think you are other than just an aggressive ant heap asking for a more aggressive
other ant heap (and more knowledgeable one) to evaporate what once was a bunch of settlers
stealing from the local US natives.

China, as empire, has a much longer history and is way ahead now of US (that cannot even land on the moon anymore)
in many fields.
A different system,
And now biden causes with all those sanction on China for your own people to pay more for household things
while they hardly have money for housing and food.

I am not so sure about humanity anymore, it seems to be stuck in dogma now
Told you s a while back:
https://www.sciencedaily.com/releases/2024/02/240206144917.htm

Your war machine running on blood:
https://www.songteksten.nl/songteksten/49312/country-joe-the-fish/vietnam.htm

Your nukes may not even work, maybe they forgot how to .........
https://arstechnica.com/space/2024/02/humanitys-most-distant-space-probe-jeopardized-by-computer-glitch/

Maybe a thousand years, or more, after WW3, some of humanity will, after climate is more suitable
recover and dig up your statue of gibberish like in that
planet of the apes movie..

:-)
Or not!
Dinos

John Larkin <jl@997PotHill.com> wrote:

>>I'm assuming the OP has tried an 8mH inductor, is happy with the result,
>>and doesn't want any more complication.
>
>Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
>current.

That is exactly what I did.

I bought a 0-10mH (in 1mH steps) variable inductor off Ebay and found
8mH does the perfect job. General Radio 940
https://www.ebay.co.uk/itm/224101042113

Got this from Mouser and will test it
https://www.mouser.co.uk/datasheet/2/54/5700_series-777305.pdf

The 1.6 amps is real, give or take a bit. Yesit surprises me it is
that much. But I can't change the drive circuit. It's simply crap.
Honeywell, BTW ;) Well, actually, from the last days of Bendix King,
around 24 years ago.

On Tue, 13 Feb 2024 13:47:06 +0000, Peter
<occassionally-confused@nospam.co.uk> wrote:

>
> John Larkin <jl@997PotHill.com> wrote:
>
>>>I'm assuming the OP has tried an 8mH inductor, is happy with the result,
>>>and doesn't want any more complication.
>>
>>Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
>>current.
>
>That is exactly what I did.
>
>I bought a 0-10mH (in 1mH steps) variable inductor off Ebay and found
>8mH does the perfect job. General Radio 940
>https://www.ebay.co.uk/itm/224101042113
>
>Got this from Mouser and will test it
>https://www.mouser.co.uk/datasheet/2/54/5700_series-777305.pdf
>
>The 1.6 amps is real, give or take a bit. Yesit surprises me it is
>that much. But I can't change the drive circuit. It's simply crap.
>Honeywell, BTW ;) Well, actually, from the last days of Bendix King,
>around 24 years ago.

1.6 amps of square wave into an LVDT is shocking. Maybe the same
person designed the LVDT and the driver.

What does it do? I mean, what mechanical thing does it measure?

On 13.2.2024 17.22, John Larkin wrote:
> On Tue, 13 Feb 2024 13:47:06 +0000, Peter
> <occassionally-confused@nospam.co.uk> wrote:
>
>>
>> John Larkin <jl@997PotHill.com> wrote:
>>
>>>> I'm assuming the OP has tried an 8mH inductor, is happy with the result,
>>>> and doesn't want any more complication.
>>>
>>> Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
>>> current.
>>
>> That is exactly what I did.
>>
>> I bought a 0-10mH (in 1mH steps) variable inductor off Ebay and found
>> 8mH does the perfect job. General Radio 940
>> https://www.ebay.co.uk/itm/224101042113
>>
>> Got this from Mouser and will test it
>> https://www.mouser.co.uk/datasheet/2/54/5700_series-777305.pdf
>>
>> The 1.6 amps is real, give or take a bit. Yesit surprises me it is
>> that much. But I can't change the drive circuit. It's simply crap.
>> Honeywell, BTW ;) Well, actually, from the last days of Bendix King,
>> around 24 years ago.
>
> 1.6 amps of square wave into an LVDT is shocking. Maybe the same
> person designed the LVDT and the driver.
>
> What does it do? I mean, what mechanical thing does it measure?

The OP's thing may be mis-identified.

It seems that there is an angle transmitter from a piece of avionics.

The usual angle transmitters in avionics are: a three-phase synchro,
a resolver (sine+cosine) and a sine-cosine potentiometer.

The drive level is suspect. An electronic synthetic shaft with two
interconnected synchros can need so much. Another place where a magnetic
core is heavily driven is a flux-valve compass sensor, but it does not
have any moving parts (like the LVDT core).

John is right: What is the thing supposed to achieve?

--

-TV

On Wednesday, February 14, 2024 at 8:14:54 PM UTC+11, Tauno Voipio wrote:
> On 13.2.2024 17.22, John Larkin wrote:
> > On Tue, 13 Feb 2024 13:47:06 +0000, Peter <occassional...@nospam.co.uk> wrote:
> >> John Larkin <j...@997PotHill.com> wrote:
> >>
> >>>> I'm assuming the OP has tried an 8mH inductor, is happy with the result,
> >>>> and doesn't want any more complication.
> >>>
> >>> Somehow I doubt that. He calculated 1.6 amps of LVDT excitation current.
> >>
> >> That is exactly what I did.
> >>
> >> I bought a 0-10mH (in 1mH steps) variable inductor off Ebay and found
> >> 8mH does the perfect job. General Radio 940
> >> https://www.ebay.co.uk/itm/224101042113
> >>
> >> Got this from Mouser and will test it
> >> https://www.mouser.co.uk/datasheet/2/54/5700_series-777305.pdf
> >>
> >> The 1.6 amps is real, give or take a bit. Yesit surprises me it is
> >> that much. But I can't change the drive circuit. It's simply crap.
> >> Honeywell, BTW ;) Well, actually, from the last days of Bendix King,
> >> around 24 years ago.
> >
> > 1.6 amps of square wave into an LVDT is shocking. Maybe the same
> > person designed the LVDT and the driver.
> >
> > What does it do? I mean, what mechanical thing does it measure?
>
> The OP's thing may be mis-identified.
>
> It seems that there is an angle transmitter from a piece of avionics.
>
> The usual angle transmitters in avionics are: a three-phase synchro,
> a resolver (sine+cosine) and a sine-cosine potentiometer.

Perhaps, but angle sensing variable transformers are real enough.

> The drive level is suspect.

24 years ago some people were rather ham-handed.
> John is right: What is the thing supposed to achieve?

Always a good question. The answer is probably to get some ancient lump pf rubbish working with the minimum investment of effort.
It's rarely a wise approach, but people under pressure can't afford wisdom.

--
Bill Sloman, Sydney

Anthony William Sloman <bill.sloman@ieee.org> wrote:

>Always a good question. The answer is probably to get some ancient lump pf rubbish working with the minimum investment of effort.
>It's rarely a wise approach, but people under pressure can't afford wisdom.

It is an artificial horizon called KI256. I need to attenuate the roll
output a bit.

I have the circuits of the driver and circuits of the KI256. I
measured the KI256 LVDT primary inductance, etc.

Some other data points are that another inductor but a small one, just
did nothing and presumably saturated.

Crazy to have such a high drive level; I agree.

On 2024-02-01, Peter <occassionally-confused@nospam.co.uk> wrote:
>
> legg <legg@nospam.magma.ca> wrote:
>
>>>It is unusual to run a square wave into an LVDT. If the source is a
>>>too-big square wave, a simple circuit would shape it into the
>>>appropriate amplitude sine. Two or three parts.
>>
>>I see no reference to an LVDT application in the Peter's posting.
>
> It is an instrument which contains an LVDT bent into a half circle, to
> return an angle.

It sounds kind of like the LVDT wanted to be a resolver.

> It is excited with 500Hz, and it is pretty well a square wave. I
> didn't design that bit :) And the output is too high, for reasons too
> complex to explain. So I need to reduce the output somehow.

Well that's a shame. You'll have to use a method that's suited to your
application.

--
Jasen.
🇺🇦 Слава Україні

Just an update.

I tested that 8mH coil from Mouser. Verified at 8mH with an LCR meter
and with the $500 micro tweezer thingy.

Doesn't work!! It behaves like it was 20mH or something like that. The
attenuation is way too high. But 8mH was the perfect value with that
funny milspec 0-10mH box I got off Ebay, which was heavy enough to
contain pretty big inductors.

So what is happening?

Must be something in the waveform which is buggering up the way these
inductors behave, in conjunction with the demodulation scheme used to
"decode" the LVDT position.

Maybe it is saturating, but saturation has the opposite effect: it
*lowers* the effective inductance.

So I bought a 2.5mH one from Mouser, again one which can do 1.5A or
so, and will try that, after the potting compound has gone off :)

On 12/03/2024 11:59 pm, Peter wrote:
> Just an update.
>
> I tested that 8mH coil from Mouser. Verified at 8mH with an LCR meter
> and with the $500 micro tweezer thingy.
>
> Doesn't work!! It behaves like it was 20mH or something like that. The
> attenuation is way too high. But 8mH was the perfect value with that
> funny milspec 0-10mH box I got off Ebay, which was heavy enough to
> contain pretty big inductors.
>
> So what is happening?
>
> Must be something in the waveform which is buggering up the way these
> inductors behave, in conjunction with the demodulation scheme used to
> "decode" the LVDT position.

An inductor in series with the excitation coils of an LVDT will shift
the phase of the current going through the LVDT. If the output of the
LVDT is being demodulated with a phase sensitive detector you'd need a
matching shift in the phase of the drive to the demodulator to get a
sensible (or useful) output.

A precision rectifier wouldn't have that problem, but they weren't all
that precise decades ago, and not all that popular. They also don't
reject noise and out-of-phase pick-up, so nobody sensible would have
used one.
> Maybe it is saturating, but saturation has the opposite effect: it
> *lowers* the effective inductance.

Worse - it could be saturating on part of the cycle and giving you a
very funny current waveform going through the LVDT - actually a rotary
variable transformer, but we've been through that,

Looking at the current waveforms is always a good idea, but not always
all that easy.

> So I bought a 2.5mH one from Mouser, again one which can do 1.5A or
> so, and will try that, after the potting compound has gone off :)

More looking a what's actually going on might be a good idea - buying
random parts before you had worked out exactly why the last one didn't
work isn't good policy.

--
Bill Sloman, Sydney