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bar magnets vs wire magnetics
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Don Kelly
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 166

PostPosted: Tue May 31, 2005 2:43 am    Post subject: Re: bar magnets vs wire magnetics Reply with quote

<jimp@specsol.spam.sux.com> wrote in message
news:d7dgmi$2er$1@mail.specsol.com...
Quote:
operator jay <none@none.none> wrote:

jimp@specsol.spam.sux.com> wrote in message
news:d7ckr4$b46$1@mail.specsol.com...
Lory <lorrainewinters80@yahoo.com> wrote:




If the compressor oscillations is 100 hz and this gets feed back
to the current that is fluatuating. Do you think putting a
resistor can make a 1:1 correspondence such that I can get
a reading of 100 hz in the voltage measurement? Does the
correspondence hold if the frequency is 100 Mhz?

Unless you do something immensely stupid like use a high inductance
wire wound resistor instead of an ordinary compostion resistor, yes,
it will give valid results into the megahertz.


There will be a cutoff frequency associated with the oscilloscope due to
input resistance and capacitance. In a lab, somewhere around 1996, we
calculated our scopes' cutoff frequencies. I believe it was in the MHz.
I
don't recall if it was low like 15MHz or high like 750MHz. It would of
course depend on the scope and I assume you could find information in
any
scope's literature. There would be scopes built for high frequency work
in
particular. However for a lot of general work I would think that
typical
scopes are fine up into MHz range and I agree that would be fine and
dandy
for Ms. Winters' application.

j

These days a cheap oscilloscope goes into the 10s of megahertz.

Lab 'scopes go to the 10s of gigahertz.

Hell, my 25 year old 'scope goes to 350 Mhz.

--
Jim Pennino

Remove .spam.sux to reply.

About 50-60 years ago there were scopes which could measure current
directly- using magnetic deflection.. The problem was that they were limited
to low frequencies -i.e a few KHz. Not a great deal better than
galvanometers (up to 125 Hz) with mirrors, and a moving film strip-i.e. an
oscillograph.
--
Don Kelly
dhky@peeshaw.ca
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PostPosted: Tue May 31, 2005 3:01 pm    Post subject: Re: bar magnets vs wire magnetics Reply with quote

Don Kelly <dhky@peeshaw.ca> wrote:

<snip>

Quote:
About 50-60 years ago there were scopes which could measure current
directly- using magnetic deflection.. The problem was that they were limited
to low frequencies -i.e a few KHz. Not a great deal better than
galvanometers (up to 125 Hz) with mirrors, and a moving film strip-i.e. an
oscillograph.
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

Trivia tidbit:

Galvanometer oscillographs were used in the Nike-Hercules missle system.

Obsoleted by the US in the mid 70's, used by some countries into the 90's.

--
Jim Pennino

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Don Kelly
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 166

PostPosted: Thu Jun 02, 2005 2:28 am    Post subject: Re: bar magnets vs wire magnetics Reply with quote

<jimp@specsol.spam.sux.com> wrote in message
news:d7hu88$37o$1@mail.specsol.com...
Quote:
Don Kelly <dhky@peeshaw.ca> wrote:

snip

About 50-60 years ago there were scopes which could measure current
directly- using magnetic deflection.. The problem was that they were
limited
to low frequencies -i.e a few KHz. Not a great deal better than
galvanometers (up to 125 Hz) with mirrors, and a moving film strip-i.e.
an
oscillograph.
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

Trivia tidbit:

Galvanometer oscillographs were used in the Nike-Hercules missle system.

Obsoleted by the US in the mid 70's, used by some countries into the 90's.

--
Jim Pennino

Remove .spam.sux to reply.
---------

They were likely quite improved over the last one I used. in the 50's. The
film had to be developed in a dark room so,until this was done, one had no
idea whether the results were any good. At least you could have a lot more
data channels than available on the "non-storage"' scopes of the day!

--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer
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PostPosted: Thu Jun 02, 2005 2:41 pm    Post subject: Re: bar magnets vs wire magnetics Reply with quote

Don Kelly <dhky@peeshaw.ca> wrote:

<snip>

Quote:
They were likely quite improved over the last one I used. in the 50's. The
film had to be developed in a dark room so,until this was done, one had no
idea whether the results were any good. At least you could have a lot more
data channels than available on the "non-storage"' scopes of the day!

--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

The Nike was much the same.

The media was photo paper (as opposed to film), but you still had to
develop it.

There was a little machine to do that, but the one time I needed the thing,
it was broken.

Nothing like developing a 15 foot length of photo paper by hand in a
tray (it took 3 people).

--
Jim Pennino

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Don Kelly
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 166

PostPosted: Fri Jun 03, 2005 3:21 am    Post subject: Re: bar magnets vs wire magnetics Reply with quote

<jimp@specsol.spam.sux.com> wrote in message
news:d7n5qt$l2q$1@mail.specsol.com...
Quote:
Don Kelly <dhky@peeshaw.ca> wrote:

snip

They were likely quite improved over the last one I used. in the 50's.
The
film had to be developed in a dark room so,until this was done, one had
no
idea whether the results were any good. At least you could have a lot
more
data channels than available on the "non-storage"' scopes of the day!

--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

The Nike was much the same.

The media was photo paper (as opposed to film), but you still had to
develop it.

There was a little machine to do that, but the one time I needed the
thing,
it was broken.

Nothing like developing a 15 foot length of photo paper by hand in a
tray (it took 3 people).

--
Jim Pennino

Remove .spam.sux to reply.
-----------------

I had to use one in a remote power plant and after using the only and last
roll of paper of the right size, found -nothing!
A repeat trip required cutting down a wider roll to fit and a 100 mile each
way trip to the plant in a Quebec winter where the road and ditches were the
same colour and the hot part of the day was -40. This time I had a tech who
took each run into the darkroom (toilet) and developed it before trying
again and finally trapped the problem.
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer
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