PSN-L Email List Message
Subject: Re: Velocity Sensor Designed Specifiically for diff input
From: "Geoffrey" gmvoeth@...........
Date: Mon, 15 Feb 2010 21:20:38 -0700
Hello Chris,
I have in the past ( like 1970s )
seen wire that is "like" 40 guage paired
magnet wire which was designed
to be used with expendable
bathythermograph probes.
( make a temp profile of the ocean waters )
I have never seen such wire
available to anything but
government.
have you ever seen such wire in any
guage at all ?
Maybe its not even copper
If I know Govt it might be silver wire
but i think it looked copper.
Lets say twin 30 gauge copper wire
which is enameled on a 1000 or more foot
spool ?
I would think this be the right kind of wire
to make a center tapped sensor coil ?
regards,
geoff
----- Original Message -----
From:
To:
Sent: Saturday, February 06, 2010 4:26 PM
Subject: Re: Velocity Sensor Designed Specifiically for diff input
> In a message dated 06/02/2010, gmvoeth@........... writes:
>
> What i mean is a coil like a center tapped inductor
>
> +.......|
> C
> O
> Gnd.....|
> I
> L
> -.......|
>
> CO part and the IL part have to be identical. I do not know if you can
> wind such a thing all at once or need two identical yet seperate coil magnet
> assemblies.
> Hi Geoff,
>
> You can wind it quite easily using two supply reels winding on both
> wires at the same time.
>
> Forget the amplifier part altogether, use what you want.
> The ordinary single opamp with four resistors will allow you to wind a
> single coil and use an amplifier of that type.
>
> I have never built such a singular thing and can only guess where to begin.
>
> I do know that inital signal strength and signal to noise ratio is
> paramount for any sensor at all and not just for areas of our own interest.
>
> Easiest way to get a good signal to noise ratio seems to be to use a two
> ton (avd.) mass instead of a two pound (avd.) one. The highest density
> material you can afford.
> That is not neccessary or desirable.
>
> Superconducting wire sounds ideal yet none at room temp as far as I know.
> There is none and unlikely to be any in the future.
>
> At the moment i am thinking two of your coil/magnet ideas in additive
> fashion connected to the same mass.
> Two coils should double the signal right from the start. Four would
> quadruple it.
>
>
> You usually do better by doubling the number of turns on a coil. A large
> increase in the output can be readily achieved by using thicker NdFeB
> magnets, rather than by using more turns on the coil. The limit is set by
> diamagnetic forces on the copper wire at the edges of the magnets. Copper wire
> varies in it's magnetic properties.
> If you use a true differential amplifier like the INA118 with a double
> wound coil, you can use finer wire since the coil resistance is not so
> important. Calculate the kT noise voltage in the coil.
>
> Regards,
>
> Chris Chapman
>
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