G
George Herold
- Jan 1, 1970
- 0
Hi all, first off I may never build this.
At the moment I'm only thinking about it, with your 'most excellent'
help.
So from a thread started by Tim W. about frig magnets,
I got onto measuring B field gradients,
In particular the gradients, in the Earth's (~50uT ) field,
on the order of 1 uT/m.
Phil H started me thinking about wiggling a coil back and forth to
measure the gradient.
The emf will go as the field gradient, times the velocity, times the
area of the coil.
(** = ^ , 10**2 = 10^2 = 100)
For a 1cm**2 coil at 1m/s that's 10**-10 V. kinda depressing.
But I can add turns, increase area, (increase velocity?)
(Can I shake something at 1m/s? non-magnetically.)
To get to a microvolt I need a 10**4 increase.
1000 turns and 10cm**2 or 100 turns and 100 cm**2?
(or something else)
I also think the coil will have to sit in a thick walled (aluminum?)
shield
that will keep out the AC magnetic fields at (and above) the shake
frequency,
but allow the DC field gradients through. So a higher frequencies
will mean a thinner shield. (my total cost of 'gizmo' ~$100-200)
(How many skin depths will I need?)
And then how do I wiggle it? I'm thinking a coil on the end of a long
I-Beam.
Maybe I can drive it resonantly with a 'upstream' peizo?
I'm looking for some crazy ideas (or maybe this just doesn't work.)
George H.
At the moment I'm only thinking about it, with your 'most excellent'
help.
So from a thread started by Tim W. about frig magnets,
I got onto measuring B field gradients,
In particular the gradients, in the Earth's (~50uT ) field,
on the order of 1 uT/m.
Phil H started me thinking about wiggling a coil back and forth to
measure the gradient.
The emf will go as the field gradient, times the velocity, times the
area of the coil.
(** = ^ , 10**2 = 10^2 = 100)
For a 1cm**2 coil at 1m/s that's 10**-10 V. kinda depressing.
But I can add turns, increase area, (increase velocity?)
(Can I shake something at 1m/s? non-magnetically.)
To get to a microvolt I need a 10**4 increase.
1000 turns and 10cm**2 or 100 turns and 100 cm**2?
(or something else)
I also think the coil will have to sit in a thick walled (aluminum?)
shield
that will keep out the AC magnetic fields at (and above) the shake
frequency,
but allow the DC field gradients through. So a higher frequencies
will mean a thinner shield. (my total cost of 'gizmo' ~$100-200)
(How many skin depths will I need?)
And then how do I wiggle it? I'm thinking a coil on the end of a long
I-Beam.
Maybe I can drive it resonantly with a 'upstream' peizo?
I'm looking for some crazy ideas (or maybe this just doesn't work.)
George H.