At 10:06 PM +0000 12/23/09, [email protected] wrote:
Date: Thu, 24 Dec 2009 09:46:13 +1300
From: Bruce Griffiths <[email protected]>
Subject: Re: [time-nuts] Cheap Rubidium
To: Discussion of precise time and frequency measurement
<[email protected]>
Joe Gwinn wrote:
Date: Thu, 24 Dec 2009 08:57:42 +1300
From: Bruce Griffiths <[email protected]>
Subject: Re: [time-nuts] Cheap Rubidium
To: Discussion of precise time and frequency measurement
>> <[email protected]>
[snip]
>> Distributed heating using wire wound or printed heaters perhaps, but to
reduce the associated magnetic field bifilar winding should be
considered.
Non-inductive power resistors, which are commercially available, have
very low magnetic fields.
The low-inductance resistors have Ayrton-Perry windings, which are
bifilar.
No, Ayrton-Perry windings arent bifilar.
Classically a flattened helical winding was made on a insulating card.
An identical winding was then wound in the opposite direction on top of
the first winding and the 2 were connected in parallel.
The idea being that the small magnetic field produced by one flattened
helix is cancelled by that of the other flattened helix.
True enough - while there are two conductors, they are not close and parallel.
Anyway, the point is that non-inductive components by definition have
low magnetic fields, and that non-inductive power resistors are
common.
To eliminate the field from the loop of resistors, one can have a
linear string of A-P resistors in series, with a pair of return wires
in parallel, with the return wires on either side of the resistor
string, thus reducing the effective loop area.
Joe
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