Don't need SQUIDs to read earth's field. Fluxgates have enough accuracy.
And the earth's natural noise floor is well above the SQUID so you don't
need to pay for all that extra. Remember, SQUIDs can observe the current
flow as metal rusts.
Check out Geometrics. They use the decay of the electron orbits in a Cesium
atom (I think) to read magnetic field to 12 digits, yes that's 12 decimal
digits. I watched the readings shift as a greyhound bus drove by deflecting
the earth's magnetic field over a city block away.
- Robert -
-----Original Message-----
From: Tom Cokenias <[email protected]>
To: Peter Poulos <[email protected]>; [email protected]
<[email protected]>
Date: Tuesday, January 25, 2000 8:15 AM
Subject: Re: Magnetic field immunity in the Arctic regions
Peter
Section 11.2 (4.7), IEC 945 (1996), describes a test to determine the
"compass safe" distance for electronic equipment. The idea here is that a
magnetic compass could be influenced by nearby metal or DC magnetic fields
associated with current flows in wires, etc. The test is to determine the
separation distance at which a maximum acceptable compass deflection will be
caused by the DUT (I'm sorry I don't have the spec available).
As I remember the test parameters chosen were to account for worst-case
geomagnetic field strengths - at the poles.
Military and others are interested in measuring magnetic field anomalies
to determine locations of submarines, hidden vehicles and I believe oil
fields. Measured parameters are very tiny and interfering fields don't have
to be very big to cause errors. Can't recall where I saw info, you might ask
your favorite search engine to look for SQUID, I believe is the acronym for
the supercooled quantum devices used to measure the variations in earth's
magnetic field.
Good luck
Best regards,
Tom Cokenias
EMC Consultant
El Granada, CA
---------
This message is coming from the emc-pstc discussion list.
To cancel your subscription, send mail to [email protected]
with the single line: "unsubscribe emc-pstc" (without the
quotes). For help, send mail to [email protected],
[email protected], [email protected], or
[email protected] (the list administrators).
