6A006"Magnetometers", "magnetic gradiometers", "intrinsic magnetic gradiometers", underwater electric field sensors, "compensation systems", and specially designed components therefor, as follows:

N.B. SEE ALSO 7A103.d.
Note:
6A006 does not control instruments specially designed for fishery applications or biomagnetic measurements for medical diagnostics.
a. "Magnetometers" and subsystems as follows:
1. "Magnetometers" using "superconductive" (SQUID) "technology" and having any of the following:
a. SQUID systems designed for stationary operation, without specially designed subsystems designed to reduce in-motion noise, and having a 'sensitivity' equal to or less (better) than 50 fT (rms) per square root Hz at a frequency of 1 Hz; or
b. SQUID systems having an in-motion-magnetometer 'sensitivity' less (better) than 20 pT (rms) per square root Hz at a frequency of 1 Hz and specially designed to reduce in-motion noise;
2. "Magnetometers" using optically pumped or nuclear precession (proton/Overhauser) "technology" having a 'sensitivity' less (better) than 20 pT (rms) per square root Hz at a frequency of 1 Hz;
3. "Magnetometers" using fluxgate "technology" having a 'sensitivity' equal to or less (better) than 10 pT (rms) per square root Hz at a frequency of 1 Hz;
4. Induction coil "magnetometers" having a 'sensitivity' less (better) than any of the following:
a. 0,05 nT (rms) per square root Hz at frequencies of less than 1 Hz;
b. 1 × 10-3 nT (rms) per square root Hz at frequencies of 1 Hz or more but not exceeding 10 Hz; or
c. 1 × 10-4 nT (rms) per square root Hz at frequencies exceeding 10 Hz;
5. Fibre optic "magnetometers" having a 'sensitivity' less (better) than 1 nT (rms) per square root Hz;
b. Underwater electric field sensors having a 'sensitivity' less (better) than 8 nanovolt per metre per square root Hz when measured at 1 Hz;
c. "Magnetic gradiometers" as follows:
1. "Magnetic gradiometers" using multiple "magnetometers" specified in 6A006.a.;
2. Fibre optic "intrinsic magnetic gradiometers" having a magnetic gradient field 'sensitivity' less (better) than 0,3 nT/m rms per square root Hz;
3. "Intrinsic magnetic gradiometers", using "technology" other than fibre-optic "technology", having a magnetic gradient field 'sensitivity' less (better) than 0,015 nT/m rms per square root Hz;
d. "Compensation systems" for magnetic or underwater electric field sensors resulting in a performance equal to or better than the specified parameters of 6A006.a., 6A006.b. or 6A006.c.;
e. Underwater electromagnetic receivers incorporating magnetic field sensors specified in 6A006.a. or underwater electric field sensors specified in 6A006.b.
Technical Note:
For the purposes of 6A006, 'sensitivity' (noise level) is the root mean square of the device-limited noise floor which is the lowest signal that can be measured.