fT
femtotesla
Magnetic flux densityexact by definition
The femtotesla is 10⁻¹⁵ of a tesla. It is the scale of magnetoencephalography, where the field outside the skull produced by a population of neurons firing together is between about 10 and 1000 fT, and of the best SQUID and optically pumped magnetometers. The factor is exact, being an SI prefix.
Watch out: The Earth's field is about 50 microteslas, ten orders of magnitude larger than the signal. Biomagnetic measurement is therefore done inside a magnetically shielded room with gradiometer sensor arrangements that reject the uniform background, and a passing lift or a car in the street outside is still visible in the data.
| 1 fT | 1.0000000e-15 T |
Solvers that use magnetic flux density