Appendix

Calibration

Older HW was using slightly different capacitors, so there sis a tiny variation in the cal functions.

MFS-Coils

MFS Coils

OLD Calibration Files are normalized by f!
e.g. the MFSXXX.txt files.

The JSON files are using mV (as the time series data) and are not normalized by f.
If you normalize the calibration you end up with a constant \(\frac{200 mV}{nT \cdot Hz}\) and 90° phase below 0.1 Hz for the MFS-06e and \(\frac{20 mV}{nT \cdot Hz}\) and 90° for the MFS-07e.

MFS-06e

\(P_{1} = i \cdot \frac{1}{4 Hz}, \enspace P_{2} = i \cdot \frac{1}{8192 Hz} \enspace\) \(P_{3} = i \cdot \frac{1}{0.72 Hz},\enspace P_{4} = i \cdot \frac{1}{28300 Hz}\)

Chopper on

\(F_{on}(f) = \frac{ mV}{nT} = 800 \enspace \frac{mV}{nT} \cdot \frac{P_1}{1+P_1} \cdot \frac{1}{1+P_2} \cdot \frac{1}{1+P_4} \)

Chopper off

\(F_{off}(f) = \frac{ mV}{nT} = 800 \enspace \frac{mV}{nT} \cdot \frac{P_1}{1+P_1} \cdot \frac{1}{1+P_2} \cdot \frac{P_3}{1+P_3} \cdot \frac{1}{1+P_4} \)

MFS-07e

\(P_{1} = i \cdot \frac{1}{32 Hz}, \enspace P_{2} = i \cdot \frac{1}{40000 Hz} \enspace\) \(P_{3} = i \cdot \frac{1}{0.72 Hz},\enspace P_{4} = i \cdot \frac{1}{50000 Hz}\)

Chopper on

\(F_{on}(f) = \frac{ mV}{nT} = 640 \enspace \frac{mV}{nT} \cdot \frac{P_1}{1+P_1} \cdot \frac{1}{1+P_2} \cdot \frac{1}{1+P_4} \)

Chopper off

\(F_{off}(f) = \frac{ mV}{nT} = 640 \enspace \frac{mV}{nT} \cdot \frac{P_1}{1+P_1} \cdot \frac{1}{1+P_2} \cdot \frac{P_3}{1+P_3} \cdot \frac{1}{1+P_4} \)