  An automated magnetometer suitable for long lasting measurement under stable
and controllable experimental conditions has been implemented. The device is
based on Coherent Population Trapping (CPT) produced by a multi-frequency
excitation. CPT resonance is observed when a frequency comb, generated by diode
laser current modulation, excites Cs atoms confined in a
$\pi/4\times(2.5)^2\times1 \textrm{cm}^3$, 2 Torr $N_2$ buffered cell. A fully
optical sensor is connected through an optical fiber to the laser head allowing
for truly remote sensing and minimization of the field perturbation. A detailed
analysis of the CPT resonance parameters as a function of the optical detuning
has been made in order to get high sensitivity measurements. The magnetic field
monitoring performances and the best sensitivity obtained in a balanced
differential configuration of the sensor are presented.
