The Micro-Magnetometer (MicroMag3) is used to sense the orientation of a profiler with respect to the earth’s magnetic field. This is a cost effective, low-power sensor that uses magneto-induction to measure the magnetic field. There are no moving parts. The MicroMag3 is mounted on a circuit board manufactured by Rockland Scientific International so that its three axes are aligned with the axes of sensitivity of the VMP’s accelerometers. Data are retrieved using the Instrument Bus by the same procedures used for the Analog-to-Digital Converter and the Sea-Bird frequency counters. The x-, y-, and z-axes are assigned, by default, to channels 34, 33 and 32, respectively. Other triplets of addresses starting with N = 0 to 15, are available. A calibration sheet is provided with each instrument that carries the magnetometer.