Production insturment

The internal details of the production instrument. The design includes a "no moving parts" direction sensor described below. It avoids the need for expensive and fragile gimbals and oil filled damping chambers used in the earlier instruments. The design uses a combination of a very low power, 3 axis magnetometer and 2 axis accelerometer. The data from these sensors are processed in the microprocessor to determine tilt and magnetic direction, and are combined with velocity sensor outputs to determine the N/S and E/W components for vector averaging.