A triaxial magnetic heading sensing apparatus includes nulling coils and netoresistive sensors having inputs and outputs. The nulling coils are arranged in parallel relation to three orthogonal planes intersecting at a common center point. The sensors are disposed along orthogonal axes in parallel relation to the orthogonal planes and in close proximity to the center point. Each sensor has a bridge configuration balanced in the absence of an applied external magnetic field and unbalanced in the presence one. Also, a signal generator is connected to the inputs of the sensors for exciting the sensors with a bipolar voltage waveform exhibiting alternating positive and negative voltage polarities punctuated by "off" states of zero volts. Further, a voltage integrator and low pass filter are connected in series with the output of a respective one of the sensors for generating an error signal representative of an imbalance due to the presence of an applied external magnetic field and for coupling the input and output of each nulling coil and of each sensor into a servo control loop such that each sensor is driven by the error signal to a magnetic nulling condition with zero steady state error. A pick-off resistor is connected to the output of the low pass filter for outputting a representation of the nulling current to provide a measure of the applied external magnetic field.

An apparatus for measuring the acceleration of the head or thoracic regions of an anthropomorphic dummy used in auto crash testing which is characterized by a mounting arrangement which provides redundant data capability meeting the required government regulations. Three pairs of acceleometers are mounted within test site cavities provided in the crash dummy within the strict government standards to provide two sets of three accelerometers instead of one. Each accelerometer of each pair is accomodated within a mounting structure relative to required standard reference planes and within a supecified location relative to their sensitive axes such that the data obtained therefrom may be used to obtain acceptable redundant force signals for purposes of the crash test.

A hand bearing compass comprises an electronic direction finding sensor fixed in a flat rectangular compass body. An actuating button causes the sensor to measure a magnetic bearing in dependence on the orientation of the compass body in a horizontal plane; measured bearings are stored in microprocessor memories for subsequent sequential recall to a display. To align the sensor horizontally in use the compass has longitudinal sights for visual alignment with a mark and a flat upper surface of the compass body for alignment with the horizon to facilitate levelling. Actuator and longitudinal sights are laterally spaced to avoid obscuring the latter, and arranged symmetrically about a median plane of the body so that use is possible in either hand.

The orientation of a moving platform with respect to a magnetic field is determined by rotating a 3-component vector magnetometer mounted on the platform about at least two axes in the magnetic field. Changes in the signals from the magnetometer are monitored, and the direction of the magnetic field relative to the platform is computed from the signal changes. It is not necessary to know the DC bias of each magnetometer channel or the component of the background magnetic field along each axis of the magnetometer.

A detector for detecting an oriented physical variable includes, in a casing, an acceleration chip-shaped sensor and a board bearing electronic components. The sensor is mounted on a first surface of an insulating part that includes a second surface fastened to the casing, and a third surface that extends parallel with the plane of the board. Conductive paths extend from the first surface, where they are connected to the sensor, and overlap the third surface, where they are connected to contacts of the board. The sensor can be oriented in a desired direction, with respect to the plane of the board. The various electric connections can be formed by ultrasonic bonding.