Dual and triple axis inertial sensors and methods of inertial sensing

An inertial sensor comprising:

• a frame;
• a mechanical stage suspended from the frame, a proof mass suspended from the mechanical stage, the mechanical stage operative to decouple movement of the proof mass in two orthogonal directions;
• a first resonant element coupled to a first portion of the mechanical stage, the first portion of the mechanical stage free to move parallel to a first axis;
• a second resonant element coupled to a second portion of the mechanical stage, the second portion of the mechanical stage free to move parallel to a second axis, the second axis being orthogonal to the first axis;
• drive means coupled to the resonant elements for vibrating each of the resonant elements;
• and a sensor assembly for detecting a shift in the resonant frequency of each of the first and second resonant elements.

An inertial sensor comprising:

• a frame;
• a proof mass suspended from the frame;
• a pair of first resonant elements coupled to the proof mass, or to an intermediate component coupled to the proof mass, each first resonant element coupled to an opposite side of the proof mass to the other, the first resonant elements being substantially identical to one another and having substantially identical coupling with the proof mass when the sensor is not accelerating;
• wherein movement of the proof mass towards or away from the first resonant elements alters the effective stiffness of the first resonant elements;
• drive means coupled to the first resonant elements for vibrating each of the first resonant elements;
• a sensor assembly for detecting a shift in the resonant frequency of each of the first resonant elements;
• and processing means to sum the shifts of each of the first resonant elements to provide a measure of temperature.