Method for calibrating an accelerometer

A method for calibrating an output signal generated by an acceleration sensor, said sensor having a rigid frame, an inertial sensing mass supported by said frame and displaceable from a first position relative to said frame towards a second position of maximal displacement relative to said frame in response to acceleration inputs applied to said frame along a sensing axis, means for generating said output signal responsive to displacement of said sensing mass relative to said frame, and means responsive to a calibration pulse for electrostatically displacing said sensing mass towards said second position without regard to application of acceleration inputs to said frame, wherein said electrostatic displacement means operates to simulate the application of an accelerating field of known magnitude to said frame along said sensing axis, said method comprising the steps of:

• receiving a first value for said output signal in the absence of said calibration pulse;
• applying said calibration pulse to said electrostatic displacement means;
• receiving a second value for said output signal while applying said calibration pulse to said electrostatic displacement means;
• and
• calibrating subsequent values for said output signal using said first and second values for said output signal.

A method for quantifying an electrostatic field used in calibrating an output signal generated by an acceleration sensor, said sensor having a rigid frame, an inertial sensing mass supported by said frame and displaceable from a first position relative to said frame towards a second position to maximal displacement relative to said frame in response to acceleration inputs applied to said frame along a sensing axis, means responsive to sensing mass displacement for generating said output signal, and means for generating said electrostatic field, said electrostatic field operating to displace said sensing mass towards said second position without regard to acceleration inputs to said frame, said method comprising the steps of:

• applying a reference force to said sensing mass simulating application of an acceleration input of known magnitude to said frame along said sensing axis;
• receiving a first value for said output signal when applying said reference force;
• receiving a second value for said output signal in the absence of application of said reference force, and in the absence of said electrostatic field;
• generating said electrostatic field to displace said sensing mass to a third position relative to said frame intermediate said first and second positions;
• receiving a third value for said output signal in the absence of application of said reference force and while generating said electrostatic field;
• and
• quantifying said electrostatic field using said first, second, and third values for said output signal.

A method for establishing a value for the instantaneous sensitivity of an acceleration sensor, said sensor having a rigid frame, an inertial sensing mass supported by said frame and displaceable relative to said frame in response to acceleration inputs applied to said frame along a sensing axis, electrostatic means acting on said sensing mass for electrostatically simulating application of an acceleration input of known magnitude to said frame along said sensing axis, and means responsive to sensing mass displacement for generating an output signal, said method comprising the steps of:

• simulating application of said known acceleration input with said electrostatic means;
• receiving a first value for said output signal when simulating application of said known acceleration input with said electrostatic means;
• receiving a second value for said output signal in the absence of said simulated acceleration input;
• and
• determining said sensitivity value using said first and second values for said output signal and the magnitude of said simulated acceleration input.