A method for closed loop operation of a capacitive accelerometer, the capacitive accelerometer comprising: a proof mass (103; 1602) moveable along a sensing axis in response to an applied acceleration; and first and second fixed capacitive electrodes (101, 102; 1604, 1606) arranged symmetrically either side of the proof mass (103; 1602) along the sensing axis with a gap defined between each of the first and second fixed capacitive electrodes (101, 102; 1604, 1606) and the proof mass (103; 1602) under zero applied acceleration; characterized in that the method comprises: applying a DC voltage of magnitude V B to the proof mass (103; 1602) based on a pre-set threshold acceleration value; applying a first drive signal V 1 to the first fixed capacitive electrode (101; 1604), a second drive signal V 2 to the second fixed capacitive electrode (102; 1606), the first and second drive signals each having a periodic waveform varying in amplitude between zero and a maximum value; sensing a displacement of the proof mass (103; 1602) in response to an applied acceleration; determining whether the applied acceleration is greater than the threshold acceleration value; in response to determining that the applied acceleration is not greater than the threshold acceleration value, applying pulse width modulation to the first and second drive signals V 1, V 2 with a variable mark/space ratio so as to provide a net electrostatic restoring force on the proof mass (103; 1602) for balancing the inertial force of the applied acceleration and maintaining the proof mass (103; 1602) at a null position; and in response to determining that the applied acceleration is greater than the threshold acceleration value, applying pulse width modulation to the first and second drive signals V 1, V 2 with a constant mark/space ratio, and changing the magnitude, V B, of the DC voltage applied to the proof mass (103; 1602) so as to provide a net electrostatic restoring force on the proof mass (103; 1602) for balancing the inertial force of the applied acceleration and maintaining the proof mass (103; 1602) at a null position. a proof mass (103; 1602) moveable along a sensing axis in response to an applied acceleration; and first and second fixed capacitive electrodes (101, 102; 1604, 1606) arranged symmetrically either side of the proof mass (103; 1602) along the sensing axis with a gap defined between each of the first and second fixed capacitive electrodes (101, 102; 1604, 1606) and the proof mass (103; 1602) under zero applied acceleration; applying a DC voltage of magnitude V B to the proof mass (103; 1602) based on a pre-set threshold acceleration value; applying a first drive signal V 1 to the first fixed capacitive electrode (101; 1604), a second drive signal V 2 to the second fixed capacitive electrode (102; 1606), the first and second drive signals each having a periodic waveform varying in amplitude between zero and a maximum value; sensing a displacement of the proof mass (103; 1602) in response to an applied acceleration; determining whether the applied acceleration is greater than the threshold acceleration value; in response to determining that the applied acceleration is not greater than the threshold acceleration value, applying pulse width modulation to the first and second drive signals V 1, V 2 with a variable mark/space ratio so as to provide a net electrostatic restoring force on the proof mass (103; 1602) for balancing the inertial force of the applied acceleration and maintaining the proof mass (103; 1602) at a null position; and in response to determining that the applied acceleration is greater than the threshold acceleration value, applying pulse width modulation to the first and second drive signals V 1, V 2 with a constant mark/space ratio, and changing the magnitude, V B, of the DC voltage applied to the proof mass (103; 1602) so as to provide a net electrostatic restoring force on the proof mass (103; 1602) for balancing the inertial force of the applied acceleration and maintaining the proof mass (103; 1602) at a null position.