Accelerometers could be single or three axis devices an average single axis system is packaged inside a 25 x 25 mm casing weighing 45 grams. This includes a pendulum (proof-mass) that senses acceleration. Relative displacement between your pendulum and casing is thought with a high gain capacitance pick-off and two coils.
A shut loop servomechanism feedback signal (proportional to acceleration) will be amplified and demodulated. This feedback signal (analogue current or digital pulses) is used towards the coils to restrain the pendulum in the null position.
The feedback needed to keep the null position is proportional towards the thought acceleration this becomes the accelerometer’s output signal. Due to the high gain from the servomechanism electronics used, pendulum displacements are restricted to microradians. An important temperature sensor provides thermal compensation. The IRU contains three devices, calculating acceleration within the longitudinal, lateral and normal axes from the aircraft.
The main sensors utilized in inertial satnav systems are accelerometers and gyros to look for the aircraft’s movement. These sensors provide outputs which are processed to supply fundamental navigation data.
The inertial navigation system must set up a local attitude reference and direction of true north for navigation purposes. In this process, the aircraft shouldn’t be moved.
MEMS based sensors
Developments in micro-electromechanical systems (MEMS) technologies have brought to plastic accelerometers which are more reliable and could be manufactured onto a built-in circuit. MEMS may be the integration of mechanical elements, sensors and electronics on the common plastic substrate through micro-fabrication technology.