`Small´ micro inertial sensors

There have been many developments in the field of silicon micromachined accelerometers and gyroscopes. These developments have produced devices with useful performance, however many of the devices have been many mm in size rather than `micron´ size. The approach at DRA Malvern has been to study true micro inertial components that are less than 1 mm*1 mm. While it was realised that these devices are never going to have the same performance as `large´ devices, it was believed that there are many current and future applications where the device will not be required to work in isolation. Rather they will work as part of a suite of sensors and systems to give the required overall system performance. An example of this is, the obvious synergy between GPS and `lower´ grade inertial components. These `true´ microsensors will offer advantages over their larger cousins. They will take full advantage of the batch production technology that make silicon chips so cheap. Being so small they will allow several devices to be built on one chip. These devices may all be the same which will improve reliability, or allow several different devices, say accelerometer, gyroscope and magnetometer to be combined on one chip. The authors review the current status of their work on polysilicon accelerometers and gyroscopes making a special reference to what they believe will be the ultimate performance of the small polysilicon devices. A working device is demonstrated. Further work on the integration of magnetometers is also described