A typical MEMS-TFG incorporates a single or dual (contra – mass-balanced) tuning fork (Proof Mass) arrangement, integrated on a silicon chip. Capacitive measurements are made between the fork tines (Proof Mass) as they contort relative to device rotation (Coriolis Effect). Current fabrication and manufacturing techniques enables the production of very small sensor devices with proof mass size typically only 1-5 mm. However, even the best commercially available MEMS gyro struggles to reach a bias performance of 1 deg/hr, with units in associated defence developments approaching 0.3 deg/hr. Oilfield applications requires the sensor have a performance capability within the range 0.1-0.01 deg/hr.
MEMS Gyros have to-date found a wide market in low performance applications. They are used in cars, smartphones, gaming systems etc. In the navigation world they are used to assist GPS acquisition in artillery shells, but have not yet been used for any form of unaided inertial navigation.The small size and mass of current sensors results in lower performance and resolution with poorer signal to noise characteristics. Their size does however lend the device to thermal shield encapsulation providing the necessary thermal operating stability. Improved performance is expected to follow as the industry succeeds in developing techniques and production methods to produce thicker and larger component parts including the proof mass. This should result in improved stability and signal to noise characteristics and hence improved performance. These developments will hopefully lead to low volume, high accuracy, high value applications and the Holy Grail for down-hole surveying in small, rugged, robust, vibration insensitive, accurate inertial navigation systems which can operate throughout all phases of the drilling process.
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