HP MEMS SEISMIC SENSOR Don Milligan Sensor Design Engineer
[email protected]
Introduction HP MEMS Inertial Sensing Technology has been optimized to produce a breakthrough performance needed for Seismic Imaging requirements.
Outline: • • • • • •
Sensor Design Specifications Noise Optimization Test Results QC Self Tests Conclusions
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HP MEMS Seismic Sensor Key Features – Three single crystal silicon wafers hermetically bonded under vacuum • •
Pressure controlled for low thermal mechanical noise CTE match of substrates results in temperature stability
– Surface Electrodes • •
Constant gap allows large proofmass travel in open loop Three phase electrode configuration allows full sensitivity and range at any orientation or wafer alignment
– Custom ASIC • • •
Low noise demodulation of capacitive sensor Low power 24 bit digital output
electrodes Cap wafer MEMS wafer
Stator wafer
suspension
bond
Sensor Node and Tether Head Assembly
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Voyager Seismic Sensor Specifications Max acceleration amplitude Noise spectral density
Peak (Highest Gain Mode)
+/- 80 mG
Peak (Lowest Gain Mode)
+/- 320 mG
Noise density
< 13 nG/rt Hz
Dynamic range
120 dB
THD @ 12Hz, 68.4 mg pk acceleration (0.7 in/s pk velocity)
< -80 dB
Depth
24 bit (20 ENOB)
Sample Rate
2ms or 4ms
Passband
1-200Hz (2ms)
Cross axis sensitivity
All axes