The AC-4x-DH sensor package, now a legacy product, was a triaxial accelerometer designed for borehole applications regarding strong motion earthquake survey and monitoring. The AC-4x accelerometer was based on the modern MEMS (Micro Electro-Mechanical Systems) technology, consisting of sensing cells assembled in a way that optimises their performances. This combined with the state of the art proprietary circuit design yielded this cost effective and reliable accelerometer.
MEMS cells include linear accelerometer sensing elements which measured the capacitance variation in response to any movement or inclination and a factory trimmed interface chip that converted the capacitance variations into analog or digital signal proportional to the motion. The DC response allowed the sensor to be easily repaired, tilt tested or recalibrated in the field. With the help of the TEST LINE the AC-4x accelerometer could be completely tested assuring proper operation.
The downhole casing contained the entire sensor system. The sensor was connected through Overvoltage Protection stage to the recorder at the surface with a cable.
Using inclinometer tubes and the provided guiding wheels, the sensor could be oriented before insertion in the tube.