The AC-23-DH sensor package, now a legacy product, was a triaxial accelerometer designed for borehole applications regarding Strong Motion earthquake survey and monitoring. The AC-2x-DH sensors were servo-accelerometers based on a standard exploration geophone mass-spring system with electronic feedback. This type of sensor gives a very good stability versus temperature or aging because of the very simple principle. The sensor did not require maintenance and had very low aging drift. With the help of the TEST LINE the sensor could be easily, completely tested.
The family of AC-2x-DH accelerometer was directly compatible with the GeoSIG recorders. 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.