GeoSIG Ltd Wiesenstrasse 39 8952 Schlieren Switzerland AC-23 / AC-22 / AC-21-DH Downhole Accelerometer Features r Full Scale ± 0.1, 0.2, 0.5, 1, 2 and 4g jumper selectable r Bandwidth 0.1 Hz to 100 Hz (optional 200 Hz) r Dynamic range > 125 dB r Excellent temperature stability r Strong-Motion, Free field and Industrial applications r No field adjustment required r Strong mechanical design r Fits in 3 inch casing Outline The AC-23-DH sensor package is a triaxial accelerometer designed for borehole applications regarding Strong Motion earthquake survey and monitoring. The AC-2x-DH sensors are servo-accelerometers based on a standard exploration geophone massspring 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 does not require maintenance and has very low aging drift. With the help of the TEST LINE the sensor can be easily, completely tested. The family of AC-2x-DH accelerometer is directly compatible with the GeoSIG recorders. The downhole casing contains the entire sensor system. The sensor is connected through Overvoltage Protection stage to the recorder at the surface with a cable. Using inclinometer tubes and the provided guiding wheels, the sensor can be oriented before insertion in the tube. Typical 100 mm casing or hole diameter Surface Borehole with or without casing Soft material Sand Sand CABLE Inclinometer tube SENSOR Hard rock Concrete Concrete Sand

Specifications AC-23 / AC-22 / AC-21-DH Downhole Accelerometer Strong Motion earthquake survey, Industrial applications requiring high sensitivity. General Characteristics Application: Full Scale Range: Factory configurable to: ± 0.1, ± 0.2, ± 0.5, ± 1, ± 2 and ± 4g for ± 10 V diff at output AC-23 NPP: ± 0.5, ± 1 and ± 2g Sensor Element Type: Servo-accelerometer based on geophones with feedback >125 dB effective at ±2 g full scale 0.1 % ± 0.4 dB max over the bandwidth 1% 0.1 Hz (1 pole) to 100 Hz (1 pole) optional 200 Hz 0.7 critical 0 < 1 mV/ C 0 < 200 ppm/ C 0 ± 10 V differential (20 Vpp) See...