DDS

The Dual Downhole System (DDS) is used to receive P- and S-waves in dry and water filled boreholes in order to determine interval velocities. The DDS consists of two stations each equipped with tri-axial sensors. The stations are mechanically connected to each other to ensure the alignment of all horizontal sensors. Both stations are coupled to the borehole wall by a pneumatic clamping system (inflatable bladder). Air is supplied to the DDS through an electro-pneumatic hybrid cable with a Kevlar tension string. A magnetic compass shows azimuthal deviation to North and can be used to get the orientation of the DDS in the borehole. The cable is terminated by a connector to the seismograph.

Technical Details

Natural sensor frequency: 28 Hz (others on request)
Sensor arrangement: Tri-axial
Operational depth: 100 m
Number of stations: 2
Station interval: 2 m
Station length: 620 mm
Station diameter: 65 mm
Station weight: 2.5 kg
Cable weight per metre: 145 g
Cable strength: 2150 N
Borehole diameter: 75 mm
Clamping system: Inflatable bladder
Orientation: Magnetic compass (+/-2.5°)
Depth indicator: Cable marking every 2 m
Connector: To any seismograph
Storage: On drum