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THE PH-44/52/70 PIEZOELECTRIC SOURCES FOR BOREHOLES
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The SWEPT IMPACT SEISMIC TECHNIQUE (SIST) consists of producing seismic signals as a series of pulses according to a deterministic time coding scheme. SIST is significantly more time-efficient than on-line stacking. The low power of the individual pulses maintains a relatively high signal frequency content, even in soft materials.
 
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      (a)                   (b)

The PH borehole piezoelectric sources are designed for investigation depths up to 1km. The seismic signals are produced by applying controlled sequences of high voltage pulses to a stack of piezoelectric crystals. The standard frequency band is 500-2500 Hz. Versions with a band of 1000-5000 Hz are also available.

The tools consist of three modules connected by steel-armored cable: the power supply&controller (out-of-the-hole), the high voltage generator (out-of-the-hole or down-hole) and the piezoelectric actuator (down-hole) equipped with an acoustic impedance converter (a) or a motor-driven sliding wedge clamping mechanism (b).

The sources are designed for minimum borehole diameters of 46 mm (PH-44), 56 mm (PH-52) and 76 mm (PH-70).

Specifications
Frequency Range: 500-3000 Hz
Working Voltages: from surface: 220 V / 50 Hz to piezocrystals: up to 6 KV
Maximum Working Depth: 1000 m
Maximum Temperature: 75 C
Minimum Hole Diameter: 56 mm
Dimensions: piezoelectric converter length: 310 mm
signal generator module length: 2100 mm
diameter: 52 - 54 mm
Mass: 23 - 25 kg (without cable)