Course GEOL-110: Seismic survey, February 2008

O.M., 14 Feb. 2008
University of Bergen, Norway
Dept. of Earth Science

1. Instrumentation diagram

Fig. 1. Instrumentation diagram, GEOL-110, February 2008

2. Filter / Amplifier settings

On each unit you can select 0 or 20 dB gain. In the 2007 survey - with identical streamer, source and instrumentation - we used 20 db gain on all units; in total 60 dB gain (= 1000 x voltage amplification).
Filter settings used 2007:

NORTRONIC unit: No filter => "DIRECT"
KROHN-HITE units: Both had identical settings:

Low-frequency cut-off: Switch x 1.0, knob: 60 => 60 Hz
High-frequency cut-off: Switch x 10, knob: 60 => 600 Hz

3. Connection of Sparker

The sparker element has no polarity.
For the record: Boomer plate HAS polarity. Brown wire should go to Sparker Control Bank "positive" terminal (left on picture below). Boomer plates will move in opposite direction (which is not desirable) if polarity is not correct.

Fig. 2. Connection of sparker. No polarity on sparker; on boomer connect "brown" wire to left terminal.

4. Grounding

Filter/amplifier and EPC plotter grounds should be connected to a common point.

Sparker ground lugs should be connected to ship's ground.

5. Sparker energy output

Ref. this picture from top of Sparker Control Bank:

Fig. 3. Selecting sparker capacitance

The wiring straps now divide the capacitance (expressed as energy - in Joules) into two sections. The one to the left is 300 + 100 + 100 Joule = 500 Joule. The section to the right also represents 500 Joules.

The large switch will either short-circuit the section to the right, or include it in operation. As shown, the right capacitor section is short-circuited.

6. Spark gap cleaning

You might need to clean spark gap terminals:

Fig. 4. The spark gap terminals may need cleaning. Use abrasive paper sheets.

7. Sparker Cables

Referering to cable numbering in fig. 1, we use these cables:

7.1 Cable S1

Fig. 5. Sparker cable S1

We have two adapters for this cable.

Fig. 6. Adapter A, for Sparker cable S1

If you use this cable, please note that fuses may blow on a 16 Amp power line that already supplies other equipment.