ALOHA Cabled Observatory
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ALOHA Cabled Observatory |
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Aloha Cabled Observatory Engineering Documentation Hydrophone Pre-Amp
Hydrophone Preamplifier The analog audio amplifier for the hydrophone consists of four stages. The first three stages are broadband and are good for seismic data. The input stage is a very high impedance bootstrapped input amplifier with a filtered 20 dB gain. Since the hydrophone is a capacitive source, an extremely high input impedance is required to extend the frequency response out into the ULF range at frequencies below 0,1 Hz. Because the settling time is very slow for such an amplifier, the Rabbit 3000 Controller can turn off the bootstrapping response during deployment so that acoustic signals can be monitored while the package is still moving. The second stage is 10 dB gain with a pre-whitening microseism filter. The third stage has a high/low gain amplifier of either 0 dB or 18 dB selectable by the Rabbit 3000 Controller (9). This signal goes to the right channel of the ADC (6). The final stage is a 10 Hz high pass audio filter for listening with a 4 dB gain. This goes to the left channel of the ADC (6).
Rev: 08/10/2007
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