Edgetech 2000-TVD, User Hardware Manual

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1.3.2 Pressure Sensor
A pressure sensor can be installed in the towfish to provide towfish depth data. This type of pressure
sensor is designed for continuous use in a corrosive liquid environment and has a 500-psi pressure range.
1.3.3 Power Loss Pinger
A power loss pinger activates when towfish power is lost and the towfish is submerged. Should this event
occur, the pinger will continuously transmit an acoustic pulse which can be received by a pinger locator.
The pinger is fully self-contained in a stainless steel or aluminum housing and includes an internal battery.
1.3.4 Responder
The responder functions with an optional acoustic tracking system to provide towfish positioning. The
tracking system deck unit provides a trigger which is input to the topside computer, and the topside
computer outputs the trigger signal to the towfish by combining the signal with the downlink command
and uplink sonar data signals.
1.4 Full Spectrum Chirp Technology Overview
EdgeTech's Full Spectrum Chirp technology has several distinct advantages over conventional side scan
and sub-bottom profiling systems. These benefits include the use of separate sub-bottom acoustic
projectors and receivers to enable simultaneous transmission and reception of acoustic signals, high
signal-to-noise ratio (SNR) for improved side scan and sub-bottom imagery, high repeatability of the
transmitted signals from pulse to pulse for high signal definition, high resolution for measurement of fine
sediment layering and display of along track and across track imagery, reduction of side lobes for minimal
reception of undesired echoes, additional processing gain for energy efficiency, and a Gaussian shaped
amplitude spectrum of the outgoing pulse to preserve resolution and bandwidth with attenuation.
1.4.1 Separate Sub-Bottom Acoustic Projectors and Receivers
The side scan sonar uses a line array of piezoelectric elements to both transmit and receive the acoustic
signals, one on the port side of the towfish and one on the starboard side. The sub-bottom sonar uses
separate acoustic projectors and receivers. The projectors are wide band piston type transducers, and the
receivers are hydrophone arrays composed of lead zirconate titanate (PZT) crystals. The transducers are
mounted in the forward section of the towfish, and the hydrophone arrays are mounted aft. The use of
separate transmitting transducers and receiving hydrophone arrays preserves linearity and allows the
simultaneous transmission and reception of the acoustic signals. The transducers and hydrophone arrays
are mounted beneath acoustic baffles which minimize direct path, towfish and surface reflections.