ERAS Sonar Test System - Low Frequency

ERAS Sonar Test System - Low Frequency is a low cost, compact and flexible sonar test system. Designed for hand-deployment from small vessels, it contains both projector and hydrophone. Transmit, repeat and test signals with the Echo Repeater Acoustic Source System (ERAS)

ERAS Sonar Test System - Low Frequency is controlled by an easy-to-use Graphical User Interface, commanding the Digital Signal Processing software to Echo Repeat, Transpond and produce calibrated complex transmissions.

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Chelsea Technologies has a distinguished history in the design of underwater acoustics technology. Our comprehensive range of standard transducers are adaptable for a wide range of applications from aquaculture to defence, whilst our sonar test system and low frequency sonar test system continues to be in use in navies around the world

ERAS Low Frequency Overview

What is ERAS?

eras sonar calibration test and training system
ERAS sonar calibration test and training system

Chelsea Technologies’ Echo Repeater Acoustic Source (ERAS) is a self-contained sonar calibration, test and training system for use on small vessels. An included ruggedised laptop computer is used to provide all signal selection and control, via a bespoke graphical user interface that can be easily operated, without the need for specialist training.

“a self-contained sonar calibration, test and training system for use on small vessels”

The only other units are a deck unit containing the signal conversion and amplification and a hand-deployable transducer. The system is useful for testing active and passive sonar range, bearing accuracy and target identification. Two frequency bands are offered in the standard ERAS system:

  • Band 1 Low Frequency (LF) – 3 kHz to 23 kHz
  • Band 2 High Frequency (HF) – 23 kHz to 50 kHz
  • There is also a low frequency variant – 280Hz to 2600Hz

ERAS can transmit at up to 171 dB re 1 µPa@1m with a flat transmit response to within ±1.5 dB across these two frequencies bands. The LF source level can be increased to 180 dB re 1µPa@1m between 7 kHz and 19 kHz.

Dual Band Acoustic Source – part of Chelsea Technologies’ acoustic design heritage

Dual Band ERAS Transducer in Transit case
Dual band ERAS transducer in transit case

As a calibrated acoustic transmitter (source mode) ERAS can generate complex test signals. This mode is aimed at testing passive sonar. The test signals can also be used to simulate some active sonar pings and approximate acoustic signatures of known targets by combining noise and tones. An external input is also provided for replaying pre-recorded acoustic signatures through the system. In summary:

  • Up to 24 tones and 5 bands of band limited noise (white, pink or PRN)
    • Each with a selectable source level and frequency
    • Each tone selectable as pulsed or CW
  • AM or FM modulated Signals, (24 Tones and 5 bands of band limited
  • Sweeps, LPM or LFM
  • Pulse trains up to 1000 pulses with stepped source level
  • Broadband noise (white, pink or PRN)

Dual Band Echo Repeater – part of Chelsea Technologies’ acoustic design heritage

The Echo Repeater Acoustic Source - Transducer Deck Cable
The echo repeater acoustic source – transducer deck cable

In “Echo Repeat” mode, ERAS can repeat signals received from a hydrophone contained in the hand-deployable, transducer head. It does this in response to a trigger event, based either on the incoming acoustic signal, an external input, or under operator control. The repeated signal can have a highlight structure imposed upon it to mimic the reflections from a target. A programmed sequence of echo repeated signals can be configured to simulate a moving target by appropriate addition of Doppler frequency shift and monotonically changing time delay. A transpond pulse can also be tagged onto the signal to indicate that the sonar ping was detected and repeated. This function is used to calibrate active sonar systems by providing a controlled acoustic target.

ERAS Low Frequency Features

ERAS Sonar Test System – Low Frequency Features:

  • Compact and lightweight system, ideal for transportation
  • Hand deployable from a range of ocean vessels
  • Acoustic source and echo repeat functions for generating and receiving signals
  • Part of Chelsea’s heritage in marine sonar test systems

ERAS Test System – Low Frequency Applications:

  • Sonar test and calibration
  • Underwater target detection
  • Sonar operator training
  • Surveillance
  • Noise signature simulation
  • At sea, acceptance trials

Low Frequency Operating Modes:

  • Complex Signal Source
  • Sequence
  • Echo Repeater
  • Transponder
  • Received Signal Monitor
  • Slant range Measurement

ERAS Low Frequency Specifications

ERAS Low Frequency Source Modes:

  • Source Transmit Generation Bandwidth 280Hz to 2600Hz
  • Pulse Lengths 3ms to 10s or CW
  • Number of Pulses Up to 1000
  • Pulse Intervals Up to 60s
  • Variable Step Levels -10 to +10 dB
  • Tones Up to 24 (each with definable source levels & frequencies – CW or pulsed
  • Sweeps LFM or LPM
  • Noise Either Broadband or up to 5 user definable bands
  • Noise Types White, Pink or Pseudo-Random
  • Modulated Signal AM or FM, user definable carrier and modulating

ERAS Low Frequency Transpond Modes

  • Frequency Range 280Hz to 2600Hz
  • Pulse Length 0.010s to 10.00s (0.001s step)
  • Variable Step Levels -10 to +10 dB
  • Trigger Types Acoustic, TTL pulse or manual
    Trigger Level & Averaging Fully user definable
  • Transpond Types LFM or LPM sweep, Monotone or Source Mode

ERAS Low Frequency Operating Modes:

  • Echo Frequency 2000Hz and 2600Hz
  • Trigger Types Acoustic, TTL pulse or manual
  • Trigger Level & Averaging Fully user definable
  • Echo Length 10ms to 5s
  • Added Doppler -40 to +40 knots
  • Added Echo Strength -30 to +40 dB
  • Echo Delay Up to 60s
  • Highlights Up to 5
  • Highlight Strength -30 to +30 dB
  • Highlight Offset: Up to 200ms
  • Moving Track Target Velocity –40 to +40 knots
  • Tag on Transpond User configurable

ERAS Low Frequency Mechanical:

  • Computer 405 x 225 x 205mm, 10kg
  • Power Amplifier: 445 x 220 x 538mm, 15kg (splashproof)
  • Transducer: 260 outer diameter x 608mm length, 8.3kg
  • Cable Length: 50m
  • Computer Power Requirement: 90 to 250V AC auto switching 50/60 Hz
  • PA Power Requirement: 95 to 130V or 185 to 260VAC auto switching 50/60 Hz

ERAS Low Frequency Downloads

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