ADCP_Ocean_Surveyor_-_Shipboard_Installlation_Guide.pdf

FRV40-224-001-010

DESCRIPTION, OPERATION, INSTALLATION AND

MAINTENANCE INSTRUCTIONS

Acoustic Doppler Current Profiler Model: Ocean Surveyor

Halter Marine, Inc.

13085 Seaway Rd.

P.O. Box 3029 Gulfport, MS 39505

50-SPNA-1-00031

PUBLISHED BY DIRECTION OF NOAA

FRV40-224-001-010

DESCRIPTION, OPERATION, INSTALLATION AND

MAINTENANCE INSTRUCTIONS

Model: Ocean Surveyor

Halter Marine, Inc.

13085 Seaway Rd.

P.O. Box 3029 Gulfport, MS 39505

PUBLISHED BY DIRECTION OF NOAA

28 FEB 2003

RECORD OF CHANGES

Change No.

Date Title and/or Brief Description Signature of Validating Officer

APPROVAL AND PROCUREMENT RECORD PAGE

APPROVAL DATA FOR: FRV40-224-001-010

TITLE OF MANUAL: Acoustic Doppler Current Profiler

APPROVAL AUTHORITY: NOAA

Contract Ship Qty Of Building Number Applicability Manuals Yard

50-SPNA-1-00031 FRV40-224 2 EA Halter Marine Inc.

REMARKS:

CERTIFICATION: It is hereby certified that FRV40-224-001-010 to be provided under contract 50-SPNA- 1-00031 has been approved by the approval data shown above.

Date:________________

VL LOGISTICS

Ocean Springs, MS 39564

CAGE CODE: 1JA28

VALIDATION PERFORMANCE

Title of Publication

Contractor Sub-Contractor(If Performing Validation)

Halter Marine Inc. VL Logistics, Inc.

Contract No. (s) and Purchase Orders, If Applicable

Chapter Section Paragraph Date Check here if Validation Not validated Completed

Contents of this manual have been validated and certified to be applicable to the equipment furnished under the above procurement as specified for Validation.

Name & Authority of Validating Officer: Signature of Validating Officer:

FOREWORD

This manual is intended to clearly and accurately reflect the actual configuration of the installed equipment described for the FRV40-224 Acoustic Doppler Current Profiler. Users are urged to report instances noted wherein the manual does not achieve this objective.

This technical manual provides the instructions necessary to operate, to perform maintenance on and troubleshooting of the Acoustic Doppler Current Profiler. The text is broken down as follows:

Section 1- Introduction

Section 2- Installation Guide

Section 3- Maintenance Guide

Section 4- Test Guide

Section 5- Troubleshooting Guide

Section 6- Ocean Surveyor User’s Guide

Section 7- Command and Output Data Format Guide

Section 8- Quick Reference Card

Section 9- Command Quick Reference Card

Section 10- Vessel Mounted Installation Guide

Section 11- Vessel Mounted DAS User’s Guide

Section 12- Vessel Mounted DAS Quick Start Guide

Section 13- Field Service Bulletins

Section 14- Interim Change Notices

Ocean Surveyor

Read This First

P/N 95A-6017-00 (January 2001)

RD Instruments Acoustic Doppler Solutions

Ocean Surveyor Shipboard

Installation Guide

P/N 95A-6019-00 (January 2001)

RD Instruments

Table of Contents 1 Introduction 2 Ocean Surveyor System Components 3 Transducer Mounting Considerations

3.1 Location

3.2 Orientation

3.3 Floating Objects

3.3.1 Sea Chest

3.3.2 Fairing

3.3.3 Acoustic Window

3.4 Air Bubbles

3.5 Flow Noise

3.6 Corrosion and Cathodic Disbondment

3.7 Ringing

3.8 Acoustic Isolation

3.9 Maintenance

3.10 Electronics Chassis Mounting Considerations

3.11 Cabling Considerations

3.12 I/O Cable

3.13 Using Trigger-In and Trigger-Out

4 Computer Considerations 5 Gyrocompass Interface Considerations

5.1 Overview of the ADCP Gyro Interface

5.1.1 Determining the Synchro Stator Voltage

5.1.2 Determining the Size of the Scaling-Resistor Pack

5.1.3 Installing the Scaling-Resistor Pack and W-Jumpers

5.1.4 Determining and Setting the Synchro Turns Ratio

5.2 Stepper Interface

5.3 Testing the Gyro Interface

5.4 Gyro Cable

6 Navigation Interface Considerations 7 Power Considerations 8 Installation Procedures (Overview) 9 Alignment Procedures (Overview) 10 Specifications

10.1 Water Velocity Specifications

10.2 Profile Parameters

10.3 Bottom Track Specifications

10.4 Echo Intensity Profile

10.5 Transducer and Hardware Specifications

10.6 Internal Sensors

10.7 System Power Specifications

10.8 Environmental Specifications

11 Outline Installation Drawings Ocean Surveyor Electronics Chassis - 96A-6000 Ocean Surveyor 38kHz Oval - SK0193 Ocean Surveyor 38kHz - SK0195 Ocean Surveyor 75kHz - SK0197 Ocean Surveyor 150kHz - SK0201

List of Figures Figure 1. Sea Chest Mounted Transducer (Sloped Hull) Figure 2. Profiler Dome Figure 3. Expanded View of a Sea Chest Figure 4. Acoustic Window Example Figure 5. I/O Cable Figure 6. Typical Ocean Surveyor Interface Cable Layout (Overview) Figure 7. Typical Ocean Surveyor Interface Cable Layout (Detail View) Figure 8. I/O Cable Wiring Figure 9. Gyro Interface Board Figure 10. Cable, Gyro Synchro/Stepper to Electronic Chassis (J2) Figure 11. Transducer Misalignment Reference Points

List of Tables Table 1: Window Thickness Table 2: Wavelength of sound in seawater (1500 m/s sound speed) Table 3: Trigger-In Input/Output Signals Table 4: Minimum Computer Hardware Requirements Table 5: Gyro Interface Options by Model Table 6: Acceptable Gyro Interface Configurations Table 7: Standard Synchro Stator Voltages and Scaling Resistance Table 8: Natel Chip, Resistor Pack, and W-jumper Sockets Table 9: Gyro Interface Switch 1 Settings Table 10: Gyro Interface Switch 2 Settings Table 11: Stepper Voltage Range Table 12: Gyro Interface Troubleshooting Guide Table 13: Water Profiling – Long Range Mode Table 14: Water Profiling – High Precision Mode Table 15: Water Profile Maximum Ping Rate Table 16: Nominal Bottom Track Altitude Table 17: Outline Installation Drawings

Ocean Surveyor Shipboard Installation Guide

P/N 95A-6019-00 (January 2001) page 1

1 Introduction This book is a guide for installing a RD Instruments (RDI) Ocean Surveyor Acoustic Doppler Current Profiler aboard a vessel (ship), or platform. Use this section to plan your installation layout. You also can use this book to see what requirements you must consider before purchasing an ADCP. We recommend you distribute this book to your organization’s decision-makers and installation engineers.

We are not experts in installing the ADCP aboard a ship. There are too many installation methods. We suggest you seek expert advice in this area because of its importance in ADCP performance. However, we can give you information about how others have installed their systems. In return, we do appreciate receiving information about your installation and the results.

2 Ocean Surveyor System Components The standard Ocean Surveyor is an AC-powered, two-part unit. It consists of a bronze transducer assembly mounted in the ship’s hull and an electron-ics chassis you can place in the ship’s lab. Several options are available.

The basic system includes:

• Transducer assembly - Contains the transducer ceramics and electronics. Standard acoustic frequencies are 38, 75, and 150kHz. See the outline drawings for dimensions and weights.

• Electronics chassis - Contains the processing electronics.

• Maintenance kit - Contains spare parts and basic tools needed for routine maintenance.

• Ocean Surveyor technical manual and user’s guide.

page 2 RD Instruments

• Waterproof dummy plug.

• VmDas Software - Controls the ADCP and displays its data through a Windows compatible computer.

• Utilities software - Several programs to help you talk directly to the ADCP (DumbTerm), view data (WinADCP) and other DOS utility programs (RDI Tools).

Standard options include:

• Input/Output (I/O) cables and connectors (length determined by customer).

• Gyrocompass (gyro) interface - Connects the ship’s gyro to the electronics chassis.

3 Transducer Mounting Considerations You must consider several potential problems before installing the trans-ducer assembly. Read this section before deciding where to install the transducer assembly. See the outline installation drawings (see “Outline Installation Drawings,” page 35) for specifications on our standard Ocean Surveyor transducer.

3.1 Location

Ideally, you want to install the transducer assembly:

• Where it is accessible both internally (for access to transducer electronics) and externally (to remove biofouling).

• Where the I/O cable length is 100 m (328 feet) or less.

• Away from shipboard protrusions that reflect ADCP energy. Al-low for a reflection-free clearance of 15° around each beam (see the outline installation drawings).

• Away from other acoustic/sonar devices, especially those operat-ing at the same frequency (or harmonic) of the ADCP.

• Close to the ship’s fore-to-aft centerline. As distance from the centerline increases, vertical accelerations caused by the roll of the ship also increase. These accelerations can cause additional uncertainties in ADCP velocity measurements.

P/N 95A-6019-00 (January 2001) page 3

3.2 Orientation

The 38kHz oval transducer should always be mounted with the transducer’s beam 3 mark on axis (forward). If you have a round Ocean Surveyor trans-ducer, then we recommend you mount the transducer head with Beam 3 mark rotated to a ship-relative angle of 45°. Figure 11, page 31 shows the beam orientation. This causes the magnitude of the signal in each beam to be about the same. This improves error rejection, reduces the effect of ring-ing (see “Acoustic Isolation,” page 10), and increases the ADCP’s effective velocity range by a factor of 1.4. If you align Beam 3 at an angle other than zero, you must nullify this offset (see “Alignment Procedures (Overview),” page 30). You can do this through our VmDas program or using a direct command.

Use the ship’s roll and pitch reference to mount the transducer head as level as possible. If the head is not level, depth cell (bin) mapping will be incor-rect. Large misalignments can cause large velocity measurement errors. If you cannot mechanically make the transducer head level, you can use VmDas to enter offset values for roll and pitch, or use direct commands for roll/pitch offsets (see “Alignment Procedures (Overview),” page 30).

3.3 Floating Objects

Our transducer assembly is sturdy, but we did not design it to withstand col-lisions with all floating objects. We strongly suggest you use one of the fol-lowing.

3.3.1 Sea Chest

A sea chest (Figure 1 through Figure 3, page 4) is a fixture that surrounds and holds the transducer head, protecting it from debris in the water. The bottom of the sea chest must be open to seawater to allow the acoustic beams to pass through freely. If using a sea chest interests you, call us for the latest information.

Figure 1. Sea Chest Mounted Transducer (Sloped Hull) page 4 RD Instruments

Figure 2. Profiler Dome

Figure 3. Expanded View of a Sea Chest

3.3.2 Fairing

A fairing is a structure that produces a smooth outline and reduces drag or water resistance. The fairing also diverts floating objects away from the transducers. A fairing shaped like a teardrop, slopped such that the leading edge (closer to the bow) is higher than the back edge, and extends below the hull (typically 12 inches) will divert the air bubbles away from the trans-ducer faces.

P/N 95A-6019-00 (January 2001) page 5

3.3.3 Acoustic Window

While we do not fully understand windows, we do believe that windows can be used to produce overall performance improvements in vessel-mounted ADCPs. Additionally, if the ship operates where there is danger of barnacle damage or a high density of ice or other floating objects, then the use of an acoustic window is the only option.

It is theoretically possible to use a window successfully, however there are several pros and cons to consider before using an acoustic window.

Advantages

• Well will not fill with air bubbles caused by the ship moving through the surface water (see “Air Bubbles,” page 8).

• Flow noise is reduced (see “Flow Noise,” page 8).

• The well can be filled with fresh water to limit corrosion (see “Corrosion and Cathodic Disbondment,” page 8).

• Barnacles can not grow on the transducer faces. Barnacle growth is the number one cause of failure of the transducer beams (see “Maintenance,” page 11).

• The transducer is protected from debris floating in the water.

Disadvantages

• The range of the ADCP can be reduced because the window can and will absorb some of the transmit and receive energy.

• The transmit signal could be reflected into the well, causing the well to “ring” like a bell. This will cause the data being col-lected during the ringing to be biased. Some ships have reported a loss in range as great as 50 meters. The ringing may be damp-ened by applying sound absorbing material on the well walls (see “Ringing,” page 9).

• The transmit signal could be reflected off of the window and back into the other beams (see “Acoustic Isolation,” page 10).

Our experience has allowed us to put together some minimum specific rec-ommendations:

Window orientation. The acoustic window should be flat and parallel to the transducer mounting plate. Note this is not an absolute requirement. How-ever, if the water temperatures inside the window and outside the window are not the same, all four beams will be refracted and actual velocity com-ponents will be rotated into a new coordinate system. In particular, some of the horizontal velocity will appear as a vertical velocity.

page 6 RD Instruments

Window material. Important acoustic properties of the window include acoustic refractive index (which should be as close as possible to that of water), insertion loss (which should be as small as possible) and speed of sound. There are two acoustic refractive indices: one for shear waves and one for plane waves. The acoustic refractive indices are simply the ratios of speed of sound in water to speed of sounds in the material. Insertion loss combines absorption and reflection of sound, and it depends on both the thickness and the material properties of the window. In particular, you should avoid using window thickness equal to odd multiples of shear mode quarter-waves (Dubbelday and Rittenmeyer, 1987; Dubbleday, 1986). Re-fer to Selfridge (1985) and Thompson (1990) for more information. Note that the speeds of sound in plastics decrease with increasing temperature and that causes the resonant frequencies to shift. This can be a large effect.

Neither Selfridge nor Thompson has much information on the temperature coefficients of sound speeds.

Our experience has shown that Polycarbonate windows are very good for the Ocean Surveyor (OS), WorkHorse (WH), and Broadband (BB) ADCPs.

The thickness of the materials depends on the frequency you intend to use.

Table 1 will help to choose the maximum thickness you should use. Note, one concern with window selection is that it be able to support the weight of the water inside the well once the ship is dry-docked. RDI recommends that you always fill/drain the well at the same time that you are either fill-ing/draining the dry dock area.

Table 1: Window Thickness Frequency Recommended Thickness Maximum Thickness

38 1.5 3 inches

75 1 2 inches

150 1 inch

Spacing between window and transducer. The primary geometrical factor in design of windows is the reflection of a beam into another beam, causing crosstalk between the beams. The distance of the Ocean Surveyor trans-ducer from the window should be at least 0.25 to 0.5 inches. If installed farther than 0.25 to 0.5 inches, then be sure your window aperture is large enough to clear the OD convex beams.

The optimum distance for the bottom of the transducer assembly from the window is 0.25 inches ±0.125 inches. Never allow the transducer to touch the window. The farther away the transducer is from the window, the more the sound is reflected off of one beam and then reflected into another beam.

P/N 95A-6019-00 (January 2001) page 7

Example Our Japanese representative uses 0.25-inch thick window. He then drills two 30mm holes in the window along the edges. The inside walls are painted with anti-fouling paint. This allows the water to be full of anti-foulant during the time the ship is docked, which is when the barnacle growth occurs. The holes allow the water to exchange when the ship is in motion and allows for draining when the ship is dry-docked (a 0.25” win-dow will not support the weight of the water). He has never had a failure with the window, and has seen only a minimal loss in range (5-30 meters).

It is best if the window is parallel to the bottom edge of the transducer. If the window is at an angle to the transducer, it will change the absorption.

We do not have experience with different angles, but we have had custom-ers use domes or have the window follow the contour of the ship bottom without noticeable degradation of the data.

GATE VALVE

TRANSDUCER

TO ELECTRONIC

CHASSIS

VENT/DRAIN

PIPE

WINDOW 25 to 76mm THICK

POLYCARBONATE SHEET

SHIP

BOTTOM

Figure 4. Acoustic Window Example Acoustically-absorbing sea chest liner. A sound absorbing material should be used inside the sea chest to minimize the effects of sound ringing within the sea chest. The material should be a minimum of one wavelength thick (include the sound speed of the absorbing material when calculating the size of a wavelength). Approximate wavelengths of sound in seawater are given below in Table 2. Using standard neoprene wet suit material has been found to work well with 75 and 150hKz frequency ADCPs.

Table 2: Wavelength of sound in seawater (1500 m/s sound speed) Frequency (kHz) Wavelength (mm)

38 40

75 20

150 10 page 8 RD Instruments

Fluid in the sea chest. The sea chest should be filled with fresh water.

Seawater can be used, but at the cost of increased corrosion. Seawater should not be circulated through the sea chest unless the sea chest has been painted with anti-fouling paint. The pressure within the sea chest should be adjusted to keep the window from bowing in and out, and thereafter, the volume should be kept constant.

3.4 Air Bubbles

Design your installation to minimize the volume of air bubbles in the path of the acoustic beams. Air bubbles attenuate (weaken) the signal strength and reduce the ADCP profiling range. Ships with a deep draft or a non-flat bottom have fewer problems with bubbles. Ways to reduce bubble flow vary with ship characteristics, but two options are available. Mount the transducers below or away from the bubble layer.

• The flow layer is usually within the first two feet below the hull.

Bubbles can be trapped in this layer. Mounting the transducer head amidship on the fore-to-aft centerline may help. For ships with propulsion systems that make large amounts of bubbles, use a mounting technique that lets you lower the transducer head be-low the hull while underway.

NOTE. If you use locally made or existing extension hardware instead of the hardware available from RDI, you may need to make an adapter plate to connect your hardware to our transducer head. See “Outline Installation Drawings,” page 35 for the bolt hole locations.

• Divert the bubble layer so it flows around the transducers - You can use fairings to alter the bubble flow (see “Fairing,” page 4).

An acoustic window (see “Acoustic Window,” page 5) may help reduce the bubble problem, but can cause ringing (see “Acoustic Isolation,” page 10) and attenuation problems.

3.5 Flow Noise

Water flowing over the transducer faces increases the acoustic noise level, which decreases the profiling range of the ADCP. You can reduce the flow across the transducer faces with a sea chest, fairing, or acoustic window.

3.6 Corrosion and Cathodic Disbondment

Never attach anodes directly to the transducer head. Additional anodes or impressed voltage systems can cause the urethane to separate from the transducer (cathodic disbondment) or cause the material of the transducer to break down. Standard anode protection used for the ship should be in-stalled outside of the well of the transducer head. Mounting of ship’s stan-

P/N 95A-6019-00 (January 2001) page 9 dard anode protection outside of the transducer well will typically not cause any problems. Our transducers are made of a material that has shown to corrode very little over time when the above precautions are met. The cor-rosion can be further reduced if the well is covered with a window and then filled with fresh water.

3.7 Ringing

The ADCP transmits an acoustic pulse into the water. The main lobe of this pulse bounces off particles in the water and the signals returned from these particles are used to calculate the velocity of the water.

As stated, the main lobe of the transmitted pulse is what we are using to process and calculate a velocity. The transmitted pulse, however, is made up of many side lobes off the main lobe. These side lobes will come in con-tact with metal of the transducer beam itself and other items in either the water or the well.

The energy from the side lobes will excite the metal of the transducer and anything bolted to the transducer. This causes the transducer and anything attached to it to resonate at the system’s transmit frequency. We refer to this as “ringing.”

If the ADCP is in its receive mode while the transducer is ringing then it will receive both the return signals from the water and the “ringing.” Both of these signals are then processed by the ADCP. The ringing causes bias to the velocity data.

All ADCPs “ring” for some amount of time. Therefore, each ADCP re-quires a blanking period (time of no data processing) to keep from process-ing the ringing energy. Each ADCP frequency has a different typical ring-ing duration. The typical ringing period for each ADCP frequency is as fol-lows; 38kHz is 16 meters, 75kHz is 8 meters, and 150kHz ADCPs is 4 me-ters. These typical ringing values are recommended as the minimum setting for all ADCPs using default setups.

It should be noted, on some installations the effects of ringing will last longer than the recommended settings above. For example, the effects of ringing will last longer if the transmit signal becomes trapped inside the transducer well. This can occur because the well itself is ringing with the transducer or when windows covering the opening of the well reflect the signal back inside the well.

The window causes the transmit signal to reflect back into the well due to the difference in impedance between the window and the water. When the transmit signal is reflected in the well it becomes trapped and this results in longer ringing periods. To keep from processing this signal, the blanking page 10 RD Instruments period must be increased. Lining the inside walls of the well with a sound absorbing material aid in dampening the ringing effect.

3.8 Acoustic Isolation

Try to minimize the acoustic coupling between the transducer head and the ship. Without adequate acoustic isolation, the transducer output will “ring” throughout the ship and feeds back into the ADCP receive circuits. Ringing causes bias errors in water-track velocities and results in the loss of data in the closest depth cells (bins). Reflections inside a sea chest with an acous-tic window also can cause ringing.

You can attain acoustic isolation several ways. At a minimum, use gaskets to isolate all contact points between the ship and the transducer head. De-sign your installation for:

• A minimum number of contact points between the transducer head and the ship.

• Minimal contact area.

• Single points of contact for positioning and support (when possible).

You also should try to separate the transducer head from the ship using in-termediate connections. This is because direct connections transfer the most acoustic energy. Texas A & M used the following installation tech-nique and had minimal ringing problems.

• Transducer head mounted to a thin steel plate

• Steel plate positioned with three pins set into mounting holes on the hull; pins isolated with gaskets

• Steel plate held in place with four I-beams welded to a frame

• Frame bolted to another frame and separated by gaskets

• Second frame bolted to the ship and separated by gaskets Acoustic isolation from other acoustic devices on the ship is also necessary.

You can do this using the following techniques.

• Mount the other acoustic devices as far apart as possible.

• Make sure neither the main lobes nor the side lobes of the acoustic devices point at the transducers, including acoustic reflections.

• Do not to operate devices that use the same frequency or a har-monic of the ADCP’s frequency.

P/N 95A-6019-00 (January 2001) page 11

3.9 Maintenance

The Maintenance guide explains routine maintenance procedures. You rarely need access to the electronics inside the transducer head. However, one external maintenance item is important enough to mention here as it may affect how you install the transducer head.

Objects deployed within about 100 meters (328 feet) of the surface are sub-ject to the buildup of organic sea life (biofouling). This means Ocean Sur-veyors are subject to biofouling. Soft-bodied organisms usually cause no problems, but hard barnacle shells can cut through the urethane transducer face causing transducer failure and leakage into the ADCP.

The best-known way to control biofouling is cleaning the ADCP transducer faces often. However, in many cases this is not possible. The other alterna-tives include the use of a window or some sort of anti-foulant protection.

Some of our users have had success applying a thin coat (≈4 mm; ≈0.16 in.)

of either a 50:50 mix of chili powder and Vaseline or chili powder and sili-cone grease to the transducer faces. The chili powder should be the hottest that can be found. Water flowing across the transducers will wash this mix away over time. The silicone mixture tends to last longer.

Some organizations may decide to use antifouling grease. However, most antifouling greases are toxic and may cause problems. Recent tests suggest antifouling grease may cause the urethane on the transducer faces to de-velop cracks. Warmer temperatures accelerate this effect.

The other method is to use antifoulant paint. At present, we recommend the following antifouling paint manufacturer and paint brand: Courtalds Fin-ishes Interlux brand paints, US Telephone: 908-686-1300, Web Page:

www.interlux.com. Contact the antifouling paint manufacturer for prepara-tion and application procedures for this and other antifoulant paints.

http://www.interlux.com/ page 12 RD Instruments

CAUTION.

1. Read the Material Safety Date Sheet before using any of the listed solvents and paints.

2. Some antifouling coatings may not be legal for use in all areas. Check with your local environmental agency before using the antifouling paint.

3. Do not arbitrarily use antifouling paints. Be aware that antifouling paints can accelerate the dezincification corrosion of brass. Once initiated, dezincificatioin will rapidly destroy the transducer.

4. RDI no longer recommends the use of Nopcocide for the prevention of biofouling. If using antifouling grease, remove it immediately after recovering the ADCP.

5. Antifouling grease is toxic. Read the product safety data sheet before using the grease. Wear gloves and a face shield when applying the grease. If the skin comes in contact with the grease, immediately wash the affected area with warm, soapy water.

6. When possible, do not coat the transducer faces with cuprous oxide or related paints that contain chemicals such as copper, chrome, or arsenic. These paints advance the corrosion of the transducer assembly and will cause the urethane to separate from the transducer cups.

7. All US Coastal States prohibit the use of tributyl-tins on boat hulls. The European Economic Commission has released a draft directive that would prohibit the use of many organo-tins after July 1989. We strongly recommend you obey your local laws.

3.10 Electronics Chassis Mounting Considerations

Place the electronics chassis (see “Outline Installation Drawings,” page 35) where there is access to the I/O cable, host computer, gyro interface cable, and navigation interface cable. You can place the rack-mountable chassis in a standard 19-inch cabinet. The chassis needs 90 to 260 VAC to operate (see “Power Considerations,” page 28). Allow enough room around the chassis for access, ventilation, and isolation from electronic and magnetic interference.

CAUTION. Do not place the electronic chassis within 3 feet of a computer monitor. Monitors are a major source of electronic interference.

P/N 95A-6019-00 (January 2001) page 13

3.11 Cabling Considerations

Several cables connect to the Ocean Surveyor system (Figure 6, page 14 and Figure 7, page 14). Use care when routing these cables through bulk-heads, deck plates, cable runs, and watertight spaces. Make allowances in cable length and engineering design plans for cable routing. When neces-sary, use strain reliefs on the cables.

The input/output (I/O) cable (Figure 5 and Figure 8, page 15) connecting the transducer assembly to the electronics chassis has the following specifi-cations.

• Minimum bend radius = 203 mm (8.0 in.)

• Typical cable OD = 19.8 mm (0.78 in.)

• Maximum pull load = 1132 N (250 lb.)

• Maximum length = 100 m (328 ft.)

• Available with either ends having straight or angled connectors or a combination thereof. The transducer-end connector is molded on, so you can use it below the waterline.

Figure 5. I/O Cable Route this cable so:

• You can install it with the connectors attached.

• It does not have kinks or sharp bends.

• You can easily replace it if it fails.

NOTE. You can order the cable with the chassis-end connector removed.

This allows easier cable routing, but requires you to solder the cable connections at your installation site. This is a difficult task.

page 14 RD Instruments

Other cables that may need routing to the chassis include the computer in-terface and the gyro interface. Other cables that may need routing to the computer include the navigation interface and the remote display interface.

COMPUTER

ENSEMBLE OUT

(OPTIONAL)

NAVIGATION DEVICE

(OPTIONAL)

G Y R O /R E P E AT E R A N D

IN T E R FA C E C A B L E

ELECTRONICS

CHASSIS

T R A N S D U C E R

A S S E M B LYS E R IA L C A B L E

I/O CABLE

Figure 6. Typical Ocean Surveyor Interface Cable Layout (Overview)

Figure 7. Typical Ocean Surveyor Interface Cable Layout (Detail

View)

P/N 95A-6019-00 (January 2001) page 15

3.12 I/O Cable

Figure 8. I/O Cable Wiring page 16 RD Instruments

3.13 Using Trigger-In and Trigger-Out

The Trigger Input allows the Ocean Surveyor to be synchronized by an ex-ternal +5Vlogic level signal. The minimum duration for the Trigger Input is 1ms. The Input resistance is at least 2.7 kOhm. The Trigger Output is a +5V logic level signal as well. The nominal source resistance of the Trig-ger Output is 50 Ohms.

The Trigger Output and Input is controlled by the CX a,b command, where a controls the Trigger Input mode, and b the Trigger Output mode. For flexibility, several modes for the Trigger Input and Output operation have been implemented. See Table 3, page 17 for a description of the command.

NOTE. Trigger-In is available only for systems using firmware version 23.xx or later and using the new electronics chassis back panel.

The Trigger In and Trigger Out B-N-C connectors use the center post as the signal input. The outside of the B-N-C connector is used for ground.

The ADCP performs a cycle of reading sensors (known as overhead), transmitting, blanking, processing, and sleep for each ping. When the CX command is enabled (by any setting of CX other than CX0,0), the ADCP will enter a transmit trigger wait state just before the transmitting portion of the cycle. It is during this wait state that the Trigger In input is read by the ADCP. This results in the following caution:

CAUTION. The ADCP does not store trigger in inputs. This means that the ADCP will only acknowledge pulses it sees during the transmit trigger wait state. For example, if 3 trigger in pulses were sent to the ADCP in quick succession only the pulse that occurred during the transmit trigger wait state would be used. The other pulses would be ignored and lost.

The setting of the CX command tells the ADCP what type of input signal (either pulse or a DC level) will be sent as the trigger. The following are the available inputs:

P/N 95A-6019-00 (January 2001) page 17

Table 3: Trigger-In Input/Output Signals Command Action: Description

CX 0,b Trigger Input off Normal operating mode.

CX 1,b Positive edge Trigger Input

Used if Ocean Surveyor is to be Triggered by other equip-ment. One ping is executed on every rising edge of the Trigger signal. Care has to be taken by the user not to exceed the maximum allowable transmit duty cycle of 15%.

CX 2,b Negative edge Trig-ger Input

Used if Ocean Surveyor to be Triggered by other equip-ment. One ping is executed on every falling edge of the Trigger signal. Care has to be taken by the user not to exceed the maximum allowable transmit duty cycle of 15%.

CX 3,b Any edge Trigger Input

Used if Ocean Surveyor to be Triggered by other equip-ment. One ping is executed on every rising and falling edge of the Trigger signal. Care has to be taken by the user not to exceed the maximum allowable transmit duty cycle of 15%.

CX 4,b High level Trigger Input

Used if Ocean Surveyor to be Triggered by other equip-ment. The OS transmits pings as long as the positive level of the Trigger signal is present. In this way, a single ping or multiple pings can be transmitted depending on the du-ration of the positive level. Care has to be taken by the user not to exceed the maximum allowable transmit duty cycle of 15%. A time between pings has to be set for cases where multiple pings should be transmitted.

CX 5,b Low level Trigger Input

Same as CX 4,b except the Trigger is active at the low-level of the Trigger signal. Care has to be taken by the user not to exceed the maximum allowable transmit duty cycle of 15%. A time between pings has to be set for cases where multiple pings should be transmitted.

CX a,0 Trigger Output off Normal operating mode.

CX a,1 Trigger Output –

XMT

The Trigger Output is at a high level during the time the Ocean Surveyor transmits.

CX a,2 Trigger Output –

RCV

The Trigger Output is at a high level during the time the Ocean Surveyor receives.

CX a,3 Trigger Output – X/R The Trigger Output is at a high level during the time the Ocean Surveyor transmits and receives.

CX a,4 Trigger Output – inverted X/R Trigger

Identical to CX a,3, except the signal is inverted. The Trig-ger Output is at a high level while the OS is not transmitting or receiving.

4 Computer Considerations We designed the Ocean Surveyor system to use a Windows® compatible computer. The computer controls the ADCP and displays its data, usually through our VmDas program. Table 4, page 18 lists the minimum computer requirements.

NOTE. It is highly recommended that you download and install all of the critical updates, recommended updates, and the service releases for the version of Windows® that you are using prior to installing any RDI software.

page 18 RD Instruments

Table 4: Minimum Computer Hardware Requirements Windows® 95 (see note), Windows® 98, or Windows® NT 4.0 with Service Pack 4 installed

Pentium class PC 233MHz (350 MHz or higher recommended)

32 megabytes of RAM (64 MB RAM recommended)

6 MB Free Disk Space (20MB recommended)

Two Serial Comports (two High Speed UART Serial Comports rec-ommended)

Minimum display resolution of 800 x 600, 256 color (1024 x 768 or higher recommended)

NOTE. VmDas has special system requirements when using Windows®

95. See the VmDas User's Guide for details.

CAUTION. Do not place the computer monitor within 3 feet of the electronic chassis. Monitors are a major source of electronic interference.

5 Gyrocompass Interface Considerations Vessel Mounted ADCPs do not contain any sensors for measuring heading, pitch, and roll. The vessel must provide this information. There are two ways to interface sensor data such as heading, pitch, and roll information with the ADCP data, either by an analog signal input or by a serial ASCII input. Further details of these interfaces are as follows.

1. Single or multi-turn synchro heading outputs and single-turn synchro tilt sensor outputs for pitch and roll or

2. Stepper heading outputs and single-turn synchro tilt sensor outputs for pitch and roll.

3. Serial ASCII data input to the host computer running the RDI ADCP software that conforms to one of the following NMEA standards.

• $_ _ HDT (NMEA 0183 standard of true heading only)

• $_ _ HDM (NMEA 0183 standard of magnetic heading only)

• $PRDID (RDI proprietary NMEA string supporting heading, pitch, and roll)

P/N 95A-6019-00 (January 2001) page 19

5.1 Overview of the ADCP Gyro Interface

A Gyro Interface board (Figure 9, page 20) is installed in the Electronic Chassis to provide attitude data for the ADCP. ADCPs can use gyro analog outputs to obtain heading, roll, and pitch data. The advantage to these op-tions is that gyro outputs can be used on vessels where flux-gate heading sensors and pendulums cannot. This is due to effects from the hull on a flux gate compass and the acceleration of the ship on pendulum pitch and roll sensors. Table 5 lists the gyro interface options.

Use the RD-SIC-0 option when only stepper heading is available. Use the RD-SIC-1 option when either synchro or stepper heading is available. This option supports single-turn (1:1), multi-turn (36:1, 90:1, 360:1), and stepper voltage outputs from a ship’s gyro or portable gyro. Use the RD-SIC-3 op-tion with a gyro capable of resolving motion across the vertical plane (i.e., tilt synchro gyro). With the RD-SIC-3 option, you can use one of the following:

• Single or multi-turn synchro heading outputs and single-turn synchro tilt sensor outputs for pitch and roll

• Stepper heading outputs and single-turn synchro tilt sensor out-puts for pitch and roll.

The Gyro Interface board uses up to three synchro-to-digital (S/D) con-verter chips. A resistor network is used to configure the board for the input synchro stator voltages, and a DIPswitch is used to configure the board for the turns ratio of a specific gyro. The S/D chip supports a wide range of input synchro frequencies (50, 60, and 400 Hz).

We usually configure the Gyro Interface board at the factory to customer specifications for synchro stator voltage and gyro turns ratio. Table 6, page 20 lists the acceptable standard configurations. Sometimes, though, the customer chooses to use a gyro other than the one originally specified. Be-cause of the need to change the gyro interface configuration “in the field,” we provide technical information in this chapter.

Table 5: Gyro Interface Options by Model Inputs Allowed Natel chips Typical Use

1 (RD-SIC-0) 0 Stepper heading only 1 (RD-SIC-1) 1 Synchro or Stepper heading only 3 (RD-SIC-3) 3 Synchro or Stepper heading, AND Synchro-only pitch and roll page 20 RD Instruments

Table 6: Acceptable Gyro Interface Configurations Gyro Heading Input (Synchro)

Frequency Input 50Hz, 60Hz, or 400Hz

Stator Voltages Through a variable scaling resistor package, the stator voltage can vary.

Starting with a minimum voltage of 11.6 volts RMS, the most common volt-ages are 11.8, 26, 50, and 90 volts RMS.

Reference Voltages 20 to 150 VAC

Turns Ratios sup-ported

Through a selectable DIP switch, the turns ratio can be 1:1, 36:1, 90:1, and 360:1

Gyro Heading Input (Stepper) Input Voltages Most common ranges are from 35 to 70 VDC, with a positive or negative common. On special request, other voltages may be possible.

Stepper Ratio Only a 6-step gyro can be used, where each step stands for 1/6 of a degree.

See table below.

ST0 ST1 ST2 DEGREE

1 1 0 (0/6) 0.000 1 0 0 (1/6) 0.167 1 0 1 (2/6) 0.333 0 0 1 (3/6) 0.500 0 1 1 (4/6) 0.667 0 1 0 (5/6) 0.833

Gyro Tilt Input (Synchro Only) Input Frequency 50Hz, 60Hz, or 400Hz

Stator Voltages Through a variable scaling resistor package, the stator voltage can vary.

Starting with a minimum voltage of 11.6 volts RMS, the most common volt-ages are 11.8, 26, 50, and 90 volts RMS.

Reference Voltages 20 to 150 VAC

Turns Ratio 1:1 only

JUMPERS SWITCHES

RESISTOR PACKS

Figure 9. Gyro Interface Board

P/N 95A-6019-00 (January 2001) page 21

5.1.1 Determining the Synchro Stator Voltage

The best way to find the synchro stator voltage is to use the value listed in the gyro manual. If the manual does not list this value, you can determine the stator voltage by using an AC voltmeter and doing some calculations.

After finding the stator voltage requirements, you will install one or more scaling-resistor packs on the Gyro Interface board. If you already know the stator voltage requirements, skip the rest of this section and go to “Determining the Size of the Scaling-Resistor Pack,” page 22 to find the size of the scaling-resistor pack.

d. With the gyro synchro at a constant angle, measure the AC voltage across the following sets of leads. You must maintain this constant angle during your readings.

1. S1 to S2: VAC = S12

2. S2 to S3: VAC = S23

3. S3 to S1: VAC = S31

e. Calculate the RMS stator voltage, VS:

voltage statorRMS =

1.5 S + S + S = V 31

2 1/2

S

Usually, VS will be a common stator voltage (11.8, 26.0, 50.0, or 90.0). If VS is about equal to one of these values, you can probably assume your gyro is using a common value. If you are unsure of your readings, retake them at a different gyro angle and re-compute VS. If you know your gyro is using an uncommon stator voltage value, you can still modify the scaling-resistor pack value for use with the Gyro Interface board (see “Determining the Size of the Scaling-Resistor Pack,” page 22).

Verify the synchro stator voltages are within acceptable limits.

Each stator-pair voltage (S12, S23, and S31) must be less than or equal to VS.

All pairs of synchro stator voltages must be within the limits given below.

For example, the check for one such pair is

1.2247

V ) S + S ( 0.7071

S

2 1/2

If these voltage checks are not within acceptable limits, then the synchro output is bad, the voltage measurements were incorrect, or the synchro an-gle was not constant during readings.

page 22 RD Instruments

5.1.2 Determining the Size of the Scaling-Resistor Pack

As explained earlier, most synchros use one of the standard synchro stator voltages (VS) listed in Table 7. The Gyro Interface board will work with any of these voltages by using the associated scaling-resistor pack to adjust the stator voltage input rating to 11.8 VAC.

Table 7: Standard Synchro Stator Voltages and Scaling Resistance Common synchro stator reference voltages Scaling resistance

11.8 VAC 0.0 kΩ (jumper)

26.0 VAC 39.2 kΩ, 1/8 W

50.0 VAC 100.0 kΩ, 1/8 W

90.0 VAC 221.0 kΩ, 1/8 W

If the gyro is using non-standard stator voltages, you can find the scaling resistance with the following equation.

)k (2.76 x VAC) 11.8 - (V R S Ω=

The tolerance for this can be as large as 10%, but the four resistors in the scaling-resistor pack must be within 0.1% of one another. For example, the exact scaling-resistance value for a VS of 50.0 VAC is 105.4 kΩ. However, resistor values of 100 kΩ are more common. Because this value is within 10% of the calculated value, you can use four 100-kΩ resistors for the scal-ing-resistor pack if they are within 0.1% of one another.

CAUTION. If you configure the gyro interface board for a lower voltage than the actual synchro stator voltage, you could damage the board or the

ADCP.

5.1.3 Installing the Scaling-Resistor Pack and W-Jumpers

After calculating the size of the scaling-resistor pack, you are ready to in-stall the pack on the Gyro Interface board (Figure 9, page 20). Before you can install the scaling-resistor pack, you may have to change the resistors now in the pack. To do so, pull the resistor pack out of its socket on the Gyro Interface board, unsolder the old resistors, and install the new resis-tors. When the scaling-resistor pack has the correct resistors soldered in place, re-install the pack in its socket. Also, make sure the appropriate W-jumpers are installed. Table 8, page 23 lists the associated resistor sock-ets and W-jumpers.

P/N 95A-6019-00 (January 2001) page 23

Table 8: Natel Chip, Resistor Pack, and W-jumper Sockets Function Natel chip socket Resistor pack socket W-jumper socket

Pitch U1 X1 W5

Roll U2 X2 W7

Heading U3 X3 W9

5.1.4 Determining and Setting the Synchro Turns Ratio

The best way to find the synchro turns ratio is to use the value listed in the gyro manual. If the manual does not list this value, you may have to ex-periment by trying the various settings on the Gyro Interface board. Table 9 lists the available turns ratios and their switch settings. To set the turns ra-tio, set the poles of switch S1 on the Gyro Interface board (Figure 9, page

20) to the appropriate position.

If you are guessing, try a 1:1 turns ratio first. The reason you want to use a 1:1 turns ratio is so you do not have to enter a heading bias (or initializa-tion) value in any software program you are using or adjustment on the front panel. That is, whenever you use a non-1:1 turns ratio or a stepper voltage, it is possible for the Gyro Interface board to be out of alignment with the heading synchro. For example, if the ship’s heading is 027° when you initialize the ADCP, the misalignment between the gyro and the Gyro Interface board will be 27°. When a misalignment condition occurs, you must account for the misalignment by either the front panel set Up/Down button, or in the software program you are using. You can use the Ocean Surveyor ADCP EV-command (Heading Bias) to align the Gyro Interface board to the gyro if you do not have the ability to initialize the Ocean Sur-veyor ADCP through the front panel or in the software. Once set, the head-ing bias value is valid until you turn off the ADCP or gyro.

Table 9: Gyro Interface Switch 1 Settings Turns ratio P1 P2 P3 P4 P5 P6 P7 P8

1:1 C O C O O C C C

36:1 C O C O O O C C

90:1 C O C O O C O C

360:1 C O C O O O O C

Stepper enable O C O C O O O O

C = CLOSED O = OPEN

page 24 RD Instruments

Table 10: Gyro Interface Switch 2 Settings Pole Setting Function

P1 C

O

Enables pitch and roll on the synchro board

Disabled pitch and roll on the synchro board

P2-3 Baud rate Baud rate P2 P3

2400 O O 4800 O C 9600 C O 19200 C C

P4-5 Display rate Display rate P4 P5

Continuous O O 10 times per second O C 2 times per second C O Once per second C C

P6 Not used

5.2 Stepper Interface

If you are using a stepper voltage instead of a synchro voltage, remove the Synchro-to-Digital chip in socket U3 on the Gyro Interface board. Be sure to protect the S/D chip from static discharge.

CAUTION. Synchro-to-Digital converter chips are expensive, so handle them with care.

Remember the following items when using the stepper interface

• Only a 6-step gyro can be used, where each step stands for 1/6 of a degree. See Table 6, page 20.

• If you are using roll and pitch inputs from a vertical gyro, the turns ratios for these inputs must be 1:1.

• Most common stepper voltage ranges are from 35 to 70 VDC, with a positive or negative common and this is what the gyro in-terface board is setup for from the factory. On special request, other voltages are possible. The gyro Interface board uses resis-tors R19, R20, and R21 to set the current for the opto isolators on the stepper interface. Use the following table to determine the correct value of these resistors.

P/N 95A-6019-00 (January 2001) page 25

Table 11: Stepper Voltage Range Stepper Voltage Resistor Value Watt

35 to 70 VDC 8.2kΩ 1

20 to 35 VDC 4.0kΩ 1

70 to 110 VDC 16.0KΩ 2

5.3 Testing the Gyro Interface

You can use the front LCD display on the Electronic Chassis to test the gyro interface. Turn on the Electronic Chassis. If the LCD heading readout agrees with the gyro at several angles, you can assume the settings are cor-rect. You also should have the gyro make a complete turn through 360°.

Some lag may appear, but the LCD readout should change smoothly and in the same direction as the gyro.

If you do not have a 1:1 turns-ratio synchro input, and the LCD readout fol-lows in the same direction but with a constant offset from the gyro value, you must use the initializing Up, Down, and SET buttons on the front of the Electronic Chassis. This entry will align the two values when properly set or one of two problems can exist.

NOTE. If you do not have the initializing buttons on the electronic chassis, then you can set the offset in the VmDas Transforms tab (see the VmDas User's Guide). If you are not using RDI’s VmDas program you can set the offset through the EV command (see the Ocean Surveyor Commands and Output Data Format guide).

• Incorrect turns-ratio value - If you are not sure of the turns ratio, try selecting the other turns-ratio values and retest the configura-tion.

CAUTION. Be sure to power down the Electronic Chassis before changing the switch settings. You also should secure the gyro signals to the Electronic Chassis, as these signals are still “live” at the Gyro Interface board terminals.

• Incorrect wiring hookup to gyro - If you are sure of the turns-ratio (i.e., found in gyro manual), the problem must be incorrect wiring. That is, the stator lines (S1, S2, S3) or reference lines (RH, RL) may be connected to the wrong gyro terminals. Use Table 12, page 26 or systematically swap pairs of stator or refer-ence leads to correct wiring problems.

page 26 RD Instruments

Table 12: Gyro Interface Troubleshooting Guide “A”

Gyro angle

“B” Angle displayed by heading readout (Shaded areas indicate reverse rotation)

000 000 120 240 240 000 120 180 300 060 060 180 300 060 060 180 300 180 300 060 240 000 120 000 120 240 120 120 240 000 120 240 000 300 060 180 300 060 180 180 180 300 060 060 180 300 000 120 240 240 000 120 240 240 000 120 000 120 240 060 180 300 180 300 060 300 300 060 180 300 060 180 120 240 000 120 240 000

“C” Possible ADCP Connector Configurations

Gyro conn.

1 2 3 4 5 6 7 8 9 10 11 12

RH RH RH RH RH RH RH RL RL RL RL RL RL

RL RL RL RL RL RL RL RH RH RH RH RH RH

S1 S1 S2 S3 S2 S3 S1 S1 S2 S3 S2 S3 S1 S2 S2 S3 S1 S1 S2 S3 S2 S3 S1 S1 S2 S3 S3 S3 S1 S2 S3 S1 S2 S3 S1 S2 S3 S1 S2

NOTE

1. With a gyro angle of “a,” the heading readout will show an angle of “b” if the gyro interface cable wires are connected as shown in “c.” For example - if the gyro is at an angle of 120° (“a”), and the heading readout is showing a value of 300° (“b”), the interface is wired in either configuration #7 or #10 (“c”). If the heading readings rotate in the same direction as the gyro, the interface is wired as #7; if the rotation is in the reverse direction, the interface is wired as #10.

2. As shown above, only configuration #1 in “c” is correct for gyro interface wir-ing.

3.…