Sequoia LISST-VSF User Manual

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LISST-VSF

Multi-angle Polarized Light

Scattering Meter

User’s Manual

Rev. B

Sequoia Scientific, Inc.

2700 Richards Road, Suite 107

Bellevue, WA 98005-4200

USA

Tel: (+1)(425) 641-0944 Fax: (+1)(425) 643-0595

www.sequoiasci.com | info@sequoiasci.com



FEATURES:

 In-situ measurements of P11 (VSF), P12 and P22 elements of the scattering Mueller

matrix from 0.1-155o (nominal) in water

 VSF (P11) only at small angles, 0.1 to 15o (nominal) in 32 logarithmic steps in angles  Integration of 0.1-155o VSF provides a good estimate of total scattering coefficient b.  Beam attenuation measured with LISST-100X optics.  Roving EyeballTM optics permit 1o resolution in scattering angles between 15 -155

 Approximately 4 sec per measurement set [involves 2 turns of Eyeball with vertical,

and horizontal polarized laser].

 Daylight rejection by laser modulation.

 Data from small and large angles in a single data stream, including depth,

temperature, date and time.

 This document is copyrighted by SEQUOIA SCIENTFIC, INC.

LISST-VSF

SPECIFICATIONS: Parameters measured

Small-angle VSF in 32 log-spaced angles, from 0.1 to 15o(nominal) VSF, P12 and P22 over 15-150o in 1o steps (nominal) Temperature from –5° to 50°C with 10 mdeg resolution Operational depth (50 m max depth @ 8 cm resolution)

Operating Concentration range

Beam attenuation from 0.13 to 20 m

Technology

Fiber Coupled TE-cooled Laser Diode @ 515 nm Ring Detector for small-angle VSF Roving Eyeball and PMT for 15-150o (nominal)

Mechanical and Electrical

LISST-VSF Instrument

Dimensions 13.3 cm (5.25”) diameter, 114.0 cm (44.9”) L Weight: 15.6 kg (34.4 lbs) in air; in water TBD Depth rating: 300 m survival depth (50 m operational depth) External power input: 12VDC @ 5A, min 9VDC, max 20VDC Sampling rate: 4 seconds for a full measurement of P11, P12, P22 Power drain: 700 mA measuring / 170mA quiescent Data storage: 128GB, equivalent to 40,000? measurements

Battery Housing

Dimensions 13.3 cm (5.25”) diameter, 71.1 cm (28.0”) L Weight: 10.3 kg (22.8 lbs]) in air; in water TBD Capacity: 14.8V, 39 A-hr.

-1

(based on >=30% transmission)

Welcome to the LISST-VSF!

Using this manual

This manual is divided into two sections.

Section One contains an introduction to the LISST-VSF instrument and the principles of its operation.

Section Two provides detailed instructions for operation Appendices provide further details …

Instrument Specific Constants

These are included in a MATLAB file, named Cal_Factors_xxxx.mat, where xxxx is the serial number of your instrument.

Technical assistance

For technical assistance please contact your local Distributor or Sequoia. Please be sure to include the instrument Serial Number with any correspondence.

Sequoia Scientific, Inc. contact information: Telephone: +1(425) 641-0944 Email: info@sequoiasci.com

Waste Electrical and Electronic Equipment

Smaltimento di apparecchiature elettriche ed elettroniche da rottamare

Table of Contents

SECTION I: LISST-VSF INSTRUMENT ........................................................................................ 13

I.1 INTRODUCTION ................................................................................................................ 13

I.2 HOW IT ALL WORKS ........................................................................................................ 17

I.3 GENERAL PRECAUTIONS ................................................................................................. 21

I.4 QUICK START.................................................................................................................. 22

SECTION II: OPERATION ............................................................................................................. 27

II.1 INSTRUMENT MOUNTING, STORAGE AND MAINTENANCE .................................................... 28

II.2 CHARGING AND CONNECTING THE LITHIUM-ION BATTERY PACK ........................................ 30

II.3 BENCH TESTING AND COLLECTING BACKGROUND DATA .................................................... 32

II.4 OFFLOADING AND ERASING DATA FILES FROM INSTRUMENT .............................................. 35

II.5 RECORDING AND STORING A SAMPLE DATA FILE .............................................................. 38

II.6 DATA PROCESSING ......................................................................................................... 40

SECTION III INSTRUMENT PROGRAMMING AND COMMAND DETAILS ............................. 54

III.1 PROGRAMMED OPERATION FOR FIELD OR LABORATORY USE ............................................ 55

III.2 LISST-VSF COMMAND SUMMARY ................................................................................... 58

APPENDIX A: DETAILS OF LISST-VSF INSTRUMENT ............................................................ 68

APPENDIX B: METHOD OF EXTRACTING P11, P12 AND P22 ................................................. 72

APPENDIX C: MATLAB SOFTWARE .......................................................................................... 75

APPENDIX D: OBSERVATION ANGLES, DATA STORAGE FORMAT AND VARIABLE NAMES

....................................................................................................................................................... 77

APPENDIX E: CONNECTOR PINOUTS FOR LISST-VSF .......................................................... 80

APPENDIX H: LISST-VSF ACCESSORIES ................................................................................ 83

WARRANTY .................................................................................................................................. 84

Thank you for purchasing a LISST-VSF instrument, and congratulations on your new purchase.

The LISST-VSF delivers a powerful suite of measurements for marine optical scientists, all from one package. It delivers the Volume Scattering Function (VSF) from small forward angles to wide angles, depolarization parameters, and the beam attenuation coefficient c. An excellent estimate of the beam scattering coefficient b, and by difference, the beam absorption coefficient a can also be derived from the data. All properties are measured at a laser wavelength of 532nm. The forward angles in water, from 0.0936 to 15.05, at which VSF is measured are spaced logarithmically. The intermediate and large angles (>15-deg) are linear, with 1-deg resolution. Because of the high angular resolution, this instrument permits examination of enhanced scattering by bubbles in the ~80-deg region.

Light Scattering and VSF

The Volume Scattering Function (VSF) describes the distribution of scattered light energy as a function of scattering angle. VSF is defined for unpolarized light source and no discrimination of polarization in the scattered light. However, scattering of light by particles always produces changes in polarization state of the scattered rays. The state of polarization is described by the Stokes vector I, with elements I,Q,U,V. The Stokes vector of the scattered light and that of the incident light Ii are related through a matrix product:

Is = P I

where P is the scattering Mueller matrix. P is a 4 x 4 matrix. It contains information regarding particle scattering characteristics. The elements of P are often denoted by Pij . The first element, P11 is identical to the volume scattering function, VSF. Elements [1,2] and [2,2] relate to changes in the linear polarization properties I and Q. For example, element P12 produces depolarization. Element P22 is known to be an indicator of sphericity of particles; so that P22 =1 everywhere implies that particles are spheres. With the LISST-VSF, it is assumed that symmetry forces elements P

and P

zero, and that P

and P21 are equal. Thus only 3 unknown are produced: P11,

P12, and P22,

At small forward angles, scattered light maintains its original polarization, so that depolarization is small. This instrument does not measure depolarization at angles smaller than 15o, because there the VSF is measured by a set of ring detectors, identical to our familiar LISST-100X instrument. A different instrument, LISST-Stokes has been developed for small-angle depolarization studies.

Section I: LISST-VSF Instrument

I.1 Introduction

LISST-VSF User’s Guide 13

Theory and Mathematical Description

Appendix A and B provide detailed description of optics of the instrument,

and of data processing method. Appendix C describes MATLAB data processing functions. If data are good, a single command make_P processes a set of files and produces elements of the P matrix, together with beam attenuation and scattering coefficients. The function name make_P derives from the scattering matrix P.

Instrument Overview

The LISST-VSF instrument employs two optical systems which combine to produce the full VSF. The small angle measurements (<15o) are done with ring detectors, identical to our LISST-100X instrument. We will often refer to data collected with these detectors as ring data, or rings data. Scattering at larger angles (>15

) is measured using a rotating ‘eyeball’ (see photo on

opposing page). This data is referred to as eyeball data. For ring data collection optics, please refer to details in one of several

publications (e.g. Agrawal & Pottsmith, 2000; included on the ship disk). A simplified explanation of the eyeball optics for large-angle measurements is offered here.

Typical volume scattering function sensors, or for polarization studies, typical polarimeters observe a common sample volume with a multiple set of detectors. In some of these systems, a single viewing telescope rotates around the sample volume. The former system can only have a small number of detectors, and each needs to be carefully calibrated. In the latter, rotating a

telescope requires cumbersome and slow mechanical systems that don’t lend

themselves to deep submerged usage. For these reasons, the present instrument employs a rotating eyeball. Instead of viewing a common sample volume, the eyeball scans the length of a laser beam, thus obtaining angular information.

In the LISST-VSF instrument, the scattered light entering the eyeball is split into its two polarization components, and each is sensed with a dedicated photomultiplier (PMT). A set of measurements comprises the recording of these two PMT outputs over 2 rotations of the eyeball. Each rotation is for a fixed polarization of the laser; e.g. the first rotation is with perpendicular laser polarized, and a second rotation is with parallel polarization. To rotate laser polarization between eyeball turns, a half-wave plate is mechanically inserted in the laser beam before it enters water. Data are stored in a single datafile that combines rings and eyeball data.

The small eyeball makes the LISST-VSF instrument compact, autonomous, and manageable underwater. As a result, this instrument may be left on a tripod or mooring.

As explained in Appendix B, due to the rotating eyeball receiver, the stored scattered light signals are a mix of the 3 parameters P11, P12 and P22. The convenience of the eyeball thus involves a price – solving for these quantities. We provide software to perform this function. For details, please see Appendix C.

14 LISST-VSF User’s Guide

Electro-Optic Components

The instrument employs a single 515nm TE-cooled diode laser for both optical systems – rings and eyeball optics. To reject ambient light, the beam is modulated at ~3 kHz. Two miniature, compact PMT’s are used to sense scattered light. Electronics control the gain of these two PMT’s. The gain can be adjusted with software commands. The output of PMT’s is digitized and stored in data files. See Appendix B.

Depth and Temperature Sensors

The depth sensor is mounted to the instrument connector endcap. The temperature sensor is also thermally bonded to this endcap. Please note that the temperature sensor is therefore slow.

Communication

A cable is provided to connect the underwater connector on the instrument endcap to a PC. Communication is at 9600baud, except when downloading data, it automatically switches to 115Kbaud.

Internals

The cylindrical case with the flat endcap contains all the transmitting optics and the 2 PMT’s. This includes the laser, a beam-expander, the polarization rotator, and laser power (output) sensor (called Laser Reference throughout this manual). The cylindrical case with the connector endcap contains the small-angle measuring ring-detector optics, i.e. a 50-mm focal length lens, the ring-detectors with its built-in sensor for laser power transmitted through water (called Transmission sensor throughout) and related electronics. The space around the eyeball in the middle is the test section, or the sample volume. The water being measured is the water in this space. For laboratory work, you will form a test chamber to hold water around the eyeball.

Two pressure windows can be seen on the two cases on either side of the eyeball. One of these windows is clear. This is the transmit side window. The other is dark. The dark window has an ND 1 filter cemented to it. This filter reduces backscatter (glow) from optics on the small-angle optics side, permitting measurements with the eyeball to about 155°.

A scheduling computer is placed alongside eyeball electronics. Communication with this computer is over a serial line. The LISST-VSF instrument can be programmed from a PC to execute a specific data collection sequence. Software for programming the instrument and recovery of data is provided. Data download is also carried out using the provided software.

Measurement Section

The eyeball is set to one side of the sample volume. This positioning permits the eyeball to view scattering from about 10o onward to about 155°. The data storage electronics are programmed to start capturing scattered light data when the eyeball is positioned to view 5o scattering. (The precise angle varies from instrument to instrument due to the setting of the optical encoder. The offset in this angle is included in your calibration files). Ring detectors and the eyeball, both cover the 5-15-degree scattering angle range. The overlap permits calibrating the eyeball data with the outermost ring detector, thus providing absolute calibration for photomultiplier signals. The 5-15 degree range of data from the eyeball also includes the laser spot on the transmit window. This spot glows brightly, thus offering a fixed target to further calibrate/verify eyeball viewing angles.

LISST-VSF User’s Guide 15

The rectangular box below the eyeball in the photo is the housing for the optical encoder which keeps track of eyeball angular position.

Figure 1 – In laboratory work, make sure the rectangular box is at top!

Laboratory and Field Use

The instrument can be used in the laboratory or in the field. It can be operated with an External Power Supply, or using the supplied rechargeable battery.

In battery-powered field usage, the instrument can be used from a wire in a profiling mode, or it can be mounted on a tripod or mooring for a time-series observation.

NEVER INSERT ANYTHING REFLECTIVE IN THIS SPACE. THE LASER POWER IS APPROXIMATELY 10mW. IT WILL DAMAGE EYES.

The windows and endcap faces should be clean if doing laboratory work. If deploying in the ocean, make sure both windows are clean. Use lens cleaner or soap and water. DO NOT USE ABRASIVE CLEANERS.

Rechargeable LiIon Battery Pack

The instrument power source is a rechargeable lithium pack. With all systems on, the instrument draws about 0.7 A current. The fully charged battery can power continuous operation of the instrument for up to ~40 hours. The instrument checks the state of battery before capturing each set of data. If the battery is low, a graceful shutdown is executed.

A battery charger is provided. While the battery is being charged, it cannot power the instrument.

A separate external power supply, with an underwater connector that mates with the instrument housing is provided for use in the laboratory.

16 LISST-VSF User’s Guide

I.2 How It All Works

Overview

After connecting power (battery or external power) and the communications cable, the instrument becomes ready for operation. When commanded to capture data, the following sequence happens: the laser is turned on for a period to reach stable power. beam emerges from the transmit window and the eyeball starts rotating. Each rotation takes about 2 seconds. During this time eyeball data are captured. The sequence is as follows: beginning when the optical encoder reads 15-degrees, the two PMT data are captured at 1degree intervals. Between 15 degree and 50-degrees of eyeball position, the laser is dimmed by the laser controller. This is done because this scattering is stronger; dimming keeps it within the PMT dynamic range. At 51 degrees encoder position laser power is returned to full. Eyeball data are recorded from the start angle for a specified number of angles, typically 150.

Ambient Light Rejection

The eyeball continues the ‘blind’ part of its rotation. During this time, rings data are captured. After ring data have been captured, the combined ring and eyeball data are written to data file. Immediately, a half-wave plate is inserted in the laser beam, so that during the next turn, PMT’s data would be captured with laser polarization rotated by 90o. During the time allocated for the halfwave plate insertion and settling of its mechanism (see figure), the laser is turned off briefly to capture an ambient light background from rings. The cycle repeats for the second rotation, only now the half-wave plate is removed. This is illustrated in Fig.2.

Figure 2 – Laser power through 1 set of 2 rotations (shading shows laser

modulation during eyeball portion of data capture), HW is half-wave plate to

rotate polarization of laser, Note that laser power is reduced for the 5-50o part

of eyeball data capture, and laser is extinguished to read dark rings (ambient

light on rings) after activating HW.

Also stored in each rotation are auxiliary parameters - depth and temperature, battery voltage, and date and time.

Each data set requires two rotations of the eyeball. The number of sets of data is controlled from the command window or from the operating modes menu. This is described in later chapters.

Black Glass Receive Window

Why is an ND filter used on the small-angle optics window? This is because internal glow from the small-angle optics contaminates particle scattering at large angles, i.e. when the eyeball is viewing scattering at around 130o or greater. The ND filter attenuates the glow.

LISST-VSF User’s Guide 17

Background Light Measurement

As with the LISST-100X instrument, so also with this instrument, a background measurement is necessary. Background light for ring detectors originates as scattering from optical surfaces. For eyeball data, background light from scattering by water itself can be significant. Ambient light does not contribute to background as it is rejected by laser chopping. A background reading is required before any data collection. The background is measured with flitered clean water in the sample volume. The measured background is subtracted from particle data in data processing.

Dynamic Range Challenge

Changing PMT

sensitivity

Because the VSF typically requires a wide dynamic range, it is not reasonable to build a fully general purpose system. By using a combination of 12-bit A/D for PMT outputs, and a factor of ~25 extension of the upper limit on scattered light by dimming the laser at small scattering angles, we achieve about 16 bits dynamic range. This is sometimes not sufficient. If so, it is possible to

increase or decrease sensitivity of PMT’s by changing the control voltage.

This is possible from the command window. The instrument is shipped with a setting that is found suitable by us. Because saturation of the A/D is possible, we recommend that you always view the raw data and look for saturation. A function view_rawfile is provided for this purpose.

PMT sensitivity may be changed from the Terminal Window by typing ~c The instrument will display a range of settings. Just hit enter for all, until the

PMT setting is displayed. Move it up or down 50 counts at a time to, respectively, increase or decrease sensitivity.

Low Battery Cutoff

The instrument checks for low-battery during sampling. If the battery is low, it shuts off the high-current components such as the eyeball motor and laser in an orderly fashion. When shut off in this mode, notification is printed to the communications port, and residual battery power is used to return the system to the command prompt.

Excess Depth Shut Off

The instrument, when deployed in profiling mode, automatically checks for depth exceeding maximum permissible for eyeball operation. If the critical depth is exceeded, the eyeball is powered down and data collection pauses until depth is again within specifications.

Data Processing

Data processing is performed in MATLAB. Software is provided to perform these functions: (i)view any data file or background file with view_rawfile, (ii) construct a mean background file from recently acquired background (pure water) data, with make_zsc, and, finally, (iii) to produce the desired end result: P11, P12, and P22, beam_c and beam_b with make_P. For convenience, a few other functions are provided, e.g. to simulate eyeball data from Mie theory. The expected measurement from, say, single size polystyrene beads can be computed using this function for comparison with actual data.

Appendix B explains the methods. A listing of provided functions is in Appendix C. The use of MATLAB permits flexibility to the scientific user.

18 LISST-VSF User’s Guide

A Tweak-able Parameter

The relative gain of the two photomultipliers is required in solving for P11 etc. This quantity cannot be reliably measured directly. Fortunately, the outputs of

the two PMT’s are theoretically exactly equal at scattering angles of 45

and 135o [see Appendix B, Eq.2b]. This permits estimating this ratio, which we call from the data. However, error in estimation of  can result in spikes in

estimates of P22. Thus, adjusting  may be required. The value of  at which the spikes are minimized is relatively easy to find.

It is not correct to use the same value of  at all times since it will depend on PMT voltage, and we do not know if it drifts significantly over time.

NOTE: A version of the LISST-VSF MATLAB software tools that allows simple modification of  during data processing is under development!

A Quick Look at End Results

For details on data processing, see the following Data Processing Overview section.

If all goes well, you should see a composite VSF as shown below: a log-log plot and a semi-log plot. Note that when working with small particles, the VSF at the smallest angles (below left) may not be smooth. This is because the amount of light on the smallest ring-detectors is very small, hence noisy. The example below shows 10 sets (curves) from 1.6 micron polystyrene beads.

Figure 3 – Laboratory data from 1.6 micron polystyrene beads.

In general, field work will not produce such difficulty with smallest angles. If you see this difficulty, and if turbulent scintillation is unlikely, it is possible to use symmetry and flatten the curves. We make this suggestion only. Please use your discretion on what is reasonable.

LISST-VSF User’s Guide 19

The software will also produce a display of P12, as well as an estimate of P22 which has a problem around 45 and 135-degrees, explained in Appendix B. P22 is unity for spherical particles, which the example below shows reasonably.

The processed data is summarized in a 2x2 plot containing the P11, P12, P22 as well as the near-forward VSF derived from the ring detectors.

Figure 4 – Summary of LISST-VSF processed data

See Appendix B for explanation of spikes in result and how to minimize them.

0 50 100 150

-2

-1

Angle [deg]

Eyeball P

-1

]

-2

Angle [deg]

Near-forward VSF [m

-1

]

0 50 100 150

-0.5

0.5

Angle [deg]

Eyeball P

-1

]

50 100 150

-1

Angle [deg]

Eyeball P

-1

]

20 LISST-VSF User’s Guide

I.3 General Precautions

Handling the Instrument

The LISST-VSF is a delicate instrument. It contains precision, highly aligned optics, and electronics. It is designed for the rigors of field use, however it should be handled with care at all times.

AVOID SHOCK at all times.

Do Not Open Instrument Case

You should never have to open the LISST-VSF or battery pack pressure cases. Doing so may void the Manufacturer’s Warranty!

Connecting Cables

Always connect this cable to the instrument first, then connect the other end to the battery pack, bench-top power source, or PC.

Use Care When Charging Battery

When closing the charging port after finishing recharging batteries, make sure the plug is fully tight.

A BATTERY CHARGER IS PROVIDED WITH THE LISST-VSF.

NEVER USE ANY OTHER CHARGER FOR BATTERY CHARGING. THIS MAY DAMAGE THE BATTERY AND VOID THE WARRANTY.

EXTREME CAUTION IS ADVISED IN CLOSING THE CHARGING

PORT AFTER BATTERY CHARGING.

CAUTION

RISK OF FIRE

WARNING

The LISST-VSF uses a powerful green laser emitting a

maximum of 10 mW of visible light at a wavelength of 515 nm.

The laser beam under normal circumstances is not a threat.

However, if objects are placed in the path of the laser beam, the light could be reflected into an eye causing permanent damage.

CAUTION

LASER RADIATION

LISST-VSF User’s Guide 21

I.4 Quick Start

Contents of shipping case

So, now you are ready to go! Open the shipping case containing the instrument. You should see the

following items inside (see also Appendix H):

1. Lexan ZSCAT Sheet

2. ZSCAT clamps (2)

3. Communications Cable

4. Battery Cable

5. Battery Charger

6. Power Supply

7. Stands (4)

8. Installation Disk

9. Manual

10. Sediment Samples

11. Spare O-rings

12. Mounting Clamps (4 sets)

13. Battery housing

14. LISST-VSF instrument

15. Test dusts in small quantities

Set Up on the Bench Top

1. First place the instrument stands approximately 1m apart.

2. Remove the instrument and cradle it on the stands.

3. Do the same with the battery case.

Do not connect the two instrument cases with the power cable yet! Let us become familiar with the various parts first.

No end-caps ever need to be opened by the user. Only recharging a battery requires opening a small access port on the battery case. The user should never try to loosen or disassemble any of the other components attached to either endcap. Doing so could immediately void any warranty.

Instrument and

Battery Connector

Endcaps

There are 3 connectors on the endcap. The 3-pin connector is for power (from battery or line power supply). The 5-pin connector is for communication. The 6-pin connnector is for auxiliary use.

See Appendix E.

22 LISST-VSF User’s Guide

Battery Housing

and Endcap

There is only one connector on the battery housing endcap. This is used for powering the instrument or for charging the battery. The instrument can not be operated with the battery while the battery is being charged.

See Appendix E for pin-outs..

Check for Clean Windows

In preparation for getting started, at this time, check the optical windows to make sure that they are clean. There are three windows: Two are on the inner endcaps, and one is on the eyeball.

The best way to check the windows is by using a flashlight. By shining light from one side, almost parallel to the window surface, and viewing from the other, the surface of the windows can be easily checked for cleanliness. If there is dirt or fingerprints on the windows clean them first by rinsing them with lukewarm water and a mild soap solution (e.g. mild hand soap, liquid dish soap) and then rinsing off all soap residue with clean, particle free water such as de-ionized water, MilliQ water or distilled water. The windows can also be wiped clean with a soft cloth (e.g. a lens cloth) and alcohol. It is not recommended to use stronger solvents, such as acetone or toluene. Also, do not use any abrasive cleaners or wipes. Treat the windows as you would an expensive camera lens.

Attach Communications Cable

Remove the Communications cable from the shipping crate. It is the 2 meter cable with the 9pin DB-9 connector on one end and the 5-pin underwater connector on the other. Remove the underwater cap from the Communications connector. The connectors will all look similar. The Communication connector is the only 5-pin connector. It is located below the engraved serial number. After removing the cap install the cable making sure that proper alignment of the cable is maintained, so that the connectors are not bent.

Install LISST-VSF Software

The software is similar to our LISST-100X instrument, with a few changes. Simply insert the CD in your PC’s CD drive (or connect the USB disk) and follow along. A program icon will appear on your desktop and under the Sequoia folder in your All Programs menu.

The MATLAB *.m files provided on the installation CD (or USB drive) will be copied to your working folder for data processing.

LISST-VSF User’s Guide 23

Form the Laboratory Test Chamber

The LISST-VSF is provided with a bendable clear plastic sheet with sealing gaskets and quick-release band clamps. This chamber has the advantages of quick and easy installation and the ability to inspect the sample being measured. Install with rectangular encoder housing facing up. Fill with clean, particle-free water (0.2 micron filtered).

Check out the Sequoia Scientific YouTube channel for a video showing how to assemble the flexible test chamber.

http://www.youtube.com/user/SequoiaScientific

NOTE: An improved test chamber for bench-top and flow-through use is in development.

Start LISST-VSF Program

Launch the software by double-clicking the icon on your desktop. If the icon does not exist, check that the software installed properly.

Connect Power

Connect the LISST-VSF to the battery pack with the supplied underwater cable, or to the bench-top power supply. The instrument is now live! It will now respond to <enter> command from the PC.

Open Terminal Window

Under the Communications menu, select Serial Settings and verify that the serial port listed is the port to which the instrument is connected.

On the menu bar, click on the icon that resembles a terminal window. This will open a window within the software window. If you hit <enter> on the PC, the instrument will respond with a LISST-VSF> prompt.

Note: The instrument communicates at 9600 baud through this window. However, when downloading data, the transfer rate automatically changes to 115k.

Basic Commands

There are basic commands for turning on the laser, powering the eyeball (so it starts turning) etc. For help, type:

L-VSF:> he

The responses are self-explanatory.

24 LISST-VSF User’s Guide

Acquiring Background Scattering File

Now try to acquire a background file. The Laboratory Test Chamber should be nearly full with clean water (so that both of the windows on inner endcaps are submerged, and the strut receiving the upper eyeball shaft is partially submerged). Make sure that the water is well-mixed (give it a stir) else scintillation will affect the small-angle measurements. At the L-VSF:> prompt, type the command

L-VSF:> za

and hit <enter>. The laser will turn on along with the eyeball. Laser warm up will take about 15 seconds. Then, 16 sets of eyeball and ring-detector data will be acquired (recall that each set is 2 turns of the eyeball). When the instrument is finished collecting the data, it will shut all systems off and the L-VSF:> prompt will be displayed in the terminal window.

The instrument will save a background file with name ZDDDHHMM.DAT. The background has 16 sets of data, each set being two turns of the eyeball, one with perpendicular laser polarization, the second with parallel.

At this point, you may download the background file, or move on to collect another file, e.g. some particle data. Let’s take some particle data.

Collecting Particle Data

Drop some particles in the test chamber (use fine particles, e.g. 0.3 micron or 1 micron polystyrene beads from Duke Scientific, Inc.). Mix the water well to homogenize the suspension. This is important!

In the command window, type the commands:

L-VSF:> pd 16 L-VSF:> go

This command means grab 16 sets of scans (again, recall each set is two rotations of the eyeball). When finished, the instrument will shut down, and you will know that because the laser will be out. The command window will return to the L-VSF:> prompt.

To collect data in a field deployment, you will need to program the instrument, i.e. set the starting delay, sample rate, length of data collection etc. This is described in section.III.2.

Downloading Data

Downloading procedure is identical to our LISST-100X. From the windows program, click on the download button. A listing of stored files will appear. Select the ones to download and click OK.

Cleaning the Instrument

Before putting the instrument away, clean the inner endcaps and windows. Drain the test chamber, wipe and dry the windows.

LISST-VSF User’s Guide 25

Put Instrument to Sleep and Waking it Up

The instrument consumes some battery power when powered on and not in low power mode. It can be put into a low power mode by pressing the sleep button on the software menu bar. Wake up the instrument by clicking the adjacent button.

Note that once put into sleep mode, it can take up to a minute to wake up the instrument.

26 LISST-VSF User’s Guide

Section II: Operation

Section Organization

This section is divided into these subheadings:

1. Instrument mounting, storage and maintenance

2. Charging and Connecting the Lithium battery pack

3. Bench-testing and collecting background data

4. Offloading and erasing data files from instrument memory

5. Recording and storing a sample data file

6. Data Processing

LISST-VSF User’s Guide 27

Horizontal Mounting

It is recommended that the instrument be mounted horizontally while in use or storage. This ensures that particles will not settle on windows and degrade data quality.

Precautions for mounting

Do not mount the instrument in a way that over-constrains it. No bending moments should arise on the instrument. Bending moments will degrade alignment, causing loss of data at small angles.

Isolate from other Metals

To reduce corrosion of aluminum parts a zinc anode is attached to the Connector endcap. This anode must be exposed to the water for it to be effective.

When mounting the instrument be sure to electrically isolate the instrument from all other metal. Any contact with other metal can greatly increase the rate of corrosion. Isolate the instrument with rubber or plastic to keep the LISSTVSF from becoming the sacrificial anode for the mounting hardware. Failure to properly isolate the instrument from all other metal will void the warranty.

A set of stainless steel clamps with rubberized interiors ships are part of the instrument package. Use these or the plastic clamps for mounting, and make sure that no metal is in direct contact with the pressure housing or other components of the instrument. If you lose the spare clamps, replacement clamps are available for purchase from Sequoia. See Appendix H for: Accessories.

Storage Notes

The LISST-VSF is a sensitive instrument. When not in use, the instrument should be stored in its shipping case.

Clean and dry the instrument before storage. Avoid storing the instrument in excessive heat or humidity. Do not store the

instrument in freezing temperatures, or in environments with wide temperature fluctuations.

When storing the instrument, unplug the battery pack. It is recommended that the venting plug on the battery case be left open for any gases to escape.

Low Power Sleep Mode

To put the instrument into low power sleep mode choose Put LISST to Sleep from the LISST menu or click the button.

II.1 Instrument Mounting, Storage and Maintenance

28 LISST-VSF User’s Guide

Cleaning the optical windows

The condition of the windows is critical to the performance of the LISST-VSF. Care must be taken when cleaning the windows. The windows and the instrument should be rinsed thoroughly with fresh water after each deployment to ensure that salts and sediments will not scratch the window during the cleaning process. The windows should be cleaned with a soft cloth or lens tissue, using a single direction wipe across the window. DO NOT SCRUB. Detergents such as Liquinox and water may be used to increase the efficiency of cleaning. For removing grease spots, finger prints, etc, alcohol may be used. Do not use stronger solvents such as Acetone or Toluene.

Abrasive powders must never be used near the optics windows; they will scratch the windows and degrade instrument performance.

O-rings

User should not need to open any endcap on LISST-VSF

Calibrations and adjustments

The LISST-VSF does not require any adjustment or calibrations. The pressure and temperature sensors can be re-calibrated if desired. The pressure sensor can be zero’ed at the surface before deployment (see ZD command) The performance of the instrument can be checked with the use of a sample of particles of a known size distribution.

Standard particles can be obtained from manufacturers of standard particles, such as:

 Duke Scientific, Inc.

(http://www.thermoscientific.com/ecomm/servlet/productscatalog?

categoryId=8736&&storeId=11152 )

 PTI (Powder Technology Inc., http://www.powdertechnologyinc.com/).  Whitehouse Scientific (http://www.whitehousescientific.com/)  Polysciences, Inc. (http://www.polysciences.com/polybead/)

Usage in the Laboratory

During prolonged usage, it is recommended that a fan be used on the VSF housing to reduce heat buildup, or operate the instrument in a water bath.

LISST-VSF User’s Guide 29

About the Recharge-able Battery Pack

The LISST-VSF is supplied with a submersible, recharge-able, Lithium-Ion battery back.

 Dimensions 13.3 cm (5.25”) diameter, 71.1 cm (28.0”) L  Weight: 10.3 kg (22.8 lbs) in air  Capacity: 14.8V, 39 A-hr.

The battery pack connects to the LISST-VSF by way of a 3-pin wet mate-able connector (bulkhead connection is MCBH-3F). This same connector is also used to connect the battery pack to the charger.

The battery pack bulkhead also contains a zinc anode and special screw-in plug for venting while charging.

Charging the Battery Pack

The Lithium-Ion cells contained in the pack must be vented while being charged. Unscrew the vent plug until the small vent hole is exposed. The vent plug cannot be unscrewed completely from the unit due to a mechanical stop, and an internal switch will prevent the batteries from charging if the plug is not unscrewed to the venting position.

Connect the supplied battery charger to the battery pack and allow 8-10 hours of charge time.

Lithium-Ion batteries prefer partial discharge to deep discharge, so avoid depleting the battery fully. LithiumIon batteries do not have a “memory”, so the cells are not harmed with partial charge. Deep discharge can damage the Li-Ion cells.

Lithium-ion batteries age. Typical lifetime is ~3 yrs.

Completion of charging is indicated by LED status indicators on the battery charger.

A BATTERY CHARGER IS PROVIDED WITH THE LISST-VSF.

NEVER USE ANY OTHER CHARGER FOR BATTERY CHARGING. THIS

MAY DAMAGE THE BATTERY AND VOID THE WARRANTY.

USE OF OTHER CHARGERS OR IMPROPER VENTING CAN RESULT IN

DAMAGE TO BATTERIES OR FIRE. USE CAUTION AND RESPECT

LITHIUM-ION BATTERIES!

II.2 Charging and Connecting the Lithium-Ion Battery Pack

30 LISST-VSF User’s Guide

After charging is complete, the vent plug must be closed before the battery can be used.

EXTREME CAUTION IS ADVISED IN CLOSING THE CHARGING PORT

AFTER BATTERY CHARGING. FAILURE TO CLOSE PROPERLY CAN

RESULT IN FLOODING, PERMANENT DAMAGE, AND EVEN FIRE.

LISST-VSF User’s Guide 31

Bench Setup

The LISST-VSF instrument should be set up on the two white plastic mounting blocks, placed roughly between the middle of each pressure case on either side of the eyeball.

Make sure that you do not add bending moments on the pressure case. Bending will cause loss of alignment, and loss of data at small angles. Photos below show instrument on a test bench, with one plastic support block showing on left.

Install Sample Chamber

Wrap the plastic sheet around the sample volume and install clamps over the gasket strips to secure the chamber to the LISST-VSF instrument. Verify that that there are no leaks. Adjust clamps and/or replace gasket material if needed.

II.3 Bench Testing and Collecting Background Data

32 LISST-VSF User’s Guide

Fill with Clean Water

Fill the sample volume with organic-free, degassed, particle-free water. Clean water should reach a level approximately 1-2 cm above the optical windows. Sequoia recommends using distilled or reverse-osmosis water which has undergone 0.2 micron (or smaller) filtration. Superior lab results have been obtained by continuously circulating (pumping) the clean water contained in the sample volume through a 0.2 micron capsule filter (e.g., Whatman PTFE, PALL Supor, GE Memtrex) for ~1 hour before sampling.

Check Instrument Alignment and Water Cleanliness

Connect communications cable. Connect battery or benchtop power supply. Run LISST-VSF software and open Terminal Window.

Connect to the instrument by clicking on the terminal window icon or selecting Terminal Window from the Communications menu. If the data acquisition program is still running, stop its execution with a <CTRL-C> or pressing the Stop button in the terminal window. The instrument will display a L-VSF:> prompt.

Select Check Instrument Alignment from the LISST menu or by pressing the corresponding button on the toolbar. After selecting the factory background scatter file to use for comparison the window will be displayed. Note: this is similar to the Collect Background functionality of the 100X, but is used in the LISSTVSF only as a simple way to verify instrument operation, alignment, and clean water quality.

LISST-VSF User’s Guide 33

Make sure that the water is well-mixed (give it a stir) otherwise scintillation will affect the small-angle measurements.

Press the BEGIN Collect button. 20 samples will be displayed to the screen as they are acquired. After all 20 are collected the average will be displayed. The values can be saved to a file for later reference. Enter the filename in the box and press the Accept and Save button to save the file for future reference.

 If there is a problem with the instrument or if the water or windows are not

clean, error messages will be displayed.

 Dirty water or windows will generally cause higher values across the

middle rings.

 Large bubbles or particles in the water can cause higher values on the

inner rings or left hand side of the display.

 High values on the inner rings combined with a lower Laser power value

can also be an indication of optical misalignment.

Record and Store Background Scattering “ZSCAT”

Connect communications cable. Connect battery or benchtop power supply. Run LISST-VSF software and open Terminal Window. Verify instrument communications by issuing DS command in the terminal window.

Clean instrument, install test chamber, fill with clean filtered water as described in Check Instrument Alignment and Water Cleanliness (page

33).

The LISST-VSF uses a dark ring detector reading to reduce sensitivity to ambient light. However, it is suggested that the sample volume be covered with a felt sheet or other opaque barrier during sampling.

Issue ZA command to start acquisition of background scattering file. After brief warm-up period, 16 sets of scans will be saved to a file Zdddhhmm.DAT, where ddd, hh, and mm, are the day of year, hour, and minute, respectively.

34 LISST-VSF User’s Guide

Connect

Instrument and

Start LISST-VSF

Software

Connect communications cable. Connect battery or benchtop power supply. Run LISST-VSF software and open Terminal Window.

Select Offload from the LISST menu or press the Offload button.

Select Files to

Offload

Choose the files to be offloaded by clicking on the file name on the list. Multiple files can be selected by hold down the CTRL key while clicking on files. Use the SHIFT key to select a range of files.

Press the OK button to accept the current selection.

Select Download

Location

A dialog box with a path for storing the downloaded data will appear. Edit the path or press on the Browse button to select a new path. Press OK to begin the offloading.

II.4 Offloading and Erasing Data Files from Instrument

LISST-VSF User’s Guide 35

The file names will remain the same as on the compact flash card. The file creation date and time will not be preserved.

A Status bar will be displayed for each file offloaded. Text in the lower left corner will display the current file being offloaded.

Changing Offload

Baud Rate

The standard offload baud rate is 115K. If you are using a long offload cable (i.e., >20 m cable), this value may be too high and cause errors during offloading. If an offload error occurs, you can change the offload baud rate as follows:

Go to Settings in the File Menu and click the Serial Port tab. In the File Offload Baud Rate drop down menu, choose a lower baud rate and try again.

Deleting Files from LISST-VSF Memory

When connected to instrument as described above: Select Erase from the LISST menu or press the Erase button. A

list of files on the LISST-VSF datalogger will appear.

36 LISST-VSF User’s Guide

Select the files to be deleted, then click the OK button. Use the CTRL key to select multiple files or the SHIFT key to select a range of files.

Confirm the files to be deleted by clicking the Yes button.

WARNING: Once a file has been

deleted there is no way to recover the data. Make sure that the file has been properly offloaded before deleting any files

LISST-VSF User’s Guide 37

In the Laboratory

Connect communications cable. Connect battery or benchtop power supply. Run LISST-VSF software and open Terminal Window. Verify instrument communications by issuing DS command in the terminal window.

Clean instrument, install test chamber, fill with clean filtered water as described in Check Instrument Alignment and Water Cleanliness (page

33).

Set the sampling parameters to start immediately on command, save a specified number of measurements, and stop sampling by issuing the following commands:

Command

Response

ST 5<ENTER>

New Start Condition Setting: Delay Start

TD 0<ENTER>

New Start Condition data = 0 Start Condition: Delay Start with 0 minute delay

SP 5<ENTER>

New Stop Condition Setting: Fixed Number Stop

PD 20<ENTER>

New Stop Condition data = 20 Stop Condition: Fixed Number Stop at 20 samples

This configures the LISST-VSF to collect 20 sets of scattering data (each including both laser polarization states). The number specified with the PD command can be changed to collect a different number of sets.

Finally, issue the GO command to start acquisition of background scattering file. After brief warm-up period, 20 sets of scans will be saved to a file Zdddhhmm.DAT, where ddd, hh, and mm, are the day of year, hour, and minute, respectively.

Alternately, issue the command “GO nn”, where nn is the number of sets to

save.

Offloading and Processing the Acquired Scattering File

The data offloading procedure is identical to that described in Section II.4. For data processing, see the following, Section II.6.

Configuring Sampling Parameters for Field Deployment

See Section III.2.

II.5 Recording and Storing a Sample Data File

38 LISST-VSF User’s Guide

LISST-VSF User’s Guide 39

II.6 Data Processing

Datafile Format

The datafile consists of sets of data. Each set contains data for two rotations of the eyeball. Each rotation contains the following variables:

Variable no. Variable Name 1-32 Rings 33 Laser transmission 34 Battery voltage 35 PMT control voltage 36 Laser Transmission 37 Depth 38 Temperature 39-40 Date and Time

41-791 150 pairs of [angle PMT1on PMT1off PMT2on PMT2off]

For more information, see Appendix D.

Data Processing Sequence

The MATLAB functions provided for processing LISST-VSF data files will prompt you for filenames. In addition to the background and data files, you will be prompted for a Factory background file, and a calibration factors file. These files have the names, respectively,

Factory_zsc_xxxx.asc and cal_factorsXXXX.mat

where XXXX is instrument serial number.

These files should be in the same folder where your MATLAB software is installed. The data processing involves these steps (this description is intended to help you follow the logic): .

1. Reading the datafile;

2. Reading the corresponding background file;

3. Subtracting the background from the data;

4. Find the laser power change factor at 50th data in eyeball rotation

5. Find the relative gain of the two PMT’s

6. Calculate the eyeball p11,p12,and p22;

7. Calculate ring-detectors net scattering (similar to LISST-100X)

8. Apply ring area and vignetting corrections to ring data

9. Match the rings and eyeball data at 15-deg scattering angle

10. Compute composite P11, as [small angle and eyeball angle]

11. Plots of VSF, p12 and p22.

Although the software is tested, you may be required to fine-tune the PMT relative gain factor  as was noted earlier.

40 LISST-VSF User’s Guide

One-Step Processing

A single command in MATLAB is set up to process datafiles and produce the VSF and depolarization parameters. This assumes that the datafile is good. The command is:

make_P.m

It outputs the eyeball VSF(p11), the angles corresponding to p11, the full VSF, P11 (combined from eyeball and rings data), and the beam attenuation and scattering coefficients respectively beam_c and beam_b. Also output are depth, temperature, battery voltage, and PMT control voltage, along with the date and time stamps on the data.

Several plots are output during the processing, and the make_P function is described in more detail in the In Depth Processing section below.

In Depth Data Processing

The following sub-sections describe a more detailed processing of LISST-VSF data.

The following command reads and displays a raw LISST-VSF data file. The raw data are also passed as output parameters from the function.

view_rawfile.m

When this script is run, a dialog box will appear for selecting the LISST-VSF Data File (*.DAT) downloaded from the instrument

[angles,rp,pp,rr,pr,rings1,rings2,LP,LREF,bat,PMT,depth,temp,date] = view_rawfile;

[p11,p12,p22,angles,P11,Angles,beam_c,beam_b,depth,temp,bat,PMT,date] = make_P;

LISST-VSF User’s Guide 41

Eyeball Signal

Output

The output variables rp, pp, rr, and pr represent PMT signal outputs for the two laser polarizations, at the 150 angles also output by view_rawfile. Note that the angles contained in the raw data are offset from the true angles. The naming convention is that the first letter indicates laser polarization and the second denotes the PMT (analyzer) polarization. Letter r is used for perpendicular, and p for parallel.

These PMT signals are also displayed by view_readfile:

Figure 5 – Log-plots of net scattering from both PMT’s, both laser polarizations.

This is the net scattering seen by the PMT’s (i.e. PMT_on – PMT_off) for the perpendicular polarized laser (top pair) and parallel polarized laser. Note the low amount of scattered light at ~90-100° for rr and pp.

PMT Saturation?

Saturation of PMT’s is indicated with red dots in these plots (not shown).

Data with saturated PMT’s will produce erroneous results. If some of your data

are found to be saturated, we do not know of any recourse but to extrapolate the missing (saturated) data.

Saturation can be avoided by lowering the PMT control voltage. This is done by using the ~c command in the Terminal window. A lot of variables are displayed. When the PMT control is displayed, adjust is up or down in steps of 50.

42 LISST-VSF User’s Guide

Ring Detector

Output

The raw ring scattering for the 32 detectors for each laser polarization is output in the rings1 and rings2 variables.

The left and right plots are for perpendicular and parallel polarization of the laser. Minor differences are due to change in concentration and density fluctuations in the sample volume, and due to slightly weaker laser when the half-wave plate is inserted in the beam.

Figure 6 – Output of ring detectors for the two polarizations of laser.

Auxiliary Data

(i) Depth (top left), (ii) laser reference (red) and transmission (bottom, left), (iii) temperature (top, right) and (iv) the ratio of laser transmission/laser reference (bottom right). The last plot serves as indicator of homogeneity of the suspension.

Figure 7 – Auxiliary data (top) and laser reference and transmission.

LISST-VSF User’s Guide 43

read_rawfile.m

Similar to view_rawfile, this command reads a raw datafile, passes the scattering, angle and aux data as output parameters, but does not provide output plots of the output data (most commonly, this command is used in the make_P function to read in a file without displaying extra plots of the raw input data).

Usage:

Depending on a variable within the function (plot_raw_onoff), it can display diagnostic plots of the raw data measured by the PMT which is used to calculate the net scattering signals rp, rr, pp, and pr.

If plot_raw_onoff is enabled, the raw data showing laser on and laser off values for all signals will be shown. Each eyeball rotation (laser polarization) is shown in a separate plot (only the first for rp and rr is shown below). In addition, it shows the net scattering (i.e. PMT_on – PMT_off). This view shows a discontinuity in PMT outputs at 50-degree nominal eyeball angle where the laser power is un-dimmed.

Figure 8 – Outputs of two PMT’s for two laser polarizations.

0 50 100 150

-1000

-500

500

1000

Angle [deg]

Signal rp [counts]

Signal rp with laser on and off

Laser On Laser Off

0 50 100 150

-5000

5000

10000

15000

Angle [deg]

Signal rr [counts]

Signal rr with laser on and off

Laser On Laser Off

0 50 100 150

-500

500

1000

1500

2000

Angle [deg]

Net Signal rp [counts]

Net Signal rp

0 50 100 150

-5000

5000

10000

15000

Angle [deg]

Net Signal rr [counts]

Net Signal rr

[angles,rp,pp,rr,pr,rings1,rings2,LP,LREF,bat,PMT,depth,temp,date] = read_rawfile;

44 LISST-VSF User’s Guide

make_zsc.m

This function reads a user-specified background raw datafile, and saves means of rr, rp, pp, pr and rings1 and rings2 to a .mat file. The key purpose of this function is to display current backgrounds in contrast to the factory backgrounds.

Usage:

The output parameters are the median values of the data contained . These are saved in a file of the same name as the input background file, but of type *.mat.

The make_zsc function will prompt for the LISST-VSF raw data file to be processed. Only files matching Z*.DAT will be shown by default. All *.DAT files can be displayed in the Open Background Scattering File dialog by selecting it from the “Files of type” list.

Following selection of the background file to be processed, the function will prompt for a factory background file for comparison. The factory background file (Factory_zsc_NNNN.mat) file is provided with the LISST-VSF MATLAB processing tools.

If no comparison of the current background to the factory background is needed, this dialog may be cancelled.

[angles,zrp,zpp,zrr,zpr,zrings1,zrings2,zLP,zLREF,zbat,zPMT, zdepth,ztemp,zdate] = make_zsc;

LISST-VSF User’s Guide 45

LISST-VSF background scattering will be read from the input file and displayed. Four signals (rp, rr, pp, pr) are displayed, along with factory values for comparison.

Figure 9 – Comparison of current and factory eyeball background light.

Such a comparison (eyeball outputs above) guides the user if the water is not clean enough and if another background file is warranted. The spike at small angles is where the laser spot emerges into water at the window. Remaining values are typically <100 or so out of a possible maximum value of 32,768.

Some small negative values may exist in the mean background. It is not a problem.

Detailed

Walkthrough of

make_P.m

You may run the make_P function in debug mode to see details of processing. It is here that the jump in raw data at 50o (seen with the view_rawfile command) is removed; laser power variation is normalized out, sample volume stretching is compensated, etc.

Several input files must be provided to make_P, selectable with typical File/Open dialog boxes:

0 50 100 150

Angle [deg]

Measured rp [counts]

0 50 100 150

Angle [deg]

Measured rr [counts]

0 50 100 150

Angle [deg]

Measured pp [counts]

0 50 100 150

Angle [deg]

Measured pr [counts]

Current Factory

46 LISST-VSF User’s Guide

Binary Data File to Process:

This is the raw file downloaded from the LISST-VSF containing scattering data. By default, files named (V*.DAT) saved from the GO command are listed. Use the Files of type dropdown box to select any file *.DAT.

Background Scattering File:

This file is the clean water background scattering file corresponding to the particle scattering file previously selected. This is the background scattering file saved via the ZA command. Processed or raw file formats can be used to load the background scattering data:

 LISST-VSF Processed Background File (*.MAT) – Processed median

background file saved with the make_zsc function

 LISST-VSF Unprocessed Background File (Z*.DAT) and LISST-VSF

Binary Data File (*.DAT) – Raw scattering file saved using the ZA command, downloaded and not processed with make_zsc

LISST-VSF User’s Guide 47

FACTORY Background Scattering File:

This is the factory background scattering file provided by Sequoia, named Factory_ZSC_XXXX.mat, where XXXX is the serial number of the instrument.

FACTORY Calibration Factors File:

This is the calibration factors file provided by Sequoia, named Cal_factorsXXXX.mat, where XXXX is the serial number of the instrument.

48 LISST-VSF User’s Guide

Depending on the settings in read_rawfile and the selection of input files, several plots may be shown in addition to those described below.

Estimates of  for all sets of rotations of eyeball: (a small spread is ideal)

Figure 10 – Estimates of  from data.

Recall that alpha is the ratio of sensitivity of the two PMT’s. In principle, it

should be fixed. Until we know better, we find the ratio from the data for each of the sets of rotations, and take a median value.

A check of how well the chosen value of applies is shown next.

How well the estimated  matches PMT’s at 45 and 135 (should be unity)

Figure 11 – How well PMT’s match at 45 and 135 with the selected .

LISST-VSF User’s Guide 49

Corrected PMT Signals (after all adjustments): Signals shown are rp(top left), pp (bottom left), rr(top right) and pr (bottom right). The rising left edge on all is the part of eyeball that is not seeing particle scattering.

Figure 12 – Corrected data after removing laser attenuation for <50°

The VSF, p12, and p22: The eyeball estimate of VSF is at top left, the rings VSF is top right, p12 is bottom left and p22 is bottom right.

Figure 13 - Eyeball data after all corrections, before merging with rings.

Note that p22 is unstable at 45 and 135o as explained in Appendix B.

50 LISST-VSF User’s Guide

Rings data are processed in exactly the same way as with our LISST-100X data. The VSF constructed with rings data is computed. Finally, a factor is found that scales eyeball data at 15-deg to rings data at 15-degree. That completes calculation of VSF and p12 and p22.

The Composite VSF (rings and eyeball): log-log axis, and log-linear.

Figure 14 –Composite VSF, combining rings and eyeball data on log-log and

log-linear axes. Note: for small particles, rings data are noisy at smallest

angles.

LISST-VSF User’s Guide 51

Adjusting PMT

Relative Gain (α)

“tweaking alpha”

In make_P, an automated procedure is used to find the relative gain () of the two PMT’s. Noisy data may require adjusting the relative gain. This is the only adjustable parameter in the LISST-VSF instrument.

To adjust the relative gain, open make_P.m in the MATLAB Editor, and enable debug mode by uncommenting the keyboard statement to enable a breakpoint, then save the file (<CTRL>+S). Make sure that cell mode is enabled: select Enable Cell Mode in the Cell menu.

% keyboard %% SET BREAKPOINT BY UNCOMMENTING keyboard COMMAND ABOVE % alpha = 1.8

Execute the make_P function as described previously. Execution will stop, the MATLAB command prompt will be “K>>” and the current statement will be

highlighted by in the editor. Place the cursor in the cell below, for example on the % alpha = 1.8 line and execute the current cell with <CTRL>+<ENTER>.

Examine the PMT ratio plots and P12, P22 results of the estimated alpha. If “tweaking” of the gain is desired, uncomment the alpha = 1.8 (or similar). Modify the value for alpha, and then re-execute the current cell with <CTRL>+<ENTER>.

The effects of changing alpha can also be examined by using the increment/decrement value function in the MATLAB editor. Place the cursor on the alpha = 1.8 line, set the increment/decrement by value to the desired

amount (0.1 works well), then use the and buttons on the toolbar to modify the value of alpha, and automatically recalculate and display the plots of PMT signal ratio, P11,P12, and P22.

When finished, press <F5> to continue execution of the script beyond the breakpoint and current cell.

RE-COMMENT THE keyboard AND alpha = … LINES

WHEN FINISHED, AND BE SURE TO SAVE CHANGES TO

MAKE_P!

52 LISST-VSF User’s Guide

Other Software

We have provided other software that makes it easy to compare your data with Mie theory, when working with single size particles. Here’s a list:

sim_data.m

This software calculates the simulated data from the photomultipliers for particles of known size and refractive index. The output is over 0:0.1:180 degrees. Uage (for diameter 1.06 microns and index 1.566):

[s_rp,s_pp,s_rr,s_pr,Mie_angles]=sim_data(1.06,1.566/1.33);

The output variables hae identical names as names given to PMT outputs, except with the prefix ‘s_’ to indicate that these are simulated values.

This software helps visualize the expected dynamic range with single-size particles, versus the realized dynamic range in the data.

fastmie.m

Calculates Mie theory prediction of scattering at specified angles, for given particle size and refractive index. Usage:

[S1,S2,Qsca,Qext,Qback] = FASTMIE(x,nrel,ang);

pol_vsf.m

This software shows the Mie theory predictions of P11, p12 and p22. Also shown are p33 etc. which are not of concern here.

Usage: [P11,P12,P22,P33,P34,P44, angles]=pol_vsf(dia,n_rel);

This software is provided to compare measured P11 p12 and p22 with Mie theory for single-size particles.

SUMMARY

To recap:

1. A single step command make_P can be used to process a set of datafiles comprising of (a) particle data; and (b) background data. The software asks for the Factory background file and the instrument calibration factors file.

2. It is possible to view each datafile using the view_file or read_file functions. Each displays raw data in different details.

3. The break in p22 at 45 and 135o is caused by the nature of these data with the rotating eyeball.

LISST-VSF User’s Guide 53

Section Organization

The LISST-VSF instrument programming for field use is very similar to the more familiar LISST-100X. In this section, we first describe this same method again, i.e. how to program (set up) the instrument before a field deployment, or even a laboratory run.

In the next section, we describe commands that permit greater control, at a deeper level.

Serial Port Settings

Communication with the LISST-VSF is via an RS-232C link. A cable that connects the instrument to a PC has been provided. This cable connects the 5-pin underwater connector on the instrument to a DB-9 serial port connector. If required, DB-9 to DB-25 pin adapters are available.

The RS232 link communicates at 9600 baud, 8 data bits, No parity, and 1 stop bit. Data file transfer is done using a YMODEM transfer at 115K baud. The transfer rate can be changed as described in Changing Offload Baud Rate in Section II.4.

Communication Software

Installing the LISST-VSF software will create an icon on your desktop to launch the software. Once connected, you will normally communicate with the LISST-VSF using this Windows software that also permits easy programming and data offload.

We have also provided Motocross software specifically for the purpose of uploading updates to the instrument firmware which may be provided from time to time.

Section III Instrument Programming and Command Details

54 LISST-VSF User’s Guide

Using the Terminal Window

Opening the Terminal Window in the LISST-VSF, or alternate terminal software such as Motocross with the proper COM port and communications settings will allow the user to communicate with the instrument. If a program is already in execution, its progress will be displayed in the terminal window.

The instrument firmware is retained in on-board flash memory and will start executing when power is applied. After a power up, pressing the ENTER key will cause an echo of the L-VSF:> prompt. The Stop button will also send the commands to turn off the main power to the laser and electronics. Pressing the Stop button when the instrument is not running will not hurt the instrument. It is recommended to press the Stop button multiple times after stopping a running program to make sure that the main power is properly shut off. Pressing the Start button will begin the collection of data using the current configuration.

Two Letter Commands

Type “HE” at the L-VSF:> prompt to see a list of two letter commands. Under most situations the LISST-VSF Windows software terminal window will be used to configure and operate the LISST-100X. However, there are times when the LISST-VSF may be interfaced with another data logger or custom program. For this purpose a set of two letter commands is available to operate the instrument. See the LISST-VSF Command Summary (Section III.2) for detailed descriptions of each command.

Start Condition

The LISST-VSF Windows software (Operating Modes under the LISST menu) or two letter commands (in a terminal window or other RS-232 link) can configure the LISST-VSF with one of five Start conditions: Depth, Time, External Mechanical Switch, External Digital Input, and Time Delay. The details of each condition are described below.

Depth Start

The built-in depth sensor of the LISST-VSF is used to check the current depth to determine if the desired start depth has been exceeded. The instrument is powered up and 5 measurements of the depth are averaged over a two-second period. If the depth exceeds the threshold the program will proceed to the data collection routine. If the depth does not exceed the threshold the instrument will power down and wait 28 seconds before checking the depth again. The program will continue checking until the depth is exceeded or until the program is stopped.

Time Start

The program will check the current time every second and compare it to the Start Time. If the Start Time is equal to or earlier than the current time the program will go directly to the data collection routine. It will continue checking the time until the Start Time is reached or until the program is stopped.

III.1 Programmed Operation for Field or Laboratory Use

LISST-VSF User’s Guide 55

External

Mechanical Switch

Start

The LISST-VSF has a white plastic lever on the endcap. This lever has a magnet imbedded in it. This magnet can activate a switch inside the pressure case. The base program looks at the status of this switch once a second. If the switch is in the on or “1” positions the program will go directly to the data collection routine. It will continue checking

the switch status until the switch is moved to the “0” position or until the program is stopped. When in the “0” position the lever is up against the

zinc anode.

External Digital

Input Start

The LISST-VSF is equipped with auxiliary inputs on the 6-pin underwater connector. Pin 2 of the 6-pin connector is the DIG 1 input (see Engineering Drawings). The program will check the status of the digital input once a second. If the voltage at the DIG 1 input is greater than 2 volts (relative to Digital Ground, Pin1) the program will go directly to the data collection routine. It will continue checking the status of the digital input until voltage exceeds 2 volts or until the program is stopped.

WARNING: The maximum permissible input voltage on the digital input line is 3.3 volts.

Time Delay Start

The time delay start condition will cause the program to wait the specified number of seconds before continuing on to the data collection routine.

Stop Condition

The LISST-VSF can be configured with one of six Stop conditions: Depth, Time. External Mechanical Switch, External Digital Input, Fixed number of samples, and Maximum Memory or Low Battery. The Stop conditions are checked after each measurement set (two rotations of the eyeball). The details of each condition are described below.

Depth Stop

The built-in depth sensor of the LISST-VSF is used to check the current depth to determine if it is less than the desired Stop depth. The averaged depth from the last sample acquired is used as the current depth. If the depth is less than the threshold the sampling will stop. If the depth is not less than the threshold the program will continue sampling as per the configuration. If the Start Condition is a Depth Start the program will wait 30 seconds and then return to looking for the Depth Start Conditions. The delay is to keep the instrument from starting and stopping too quickly as the instrument is moving up and down. If the Start Condition is Depth Start the Base program will return to checking for the Start Conditions. For all other Start Conditions the when the current depth is less than the threshold the program will stop and return to the L-VSF:> prompt.

Time Stop

The program will check the current time after each sample or burst and compare it to the Start Time. If the Start Time is equal to or later than the current time the program will stop and return to the L-VSF:> prompt.

56 LISST-VSF User’s Guide

External

Mechanical Switch

Stop

After each measurement set the status of the Switch lever is checked.

If the switch lever is in the off or “0” position sampling will stop. If the

Start Condition is a Switch Start the program will return to checking the start condition. For all other Start conditions the program will stop and return to the L-VSF:> prompt.

External Digital

Input Stop

The status of the Dig 1 input is checked after each sample or burst. If the voltage at the input is less than 0.7 volts the sampling will stop. If the Start Condition is a Digital Input Start the program will return to checking the start condition. For all other Start conditions the program will stop and return to the L-VSF:> prompt.

Fixed Number of

Samples Stop

The program will acquire a fixed number of samples before stopping. The number of samples saved is checked after each measurement set is saved. When the number of sample to be saved has been reached the program will stop and return to the L-VSF:> prompt.

Maximum Memory

or Low Battery

Stop

The Maximum Memory or Low Battery Stop condition will continue to sample until the memory capacity has been reached or when the battery voltage has dropped to less than 6 volts. The program will continue to sample until one of these conditions is met. It will then return to the L-VSF:> prompt.

LISST-VSF User’s Guide 57

III.2 LISST-VSF Command Summary

Display Commands

Display Current Battery Voltage

Display current Disk Directory

Display current status information

Display Current Time and Date

Display general help messages and command list

Setup Commands

OM x

Set Operating mode.

ST x

Set Start Condition.

TD x

Set Start Condition Data

SP x

Set Stop Condition

PD x

Set Stop Condition Data

SI x

Set Sample interval

MA x

Set samples per average equal to x

SC mm/dd/yy hh:mm:ss

Set Clock with time and date, where mm=month, dd=day, yy=year, hh=hour(24 format), mm=minute, ss=seconds, Example: ST 01/05/2005 21:05:03

Autostart Setting

Store Current Settings as Default

Store Mode Setting

Reset Depth Sensor Offset

Acquisition/Action Commands

DL filename

Delete File

Start Data collection using current parameters

Display Raw data to screen when average saved

YMODEM offload of file at 115K Baud

Acquire 16 samples (ring and eyeball) and save to Zdddhhmm.DAT file.

Acquire 16 samples and transmit them. Used by Check Alignment Function.

Go into deep sleep mode (minimum power consumption)

58 LISST-VSF User’s Guide

Display Commands

Display Battery Voltage

Syntax:

DB or db

Description:

The current battery voltage is displayed to the screen. Note that the instrument will turn on the eyeball motor, laser, and AOM in order to determine the battery voltage under load.

Example:

input: DB output: Current Battery voltage: 8.90 volts

Display Disk Directory

Syntax:

DD or dd

Description:

Display current disk directory in DOS type format. Includes total bytes used and bytes available.

Example:

input: DD output:

L-VSF:>dd LISST-100X Disk Directory

Volume in drive C is NONAME Volume Serial Number is 778B-155F

Directory of C:\ L040305_.BIN 4,136 03-05-04 6:30p L183705.BIN 1,672 03-05-04 6:37p

2 file(s) 5,808 bytes 0 dir(s) 15,933,440 bytes free

L-VSF:>

Display current status information

Syntax:

DS or ds

Description:

The instrument settings and status are displayed to the screen.

Example:

input: DS output:

LISST-VSF Current Status and Settings

Serial number = 1425 Firmware Version 0.920 Jul 23 2012 17:34:17 Operating Mode: Fixed Rate Mode Start Condition: Delay Start with 0 minute delay Stop Condition: Fixed Number Stop at 20 samples Measurements per Average: 10 Sample Interval: 3

Start Degree = 5 Offset Index = 0

LISST-VSF User’s Guide 59

Number of Degrees = 150

Depolarizer Servo Number = 250 [removed in 2/2012]. No Polarizer Servo Number = 0 Half Wave Plate polarizer Servo Number = 500 Motor Controller Setpoint = 45

PMT Sensitivity = 500 AOM Analog Value = 200

Battery Voltage is 10.75

Current Date/Time: Tuesday, August 07, 2012 16:18:36 Current Day of the Year: 220

input: DS 1 output:

LISST-VSF Current Status and Settings SN = 1425 OM = 3 ST = 5 TD = 0 SP = 5 PD = 20 MA = 10 SI = 3 BI = 1 SB = 1 BB = 0 CT = 0 IC = 0 Current Time = 08/07/2012 16:21:36 Battery= 1079 Switch= 0

Memory= 128245760

Display general help messages and command list

Syntax:

HE or he

Description:

Displays the list of command to the screen.

Example:

input: HE output: LISST-100X Commands (followed by 30 lines of text)

Setup Commands

Set measurements per average

Syntax:

MA x or ma x Where x = number of samples per average

Description:

Each recorded or displayed measurement is based on an average of

60 LISST-VSF User’s Guide

measurements. The number of measurements per average is set using the SA command. If no value follows command, prompts will be displayed for the value.

Example:

input: MA 10 output: New Measurements per Average: 10

Cautions:

None

Set Start Condition

Syntax:

ST x or st x, where x is the start condition code described below

Description:

The ST command sets the start condition to be used when the GO command is issued. The start condition options are:

1 = Depth Start 2 = Time/Date Start 3 = Mechanical Switch Start 4 = Digital Input Start 5 = Delay Start

If no value follows command, prompts will be displayed for the value.

Example:

input: ST 5 output: New Start Condition Setting: Delay Start

Set Start Condition Data

Syntax:

TD x or td x, where x is the start condition data described below

Description:

The TD command sets the start condition data to be used when the GO command is issued. The start condition data is used with the Start Condition setting as follows:

 If the Start Condition is Depth Start (option 1) the input will be start depth

in meters.

 If the start condition is set to Time/Date Start (option 2) the input for TD

will be the start date and time.

 If the Start Condition is Delay Start (option 5) the input will be time delay

in seconds.

 The TD setting is ignored for Mechanical Switch Start (option 3) or Digital

Input Start(option 4).

If no value follows command, prompts will be displayed for the value.

Example:

input: TD 3 (if Start Condition = 1 (Depth Start)) output: New Start Condition data = 3 Start Condition: Depth Start at 3 meters

input: TD 12/31/05 23:59:59 (if Start Condition = 2 (Time/Date Start)) output: New Start Condition data = 12/31/05 23:59:59 Start Condition: Time Start at 12/31/05 23:59:59

Input: TD 2 (if Start Condition = 5 (Delay Start)) Output: New Start Condition data = 2 Start Condition: Delay Start with 2 minute delay

Set Stop Condition

Syntax:

SP x or sp x, where x is the stop condition code described below

LISST-VSF User’s Guide 61

Description:

The SP command sets the stop condition to be used when collecting data. The stop condition options are:

1 = Depth Stop 2 = Time/Date Stop 3 = Mechanical Switch Stop 4 = Digital Input Stop 5 = Fixed Number of Samples Stop 6 = Maximum memory or Low Battery Stop

If no value follows command, prompts will be displayed for the value.

Example:

input: SP 5 output: New Stop Condition Setting: Fixed Number Stop

Set Stop Condition Data

Syntax:

PD x or pd x, where x is the stop condition data as described below

Description:

The PD command sets the stop condition data to be used when the collection data. The stop condition data is used with the Stop Condition settings as follows.

 If the Stop Condition is Depth Stop (option 1) the input will be stop depth

in meters.

 If the stop condition is set to Time/Date Stop (option 2) the input for PD

will be the stop date and time.

 If the Stop Condition is Fixed Number Stop (option 5) the input will be the

number of samples to collect before stopping.

 The PD setting is ignored for Mechanical Switch Stop (option 3), Digital

Input Stop (option 4) or Maximum memory or Low Battery Stop (option

6).

Example:

input: PD 3 (if Stop Condition =1 (Depth Stop)) output: New Stop Condition data = 3 Stop Condition: Depth Stop at 3 meters

input: PD12/31/05 23:59:59 (if Stop Condition = 2 (Time/Date Stop)) output: New Stop Condition data = 12/31/05 23:59:59 Stop Condition: Time Stop at 12/31/05 23:59:59

input: PD 2 (if Stop Condition = 5 (Fixed Number of Samples Stop)) output: New Stop Condition data = 2 Stop Condition: Fixed number Stop at 2 samples

Set Sample Interval

Syntax:

SI x or si x, where x is the number of seconds between samples, from 1 to 10,000.

Description:

In Fixed Rate Mode (OM = 3) or Burst Rate Mode (OM = 2), the sample interval is the number of seconds between two consecutive samples, each composed as an average of a number of measurements (specified by the MA command).

Example:

input: SI 5 output: New Seconds between Samples: 5

Set Burst Interval

Syntax:

BI x or bi x, where x is the number of seconds between the start of 2 consecutive bursts, from 1 to 10,000 seconds.

Description:

In Burst Mode (OM = 2), the burst interval is the number of seconds between two

62 LISST-VSF User’s Guide

consecutive bursts, each burst composed of a number of samples per burst (specified by the SB command).

Example:

input: BI 900 output: New Seconds between Bursts: 900

Set Samples per Burst

Syntax:

SB x or sb x, where x is the number of samples per burst. Each sample is taken at the sample interval (in seconds) set by the SI command.

If no value follows command, prompts will be displayed for the value.

Example:

input: SB 10 output: New Samples per Burst: 10

Set Clock with time and date

Syntax:

SC mm/dd/yy hh:mm:ss or sc mm/dd/yy hh:mm:ss Where mm=month, dd=day, yy=year, hh=hour (24 hour format), mm=minute, ss=seconds

If no values follow the “SC” or “sc” command, prompts for entering the time and

date will be displayed.

Example:

input: SC 01/05/2001 21:05:03 output: Command Data in SC is: 01/05/01 21:05:03 Current Date/Time: Friday, January 05, 2001 21:05:03

Autostart Setting

Syntax:

AS x or as x, where x is 1 (yes) or 0 (no)

Description:

With Autostart enabled, the firmware will immediately start the sampling program that is stored in the EEPROM of the Persistor datalogger upon power up of the instrument.

Use the SD command to store the current settings as default values to be used in conjunction with the AS command.

Example:

input: AS 1 output: AutoStart will occur upon power up!

Cautions:

1) If Autostart is enabled, the user cannot talk to the instrument when powering it up – it will immediately start sampling according to the SD defaults. In order to stop sampling and establish normal communication, the user must issue a stop command, by either pressing the STOP button or issuing a CTRL-C command in the terminal window when the instrument is powered up.

2) Make sure the current program settings are as desired and saved as default settings (see SD).

Store Current Settings as Default

Syntax:

SD or sd

Description:

Issue the SD command to verify the current settings. Then confirm (1 = yes, 0 = no) that these settings should be burned into the EEPROM to be used with the AutoStart setting.

Example

input: SD output: LISST-100X Current Status and Settings

LISST-VSF User’s Guide 63

Serial number = 1335 Firmware Version 1.997 Feb 16 2011 14:18:45 Operating Mode: Fixed Rate Mode Start Condition: Delay Start with 3 minute delay Stop Condition: Fixed Number Stop at 2 samples Measurements per Average: 10 Sample Interval: 5

Battery Voltage is 7.28 Current Date/Time: Wednesday, August 17, 2011 12:24:14

Current Day of the Year: 229 Do you wish to set current settings to be defaults? (1=yes,0=no): [0] ? 1 Current Settings being saved to EEPROM... Current Settings saved as defaults!!!

Cautions:

If you change any of the settings after issuing the SD command you must reissue the SD command to save the updated settings.

Store Mode Setting

Syntax:

SM x or sm x, where x is 1 or 0

Description:

The Store Mode setting disables (x = 1) or enables (x = 0) data storage on the internal drive. No Ldddhhmm.DAT file will be created if store mode is disabled.

It is intended to be used for long-term real-time deployments, where it may not be desirable to have the data stored on the datalogger to avoid it filling up.

Example:

input: SM 1 output: Data will NOT be stored after each sample!!!

input: SM 0 output: Data will be stored after each sample!!!

Cautions:

Be very careful that the correct store mode is selected before a deployment where it is the intent to store the data internally on the instrument datalogger!

Issue a DS command to verify the status of the store mode setting. A warning will be displayed as part of the DS status if the store mode is disabled: WARNING: Data storage disabled. Data will not be saved!!!

Reset Depth Sensor Offset

Syntax:

ZD or zd

Description:

The ZD (or zd) command resets the depth sensor offset so that the sensor reads a depth of 0m at zero depth (in air). You must issue the ZD command, then select 1 (yes) or 0 (no) to reset depth sensor

Example:

input: ZD output: Depth Sensor Offset Reset Procedure Started.

Instrument must be at zero depth and similar temperature to field conditions.

64 LISST-VSF User’s Guide

Do you wish to reset Depth Sensor offset? (1=yes,0=no): [0] ? 1 Previous offset was -14.03. New offset is -13.87. Previous Depth was -0.15 meters. New Depth using corrected offset is 0.00 meters.

Cautions:

None

Acquisition/Action commands

Delete file from Compact Flash Module

Syntax:

DL filename or dl filename where filename is the name of the file to be deleted.

Description:

DL command is used to delete file from the Compact flash module. Wildcards such as *.* can be used.

Example:

Input: DL L159*.dat Output: Are you sure (Y/N)…

Cautions:

WARNING: Make sure that the file being delete has already been offloaded before deleting the file. Once the file is delete it can not be recovered.

Start Data Collection using current Settings

Syntax:

GO or go

Description:

Starts Fixed Rate or Burst Mode Data collection using current settings.

Example:

Input: GO Output: Waiting for start conditions…

Cautions:

To stop data acquisition before it is complete press the Stop button or CTRL-C.

Display Raw data to screen when average saved

Syntax:

XR x or xr x, where x =1 (yes) or x = 0 (no)

Description:

If display of raw data is enabled, the RAW data will be printed to the serial port between curly brackets in 40 rows: { …. 32 ring values + 8 Aux parameters }

Example:

input: XR 1 output: Raw data WILL be transmitted when data is stored

Cautions:

None

YMODEM Offload

Syntax:

YS filename or ys filename where filename is the name of the file to be offloaded.

Description:

Offloads file from Compact Flash Module to PC using YMODEM offload at 115 Kbaud

Example:

Input: YS L1391205.dat Output: Starting…

LISST-VSF User’s Guide 65

Notes:

The YS will initiate the YMODEM offload on the instrument. A YMODEM file transfer must be started on the PC to accept the data. HyperTerminal can accept YMODEM file transfers at 115K baud.

Collect Ring and Eyeball Background Scattering

Syntax:

ZA or za

Description:

Acquires 16 measurement sets and saves the results to Zdddhhmm.DAT. The ZA command should be used to collect the background scattering data used in processing LISST-VSF data.

Example:

Input: ZA Output: <Status information during sampling>

Notes:

The ZS command does not store the sample to a datafile, but average detector ring values may be written to a text file using the LISST-VSF software.

Grab 20 samples and transmit

Syntax:

ZS or zs

Description:

Acquires 20 averaged sample and displays the result to the screen. The ZS command is used by the LISST-VSF program for the Check Alignment function.

Example:

Input: ZS Output: { …. 32 ring values + 8 Aux parameters }

repeat 20 times

Notes:

The ZS command does not store the sample to a datafile, but average detector ring values may be written to a text file using the capture functions of the Motocross terminal software.

Go into deep sleep mode (minimum power consumption)

Syntax:

ZZ or zz

Description:

Sends LISST-VSF in to low power sleep mode. Instrument will wake up every 10 seconds and wait for a response. If there is no response within 2 seconds, the instrument will return to sleep mode.

Example:

Input: ZZ Output: Deep Sleep… Enter zz to wake up Deep Sleep… Enter zz to wake up Deep Sleep… Enter zz to wake up

Cautions:

The background scattering data and other settings are not affected by the ZZ command.

66 LISST-VSF User’s Guide

LISST-VSF User’s Guide 67

Appendix A: Details of LISST-VSF Instrument

Fundamentals: The Volume Scattering Function (VSF) is an inherent optical property of water. It describes how an incident photon is scattered into different directions. The integral of the VSF produces the total scattering coefficient, usually denoted as b. The attenuation of light is described with a beam attenuation coefficient, c. It is an axiom of optics that attenuation equals the sum of absorption, denoted with a and scattering, i.e. c = a + b. The present instrument measures c directly with an attenuation sensor, b indirectly via the VSF, thus by subtraction, also permitting an indirect estimate of absorption a.

The scattering of light is almost always a polarizing event, i.e. the state of light scattered by particles is altered from the state of the incident light. The scattering properties of particles are described by a 4 x 4 scattering Mueller matrix. The present instrument measures the top left set of these elements. The relation between the incident state and scattered state of polarization is described by Mueller algebra:

S where I, Q, U and V are conventionally symbols used to denote the elements of the Stokes Vector of

light, S. For more details, see Bohren and Huffman(2004). The Mueller matrix has these simplifications due to symmetry: P13 = P14 = P23 = P24 = 0; and P31 = P32 = P41 = P42 = 0; For spherical particles, further simplifications result:

P12 = P21 P11 = P

It follows that:

(i) When the light source is unpolarized, with its Stokes vector being [1 0 0 0]’, the

(ii) When the light source is vertically polarized, with its Stokes vector being [1 1 0 0]’, the

(iii) When the light source is horizontally polarized, with its Stokes vector being [1 -1 0 0]’,

scattered

= P S

(1)

incident

scattered light has a Stokes vector [P11 P21 0 0].

scattered light has a Stokes vector [P11+P12 P21+P22 0 0].

the scattered light has a Stokes vector [P11-P12 P21-P22 0 0].

The 3 unknowns P11 P21 and P22 can thus be extracted with these measurements. In particular, the total scattered light power in case (i) above is simply the VSF. In this case, the difference in the two

polarizations, measured by two PMT’s corresponds to M

. Cases (ii) and (iii) above permit

extraction of P22 with some redundancy to get a best estimate. These ideas are incorporated in the LISST-VSF instrument.

In addition to the ‘roving eyeball’ element of this instrument, we have incorporated the small-angle forward scatter VSF measuring optics, commonly used in the LISST-100X instrument manufactured by this company. In this manner, this instrument is designed to measure the VSF and 2 other elements of the scattering matrix from 0.1-degree to 165 degrees (nominal).

The Key Idea: It is common practice to use a discrete number of distinct detectors, all viewing a common illuminated volume of water, to get the VSF at those distinct angles. Our essential

68 LISST-VSF User’s Guide

innovation was to not be constrained by looking at a fixed point along a beam. Instead, we have chosen to look from a fixed receiver that rotates to view different portions of a laser beam. This

reduces the receiving optics to a small ‘roving eyeball’ (later). This key innovation makes the

instrument totally submersible, autonomous, and field deployable. The beam transmission sensor has a very low acceptance angle, which improves estimates of

beam-c (Boss and Slade, 2009). Ambient light rejection is important while measuring weak scattering from marine particles. We

employ an acousto-optic cell to modulate the laser and use synchronous detection to reject ambient light. We also exploit this ability to modulate laser power to extend the dynamic range of VSF measurement. This is done by dimming of laser power while measuring near-forward scattering (to 50 degrees), and then using full power for larger angles. This permits extension of VSF data from 12 bits to 16 bits.

Simplified Optics Diagram: The LISST-VSF optical design consists of a 1 mm diameter green (532 nm) laser beam originating

from a TEC laser module (1), then folded by a prism (3) onto the primary instrument optical axis. The default laser polarization is determined by rotation of the laser module and a polarizing beamsplitter (4). Only the diffracted (modulated) AOM beam is passed by an iris (5) and then expanded to 3 mm by a beam expander (6). The expanded beam is sampled (7) to measure reference laser power by a photodiode (8), calibrated to incident laser power entering the sample volume. A half-wave plate (9) can be mechanically inserted into the laser beam to change the incident polarization between perpendicular and parallel. The beam then passes through the pressure window (10) into water within the sample volume. Behind the receive side pressure window covered in ND glass (12) is the receive lens (13). This lens focuses the scattered light on to the ring detector (14), and the focused beam passes through a central hole to a photodiode (15) which measures beam transmission. The eyeball (11) receives scattered light from the sample volume, and is also shown in a side view. Scattered light viewed by the eyeball passes through a spatial filter (16) to limit the viewing angle of the eyeball, and interference filter (17) allowing only light at the laser wavelength. Received scattered light is then split into parallel and perpendicular polarization components by the beamsplitter (18) and measured by the two PMT modules (19) and (20).

Engineering Design

LISST-VSF User’s Guide 69

Opto-mechanical Design: CAD drawings of the instrument layout is shown in Figure A-15. The top

figure shows the open center section for water. The eyeball is barely visible. The first level of detail is in the middle drawing, On the left is the transmit optics of Error! Reference source not found.. n the right is the optics to sense small-angle scattering, comprising a receive lens, an ND filter to attenuate the powerful laser, and the ring detector. An attempt is made to show all components in the lowest figure.

Electronics: Subsystems: The following subsystems are involved:

 Power for (i) laser; (ii) eyeball motor; (iii) photomultipliers, and (iv) signal processing and

data storage electronics.

 Microcomputer for control and data storage.  Photomultipliers, amplifiers, and control voltage connection.

The master clock is derived from the rotating eye-ball and an encoder. This ensures perfect synchronism of all data capture electronics with angle location of the eyeball.

Upon power up, the laser deliver laser power in water. The eyeball motor is energized to generate a timing clock for data capture. This system employs a phase-lock loop. The system tolerates fluctuations in motor speed arising from ‘O’-ring friction. Based on control setting, a high-voltage control sets PMT sensitivity individually. Data are captured in the following sequence:

1. First rotation: Perpendicularly polarized laser propagates in water; VSF signals are captured from both PMTs, then ring-detector signals captured.

2. : Half wave plate is inserted, VSF data is captured with PMT’s, then ring-detector data is captured.

3. Data file is written to memory.

4. If selected, another set of eyeball rotations are begun, and so on.

For each data acquisition sequence, a background scattering is measured. This is done with

0.2micron filtered water. This background is subtracted from particle data, to retain contribution of particles alone. The background from pure water was verified to appear similar to Rayleigh scattering.

70 LISST-VSF User’s Guide

Figure A-15 – Laser (1) emits light toward left, and is reflected by prism (3) to go to right. An iris (4)

rejects undiffracted beam, and a beam-expander (5) changes beam diameter to 3mm. The beam

passes through a pellicle beam sampler (6) which splits the beam for measurement by a photodiode;

then through either a ½-λ plate (7), and enters water through transmit window (9). The beam and

forward scattered light enter the receive window(10) and are focused by lens (11) through an ND

filter (12) to ring detector (13). The large-angle scattering is sensed by the eye (14) and the scattered

light beam is then steered to a polarization separator and twin-PMT assembly. This figure is out of

date.

LISST-VSF User’s Guide 71

Appendix B: Method of Extracting P11, P12 and P22

The Signals: The forward model is that, following Figure 2, the scattered light, with Mueller scattering matrix P is first multiplied with the Stokes vector of the laser. Then, the light reflected by the lower prism is rotated by the

same angle as the scattering angle to make it’s polarization axes normal to the second prism. A final matrix

product with the Mueller matrix of a linear polarizer is performed to separate the two components of this light.

The Laser Stokes vectors are: (note only the second element changes)

S= [1 ±1 0 0].

The Mueller matrix of scattering is (following data displayed by Voss and Fry, 1984, Figure 1, we set the off block diagonal elements to zero):

P =[P11 P12 0 0 P12 P22 0 0

0 0 P33 P34

0 0 P43 P44]

Rotation matrix is:

R =[ 1, 0, 0, 0] [ 0, cos(2*), sin(2*), 0] [ 0, -sin(2*), cos(2*), 0] [ 0, 0, 0, 1]

And transmission through the two analyzers in front of the PMT’s is represented by the Mueller matrix:

= ½ [ 1 ±1 0 0]

1,2

[±1 1 0 0] [ 0 0 0 0] [ 0 0 0 0]

The light transmitted by the two polarizers has a Stokes vector: L*R*P*S.

Case I: Perpendicular Polarization

PMT1H: a = P11 – P12 + cos(2) * [P12 - P22] (B2a)

PMT2H: c = {P11 – P12 - cos(2) *[P12 - P22]} (B2b)

where  is the relative gain of the two photomultipliers. is not known a priori, it is determined

from data.

Determining the Relative Gain of the Two Photomultipliers:

72 LISST-VSF User’s Guide

 = c/a ; at and yields two estimates of . (B3)

 = d/b ; at and yields two estimates of . (B5)

 is estimated from the convenient result that at and equations B2a and B2b reduce

to:

PMT1H: a = P11 – P12, at and  (B2c)

PMT2H: c = {P11 – P1} at and  (B2d)

So that:

(B3)

Case II: Parallel Polarization

PMT1V: b = P11+P12 + cos(2) * [P12 + P22] (B4a)

PMT2V: d = {P11+P12 - cos(2) * [P12 + P22]} (B4b)

So that, in a manner identical to eq. B3, another estimate of the photomultiplier relative gain is obtained from:

PMT1V: b = P11+P12 at and  (B4c) PMT2V: d = {P11+P12} at and  (B4d)

   

Extracting VSF (P11):

It follows from summing Eqs. B1a,b

a + b +[ c +d]/ = 4 P11, (B6)

Extracting P12:

From B2 and B4, it follows that:

[b - a +(d - c )/ ] = 4 P12 (B7)

Extracting P22:

Note that P22 always occurs in combination with P12 in Eqs. B2a,b and B4a,b. Thus, only a best estimate of P22 is extracted. Usually, this involves fine-tuning the relative gain factor . Also, note from Eqs.2a-d, at 45 and 135o , the measurement contains no information on P22. In reverse, solving for P22 blows up at these angles.

Extracting P22 does sometimes require the tweeking of the relative gain of the photomultipliers. This can be done within the make_P function. Experienced MATLAB users will know how. We will provide a description shortly.

These equations are implemented in the MATLAB function make_P.

LISST-VSF User’s Guide 73

Absolute Calibration of P11: Since P12 and P22 are conventionally displayed after normalization by P11, only the absolute calibration of P11 is required.

The calibration is performed by matching P11 from PMT data with the P11 from Ring 32 of the forward small-

angle VSF. The latter is absolutely calibrated as reported in: Agrawal YC, Mikkelsen O. A (2009):

Empirical forward scattering phase functions from 0.08 to 16 deg. for randomly shaped terrigenous 1-21 µm sediment grains. Optics Express 17:8805–8814.

74 LISST-VSF User’s Guide

Appendix C: MATLAB Software

The MATLAB functions perform these functions:

read_rawfile Reads a raw data file, displays raw data (optional), and outputs uncalibrated

variables;

view_rawfile Reads a raw data file, displays PMT and ring signals and aux data, and outputs

uncalibrated variables;

make_zsc Reads a raw data file acquired as a background file, outputs mean uncalibrated

background file. Useful to compare with factory background.

make_P: Reads particle data file and background data file(.DAT or .MAT produced by

make_zsc) and outputs the parameters P11, P12 and P22, depth, temperature, date, etc.. P11 includes small angle VSF for angles of Appendix D.

sim_abcd Simulates Mie theory estimate of a,b,c,d for given particle size and complex

refractive index, to compare with data seen with read_vsf.

fastmie.m Function to compute Mie scattering for arbitrary sphere diameter and relative

refractive index (may be complex)

pol_vsf.m Function to compute Mueller matrix elements for particle of arbitrary diameter and

relative refractive index (may be complex). Uses bhmie.m. Outputs at 0.1 degree intervals.

Overview of MATLAB Software

read_vsf.m This function opens the data file, displays the raw data with laser on and off, assigns variables such as PMT1plus, PMT2plus, etc., and depth, temperature, PMT setting etc. The display of raw data (laser on and off) helps in spotting errors, or glitches.

make_zsc This function reads a file that is taken with clean water. It edits out bad points that may arise due to glitches or floating particles, and generates a mean value of the output of rings, and of PMT’s. The function uses the median values, instead of means, to reject the occasional floating particle. Additionally, this function also shows a comparison of the current background and the factory background. This is then, the health-check of the instrument as well as a check on the quality of the background. The mean background is saved as an .asc file.

make_P: This function reads the background data file (binary or ascii) and the particle data file and outputs the 3 desired variables of P for all 182 angles, along with the angles. Corrections include: attenuation correction of scattering signals, subtraction of backgrounds from particle data, and correction for laser reference drift. Absolute sensitivity of PMT’s is adjusted to match the VSF estimated from ring 32. Estimates of the relative gain parameter  are obtained from data. The output is not averaged over scans. VSF and depolarization can then be plotted against depth.

LISST-VSF User’s Guide 75

Auxiliary Files: In addition to the functions above, the calibration factors and others:

cal_factorsXXXX.mat Calibration factors for sensors for laser power, depth, temperature. Each calibration factor is identified with a slope and offset; e.g. the calibration for laser reference sensor is called LREF_slope and

REF_offset, etc.

Variable Names:

The datafile contains two rotations of 40 + 5*150 16-bit values, per set. In each rotation, the first 40 variables are identical in format to our LISST-100X, i.e these contain the output of ring detectors for forward scattering, laser transmission, battery voltage and PMT control voltage (new for LISSTVSF), laser reference, depth, temperature, and date and time. Then for each of 150 angles, a 5 parameter subset follows. Each subset contains PMT1_ON, PMT1_OFF, PMT2_ON, PMT2_OFF, ANGLE. The ‘on’ and ‘off’ refer to PMT outputs in digital counts summed for several cycles of laser chopping. See Appendix D for full details.

variable name laser polarization PMT polarization

rp perpendicular PMT1: parallel rr perpendicular PMT2: perpendicular

pp parallel PMT1: parallel pr parallel PMT2: perpendicular

P11 Composite VSF, includes small-angle and eyeball data angles, Angles over which eyeball data is useful (in degrees) Angles Composite angles at which P11 is presented beam_b Beam scattering coefficient, (m-1) over 0.09 to 150 degrees. beam_c Beam attenuation coefficient, (m-1) Bat Battery voltage date Date and time, two variables, [day*100+hr] and [min*100+sec]. depth Depth in 0.01 m steps p11 VSF seen by eyeball (over eyeball angles), units m-1 sr

-1

p12, Depolarization p22, Depolarization PMT PMT Control voltage (in mV); sets PMT gain. rings1 40 variables from 32 rings etc. for perpendicular laser polarization rings2 40 variables from 32 rings etc. for horizontal laser polarization temp Water temperature, 0.01 oC steps, at endcap on ring-detector side.

These variable names appear in data processing MATLAB software, and in function calls.

76 LISST-VSF User’s Guide

Angles in Water at which VSF is measured

The following Table shows 32 angles at which small-angle VSF is measured, and eyeball angles beyond. ‘Lower’ and ‘Upper’ refer to angle range covered by each ring detector. These data are provided an .asc file: Observation_Angles_in_Degrees angles.asc and also as a MATLAB file, Observation_Angles_in_Degrees angles.mat. These angles are in water.

Ring #

Lower

Upper

Median

0.0862

0.1017

0.0936

0.1017

0.1200

0.1104

0.1200

0.1416

0.1303

0.1416

0.1671

0.1538

0.1671

0.1972

0.1815

0.1972

0.2327

0.2142

0.2327

0.2746

0.2525

0.2746

0.3240

0.2983

0.3240

0.3823

0.3520

0.3823

0.4512

0.4153

0.4512

0.5324

0.4901

0.5324

0.6283

0.5784

0.6283

0.7414

0.6825

0.7414

0.8748

0.8054

0.8748

1.0323

0.9503

1.0323

1.2181

1.1214

1.2181

1.4372

1.3231

1.4372

1.6957

1.5611

1.6957

2.006

1.8419

2.006

2.3600

2.1729

2.3600

2.7837

2.5631

2.7837

3.2827

3.0229

3.2827

3.8703

3.5644

3.8703

4.5613

4.2016

4.5613

5.3731

4.9506

5.3731

6.3250

5.8296

6.3250

7.4384

6.8591

7.4384

8.7365

8.0614

8.7365

10.2430

9.4598

10.2430

11.9804

11.0777

11.9804

13.9674

12.9358

13.9674

16.2149

15.0493

Angles 33 to 182

6-155

Appendix D: Observation Angles, Data Storage Format

and Variable Names

LISST-VSF User’s Guide 77

Raw Data Storage Format

The values in the binary raw data file (.DAT extension ) are stored in the order shown in the table below.

Elements

Parameter

Record 1:

First eyeball rotation with laser polarized perpendicular

1:32

Light intensity of ring detectors, 1-32

Laser transmission sensor (used in beam-c computation)

Battery voltage

PMT Control Voltage [e.g. 550 means 0.550V; max can be 1V]

Laser reference sensor (monitors laser emission), raw counts

Pressure, in digital counts, each count is 0.1m

Temperature in units of 1/100th of 1o C

(Day*100 + Hour) at which data taken

(Minutes*100 + seconds) at which data taken

41-790

150 sets of [angle, PMT1_on, PMT1_off, PMT2_on, PMT2_off]

Record 2:

Second eyeball rotation with laser polarized parallel

1:32

Light intensity of ring detectors, 1-32

Laser transmission sensor (used in beam-c computation)

Battery voltage

PMT Control Voltage [e.g. 550 means 0.550V; max can be 1V]

Laser reference sensor (monitors laser emission), raw counts

Pressure, in digital counts; each count is 0.1m

Temperature in units of 1/100th of 1o C

(Day*100 + Hour) at which data taken

(Minutes*100 + seconds) at which data taken

41-790

150 sets of [angle, PMT1_on, PMT1_off, PMT2_on, PMT2_off]

The raw data file is binary, of type *.dat. Each VSF requires two rotations of the eyeball, so that two records are stored per measurement of VSF. One record is with laser polarization being vertical, the second is with polarization rotated horizontal.

[Note: vertical and horizontal terms are used here simply to donate polarizations with respect to the instrument optical bench; they are not meaningful with respect to true horizontal!.]

Each record represents one full turn of the eyeball. It contains these data: 40 variables for rings data and aux measurements, and 150 sets of 5 measurements each for each degree of eyeball rotation. Each set being: PMT1_on, PMT1_off, PMT2_on, PMT2_off, angle. The ‘on’ and

‘off’ refer to laser being modulated on or off. Both ‘on’ and ‘off’ values are stored so that

saturation of A/D may be recognized as an error.

78 LISST-VSF User’s Guide

Output Variable Sizes from read_VSF.m

For N sets of VSF (i.e. 2N rotations of the eyeball) the following are variable sizes output by function read_vsf.m

Elements

Parameter

N x 150

rings1

N x 40

rings2

N x 40

N x 2

(laser power is recorded for each rotation of the

eyeball)

LREF

N x 2

(laser reference output is recorded for each rotation

of the eyeball)

PMT

N x 2

(even though fixed for all rotations in a file)

The data format is the same for background files, and for particle-data files. A file can be opened in MATLAB using the command:

[angles,rp,pp,rr,pr,rings1,rings2,LP,LREF,bat,PMT,depth,temp,date]=view_rawfile(filename);

Refer to Data Processing section for further details. The variable names are:

rings1 and rings2 refer to ring data (40 variable format) corresponding to the two rotations of the eyeball for each measurement of VSF.

LP: laser power transmitted through water, 1 measurement for each of 2 turns per VSF LREF: laser reference power, used for normalization and compensation of laser drift PMT: Control voltages of PMT. The PMT high-voltage supply is controlled by a 0-1V setting. This

setting is stored. PMT gain depends on actual high-voltage. Mainly used to distinguish data at different settings. This data is not used otherwise.

LISST-VSF User’s Guide 79

The LISST-VSF has 3 separate underwater connectors: A 5-pin, a 6-pin, and a 3-pin connector. The photograph shows the placement of each connector. The following text describes the detailed wiring for each connector. xxx

Appendix E: Connector Pinouts for LISST-VSF

80 LISST-VSF User’s Guide

Connector Pin #

Use

Serial Ground

No Connection

Serial Ground

Serial Out (to DB-9 Pin 2)

Serial In (to DB-9 Pin 3)

Communications Connector (5 pin connector)

Connector Manufacturer: Impulse Enterprise, Inc. San Diego, CA, USA Connector Part Number (Bulkhead): MCBH (WB)-5-MP Stainless Steel Mating Cable Part Number: MCIL-5-FS xxx

LISST-VSF User’s Guide 81

Connector Pin #

Use

Digital Ground

Digital In #1

Digital In #2

No Connection

Analog In (0 to 2.50V max)

Analog Ground

Connector Pin #

Use

Power Ground

Custom Lithium Battery Charger Input, 14.8V nom.

Power Out (12V nom. 9V-16.9V actual)

Auxiliary Input Connector (6 pin connector)

Connector Manufacturer: Impulse Enterprise, Inc. San Diego, CA, USA Connector Part Number (Bulkhead): MCBH (WB)-6-MP Stainless Steel Mating Cable Part Number: MCIL-6-FS xxx

Battery/Power Connector (3 pin connector)

Connector Manufacturer: Impulse Enterprise, Inc. San Diego, CA, USA Connector Part Number (Bulkhead): MCBH (WB)-3-MP Stainless Steel Mating Cable Part Number: MCIL-3-FS xxx

82 LISST-VSF User’s Guide

a. Lexan ZSCAT Sheet b. ZSCAT clamps (2) c. Communications Cable d. Battery Cable e. Battery Charger f. Power Supply g. Stands (2) h. Installation Disk i. Manual j. Sediment Samples k. Spare O-rings l. Mounting Clamps (4 sets)

Appendix H: LISST-VSF Accessories

LISST-VSF User’s Guide 83

This Statement of Limited Warranty applies to all Sequoia Scientific, Inc. (“SEQUOIA”) products ("Products").

Any additional or different terms, including any terms in any purchase order, will be of no effect unless agreed to in writing by an authorized representative of SEQUOIA as reflected in a written SEQUOIA quotation.

1. Limited Warranty SEQUOIA warrants that upon delivery by SEQUOIA (a) the Products will be free from defects in materials and workmanship, (b) the Products will perform substantially in accordance with SEQUOIA's applicable specifications, and (c) any Products (or components or parts thereof) that are manufactured by SEQUOIA do not infringe any U.S. patent or copyright.

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6. No Consequential Damages SEQUOIA will not be liable for any indirect, incidental, special or consequential damages, any cover, or any loss of revenue, profit, data or use.

7. Limitations of Liability

Warranty

STATEMENT OF LIMITED, EXTENDED WARRANTY

84 LISST-VSF User’s Guide

SEQUOIA's liability (whether in contract, tort, or otherwise; and notwithstanding any fault, negligence, strict liability or product liability) with regard to any Product (including, but not limited to, any breach of or default by SEQUOIA) will in no event exceed the purchase price paid by Customer to SEQUOIA for such Product. Further, SEQUOIA will not be liable for, or be in breach of or default on account of, any delay or failure to perform as a result of any cause, condition or circumstance beyond SEQUOIA's reasonable control.

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Customer acknowledges and agrees that it is Customer’s responsibility to provide for redundancy and/or other

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52.227-19, as applicable. Portions of these items may be unpublished. SEQUOIA reserves all rights under applicable copyright laws.

12. Controlling Document In the event of any conflict or inconsistency between any provision of this Statement of Limited Warranty and any other provision of the Order, the provision of this Statement of Limited Warranty will control.

13. Controlling Law This Statement of Limited Warranty will be governed by the laws of the State of Washington without reference

to its rules relating to choice of law for the purpose of applying another jurisdiction’s law. The U.N. Convention

on Contracts for the International Sale of Goods will not apply.

LISST-VSF User’s Guide 85

Revision

Date

Description

Author

2012/08/28

Draft document

YCA/WHS/RS

2013/03/08

Updated for non-AOM units

RS/WHS

Document History

86 LISST-VSF User’s Guide

Sequoia LISST-VSF User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual