ECO Volume Scattering Function Meter

ECO Volume Scattering Function Meter
ECO Volume Scattering
Function Meter
(VSF)
User’s Guide
The user’s guide is an evolving document. If you find sections that are unclear, or
missing information, please let us know. Check our website periodically for updates.
WET Labs, Inc.
P.O. Box 518
Philomath, OR 97370
541-929-5650
fax: 541-929-5277
www.wetlabs.com
ECO VSF User’s Guide (VSF)
Revision AJ
11 Sept. 2007
ECO Sensor Warranty
This unit is guaranteed against defects in materials and workmanship for one year from
the original date of purchase. Warranty is void if the factory determines the unit was
subjected to abuse or neglect beyond the normal wear and tear of field deployment, or in
the event the pressure housing has been opened by the customer.
To return the instrument, contact WET Labs for a Return Merchandise Authorization
(RMA) and ship in the original container. WET Labs is not responsible for damage to
instruments during the return shipment to the factory. WET Labs will supply all
replacement parts and labor and pay for return via 3rd day air shipping in honoring this
warranty.
Shipping Requirements for Warranty and Out-of-warranty
Instruments
1. Please retain the original shipping material. We design the shipping container to meet
stringent shipping and insurance requirements, and to keep your meter functional.
2. To avoid additional repackaging charges, use the original box (or WET Labsapproved container) with its custom-cut packing foam and anti-static bag to return the
instrument.
• If using alternative container, use at least 2 in. of foam (NOT bubble wrap or
Styrofoam “peanuts”) to fully surround the instrument.
• Minimum repacking charge for ECO meters: $25.00.
3. Clearly mark the RMA number on the outside of your shipping container and on all
packing lists.
4. Return instruments using 3rd day air shipping or better: do not ship via ground.
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Attention!
Return Policy for Instruments with Anti-fouling
Treatment
WET Labs cannot accept instruments for servicing or repair that are treated with antifouling compound(s). This includes but is not limited to tri-butyl tin (TBT), marine antifouling paint, ablative coatings, etc.
Please ensure any anti-fouling treatment has been removed prior to returning instruments
to WET Labs for service or repair.
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Table of Contents
1.
Specifications........................................................................................................... 2
1.1
Connectors ......................................................................................................................3
1.2
Delivered Items...............................................................................................................4
1.3
Optional Equipment ........................................................................................................5
2.
Theory of Operation................................................................................................. 7
3.
Instrument Operation............................................................................................... 9
3.1
Initial Checkout...............................................................................................................9
3.2 Operating the Sensor for Data Output ............................................................................9
3.3
Bio-wiper™ Operation..................................................................................................10
3.4
Deployment...................................................................................................................10
3.5
Upkeep and Maintenance..............................................................................................11
4.
VSFB and VSFSB: Using Internal Batteries ........................................................... 14
4.1 Removing End Flange and Batteries.............................................................................14
4.2 Replacing End Flange and Batteries .............................................................................15
4.3
Checking Vent Plug, Changing O-Rings:.....................................................................16
5.
Data Analysis............................................................................................................ 17
5.1
Data Corrections ...........................................................................................................17
5.2
Determining other Angle-Specific Coefficients ...........................................................18
6.
Testing and Calibration ........................................................................................... 19
6.1
Testing...........................................................................................................................19
6.2
Calibration.....................................................................................................................19
7.
General Terminal Communications........................................................................ 22
7.1 Communication Settings................................................................................................22
7.2
ECO Command List and Data Format..........................................................................22
8.
Device and Output Files .......................................................................................... 23
8.1
Plot Header....................................................................................................................23
8.2
Column Count Specification.........................................................................................23
8.3
Column Description ......................................................................................................23
8.4
Sample Device File .......................................................................................................24
8.5
Sample Output File .......................................................................................................24
Appendix A:
Mounting Bracket Drawing.................................................................... 25
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1.
Specifications
Model
Mechanical
Diameter
Length
Weight, in air
Material
Environmental
Temperature range
Depth rating
Optional pressure sensor
Optional thermistor
Electrical
Output resolution
Internal data logging
Internal batteries
Connector
Input
Current, typical
Current, sleep
Data memory
Sample rate
RS-232 output
Optional Anti-fouling
bio-wiper™
Bio-wiper™ cycle
Optical
Wavelength
VSF(RT)
VSF
VSFS
VSFB
6.3 cm
13.3 cm
25.4 cm
0.5 kg
Acetal copolymer
12.7 cm
0.4 kg
VSFSB
26.0 cm
0.96 kg
0–30 deg C
600 m
300 m
---
Y
Y
12 bit
N
Y
N
Y
MCBH6M
7–15 VDC
85 mA
80 µA
50,000 samples
to 8 Hz
19200 baud
--
N
-
Y
Y
N
140 mA
-
Y
470, 532, or 660 nm
1.24 x 10-5 m-1 sr-1
0.0012–5 m-1
Sensitivity
Range, typical
99% R2
Linearity
VSF(RT)—Provides an RS-232 serial output with 4000-count range. This unit can be programmed for
continuous operation.
VSF—Provides an RS-232 serial output with 4000-count range. This unit can be programmed for
continuous operation or periodic sampling.
VSFS—Provides the capabilities of the VSF with an integrated anti-fouling bio-wiper™.
VSFB—Provides the capabilities of the VSF and self-recording with internal batteries for autonomous
operation.
VSFSB—Provides the capabilities of the VSF with an integrated anti-fouling bio-wiper™ and self-recording
with internal batteries for autonomous operation.
Specifications subject to change without notice.
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1.1
Connectors
ECO VSF meters use a six-pin bulkhead connector. The pin functions for this connector are
shown in Figure 1. Table 1 summarizes pin functions for the bulkhead connectors.
Figure 1. ECO VSF connector schematic
Table 1. Pinout summary for ECO connectors
Pin
Function
(or Socket)
1
Ground
2
RS-232 (RX)
3
Reserved
4
V In
5
RS-232 (TX)
6
Configurable
WARNING
If you are going to build or use a non-WET Labs-built cable, do not use the wire
from pin 3 or the ECO meter will be damaged.
Input power of 7–15 volts DC is applied to pin 4. The power supply current returns through
the common ground pin. The input power signal has a bi-directional filter. This prevents
external power supply noise from entering into the ECO VSF, and also prevents internally
generated noise from coupling out on to the external power supply wire. Data is sent out pin
5.
1.1.1 ECO VSFB and VSFSB Connectors
ECO VSFB and VSFSB (units with internal batteries) have an second bulkhead connector
that comes with a jumper plug to supply power to the unit. The pin functions for this
connector are shown in Figure 2. Table 2 summarizes pin functions for the 3-socket
bulkhead connector.
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Figure 2. ECO VSFB and VSFSB connector schematic
Table 2. Pinout summary for ECO 3-socket connector
Pin (or Socket)
Function
1
V in
2
N/C
3
Battery out
1.2
Delivered Items
The standard VSF delivery consists of the following:
• the instrument itself
• protective cover for optics
• dummy plug with lock collar
• this user’s guide
• ECOView user’s guide
• ECOView host program and device file (on CD)
• instrument-specific calibration sheet
• VSF(RT), VSF, VSFS: stainless steel mounting bracket and hardware (See Appendix A
for details)
• One 3/32-in. hex key for bio-wiper™ removal
• Three 4-40 x 3/8 in. 316 stainless steel replacement screws for bio-wiper™
• Internal battery units: six 9-V Lithium batteries (installed)
• spare parts kit (battery units only):
Two end flange O-rings (size 224)
Two vent plug O-rings (size 010)
Two jacking screws for connector flange removal
One 3/32-in. hex key for jacking screws
Power plug for autonomous operation
Three pre-cut segments (7 inches) of 0.036-inch diameter monofilament for end flange
Three pre-cut segments (0.25 inches) of 0.094-inch diameter white nylon bar stock for
replacing the white plastic dowel pin
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1.3
Optional Equipment
1.3.1 Test Cable
A test cable is supplied with each unit. This cable includes three legs:
1. A connector for providing power to the instrument from a user-supplied 9V battery.
2. A DB-9 serial interface connector.
3. A six-socket in-line connector for providing power and signal to the instrument.
1.3.2 Copper Faceplate
ECO meters are optionally equipped with copper faceplates to improve the meter’s
resistance to biofouling. Refer to Section 3.5.1 for important details on maintenance and
cleaning.
1.3.3 Bio-wiper™ and Copper Faceplate
The BBS and BBBS are equipped with an integrated non-contact anti-fouling bio-wiper™
and copper faceplate for use in extended deployments. This wiper can be manually
controlled by a host controller package, or can perform autonomously as part of a preprogrammed sampling sequence upon instrument power-up. The rate of opening and closing
depends on both temperature and depth.
Refer to Section 3.5.1 for important details on the maintenance and cleaning of the Biowiper™ and copper faceplate.
WARNING!
Do NOT rotate the Bio-wiper™ manually. This can damage the wiper motor and will void
the warranty.
1.3.4 Batteries
ECO units with internal batteries are supplied with six 9-volt Lithium batteries as their
power source. They can use either standard alkaline cells for a total capacity of
approximately 1000 mA-hrs, or for longer deployments, LiMnO2 cells to achieve more
than 2000 mA-hrs of operational capacity. Actual total usage time of the internal batteries
is a function of several parameters. These include nominal water temperature, sequence
timing, sample periods, and total deployment duration.
1.3.5 External Thermistor
ECO meters are optionally equipped with an external thermistor. The thermistor is
calibrated at WET Labs and the calibration coefficients are supplied on the instrument’s
calibration sheets. Thermistor output is in counts and can be converted into engineering
units using the instrument’s device file and ECOView software or the raw data can be
converted in the user’s software (e.g. MATLAB or Excel) using the calibration equation:
Temperature (deg C) = (Output * Slope) + Intercept
1.3.6 Pressure Sensor
ECO meters are optionally equipped with a strain gauge pressure sensor. The pressure
sensor is calibrated at WET Labs and the calibration coefficients are supplied on the
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instrument’s calibration sheets. Pressure sensor output is in counts and can be converted
into engineering units using the instrument’s device file and ECOView software or the
raw data can be converted in the user's software (e.g. MATLAB or Excel) using the
calibration equation:
Relative Pressure (dbar) = (Output * Slope) + Intercept
Note that 300 meters ≈ 500 psi ≈ 345 dbars
Please note that strain gauge pressure sensors are susceptible to atmospheric pressure
changes and should be “zeroed” on each deployment or profile. The calibration equation
for pressure above should be used first to get the relative pressure and the cast offset
should then be subtracted to get the absolute pressure:
Absolute Pressure (dbar) = Relative Pressure (dbar) - Relative Pressure at
Atmospheric/Water interface (dbar)
WARNING!
Do not exceed the pressure sensor’s depth rating (see calibration sheet).
A plastic fitting filled with silicone oil provides a buffer between the pressure transducer
and seawater. The transducer is both sensitive and delicate. Following the procedures
below will ensure the best results and longest life from your pressure sensor.
Pressure is transmitted from the water to the stainless steel transducer diaphragm via a
plastic fitting filled with silicone oil. The inert silicone oil protects the pressure sensor
from corrosion, which would occur after long exposure to salt water. The fitting will
generally prevent the oil from escaping from the reservoir into the water. However, you
may occasionally wish to ensure that oil remains in the reservoir on top of the
transducer.
WARNING
Never touch or push on the transducer.
1. Thoroughly clean the top of the instrument.
2. Completely remove the white nylon Swagelock fitting using a 9/16-in. wrench.
3. Check for obstructions in the tiny hole. Blow clear with compressed air or use a
small piece of wire.
4. Wipe clean the o-ring at the base of the Swagelock fitting.
5. Screw the Swagelock fitting into the end flange until finger tight.
6. Tighten it an additional 1/8 turn using a wrench only if necessary.
7. Wipe up any excess oil.
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2.
Theory of Operation
The angular distribution of scattered radiation in the backward hemisphere is important in the
interpretation of remote sensing measurements, investigations of particle shape, and models of
visibility in seawater. The ECO VSF measures the optical scattering at 100, 125, and 150 degrees,
thus providing the shape of the Volume Scattering Function (VSF) throughout its angular domain.
Motivated by the need to better understand the relationship of water-leaving radiance with the
backscattering into the same direction, the three-angle measurement allows determination of
specific angles of backscattering through interpolation. Conversely, it also can provide the total
backscattering coefficient by integration and extrapolation from 90 to 180 degrees.
Figure 3 shows the optical configuration for the VSF. The ECO VSF consists of a potted
monolithic optical flange and a housing containing the signal processing and controller circuitry.
The optics include three LED-based transmitters that couple to a single receiver. The transmitters
and receiver are located to establish centroid light scattering angles of approximately 100, 125,
and 150 degrees respectively. For each angle the region of intersection encompasses a FWHM
bandwidth of about 18 degrees.
Figure 3. Optical configuration of ECO-VSF
The controller electronics sequence through the individual transmitters at approximately 1 Hz per
sample cycle. The individual transmitters operate synchronously with the receiver to reject
ambient light. A directly coupled reference detector indicates relative LED intensity during
operation. Signals from the receiver and reference detector are digitized and subsequently stored
or telemetered from the instrument.
The ECO VSF can be configured for a variety of applications. In addition to providing a
continuous output, the instrument can internally record up to 65,000 samples of data.
Additionally, for long-term deployments, the instrument can come equipped with an anti-fouling
shutter to retard bio-fouling of the optical surfaces. Models with internal and external batteries are
also available. Each sensor operates at one wavelength. Presently these wavelengths are factory
configurable for 470 nm, 530 nm, and 660 nm.
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3.
Instrument Operation
Please note that certain aspects of instrument operation are configuration-dependent. These are
noted where applicable within the manual. ECO sensors can be used in a moored or profiling
mode, with or without a host computer/data logger. The ECOs are versatile instruments, capable
of operating under a variety of user-selected settings
3.1
Initial Checkout
Supplied from the factory, ECOs are configured to begin continuously sampling upon poweron. Electrical checkout of ECO is straightforward.
Connect the 6-socket connector on the test cable to the instrument to provide power to the
LEDs and electronics (see Section 1 for a diagram of the pinouts of ECO VSF). Connect the
battery leads on the test cable to the 9V battery supplied with the meter. Light should emanate
from the meter.
3.2
Operating the Sensor for Data Output
Note
ECO scattering meters are sensitive to AC light. Before making measurement,
turn AC lighting off.
1. Connect the 6-socket connector to the instrument to provide power to the LEDs and
electronics. Connect the DB-9 connector to a computer with the ECOView host program
installed on it.
WARNING!
Always use a regulated power supply to provide power to ECO sensors if not using the 9V
battery provided with the test cable: power spikes may damage the meter.
2. Start ECOView. Select the appropriate COM Port and Device File. Supply power to the
meter, then click on the Start Data button. Output will appear in the Raw Data window.
Place the flat of your hand in front of the sensor face and note that the signal will increase
toward saturation (maximum value on calibration sheet) as your hand gets closer. When
applying power to sensors with a bio-wiper™, it will open and, depending on the settings,
operate until you select Stop Data in ECOView (or input !!!!! in a terminal program)
The bio-wiper™ will close and the instrument will await the next command.
3. If the sensor completes the requested samples (this is common for meters set up in moored
applications), it will go into sleep mode, and the meter will not light when power is
cycled. To “wake” the meter, click Stop Data five times at the rate of two times per
second immediately upon applying power. This interrupts the sensor, returning it to a
“ready” state, awaiting commands.
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4. Check the settings for the ECO and change if necessary. ECOView factory settings for
continuous operation:
Set Number of Samples = 0
Set Number of Cycles = 0.
5. If the meter does not light after performing step 3, check the battery. Replace if necessary,
perform steps 2 and 3 to verify communication. If it still does not light, contact WET
Labs.
Refer to the ECOView User’s Guide for details about using the software.
3.3
Bio-wiper™ Operation
The ECO-VSFS and -VSFSB are provided with an anti-fouling bio-wiper™ (Figure 4). The
bio-wiper™ extends the possible deployment duration by retarding biological growth on the
instrument’s optical surface. The bio-wiper™ covers the optical surface: 1) while the
instrument is in “sleep” mode; 2) when it has completed the number of samples requested; and
3) when the user selects Stop Data in ECOView or types “!!!!!” in a terminal program. When
the meter wakes up, the optical surface is exposed by the bio-wiper’s™ counter-clockwise
rotation.
WARNING!
Do NOT rotate the Bio-wiper™ manually. This voids the warranty.
If power is shut off in mid cycle, the bio-wiper™ will reinitialize to the beginning of the userselected settings when power is applied again.
3.4
Deployment
The ECO VSF meter requires no pump to assure successful operation. Once power is
supplied, the unit is ready for submersion and subsequent measurements. Some consideration
should be given to the package orientation. Do not face the sensor directly into the sun or
other bright lights. For best output signal integrity, locate the instrument away from
significant EMI sources.
Caution
The VSF should be mounted so that the LED source will not “see” any part of a cage
or deployment hardware. This will affect the sensor’s output.
Other than these basic considerations, one only needs to make sure that the unit is securely
mounted to whatever lowering frame is used and that the mounting brackets are not damaging
the unit casing. The instrument can be used in a moored or profiling mode.
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3.5
Upkeep and Maintenance
We highly recommend that ECO meters be returned to the factory annually for cleaning,
calibration and standard maintenance. Contact WET Labs or visit our website for details on
returning meters and shipping.
After each cast or exposure of the instrument to natural water, flush with clean fresh water,
paying careful attention to the sensor face. Use soapy water to cut any grease or oil
accumulation. Gently wipe clean with a soft cloth. The sensor face is composed of ABS
plastic and optical epoxy and can easily be damaged or scratched.
WARNING!
Do not use acetone or other solvents to clean the sensor.
3.5.1 Bio-wiper™ and Faceplate Cleaning and Maintenance
The bio-wiper™ and the copper faceplate need to be removed from the meter for thorough
cleaning to maximize anti-fouling capability.
1. Be sure the meter is NOT powered or connected to a power source prior to
uninstalling the bio-wiper™ and faceplate.
WARNING!
Manually turning the motor shaft can damage the wiper motor and will void the warranty.
Make sure the bio-wiper™ is loosened from the shaft before attempting to rotate
the bio-wiper™.
2. Remove bio-wiper™: Use the factory-supplied 3/32-in. hex key to loosen the screw
that secures the wiper to the shaft on the instrument. It may be necessary to remove the
screw from the clamping hole and screw it into the releasing hole, tightening it just
enough to free the bio-wiper™ from the shaft.
clamping screw hole
releasing screw hole
WARNING!
Be sure to retain and re-use the factory-installed screws as they are vented for
pressure compensation.
3. Remove faceplate: Use a small Phillips screwdriver to remove the screws that attach
the plate to the optics head.
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4. Wash bio-wiper™ and/or copper faceplate with soapy water. Rinse and dry
thoroughly. Note the condition of the copper on the instrument side of the wiper. It is
normal for copper to corrode and turn green, especially after the instrument has been
removed from the water. This corrosion will slightly reduce the shutter’s anti-fouling
ability the next time it is deployed.
5. Buff each with a pad of green Scotch Brite® (or similar) until shiny.
6. Clean the bio-wiper™ shaft and the shaft hole using an isopropyl alcohol-saturated
cotton swab. Allow to dry.
7. Re-install faceplate.
8. Check the screw used to secure the bio-wiper to the shaft: a hex key must fit
snugly into the screw socket. If the socket is in any way compromised, use a new
screw (4-40 x 3/8 in. 316 stainless steel treated with anti-seize. These are shipped
as part of the meter’s spare parts kit.)
9. Slide the bio-wiper™ over the shaft. Be careful not to twist it on, thus rotating the
shaft. If the wiper does not slide on easily, insert the screw into the expander hole,
turning slowly until the bio-wiper™ slides easily onto the shaft.
10. Rotate the bio-wiper™ into the closed position.
11. Set the gap between the bio-wiper™ and the instrument face to 0.03 in. (0.8 mm).
An improperly set gap will either fail to clean the face or cause the motor to draw
excessive current.
To gauge 0.03 in., fold a piece of paper in
half, then in half again, then fold a third time,
creasing the edges. It’s now 8 sheets and
about 0.03 in. thick.
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Not enough flex.
Proper flex.
Too much flex.
Wiper may not be effective.
Wiper maintains contact with
instrument face and
optical window.
Wiper may cause too much
friction, using excessive
power.
12. Use the 3/32-in. hex key to tighten the screw to “finger-tight,” then snug an
additional quarter-turn.
13. Run the instrument to verify operation. The bio-wiper™ must rotate 180 degrees to
clear the optics before sampling, and 180 degrees to cover the optics after sampling.
14. If the wiper needs adjusting, loosen the screw, make any necessary adjustments, and
repeat steps 9 through 13 to ensure the wiper is performing properly.
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4.
VSFB and VSFSB: Using Internal Batteries
ECO meters with internal batteries can be powered in several ways.
1. The meter can be powered from the six-pin bulkhead connector using the test cable (set to ON
BATT) or from an external source (test cable set to ON AUX). Communication is possible in
this mode.
2. Alternatively, the meter can be powered using a jumper plug in the three-socket bulkhead
connector. This is particularly useful for moored applications. The meter will run according to
its stored settings.
3. If the jumper plug is in place on the meter and supplying power and the test cable is
connected, power will be supplied by the equipment supplying the highest voltage. To
conserve the internal batteries, it is advisable to use the test cable and an external power
source set to 10–15 V.
4.1
Removing End Flange and Batteries
WARNING!
Changing the batteries will require opening the pressure housing of the ECO sensor. Only
people qualified to service underwater oceanographic instrumentation should perform
this procedure. If this procedure is performed improperly, it could result in catastrophic
instrument failure due to flooding or in personal injury or death due to abnormal internal
pressure as a result of flooding.
WET Labs Inc. disclaims all product liability from the use or servicing of this equipment.
WET Labs Inc. has no way of controlling the use of this equipment or of choosing
qualified personnel to operate it, and therefore cannot take steps to comply with laws
pertaining to product liability, including laws that impose a duty to warn the user of any
dangers involved with the operation and maintenance of this equipment. Therefore,
acceptance of this equipment by the customer shall be conclusively deemed to include a
covenant by the customer to defend and hold WET Labs Inc. harmless from all product
liability claims arising from the use and servicing of this equipment. Flooded instruments
will be covered by WET Labs Inc. warranties at the discretion of WET Labs, Inc.
1.
2.
3.
4.
5.
6.
Make sure the instrument is thoroughly dry.
Remove the dummy plugs.
With connector end flange pointed downwards away from face, release seal vent plug.
Remove moisture from vent plug area.
Using needle nose pliers, remove filament from end flange.
Lift flange from pressure housing until seal is broken. The jacking screws provided with
sensor can be used to “push” the flange from the pressure housing and can then be
removed or left in the end flange.
7. Remove excess moisture from flange–can seal area.
8. Work the end flange out of the pressure housing and remove any residual moisture.
Remove the foam spacer and the neoprene insulator.
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9. The battery pack is connected to the processor boards by a six-pin Molex connector: do
NOT pull too hard or far on the battery pack or it will come unplugged and the unit will
need to be returned to WET Labs.
10. Gently pull the white cord at the loop to remove the battery pack from the pressure
housing.
11. Remove the black plastic protectors from the ends of the long screws securing the
batteries.
12. Loosen and remove the screws (3/16-in slotted driver).
4.2
Replacing End Flange and Batteries
1. Replace the batteries
2. Re-install the screws:
• Align the groove in each of the plates so the six-wire extension bundle will fit in it
along its length.
• Be careful not to cross-thread into the bottom end plate nor to over-tighten the screws.
• If they are too tight, the fiber washers that act as separators between the batteries will
flex.
• Make sure there are equal amounts of screw threads protruding from the bottom end
plate when they are secure. This will ensure the pack is straight and will fit into the
pressure housing with no difficulty.
1. Re-install the black plastic protective covers on the ends of the screws.
2. Remove and check the pressure housing O-ring for nicks or tears. Replace if necessary.
Before re-installing, apply a light coat of vacuum grease on the O-ring.
3. Carefully replace the battery pack in the pressure housing. Place the neoprene insulator on
the battery assembly and lay the white cord on the top.
4. Plug in the two-pin, then the six-pin Molex connectors. Sensor operation can now be
tested if desired.
5. Align the hole in the end flange (NOT the jack screw holes) with the white dowel pin.
While coiling the six wire bundle and making sure none are pinched between the end
flange and the pressure housing, position the flange on the housing. Leave space to reinsert the gray foam spacer, making sure the cut-out accommodates the vent plug screw.
6. Push the end flange all the way on to the pressure housing, making sure no wires are
pinched. Be sure the vent plug does not pop up. If it does, you’ll need to re-position the
foam spacer.
7. Re-insert the monofilament.
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4.3
Checking Vent Plug, Changing O-Rings:
If there is fouling on the vent plug, it should be cleaned and the two 010 O-rings replaced.
Otherwise, this mechanism should be maintenance-free.
WARNING!
The pressure housing is made of plastic material that scratches easily. Do
not let the screwdriver slip and scratch the can when removing or replacing
the vent plug. Use a toothpick (something softer than the plastic) to remove
the O-rings from the vent plug.
1. Pull vent plug out about half way; hold plug while unscrewing the truss screw. When
screw is removed, pull vent plug from end flange.
2. “Pinch” bottom O-ring around vent plug to form a small gap you can work a toothpick
into. Use the toothpick to help roll the bottom O-ring off the plug.
3. Perform the same procedure with the top O-ring.
4. Clean the vent plug and vent plug hole using a dry lint-free tissue or cotton swab.
5. Lightly coat two undamaged or new O-rings with silicon grease. Install the top O-ring
(nearest to large end of plug) first, then the bottom one.
6. Insert vent plug into its hole in the end flange and hold it while inserting the truss screw.
Rotate the vent plug to begin tightening the screw. Finish tightening using a screwdriver,
being careful not to overtighten truss screw.
Note
A portion of the truss screw head has been removed to allow for venting in case of pressure
buildup.
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11 Sept. 2007
5.
Data Analysis
Data from the ECO VSF represents raw output from the sensor. Applying linear scaling constants,
this data can be expressed in meaningful forms of inverse meters for each of the respective angles.
5.1
Data Corrections
Attenuation coupling—Many scattering sensors require a subsequent attenuation correction
for pathlength coupling of the transmitted and scattered light. This is typically a function of
the propagation distances of the light as well as the magnitude of the water attenuation.
Because the ECO VSF incorporates very short pathlengths and scattering volumes in its
measurements, it is relatively immune to this pathlength coupling (Figure 6). For attenuation
coefficients up to approximately 4 m-1 no data correction is required. If you are operating the
meter in waters with greater turbidity, contact the factory for configuration information.
Typical VSF Response
100
1400
125
150
1200
Raw Counts
1000
800
600
400
200
0
0
0.5
1
1.5
2
2.5
3
3.5
4
1/m
Figure 4. Linearity Response
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17
Temperature correction—Output from an LED reference detector is provided, which gives an
indication of relative LED intensity during operation.
Obtaining angular values in inverse meters—The primary angular values for each angle of
backscattering are directly calculated by ECOView or alternatively can be applied upon raw
data downloaded from the instruments. Determination is made by subtracting the clean water
offset from the measured value and multiplying the result by the scaling factors provided in
the calibration sheet.
The scaling coefficients for these values are determined by our instrument calibration process
as described in Section 6.2.
5.2
Determining other Angle-Specific Coefficients
Other angular scattering coefficients can be determined through interpolation between the
measured angles. At this time WET Labs offers no preference in the type of curve fit to use
for deriving these coefficients.
5.2.1 Determining Backscattering Coefficient
The most accurate method of determining the backscattering coefficient, bb, from the VSF
measured at the three angles of the ECO VSF is as follows:
1. Multiply the corrected β values by 2πsinθ to convert to a polar steradian area.
2. Fit a 3rd order polynomial to the three measured points and a fourth value of π radians
= 0 (sin (π radians) = 0).
3. Integrate under the curve fit from π/2 to π radians.
4. Add 1.3 percent to the backscattering estimate.
Testing this approach with all the Petzold (1972) VSFs results in a maximum error of
about 1 percent.
(Petzold, T.J., 1972. Volume scattering functions for selected natural waters. Scripps Institution of
Oceanography, Visibility Laboratory, San Diego, CA, SIO Ref. 71–78.)
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11 Sept. 2007
6.
Testing and Calibration
Prior to shipment, each ECO is characterized to ensure that it meets the instrument’s
specifications.
6.1
Testing
When the instrument is completely assembled, it goes through the tests below to ensure
performance.
6.1.1 Pure Water Blank
Pure, de-ionized water is used to set the “zero” voltage of the meter. This zero voltage is
set for 150 counts (+/-50) on all models.
6.1.2 Pressure
To ensure the integrity of the housing and seals, ECOs are subjected to a wet hyperbaric
test before final testing. The testing chamber applies a water pressure of at least 50 PSI.
6.1.3 Mechanical Stability
Before final testing, the ECO meters are subjected to a mechanical stability test. This
involves subjecting the unit to mild vibration and shock. Instrument functionality is
verified afterwards.
6.1.4 Electronic Stability
This value is computed by collecting a sample once every 5 seconds for twelve hours or
more. After the data is collected, the standard deviation of this set is calculated and
divided by the number of hours the test ran. The stability value must be less than 3 counts.
6.1.5 Noise
The noise value is computed from a standard deviation over 60 samples. These samples
are collected at one-second intervals for one minute. A standard deviation is then
performed on the 60 samples, and the result is the published noise on the calibration form.
The calculated noise must be below 3 counts.
6.1.6 Voltage and Current Range Verification
To verify that the ECO operates over the entire specified voltage range (7–15 V), a
voltage-sweep test is performed. ECO is operated over the entire voltage range, and the
current and operation is observed. The total power consumption (voltage times current)
must remain below 600 mW over the entire voltage range.
6.2
Calibration
Calibration of the ECO VSF involves the following steps.
1. Numerical determination of the volume weighted angular region for each scattering angle.
ECO VSF User’s Guide (VSF)
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11 Sept. 2007
19
∆y
∆z
∆x
σs
σd
θd
θs
(S)
source
(D)
detector
Figure 5. General geometry of the sensor
The detector (D) and the source (S) are separated by a distance SD.
The angle of the center of the detector beam with the line SD is θδ.
The half-angle of the detector cone is σδ.
The corresponding angles for the source are θσ and σσ.
The volume above the SD line is broken up into the small volumes ∆x∆y∆z. z is in the same
plane as the SD line.
The small volume, ∆V = ∆x∆y∆z at (x,y,z) was determined by simple geometry. It was then
determined whether the ∆V was in the intersection of the source beam and the field of view of
the detector (both conical shapes). The intersection of each cone and the plane is an ellipse
and the illuminated area is the intersection of those ellipses. The signal strength was
determined for each elementary volume, and then integrated over the illuminated area to
obtain the weighting function. Weighting functions were determined in this manner for each
source–detector pair (nominal angles of 100, 125, and 150 degrees) and are plotted in the
figure below.
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0.06
weightingfunction
0.05
0.04
0.03
0.02
0.01
0
60
80
100
120
angle in degrees
140
160
180
Figure 6. Weighting functions for source–detector pairs
2. Mie scattering determination into these regions for a known distribution of spherical
scatterers (Polystyrene beads).
Spherical or spheroid particles with a known particle size distribution can be quite
accurately modeled for scattering behavior using Mie theory. We thus obtain NISTtraceable bead standards and calculate their scattering response using the derived
weighting functions.
3. Determination of angular coefficients through direct measurement of spherical beads.
Once the weighting functions are determined and the scattering response for our
calibration medium determined, we then run a dilution series of measurements, using the
medium in water. From the curves obtained with varying concentration we then calculate
the absolute response of the instrument. These are the scaling coefficients supplied with
each instrument.
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21
7.
General Terminal Communications
While WET Labs supplies a host software package for instrument configuration and data
retrieval, the unit sensors can be controlled from a terminal emulator or customer-supplied
interface software. This section outlines hardware requirements and low-level interface
commands for this type of operations.
7.1
Communication Settings
baud rate:
19200
data bits:
8
parity:
none
stop bits:
1
flow control:
none
7.2
Command
22
ECO Command List and Data Format
Parameters passed
!!!!!
none
$ave
$clk
$dat
$emc
$get
single number, 1 to 65535
24hr format time, hhmmss
date, format ddmmyy
none
none
$int
$mnu
$pkt
$rec
$rls
$run
$set
$sto
24hr format time, hhmmss
none
single number, 0 to 65535
1 (on) or 0 (off)
none
none
single number, 0 to 65535
none
ECO VSF User’s Guide (VSF)
Description
Stops data collection; allows user to input setup parameters.
Note that if the meter is in a sleep state, the power must be
turned off for a minute, then powered on while the “!” key is
held down for several seconds. If this does not “wake” the
meter, refer to the ECOView user’s guide Operation Tip to
“wake” a meter in a low power sleep state to enable inputting
setup parameters.
Number of measurements for each reported value
Sets the time in the Real Time Clock
Sets the date in the Real Time Clock
Erases the Atmel memory chip, displays menu when done
Reads data out of Atmel memory chip. Prints "etx" when
completed.
Time interval between packets in a set
Prints the menu, including time and date
Number of individual measurements in each packet
Enables or disables recording data to Atmel memory chip
Reloads settings from flash
Executes the current settings
Number of packets in a set
Stores current settings to internal flash
Revision AJ
11 Sept. 2007
8.
Device and Output Files
Each meter is shipped with a CD containing the meter-specific device file, a sample output file,
characterization information, and the applicable user’s guides.
The ECOView host program requires a device file to provide engineering unit outputs for any of
its measurements. Except for the first line in the device file, all lines of information in the device
file that do not conform to one of the descriptor headers will be ignored. Every ECOView device
file has three required elements: Plot Header, Column Count Specification, and Column
Description.
8.1
Plot Header
The first line in the device file is used as the plot header for the ECOView plots.
8.2
Column Count Specification
The Column Count Specification identifies how many columns of data to expect. It follows
the format “Column=n.” The Column Count Specification must be present before any of the
Column Descriptions are listed.
8.3
Column Description
Every column in the ECO meter’s output must have a corresponding Column Description in
the device file. The following notation is used in identifying the elements of each Column
Description.
x = the column number, starting with 1 as the 1st column
sc = scale
dc = dark counts: meter output in clean water with optics head taped
mw = measurement wavelength—wavelength used by the sensor for its measurement
dw = display wavelength—display wavelength—wavelength/color range (380–780 nm)
v = measured volts dc (not used on VSF)
Valid Column Descriptions are listed below.
Date=x
MM/DD/YY
Time=x
HH:MM:SS
REF=x
Reference Counts—Currently not used by ECOView
N/U=x
The column is Not Used
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23
8.4
Sample Device File
Below is the standard device file for a VSF at 530 nm.
ECO VSF-059g
Created on: 10/30/03
Columns=7
Date=1
Time=2
ref=3
vsf100=4
vsf125=5
vsf150=6
N/U=7
1.36E-03
1.46E-03
1.39E-03
73
86
103
8.5
Sample Output File
Below is a sample output file for a VSF. From left to right, columns describe:
1. Date (MM/DD/YY)
2. Time (HH:MM:SS)
3. Reference
4. 100 degree angle output signal
5. 125 degree angle output signal
6. 150 degree angle output signal
7. Thermistor
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
9/17/2003
24
13:11:20
13:11:21
13:11:22
13:11:23
13:11:24
13:11:25
13:11:26
13:11:27
13:11:28
13:11:29
13:11:30
13:11:31
ECO VSF User’s Guide (VSF)
1745
1743
1742
1742
1741
1741
1741
1740
1740
1740
1740
1740
165
168
162
167
163
167
163
168
166
164
166
165
173
176
176
177
174
174
180
176
174
174
174
176
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400
396
396
394
392
396
398
390
393
393
394
395
543
543
542
542
542
542
542
542
542
542
542
541
11 Sept. 2007
Appendix A: Mounting Bracket Drawing
ECO VSF User’s Guide (VSF)
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11 Sept. 2007
25
Revision History
Revision
A
Date
04/06/00
Revision Description
New document (DCR 22)
B
C
09/20/00
09/25/00
D
E
10/18/00
10/31/00
F
G
11/13/00
01/18/01
H
I
07/12/01
09/18/01
J
K
L
M
N
O
P
11/5/01
11/15/01
01/16/02
03/13/02
04/10/02
04/16/02
07/08/02
Q
07/25/02
R
S
T
2/10/03
2/24/03
4/14/03
T1
10/30/03
U
11/24/03
V
W
11/25/03
2/17/04
X
3/10/04
Y
5/11/04
Z
AA
6/29/04
9/28/04
AB
10/14/04
AC
7/26/05
AD
AE
1/13/06
5/31/06
AF
6/28/06
Add vent plug maintenance steps (DCR 55)
Add explanation of ECO Host date format (DCR
56)
Add lithium battery warning (DCR 65)
Add ECO Host 4, Shuttered specs, jumper plug
note (DCR 68)
Add aux. output explanation (DCR 72)
Correct setup and testing procedure,
explanation of Interrupt Autostart on shuttered
units (DCR 78)
Update to ECO Host v. 4.1.2 (DCR 130)
Add spare monofilament and plastic bar stock to
shipping list (DCR 146)
Change LED wavelength values (DCR 159)
Add references to device file (DCR 161)
Update reference to test cable (DCR 185)
Correct VSFS/VSFB weights (DCR 201)
Update Section 3 (DCR 204)
Add max. samples to specifications (DCR 215)
Add internal battery option to spec. table (DCR
228)
Delete inaccurate references to shutter
specifications (DCR 238)
Delete lithium battery warning (DCR 272)
Change “shutter” to “bio-wiper™” (DCR 280)
Add stop command to terminal communications
(DCR 292)
Delete references to ECO Host, update to round
board specs (draft)
Delete references to ECO Host, update to round
board specs (DCR 344)
Update Specifications (DCR 338)
Update bio-wiper maintenance and column
description for device files (DCR 367)
Add new test cable description, operational
description, mounting diagram (DCR 381)
Remove pin 6 from warning in section 1 (DCR
390)
Update Specifications (DCR 400)
Add text for optional thermistor and pressure
sensor (DCR 429)
Add references to Lithium batteries for
applicable models (DCR 433)
Replace Clean Water Offset with Dark Counts
(DCR 468)
Clarify warranty statement (DCR 481)
Add annual maintenance recommendation
(DCR 498)
Cleaning and maintenance of modified bio-wiper
(ECN 230, DCR 502)
ECO VSF User’s Guide (VSF)
Revision AJ
Originator
C. Carlock, C. Moore, W.
Strubhar
D. Whiteman
C. Carlock
H. Van Zee
C. Carlock, H. Van Zee
W. Strubhar
C. Carlock
C. Carlock
H. Van Zee
H. Van Zee
D. Whiteman
M. Avery
H. Van Zee
D. Whiteman
D. Whiteman
H. Van Zee
H. Van Zee
D. Whiteman
H. Van Zee
W. Strubhar
H. Van Zee
D. Romanko, H. Van Zee, D.
Whiteman
I. Walsh
A. Derr, I. Walsh
A. Derr, D. Whiteman
I. Walsh
I. Walsh
I. Walsh
I. Walsh
M. Johnson
A. Gellatly, S. Proctor
S. Proctor
A. Derr, H. Van Zee
11 Sept. 2007
AG
7/27/06
AH
AH1
9/26/06
10/30/06
AI
11/1/06
AJ
9/11/07
Change length of securing screw on bio-wiper
(ECN # not assigned; DCR 504)
Update specifications (DCR 507)
Correct Pressure Sensor and Thermistor output
calculations (draft)
Finalize pressure sensor and thermistor output
calculations (DCR 509)
Delete reference to refilling pressure sensor,
update shipping requirements (DCR 531)
ECO VSF User’s Guide (VSF)
Revision AJ
J. da Cunha, H. Van Zee
M. Johnson
M. Johnson
M. Johnson
M. Johnson, H. Van Zee
11 Sept. 2007
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