Wet Labs ac-9 User’s Guide
Absorption and
Attenuation Meter
WET Labs, Inc.
P.O. Box 518
Philomath, OR 97370
541 929-5650
www.wetlabs.com
(ac-9)
User’s Guide
ac-9 User’s Guide (ac-9) Revision R 21 May 2008
Attention!
Return Policy for Instruments with Anti-fouling Treatment
WET Labs cannot accept instruments for servicing or repair that
are treated with anti-fouling compound(s). This includes but is not
limited to tri-butyl tin (TBT), marine anti-fouling paint, ablative
coatings, etc.
Please ensure any anti-fouling treatment has been removed prior to
returning instruments to WET Labs for service or repair.
ac-9 User’s Guide (ac-9) Revision R 21 May 2008
ac-9 Warranty
Standard 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.
Annual Servicing Extended Warranty
WET Labs will extend the warranty on this unit to five years if it is returned
annually for servicing. This includes calibration, standard maintenance, and
cleaning. Charges associated with this annual service work and shipping are the
responsibility of the customer.
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 Labs-
approved 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 ac meters: $240.00.
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.
ac-9 User’s Guide (ac-9) Revision R 21 May 2008
Table of Contents
1.
Operation ................................................................................. 1
1.1 Installing WETView .......................................................................................... 1
1.2 Bench Testing .................................................................................................... 2
1.3 Air Tracking ....................................................................................................... 2
1.4 Cleaning ............................................................................................................. 3
1.5 System Requirements......................................................................................... 4
1.6 Operating the Meter ............................................................................................ 6
2.
Instrument Description ........................................................... 12
2.1 Instrument Overview ....................................................................................... 12
2.2 Optics ............................................................................................................... 14
2.3 Electronics........................................................................................................ 16
2.4 Pressure Housing Material ............................................................................... 16
2.5 Signal Processing ............................................................................................. 16
3. Data Processing ........................................................................ 18
3.1 Analog Acquisition .......................................................................................... 18
3.2 Analog-to-Digital Conversion ......................................................................... 18
3.3 Digital Processing and Data Output ................................................................. 18
4. Calibration and Characterization ............................................... 28
4.1 Temperature Correction ................................................................................... 28
4.2 Precision ........................................................................................................... 28
4.3 Absolute Calibration ........................................................................................ 29
4.4 Linearity and Dynamic Range ......................................................................... 29
4.5 Air Calibration and Tracking ........................................................................... 29
5. Specifications ............................................................................ 32
5.1 Connectors ....................................................................................................... 32
5.2 Power Requirements ........................................................................................ 34
6. References ................................................................................ 35
Appendix A:
Appendix B:
Optional Connectors ............................................... 36
Pressure Sensor Use and Care .............................. 38
ac-9 User’s Guide (ac-9) Revision R 21 May 2008 i
1. Operation
This section provides an introduction to the ac-9 and describes how to perform air tracking and
bench testing prior to deploying the ac-9.
The ac-9 is delivered in a sturdy wooden shipping container with the following components:
• ac-9, with one absorption flow tube and one attenuation flow tube
• four flow sleeves
• four protective black plastic caps
• dummy plug with lock collar
• this manual
• ac-9 Protocol Document
• WETView User’s Guide
• WETView software and instrument-specific calibration information
• Ten-foot test cable
• double “Y” de-bubbler tubing
• stainless steel intake screens
Familiarize yourself with the ac-9: remove the black plastic flow tubes by grasping the flow
tube sleeves and sliding them away from the ends of the flow tube (toward the middle of the
flow tube). You only have to slide the collars about ½ in. to unlock the flow tube from its
fixed position. The flow tube will lift out, exposing the transmitter and detector windows on
the lower and upper flanges respectively. Observe the flow tubes. The attenuation tube is
different from the absorption tube. Its flow chamber is plastic and the two sleeves on the tube
are identical. This tube installs on the ‘c’ side of the instrument (the side with the identical
looking windows). The ‘c’ tube has no “up or down” orientation. The absorption tube is lined
with a quartz tube and one of the two sleeves is flat on top (the lip present on all the other
sleeves is missing). This tube installs on the ‘a’ side of the instrument, which can be
identified by the ‘a’ detector on the upper flange and is the only window, which is clearly
different from the other three. The flat flow tube sleeve goes on this detector.
You may want to mark the tubes and their orientation with tape or marking pen before using
the instrument at sea so that there is no confusion on reinstalling the tubes after cleaning the
optics. Reinstall the flow tubes before bench testing your instrument. If you have removed
the plastic caps from the stainless nozzles, replace them at this time.
1.1 Installing WETView
WETView displays data produced by WET Labs instruments. It runs on PC-compatible
computers with at least 16 Mb of memory and 3 Mb free hard disk space.
1. Place the WETView floppy disk in the floppy disk drive.
2. Open the floppy and double-click on the SETUP.EXE icon. Setup will guide you through
the rest of the installation process.
When installed, the following files should be on the hard disk: WETVIEW.EXE,
WETVIEW.UIR, AC9XXX.DEV, AIRXXYYY.CAL. The .DEV and .CAL files are the
calibration files for your particular instrument.
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Caution
If you have old device files from previous calibrations, you should rename them or
archive them in a different directory so that they will not be overwritten.
1.2 Bench Testing
The following items are needed to bench test the ac-9:
• A clean, solid lab table or work bench
• The ac-9 with 10-foot test cable (or sea cable)
• A 12–15 volt power supply (the ac-9 requires 10–18 VDC)
• A PC with WETView installed.
1. Connect the test cable to COMM1 or COMM2 of the computer. Connect the power leads
to a 12–15 volt power supply. The black lead is the V+ lead. Before connecting the cable
to the instrument, use a multi-meter to check the input power.
2. Connect the ground probe to pin 1 on the pigtail connector (the large pin as you are
looking into the connector). Connect the hot probe to pin 4 (the pin directly opposite from
pin 1). You should measure 12–15 volts across these two pins.
3. Turn the power supply off.
4. Connect the pigtail to the instrument. Pin one, marked on the outside of the connector by
a small rubber bump, engages the large socket on the instrument’s bulkhead connector.
Push the connector straight on to avoid damaging the pins. Apply power to the instrument
and allow it to begin warming up.
5. Run WETView. When the interface is displayed, you will need to provide a .DEV file
name. Click on the <O> button in the center top of the screen or choose “Open Device
File” from the File Menu at the top left of the screen. The program will ask you to choose
the proper COMM port. Select COMM1 or COMM2 as appropriate. Note that WETView
supports COMM1 through COMM4 only.
6. Click on the center button or <F1> to start displaying data. After 5–10 seconds, tabular
data should be displayed on the right side of the screen. A real time graph will begin to
develop, depending on the graph parameters set at the time. Refer to the WETView
User’s Guide for details of running the WETView software.
7. After a short time, again click on the center button that will stop the data collection and
ask for a file name to apply to the data if you should want to archive it. Press ESC if you
do not want to save the data. To quit the program, choose QUIT from the File menu. At
this point you have successfully completed a bench test of the instrument.
1.3 Air Tracking
We provide an air calibration (.CAL) file similar to the device (.DEV) file and can be applied
in WETView in the same manner. The DEV file provides the clean water offsets so that
2 ac-9 User’s Guide (ac-9) Revision R 21 May 2008
when measuring clean, fresh water, the instrument’s output should be very nearly 0.0 for all
channels. The .CAL file provides the offsets that provide 0.0 values when the instrument is
clean and dry and measuring air values. This is a useful tracking tool for catching instrument
drift, filter aging and improper cleaning.
When you installed WETView, the latest air .CAL file should have been transferred to your
WETVIEW directory. The name of the file takes the form:
AIRXXYYY.CAL where XX is the calibration number; YYY is the instrument number.
When a .DEV file is opened in WETView, it will display *.DEV in the dialog box, which
will list all the .DEV files on the default drive. If you change the *.DEV to *.CAL, the
available .CAL files will be displayed. Select the latest .CAL file and start collecting data.
Make sure the black plastic caps are installed on the flow tube nozzles so no ambient light
can enter the flow tubes. If the instrument is clean and dry, the values displayed in WETView
should be very close to 0.0 (within 0.005–0.01). If the values are within this range, the
instrument is clean and ready to deploy. If the values are outside this range, the first step is to
re-clean the instrument and then reapply the .CAL file offsets.
1.4 Cleaning
1. Remove flow tubes and all O-rings. Remove the collars from the flow tubes. Wash with a
mild detergent diluted with distilled, reverse osmosis-filtered (RO) or de-ionized (DI)
water to gently wash all of the windows and rinse the flow tubes. Use Kimwipes or other
lint-free tissues to wash the windows. Rinse off the meter completely with water to
ensure no soap residue is left inside the flow tubes or on the windows.
2. Dry the meter. Place the instrument in a protected area where it can dry completely.
Using a small heater to blow warm air over the meter may help speed the process. Using
dry nitrogen to blow-dry the meter and remove water from the small grooves around the
windows will also help speed the process. It is suggested that the instrument be left
overnight to dry out completely. Reassemble the meter. Carefully replace O-rings and
slide collars back on to the flow tubes. Replace O-rings around the windows.
3. Clean windows using a Kimwipe or lens paper. Place a couple of drops of methanol or
ethanol on the Kimwipe. With firm pressure, gently wipe the windows with methanol.
This should remove any visible streaks on the windows. If necessary, follow with a dry
wipe in one direction across the window face. Blow off any lint or dust with a dry air
source.
4. Clean the flow tubes by putting a few drops of methanol on a Kimwipe and, using a
wooden dowel rod, carefully slide the Kimwipe through the flow tube. Repeat this
procedure with both flow tubes. Examine each flow tube when you are through to ensure
there are no streaks or small pieces of lint left on the inside of the flow tube.
5. Dry the windows. Since small amounts of moisture can affect the air readings, it is
important to ensure the meter is completely dry. Using nitrogen to blow dry the windows
immediately before replacing the flow tubes works very effectively. This will remove any
water or methanol trapped in the small grooves around the window.
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6. Replace the flow tubes. Carefully slide the flow tubes into place without sliding dirt
across the windows. Slide the sleeves up around the windows and over the O-rings,
making certain they are firmly in place and aligned correctly. Use small black caps, or
black electrical tape, over each of the nozzles on the flow tube to provide a dark
environment and to keep the meter clean and free of moisture while obtaining data.
7. Turn the meter on and allow it to warm up for at least 15 minutes. When the meter is
stable you should be able to collect 10 minutes worth of data and the values should not
vary more than 0.005 m-1 over the 10-minute time period.
8. Collect data. Record a one- to two-minute file and save data. Repeat steps 4–6 until you
can collect three data files, cleaning after each file, such that the average values for each
channel vary by no more than 0.005 m-1.
The meter is calibrated over a specific range of internal temperatures (refer to your
calibration sheet). If the meter’s internal temperature is higher than the maximum calibration
range, it may be operating out of spec. Setting the meter in a shallow pan of water (immerse
most of the lower can) can help keep the instrument cool. This process should be repeated
until the air values are within specification. This may take three or more iterations but is very
important to be done carefully before taking your instrument to sea. The air calibration
procedure should be done again at the end of a cruise or data collection period to track the
instrument’s performance over time.
1.5 System Requirements
This section explains the basic system components necessary to operate the ac-9. If you are
using the instrument in a standard profiling configuration, you will generally need the
components described below. Other configurations, such as mooring and underway flowthrough systems, will require additional components such as battery packs, data loggers, antifouling canisters and/or de-bubblers. Test cables, software, and system configuration
engineering may be obtained by calling WET Labs. Alternatively, you will find additional
information about the various system components in the Technical Reference Section of this
manual. This manual concentrates on the use of the ac-9 as an optical profiling instrument.
The ac-9 was designed for easy use. However, certain system requirements for power and
communication with the instrument must be met. Figure 1 shows a block diagram of the
basic system components required for instrument operation. An explanation of these various
components follows the diagram. More detailed information on most of the system, the
instrument, and data output format can be found in the Technical Reference Section of this
manual. Details about hooking the unit up and acquiring data are included in this section.
4 ac-9 User’s Guide (ac-9) Revision R 21 May 2008
Figure 1. Typical ac-9 configuration
Required system components include:
Instrument
The ac-9 and its flow tube assembly form the basic optical sensor.
Pump
The flow-through system will typically require an ancillary pump in order to assure proper
operation. Pump requirements depend upon desired flow rates, required depth of operation,
power availability, and existing hardware.
Cabling
The ac-9 requires a minimum of four conductors for power and RS-485 output. (Three
conductors for RS-232 output).
Power Supply
The ac-9 requires a 10–18 VDC supply, capable of providing a minimum of 9 watts
continuous output. If a longer cable is used, power losses must be accounted for in
determining the power supply voltage and power requirements.
Serial Communications
Data from the ac-9 is transmitted via both RS-232 and RS-485 depending on which sockets
are connected to the instrument’s bulkhead connector. The exact configuration is described in
your instrument’s configuration in Section 5.1. Regardless of the mode of transmission you
use, you must have a serial interface on your computer or data logger capable of accepting
data from the instrument. If you have an instrument with RS-485 output and are using a
computer with standard RS-232 communication ports, an optional protocol converter can be
readily obtained (one such converter is manufactured by B&B Electronics—model number
of 485COSR).
Host/Data Logger
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The ac-9 can be interfaced to any computer or data logger capable of supporting a 19,200
baud rate serial interface. If you plan to use our WETView software acquisition package you
will need a Pentium® class IBM-compatible computer running Windows 95, Windows 98 or
Window NT to support the software package.
Software
The WETView host software package interfaces directly to the ac-9 via your computer serial
port. WETView allows real-time graphical visualization of the data in any of several ways
such as a function of time, depth or wavelength. WETView automatically applies calibration
constants, temperature corrections and generates a tab-delimited ASCII text file that can be
imported into programs such as Excel or MatLab for post processing or manipulation. The
data output format of the ac-9 is defined in the Technical Reference Section of this manual.
1.6 Operating the Meter
1.6.1 Basic Power On
a. Check wiring of cable. Make sure the “+” lead of the test cable is connected to the
“+” terminal of your power supply. Make sure the “–” lead of the test cable is
connected to the “–” terminal of your power supply. Verify that your power supply is
providing between 10 and 18 VDC, and is rated for at least 2 amps. See section 3.1
for details of connector wiring.
WARNING
Power input on this unit is diode-protected from reverse polarity power-up, but
this is not 100 percent insurance against damaging the meter, nor will it protect it
from over-voltage.
b. Cable connections. The surface (dry) end of the cable should have terminations for
an RS-232 connection into the computer and leads that connect to a power supply.
Attach the power leads to a stable power source that supplies 10–18 VDC to the ac-9.
Make sure the polarity is correct before switching on the power supply. Connect the
RS-232 connector to the desired serial port of the data collection computer. If your
instrument is sending data in the RS-485 format, an RS-485 to RS-232 converter is
required to allow proper operation. Plug the submerged (wet) end of the cable into the
ac-9. Applying a small amount of silicone grease or equivalent to the base of the
instrument bulkhead makes the plug insertion easier and provides greater assurance of
a good seal. Use a connector lock ring if one is available.
c. Turn on power supply. To verify basic operation when not hooked directly to a
computer, remove one of the flow tubes and, in a darkened environment, place a
white piece of paper into the beam path. You should be able to see the beam image on
the piece of paper. You should be able to hear a faint whirring of the filter wheel
motor if you place your ear directly against the lower can. If you neither hear the
motor nor see the beam, the unit is not working. In this case, check your connections
and your power supply. If the instrument still does not run, you may want to seek
technical assistance from the factory.
6 ac-9 User’s Guide (ac-9) Revision R 21 May 2008
d. For optimum stability allow the instrument to warm up for 3–5 minutes before
acquisition. While this is not an absolute requirement, the instrument’s electro-optics
are subject to an initial stabilization period.
1.6.2 Mounting Meter
ac-9 operation is optimized for a vertical to forty-five degrees off-vertical orientation
with the bulkhead connector facing upward (Figure 2). If your application requires a
horizontal mounting, take care to provide proper pump priming and to avoid trapping air
bubbles in the flow tubes. This can be accomplished by taking the system to a depth of 20
meters and allowing the required in-water warm up period to occur at depth. This helps
the pump to prime properly and compresses small air bubbles, allowing them to be
expelled from the ac-9.
In addition, operating the instrument in the horizontal position could potentially cause
small variations in the meter’s response due to the different orientation of the filter
wheel’s rotational plane. Therefore, we recommend that both air and water calibrations
be done in the orientation in which the meter will be deployed to obtain the best results.
Figure 2. ac-9 mounting positions
Specific mounting instructions will depend upon implementation of the sensor. To assure
long term instrument integrity and optimum operation, observe the following basic
procedures:
a. Do not make direct contact between the ac-9 pressure housing and a metal frame
or hose clamp. The ac-9 is available in one of two pressure-housing materials.
Aluminum is used for full ocean depth rated units and an acetal copolymer plastic is
used for the standard units rated to 500 meters. The aluminum housing is hard
anodized with a special plastic impregnation to assure minimum corrosion damage
and to provide electrical isolation from the aluminum housing and its surrounding
environment. However, metal-to-metal contact with the housing can damage this
coating and result in possible corrosion of the pressure case. We recommend a
ac-9 User’s Guide (ac-9) Revision R 21 May 2008 7
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