Frequently Asked Questions (FAQs) --
General Instrument Questions

FAQs have been organized into the following categories:

General instrument questions (this page)

• How do instruments that can be internally or externally powered handle external power if internal batteries are installed?
• For an RS-232 Sea-Bird instrument, what is the maximum cable length for real-time data?
• Why do some instruments have zinc anodes, while others do not?
• Do Anti-Foulant Devices affect the conductivity cell calibration?
• What is Triton? Does it harm sensors? Do I need to purchase it from Sea-Bird?
• Where can I get information about safe handling/hazards associated with chemicals used with Sea-Bird equipment, such as Anti-Foulant Devices and Triton X-100 detergent?
• Why is Teflon tape used?
• My CTD has a Digiquartz pressure sensor. Can I use it above its rated pressure?
• My CTD has a Druck pressure sensor. Can I use it above its rated pressure?
• What do you recommend for cleaning barnacles off the exterior of the instrument?
• Why is the color on my instrument housing changing? Can I use hydrochloric acid to clean the outside of the housing?
• Why am I getting negative density values when testing the instrument?
• What is a wet-pluggable or wet-mateable or MCBH connector? Can I mate and unmate a cable with this connector underwater?

	General oceanographic questions What is the difference between psu and ppt? Is the salinity calculated by Sea-Bird valid above 42 psu? Does Sea-Bird software output Practical Salinity (psu) or Absolute Salinity? What is the difference between IPTS-68 and ITS-90? What is the difference between initial accuracy and resolution? Why is sound velocity (SV) computed from a CTD better than sound velocity from direct measuring instruments? Which algorithm for calculating sound velocity (SV) from CTD data should I use? What is hydrostatic head effect? How can I find the density of seawater at different temperatures and/or salinities? What is the cause of conductivity drift? Does it matter whether you use natural or artificial seawater for calibrations? Which does Sea-Bird use? Where can I purchase standard seawater? Why is my CTD data showing hysteresis?
	Recommended practices What are the major steps involved in taking a cast with a Profiling CTD? Should I collect water samples (close bottles) on the downcast or the upcast? Can I deploy my profiling CTD for monitoring an oil spill? What are the major steps involved in deploying a moored instrument? What are the recommended practices for mating and unmating connectors? How can I tell if my connectors have leaked, and what do I do about corrosion on connector pins? What are the recommended practices for replacing a bulkhead connector? What are the recommended practices for inspecting and cleaning o-rings and mating surfaces? How often should I replace o-rings? How should I handle my CTD to avoid cracking the conductivity cell? What is an Anti-Foulant Device? How often should I replace it? Does it require special handling? What are the recommended practices for deploying in frazil or pancake ice, or deploying at low temperatures? Does it matter if I deploy my moored instrument, which includes a conductivity sensor, in a horizontal or vertical position? How many / what kind of spares should I have on ship for my instrument? How many/what kind of spares should I have on ship for my SBE 9plus? How will my CTD be affected by adjacent objects? What are the safety concerns/procedures if the instrument floods? Can the instrument explode? Is it necessary to put my instrument in water to test it? Will I destroy the conductivity cell if I test it in air? How should I store my conductivity sensor if there is danger of freezing? What are the recommended practices for cleaning and lubricating winch cables? What are the recommended practices for splicing cables?
	Service How often do I need to have my instrument and/or auxiliary sensors recalibrated? Can I recalibrate them myself? I am planning to ship my instrument to Sea-Bird for calibration and minor repairs. What is the typical turn-around time? I am planning to ship my instrument to Sea-Bird for calibration and minor repairs. Should I also send the auxiliary sensors from other manufacturers? My auxiliary sensor (not manufactured by Sea-Bird) needs to be repaired / recalibrated. Where should I send it for servicing? I want to add an auxiliary sensor to my CTD. Assuming the auxiliary sensor is compatible with the instrument, what is the procedure? Do I need to remove batteries before shipping my instrument for a deployment or to Sea-Bird? Do I need to clean the exterior of my instrument before shipping it to Sea-Bird for calibration? I want to change the pressure sensor on my CTD, swapping it as needed to get the best data for a given deployment depth. Can I do this myself, or do I need to send the instrument to Sea-Bird? Can I brush clean and replatinize the conductivity cell myself? How often should this be done? I sent my conductivity sensor to Sea-Bird for calibration, and you also performed a Cleaning and Replatinizing (C&P). You sent the instrument back with 2 sets of calibration data. What does this mean? How can I tell if the conductivity cell on my CTD is broken? What are Configuration Sheets, and where can I find them for my instrument? What is Sea-Bird's policy on upgrading instruments? Should I purchase spare pressure sensors for my SBE 9plus? What do I need to send to Sea-Bird for calibration of my SBE 9plus? What do I need to send to Sea-Bird for calibration of my SBE 25?
	Ordering How do I find information about the options available with each instrument? Where do I find pricing information for new instruments, calibration services, and/or repair services? Which Sea-Bird profiling CTD is best for my application? I want to integrate a moored CTD with some auxiliary sensors (transmissometer, fluorometer, etc.). Which CTD should I use? How should I pick the pressure sensor range for my CTD? Would the highest range give me the most flexibility in using the CTD? I am ordering a CTD and want to use auxiliary sensors. Should I order them from Sea-Bird also, or deal directly with the sensors' manufacturers? What are the pros and cons of ordering wet-pluggable connectors? Can Sea-Bird provide some guidance for ordering cable, winch, and deck gear?
	Software I am confused by all these software names. Which software does what? Can I install my Sea-Bird CD-ROM on multiple computers or give it to another interested scientist? How can I copy the setup of my Sea-Bird software onto another computer? How can I view CTD data? What is a configuration (.con or .xmlcon) file and how is it used? What is a .psa file and how is it used? What is a .cfg file and how is it used? Does SEASOFT have a provision for converting to MatLab data files? Can I use SEASOFT on a Macintosh, Unix, or Linux system? Is the Windows version of SEASOFT compatible with Microsoft's Vista operating system? Is the Windows version of SEASOFT compatible with Microsoft's Windows 7 operating system? Can I use SEASOFT-DOS on a computer with Windows 95/98/NT/2000/XP operating system? Your website Download Software from FTP Site page defines the latest software revision, but I cannot find the latest revision on the FTP site. Is it not posted yet? Why am I having trouble downloading software from your FTP site? How does Sea-Bird software calculate conductivity, temperature, and pressure in engineering units? How does Sea-Bird software calculate derived variables such as salinity, sound velocity, density, depth, thermosteric anomaly, specific volume, potential temperature, etc.? What is the flag variable column that is added to the data file by SBE Data Processing's Data Conversion or ASCII In module? What formula does Sea-Bird software use to convert pressure data to depth? In Sea-Bird software, is noon on January 1 Julian Day 0.5 or Julian Day 1.5? Can I edit my .dat data file to add some explanatory notes to header? Can I edit my .hex data file to add some explanatory notes to header? Why am I getting a class not registered error when running SBE Data Processing?
	Data analysis and processing Why and how should I align data from a 911plus CTD? What are the typical data processing steps recommended for each instrument? Where can I find formulas for calculating conductivity, temperature, pressure, and derived parameters such as salinity, sound velocity, density, depth, thermosteric anomaly, specific volume, potential temperature, etc.?
	Manufacturing Does Sea-Bird pressure test each instrument before shipping to verify integrity of housing, o-rings, assembly, etc.? Does Sea-Bird check and calibrate all sensors on a CTD system prior to shipping? Do Sea-Bird instruments have CE certification? Do Sea-Bird instruments have ISO certification?

Our Glossary page is another good source of information.

Sea-Bird instruments that are designed to be powered internally or externally incorporate diode or'd circuitry, allowing only the voltage that has the greater potential to power the instrument. You can power the instrument externally without running down the internal batteries. This allows you to lab test using external power that has higher voltage than the internal batteries, and then deploy using internal power, knowing that the internal batteries are fresh.

Cable length is one of the most misunderstood items in the RS-232 world. The RS-232 standard was originally developed decades ago for a 19200 baud rate, and defines the maximum cable length as 50 feet, or the cable length equal to a capacitance of 2500 pF. The capacitance rule is often forgotten; using a cable with low capacitance allows you to span longer distances without going beyond the limitations of the standard. Also, the maximum cable length mentioned in the standard is based on 19200 baud rate; if baud is reduced by a factor of 2 or 4, the maximum length increases dramatically. 

Using typical underwater cables, the following table defines allowable combinations of cable length and baud rate for Sea-Bird instruments communicating with RS-232:

A zinc anode attracts corrosion and prevents aluminum from corroding until all the zinc is eaten up. Sea-Bird uses zinc anodes on an instrument if it has an aluminum housing and/or end cap. Instruments with titanium or plastic housings and end caps (for example, SBE 37 MicroCAT) do not require a sacrificial anode.

Anti-Foulant Devices have no effect on the calibration, because they do not affect the geometry of the cell in any way. The Anti-Foulant Devices are mounted at either end of the conductivity cell.

For an in-depth explanation of how Sea-Bird makes the conductivity measurement, see Conductivity Sensors for Moored and Autonomous Operation.

Triton X-100 is Octyl Phenol Ethoxylate, a reagent grade non-ionic surfactant (detergent). Sea-Bird uses it to help keep our conductivity cells clean and the electrodes wetted and ready for immediate use in water (a dry cell requires a few minutes to become completely wetted after immersion). Triton X-100 will not harm conductivity cells, temperature sensors, or pumped fluorometers. Do not place concentrated Triton X-100 directly on the membrane of a dissolved oxygen sensor.

Triton X-100 is supplied in 100% strength.

• Conductivity sensors -- Triton is typically diluted to 0.1% strength (by 1000) for rinsing and for rewetting the conductivity cell just before deployment, and to 1% to 2% strength (by 50 to 100) for cleaning the conductivity cell. Refer to Application Note 2D: Instructions for Care and Cleaning of Conductivity Cells and to the maintenance section in the instrument manual for details.
• Dissolved Oxygen sensors -- Triton is typically diluted to 0.1% strength (by 1000) for rinsing, and to 1% (by 100) for cleaning. Prolonged exposure of the sensor membrane to Triton is harmful, and causes the sensor's calibration to drift. Refer to Application Note 64: SBE 43 Dissolved Oxygen Sensor - Background Information, Deployment Recommendations, and Cleaning and Storage for details.

Triton X-100 can be ordered from Sea-Bird, but should also be available locally from a chemical supply or laboratory products companies. It is manufactured by Mallinckrodt Baker (see http://www.mallbaker.com/changecountry.asp?back=/Default.asp for local distributors). See our MSDS page to view the Material Safety Data Sheet.

See Material Safety Data Sheets (MSDS) for chemicals commonly used with Sea-Bird instruments.

Adhesive Teflon tape (actually, UHMW tape -- Ultra High Molecular Weight polyethylene) provides insulation to prevent damage due to contact of dissimilar metals. It is typically used by Sea-Bird on the inside of hose clamps used for mounting instruments, where U-bolts hold a Carousel Water Sampler frame to an extension stand, etc. The tape can be ordered from Sea-Bird; part number 30409 is 1 inch wide x 0.1 inch thick x 1 foot long (2.5 cm x 0.25 cm x 0.3 m). It can also be purchased from the manufacturer, Crown Plastics (see www.crownplastics.com for local distributors).

The overpressure rating for a Digiquartz (as stated by Paroscientific) is 1.2 * full scale. The sensor will provide data values above 100% of rated full scale; however, Sea-Bird does not calibrate beyond the rated full scale.

Note: If you use the instrument above the rated range, you do so at your own risk; the product will not be covered under warranty.

The overpressure rating for a Druck is 1.5 * full scale. The sensor will provide data values above 100% of rated full scale; however, Sea-Bird does not calibrate beyond the rated full scale.

Note: If you use the instrument above the rated range, you do so at your own risk; the product will not be covered under warranty.

Plug the ends of the conductivity cell to prevent the cleaning solution from getting into the cell. Then soak the entire instrument in white vinegar. After scraping off the barnacles and marine growth, rinse the instrument well with fresh water.

Note: If sending the instrument to Sea-Bird for calibration, remove as much biological material as possible before shipping. Sea-Bird cannot place an instrument with a large amount of biological material on the housing in our calibration bath; if we need to clean the exterior before calibration, we will charge you for this service.

The housings of some of our instrument are made from anodized aluminum. In our experience it is very common to see color change when anodized housings are moored in seawater. We even see some discoloration during the brief time instruments undergo calibration and testing.

There are probably several causes of discoloration:

• Zinc from the protective anodes tends to deposit on the surface, causing the color to lighten toward gray.
• Some seawater components, for example, carbonates, may precipitate onto the surfaces.
• The anodized coating does not completely cover the aluminum: at microscopic scale the coating has the appearance of a dry lake bed ‑ there are patches of anodizing surrounded by cracks. These cracks allow water to reach bare aluminum and cause local oxidation that is light in color. Fortunately, once a thin oxide coating forms on aluminum, further corrosion tends to be inhibited. Unless you see severe pitting, there is usually no danger to the safety of the housing.

We do not advise using hydrochloric acid (HCl) to clean instrument housings. Such highly corrosive acids will not hurt the anodized surfaces, but will attack any bare aluminum ‑ including the aluminum in the cracks ‑ and can also damage O-rings, connectors, and other sensor components. A milder acid, for example household (cooking) vinegar, is a better choice.

Several customers who have completely wrapped their instrument housings with plastic tape report good results. The bio-organisms still grow, but after recovery it is easy to peel off the tape, shells and mussels and all!

The density equation is not valid for a salinity less than 2 psu, so if you test your instrument in fresh water your data will show negative density. For more information on the practical salinity scale, refer to UNESCO Technical Papers of Marine Science 44.

Note: Many Unesco marine science publications are available through Unesco's website. Go to http://unesdoc.unesco.org/ulis/ioc/.

1. In the Series title box, select UNESCO technical papers in marine science.
2. Select Widen the search to all UNESCO documents/publications.
3. Click the Search button.

Wet-pluggable (also referred to as wet-mateable or MCBH) connectors, an option on many of our instruments, may be mated in wet conditions. Their pins do not need to be dried before mating. By design, water on the connector pins is forced out as the connector is mated. However, they must not be mated or un-mated while submerged. Wet-pluggable connectors have a non-conducting guide pin to assist pin alignment and require less force to mate, making them easier to mate reliably under dark or cold conditions, compared to our standard (Impulse XSG/RMG) connectors (standard connectors may not seal well in extreme cold; we recommend connecting cables in warm ship’s lab rather than on deck for these conditions). Like standard connectors, wet-pluggables need proper lubrication and require care during use to avoid trapping water in sockets.

When should you consider configuring your instrument with wet-pluggable connectors? Of course, cost is always a concern, but consider the following guidelines:

• Internal recording with a profiling CTD (for example, SBE SBE 9plus with 17plus V2, SBE 19plus V2, SBE 25) -- Connecting/disconnecting frequently to the CTD is typical for these systems, for uploading of the internally recorded data. Wet-pluggable connectors are recommended for these applications.

• Autonomous water sampling (SBE 32 Carousel with AFM or 17plus V2, or SBE 55 ECO Water Sampler) and internal recording with a profiling CTD -- Connecting/disconnecting to the underwater electronics is required after every cast, to re-arm the electronics for autonomous water sampling. Connecting/disconnecting is often done on deck, where the connectors are exposed to splashing and rain; wet-pluggable connectors are strongly recommended for these applications.

• Real-time data acquisition with a profiling CTD (for example, SBE 9plus with 11plus Deck Unit, SBE 19plus V2 with PDIM and SBE 33 or 36 Deck Unit, SBE 25 with PDIM and SBE 33 or 36 Deck Unit) -- The underwater units in these systems are plugged into the sea cable, and typically are disconnected infrequently. Wet-pluggable connectors are not as important for this application.

• Moored instruments --
  - If data upload after recovery will occur on deck to allow for quick redeployment, wet-pluggable connectors are recommended.
  - If data upload after recovery will occur in a lab, wet-pluggable connectors are not as important for this application.

Last modified: 05 Nov 2010

Sea-Bird Home     Phone: (+1) 425-643-9866     Fax: (+1) 425-643-9954     E-mail: seabird@seabird.com