Frequently Asked Questions

Cells that have been contaminated with foreign material generally read low of the actual conductivity. Your zero (in air) conductivity reading is generally unaffected.

The conductivity error due to fouling will generally be proportional to the conductivity value. Conductivity is corrected not as an offset but as a ratio (multiplicative) error compared to a reference.

Salinity is a derivative measurement of temperature, conductivity, and pressure, and should be corrected by adjusting the component measurements. Generally speaking, an error in the conductivity measurement will correlate to a directly proportional error in the salinity measurement.

Cells that have been contaminated with foreign material generally read low of the actual conductivity. Your zero (in air) conductivity reading is generally unaffected.

The conductivity error due to fouling will generally be proportional to the conductivity value. Conductivity is corrected not as an offset but as a ratio (multiplicative) error compared to a reference.

Salinity is a derivative measurement of temperature, conductivity, and pressure, and should be corrected by adjusting the component measurements. Generally speaking, an error in the conductivity measurement will correlate to a directly proportional error in the salinity measurement.

The pH sensor will be shipped dry but was pre-conditioned in seawater (generally from Pacific Ocean waters near Hawaii). While conditioning and evaluating the pH sensor, only expose it filtered, sterilized natural seawater. Do not use seawater CRMs (Certified Reference Material), synthetic seawater, deionized water, NaCl Solutions, or tap water.

Before pre-deployment testing, you will need to fill the plumbing around the pH sensor with natural seawater. The pH sensor needs time to acclimate to the ionic concentration of region specific waters. Once wet, the time to recondition the sensor so that it will report within its accuracy specification depends on several factors, including the ionic composition of the seawater used and the amount of time the pH sensor was stored dry. This time can range from several hours to up to three days.

When the seawater bridge between Counter Electrode and ISFET is broken for longer than 10 seconds, it will be necessary to re-condition the sensor. The sensor does not require recalibration after being re-conditioned.

To prepare the sensor for deployment, it is recommended that several days prior to deployment, the isolated battery is connected via the float interface and the pH sensor is stored in water that is similar to the deployment site. The sensor should be stored dry to avoid bio-fouling of the ISFET and the battery may be removed during storage. Seawater creates a half cell bridge between the Counter Electrode and ISFET, and power to that circuit is provided by the isolated 9V cell. Without seawater, the battery is unnecessary and may be disconnected.

SUNAs ordered with the 5mm path length coupler as a factory option will perform much better in low light transmission waters due to the shorter length the light needs to travel leading to less absorption. Equipping your SUNA with the factory bio-wiper option will also perform better and be less susceptible biofouling or buildup of other material that can reduce light transmission.

There are also some maintenance practices and device settings that can give SUNA a better probability of being able to capture enough light for a sample. Enable adaptive integration will trigger the SUNA to increase the lamp on time when light received by the spectrometer is low. It is also important to clean the windows as frequently as possible and monitor lens for scratches. Finally, you want your maximum light spectral counts at the peak wavelength (around 240nm) to be between 45,000 and 55,000 counts in pure or deionized water. This can be viewed in the “Spectra” tab in UCI when sampling or replaying data. If your peak spectrometer output is below 45,000 counts after cleaning the window, you may increase the integration period by 25 to 50 ms if needed (but not more; further changes require a factory recalibration). After adjusting the integration period, always perform a reference spectrum update per the instructions in the SUNA manual.

The pH sensor will be shipped dry but was pre-conditioned in seawater (generally from Pacific Ocean waters near Hawaii). While conditioning and evaluating the pH sensor, only expose it filtered, sterilized natural seawater. Do not use seawater CRMs (Certified Reference Material), synthetic seawater, deionized water, NaCl Solutions, or tap water.

Before pre-deployment testing, you will need to fill the plumbing around the pH sensor with natural seawater. The pH sensor needs time to acclimate to the ionic concentration of region specific waters. Once wet, the time to recondition the sensor so that it will report within its accuracy specification depends on several factors, including the ionic composition of the seawater used and the amount of time the pH sensor was stored dry. This time can range from several hours to up to three days.

When the seawater bridge between Counter Electrode and ISFET is broken for longer than 10 seconds, it will be necessary to re-condition the sensor. The sensor does not require recalibration after being re-conditioned.

To prepare the sensor for deployment, it is recommended that several days prior to deployment, the isolated battery is connected via the float interface and the pH sensor is stored in water that is similar to the deployment site. The sensor should be stored dry to avoid bio-fouling of the ISFET and the battery may be removed during storage. Seawater creates a half cell bridge between the Counter Electrode and ISFET, and power to that circuit is provided by the isolated 9V cell. Without seawater, the battery is unnecessary and may be disconnected.

The pH sensor will be shipped dry but was pre-conditioned in seawater (generally from Pacific Ocean waters near Hawaii). While conditioning and evaluating the pH sensor, only expose it filtered, sterilized natural seawater. Do not use seawater CRMs (Certified Reference Material), synthetic seawater, deionized water, NaCl Solutions, or tap water.

Before pre-deployment testing, you will need to fill the plumbing around the pH sensor with natural seawater. The pH sensor needs time to acclimate to the ionic concentration of region specific waters. Once wet, the time to recondition the sensor so that it will report within its accuracy specification depends on several factors, including the ionic composition of the seawater used and the amount of time the pH sensor was stored dry. This time can range from several hours to up to three days.

When the seawater bridge between Counter Electrode and ISFET is broken for longer than 10 seconds, it will be necessary to re-condition the sensor. The sensor does not require recalibration after being re-conditioned.

To prepare the sensor for deployment, it is recommended that several days prior to deployment, the isolated battery is connected via the float interface and the pH sensor is stored in water that is similar to the deployment site. The sensor should be stored dry to avoid bio-fouling of the ISFET and the battery may be removed during storage. Seawater creates a half cell bridge between the Counter Electrode and ISFET, and power to that circuit is provided by the isolated 9V cell. Without seawater, the battery is unnecessary and may be disconnected.

SUNAs ordered with the 5mm path length coupler as a factory option will perform much better in low light transmission waters due to the shorter length the light needs to travel leading to less absorption. Equipping your SUNA with the factory bio-wiper option will also perform better and be less susceptible biofouling or buildup of other material that can reduce light transmission.

There are also some maintenance practices and device settings that can give SUNA a better probability of being able to capture enough light for a sample. Enable adaptive integration will trigger the SUNA to increase the lamp on time when light received by the spectrometer is low. It is also important to clean the windows as frequently as possible and monitor lens for scratches. Finally, you want your maximum light spectral counts at the peak wavelength (around 240nm) to be between 45,000 and 55,000 counts in pure or deionized water. This can be viewed in the “Spectra” tab in UCI when sampling or replaying data. If your peak spectrometer output is below 45,000 counts after cleaning the window, you may increase the integration period by 25 to 50 ms if needed (but not more; further changes require a factory recalibration). After adjusting the integration period, always perform a reference spectrum update per the instructions in the SUNA manual.

There are several considerations when determining whether the deck box and CTD underwater unit will be compatible.

(1) In most cases (with the exception being (2), below), instruments with the “-plus” designation are compatible with each other, but the “-plus” variants are not compatible with the variants that do not have “-plus” in their model number (i.e., an SBE9plus CTD must be used with an SBE11plus, and cannot be used with an older SBE11 deck unit).

(2) If you have an SBE9/11plus system with the serial uplink feature installed, then both the deck box and the CTD must have the same hardware configuration from the factory (either enabled or disabled). Otherwise, no telemetry will be received from the CTD by the deck box.

(3) For older instruments that do not have “-plus” in their model number, you need a matching pair of SBE9 and SBE11. There was no standard configuration, and different CTDs and deck units could have telemetry word/rate differences (4/24, 8/24, 12/24, etc.) and power differences (standard low power or high power). You would need to consult the original documentation that shipped with the instruments or send them to Sea-bird service for a repair evaluation to determine compatibility.

Cells that have been contaminated with foreign material generally read low of the actual conductivity. Your zero (in air) conductivity reading is generally unaffected.

The conductivity error due to fouling will generally be proportional to the conductivity value. Conductivity is corrected not as an offset but as a ratio (multiplicative) error compared to a reference.

Salinity is a derivative measurement of temperature, conductivity, and pressure, and should be corrected by adjusting the component measurements. Generally speaking, an error in the conductivity measurement will correlate to a directly proportional error in the salinity measurement.

The pH sensor will be shipped dry but was pre-conditioned in seawater (generally from Pacific Ocean waters near Hawaii). While conditioning and evaluating the pH sensor, only expose it filtered, sterilized natural seawater. Do not use seawater CRMs (Certified Reference Material), synthetic seawater, deionized water, NaCl Solutions, or tap water.

Before pre-deployment testing, you will need to fill the plumbing around the pH sensor with natural seawater. The pH sensor needs time to acclimate to the ionic concentration of region specific waters. Once wet, the time to recondition the sensor so that it will report within its accuracy specification depends on several factors, including the ionic composition of the seawater used and the amount of time the pH sensor was stored dry. This time can range from several hours to up to three days.

When the seawater bridge between Counter Electrode and ISFET is broken for longer than 10 seconds, it will be necessary to re-condition the sensor. The sensor does not require recalibration after being re-conditioned.

To prepare the sensor for deployment, it is recommended that several days prior to deployment, the isolated battery is connected via the float interface and the pH sensor is stored in water that is similar to the deployment site. The sensor should be stored dry to avoid bio-fouling of the ISFET and the battery may be removed during storage. Seawater creates a half cell bridge between the Counter Electrode and ISFET, and power to that circuit is provided by the isolated 9V cell. Without seawater, the battery is unnecessary and may be disconnected.

The primary maintenance procedures that are outlined in the manual are for the bio-wiper (shutter) installation, the internal battery replacement and the bulkhead connector inspection. The shutter replacement is not always necessary; however, having the copper shutter and face plate parts available to swap out as needed is a good idea.

Otherwise, the optics face should be inspected for film/streaks. The wiper may not work effectively if the copper faceplate condition deteriorates and damages the rubber blade. Some environmental conditions can start to “pit” the face plate surface, shredding the wiper blade. Replacing the face plate should be done if the wiper blade is getting damaged by being dragged across it. Otherwise, cleaning the active optics sensor area usually only requires DI water and a lab wipe (i.e. Kimwipe). Superficial scrapes and scratches on the optics face are unlikely to significantly affect the measurement.

Working with the shutter, moving it for inspection and/or removing it to install a new one, requires the instrument to be powered ON… keeping power to the shutter motor and commanding the open/close positions via software command/control. When moving/removing the shutter, it should NOT BE MOVED MANUALLY! There are gears in the ECO shutter motor that can strip easily with the wrong manual motion, unpowered. The manual motion in the wrong direction and speed, can overcome some of the gear ratios at play when they are back-driven.

Terminal emulator programs (as opposed to ECO View) are the most direct platform for working with the ECO’s. However, their use depends on one’s preference for how to interface with the instruments.

An RTC (real time clock) is an electronic component which maintains an accurate time reference for the CTD.  In the past, clock chips could be periodically calibrated to account for slow drift.  As of the early 2000s, Sea-bird has been using components with improved stability to the point where recalibration is no longer necessary over the lifespan of an instrument.

SUNAs ordered with the 5mm path length coupler as a factory option will perform much better in low light transmission waters due to the shorter length the light needs to travel leading to less absorption. Equipping your SUNA with the factory bio-wiper option will also perform better and be less susceptible biofouling or buildup of other material that can reduce light transmission.

There are also some maintenance practices and device settings that can give SUNA a better probability of being able to capture enough light for a sample. Enable adaptive integration will trigger the SUNA to increase the lamp on time when light received by the spectrometer is low. It is also important to clean the windows as frequently as possible and monitor lens for scratches. Finally, you want your maximum light spectral counts at the peak wavelength (around 240nm) to be between 45,000 and 55,000 counts in pure or deionized water. This can be viewed in the “Spectra” tab in UCI when sampling or replaying data. If your peak spectrometer output is below 45,000 counts after cleaning the window, you may increase the integration period by 25 to 50 ms if needed (but not more; further changes require a factory recalibration). After adjusting the integration period, always perform a reference spectrum update per the instructions in the SUNA manual.

There are several considerations when determining whether the deck box and CTD underwater unit will be compatible.

(1) In most cases (with the exception being (2), below), instruments with the “-plus” designation are compatible with each other, but the “-plus” variants are not compatible with the variants that do not have “-plus” in their model number (i.e., an SBE9plus CTD must be used with an SBE11plus, and cannot be used with an older SBE11 deck unit).

(2) If you have an SBE9/11plus system with the serial uplink feature installed, then both the deck box and the CTD must have the same hardware configuration from the factory (either enabled or disabled). Otherwise, no telemetry will be received from the CTD by the deck box.

(3) For older instruments that do not have “-plus” in their model number, you need a matching pair of SBE9 and SBE11. There was no standard configuration, and different CTDs and deck units could have telemetry word/rate differences (4/24, 8/24, 12/24, etc.) and power differences (standard low power or high power). You would need to consult the original documentation that shipped with the instruments or send them to Sea-bird service for a repair evaluation to determine compatibility.

When your max lamp counts drop below 30,000 during the self test and cannot recover with cleaning, you can send the lamp in for inspection.

If your lamp time remaining is less than 25% then it is best to send the SUNA in for a lamp replacement. We will automatically replace lamps during service if they have less than 30% time remaining, as we want the SUNA to have enough lamp hours to last until your next yearly service.

When your max lamp counts drop below 30,000 during the self test and cannot recover with cleaning, you can send the lamp in for inspection.

If your lamp time remaining is less than 25% then it is best to send the SUNA in for a lamp replacement. We will automatically replace lamps during service if they have less than 30% time remaining, as we want the SUNA to have enough lamp hours to last until your next yearly service.

For Sea-Bird instruments that use alkaline D-cells, Sea-Bird uses Duracell MN 1300, LR20. While rare, we have seen a few problems with cheaper batteries over the years: they are more likely to leak, may vary in size (leading to loose batteries causing a bad power connection), and may not last as long.

For SBE 4 conductivity calibrations, Sea-Bird uses natural seawater that has been carefully collected, stored, UV irradiated, and filtered. Artificial seawater is not adequate if calibration errors are to be kept below 0.010 psu.
Note: SBE 4 is the conductivity sensor in the SBE 9plus, 25, and 25plus profiling CTDs.

The primary difference between natural and artificial seawater is the behavior of conductivity versus temperature. The practical salinity scale 1978 equations include a term rt. This term is expanded into a fourth order equation that describes the variation of conductivity versus temperature for a sample of constant salinity. The equation’s coefficients are derived by fitting to natural seawater samples. Artificial seawater does not have the same conductivity versus temperature characteristic, providing incorrect coefficients and causing a slope error in the calibration.

For calibrations of conductivity sensors other than the SBE 4, Sea-Bird uses artificial seawater (NaCl solution). However, we place an SBE 4 conductivity sensor in each bath, providing a standard for reference to the natural seawater calibration. This allows us to correct errors in the coefficients and slope introduced with the artificial seawater calibration.

For calibration of temperature sensors, Sea-Bird uses artificial seawater (NaCl solution).

The Anti-Foulant Device is an expendable device that is installed on each end of the conductivity cell, so that any water that enters the cell is treated. Anti-Foulant Devices are typically used with moored instruments (SBE 16, 16plus, 16plus-IM, 16plus V2, 16plus-IM V2, 37-SM, 37-SMP, 37-SMP-IDO, 37-SMP-ODO, 37-SI, 37-SIP, 37-SIP-IDO, 37-IM, 37-IMP, 37-IMP-IDO, 37-IMP-ODO, HydroCAT, HydroCAT-EP), thermosalinographs (SBE 21 and 45), glider CTDs (Glider Payload CTD), moored profilers (SBE 52-MP), and drifters (SBE 41/41CP Argo float CTDs), and optionally with SBE 19plus, 19plus V2, and 49 profilers.

Anti-Foulant Devices have no effect on the calibration, because they do not affect the geometry of the conductivity 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.

Useful deployment life varies, depending on several factors. We recommend that customers consider more frequent anti-foulant replacement when high biological activity and strong current flow (greater dilution of the anti-foulant concentration) are present. Moored instruments in high growth and strong dilution environments have been known to obtain a few months of quality data, while drifters that operate in non-photic, less turbid deep ocean environments may achieve years of quality data. Experience may be the strongest determining factor in specific deployment environments. Sea-Bird recommends that you keep track of how long the devices have been deployed, to allow you to purchase and replace the devices when needed.

Note that the anti-foulant device does not actually dissolve, so there is no way to visually determine if the anti-foulant device is still effective.

The cost of the anti-foulant devices is small compared to the deployment costs, so we recommend that you replace the devices before each deployment. This will provide the maximum bio-fouling protection, resulting in long-term data quality. 

Shelf Life and Storage: The best way to store Anti-Foulant Devices is in an air-tight, opaque container. The rate of release of anti-foulant is based on saturation of the environment. The anti-foulant will release until the environment is fully saturated (100% saturated) and then it will no longer release any anti-foulant. So if you keep Anti-Foulant Devices sealed well in an air-tight container, theoretically they will stay good for extended periods of time. Exposure to direct sunlight can also affect the release of anti-foulant; we recommend storage in an opaque container.

Handling:

• For details, refer to the Material Safety Data Sheet, enclosed with the shipment and available on our MSDS page.
• Anti-Foulant Devices are not classified by the U.S. DOT or the IATA as hazardous material.

Sea-Bird opened a calibration/service center in Kempten, Germany in 2011, providing duty-free servicing for EU customers. The dedicated technical support staff and calibration technicians were extensively trained by Sea-Bird experts. Calibration cross-referencing between the US and Germany facilities ensures Sea-Bird factory quality and accuracy. The German facility stocks a full range of parts and supplies to support repairs. Details.

For calibration of the temperature and conductivity sensors, only the sensor modules need to be sent to Sea-Bird. It is not necessary to send the CTD main housing. See Shipping SBE 9plus, 25, and 25plus Temperature and Conductivity Sensors for details.

It is usually not necessary to recalibrate the pressure sensor as frequently as the temperature and conductivity sensors. Experience has shown that the sensor’s sensitivity function almost never changes; only the offset drifts. The offset drift can easily be measured by reading deck pressure against a barometer. This small drift is easily corrected (Seasave V7 and SBE Data Processing provide an entry for the offset drift in the instrument .con or .xmlcon file).

• SBE 9plus and 25plus — If the pressure sensor does need to be calibrated, the entire CTD must be shipped to Sea-Bird.
• SBE 25 — If the pressure sensor does need to be calibrated, only the modular SBE 29 pressure sensor needs to be sent to Sea-Bird. It is not necessary to send the CTD main housing.

It is our policy to update firmware in instruments while they are here for calibration at no cost to the customer, but it is not our policy to routinely upgrade circuit cards. On some very old units that are being upgraded to support more external sensors, new pressure sensors, or other repairs, we sometimes discount the new circuit cards as part of the larger upgrade, as that makes the work easier for us to complete.

Configuration Sheets detail instrument communication settings, system configuration (auxiliary sensors, which channels are set up for which sensors), and sensor calibration coefficients. Configuration sheets are provided with the instrument, in both paper form (may be part of the manual) and on the CD-ROM.

Configuration Sheet locations vary, depending on the type of instrument and when it was shipped. If you cannot locate them, contact Sea-Bird and we will email copies.

The post-cruise calibration contains important information for drift calculations. The post-cruise calibration is performed on the cell as we received it from you, and is an indicator of how much the sensor has drifted in the field. Information from the post-cruise calibration can be used to adjust your data, based on the sensor’s drift over time. See Application Note 31: Computing Temperature and Conductivity Slope and Offset Correction Coefficients from Laboratory Calibrations and Salinity Bottle Samples.

If the sensor has drifted significantly (based on the data from the post-cruise calibration), Sea-Bird performs a C & P to restore the cell to a state similar to the original calibration. After the C & P, the sensor is calibrated again. This calibration serves as the starting point for future data, and for the sensor’s next drift calculation.

The C & P tends to return the cell to its original state. However, there are many subtle factors that may result in the post-C & P calibration not exactly matching the original calibration. Basically, the old platinizing is stripped off and new platinizing is plated on. Anything in this process that alters the cell slightly will result in a difference from the original calibration. We compare the calibration after C & P with the original calibration, not to make any drift analysis, but to make sure we did not drastically alter the cell, or that the cell was not damaged during the C & P process.

Brush-cleaning and replatinizing should be performed at Sea-Bird. We cannot extend warranty coverage if you perform this work yourself.

The brush-cleaning and replatinizing process requires specialized equipment and chemicals, and the disassembly of the sensor. If performed incorrectly, you can damage the cell. Additionally, the sensor must be re-calibrated when the work is complete.

Sea-Bird determines whether brush-cleaning and replatinizing is required based upon how far the calibration has drifted from the original calibration. Typically, a conductivity sensor on a profiling CTD requires brush-cleaning and replatinizing every 5 years.

Alkaline batteries can be shipped installed in the instrument. See Shipping Batteries for information on shipping instruments with Lithium or Nickel-Metal Hydride (NiMH) batteries.

Sea-Bird does not repair or recalibrate other manufacturers’ instruments that have been integrated with Sea-Bird equipment. If an auxiliary sensor needs to be repaired or recalibrated, we recommend that you send it directly to the manufacturer. If you send it to Sea-Bird, we will have to send it to the manufacturer, resulting in additional shipping (and possibly customs) expenses for you.

Note: Apparent malfunctioning of an auxiliary sensor can be caused by many things, including incorrect configuration (.con or .xmlcon) file, incorrect instrument setup, incorrect or leaky cables, poor mounting scheme, etc.

• If you are not certain that the auxiliary sensor needs to be repaired, Sea-Bird can help you troubleshoot the system by phone or e-mail at no charge.
• Alternatively, if you ship us the entire system, we can troubleshoot at the factory for our standard charges (see the FAQ above this for troubleshooting description). If we determine that the auxiliary sensor does need to be repaired, we will coordinate with you on shipment of the sensor to the manufacturer.

The answer to this question depends on your budget and your level of confidence that the entire system is functioning properly. When Sea-Bird receives CTDs that have integrated auxiliary sensors produced by other manufacturers, we test the functionality of the entire system. For a standard charge, we:

• Visually inspect the physical condition of the auxiliary sensor, connector, and interface cable.
• Visually inspect the mounting scheme of the auxiliary sensor on the CTD (a poor mounting scheme can result in poor data).*
• (For voltage sensors) Measure the open voltage and block voltage to ensure that the auxiliary sensor responds through the full 0 – 5V range.
• Check that the auxiliary sensor reads correctly when submerged in our cold salt water test baths for 30 – 60 minutes.

If the auxiliary sensor does not meet our standards*, we recommend that the sensor be sent to the other manufacturer for service. If the sensor is sent to the other manufacturer, we perform the same tests when it returns to us after servicing. Additionally, we update the configuration (.con or .xmlcon) file with any new calibration coefficients.

*Note: Sea-Bird can fix mounting scheme issues; we do not send the sensor to the other manufacturer for this.

Typically, Sea-Bird can calibrate the instrument and perform minor repairs within 3 – 4 weeks, plus shipping time. However, this may vary, depending on current backlog. Before shipping an instrument to us, go to our Online RMA and Service Request Form page to obtain an RMA number, so that we know your instrument is on the way and can schedule appropriately. If time is critical, contact us before shipping to verify that we can meet your schedule.

Notes:

• The typical 3 – 4 week turnaround does not apply to recalibrating / repairing auxiliary sensors produced by other manufacturers. Recalibration / repair of these sensors must be performed by the manufacturers. 
• Sea-Bird opened a calibration and repair center in Germany in 2011, which can provide faster shipping for European customers.

Shipping: Sea-Bird carefully packs the CTD in foam for shipping. If you are shipping the CTD or conductivity sensor, carefully pack the instrument using the original crate and packing materials, or suitable substitutes.

Use: Cracks at the C-Duct end of the conductivity cell are most often caused by:

• Hitting the bottom, which can cause the T-C Duct to flex, resulting in cracking at the end of the cell.
• Removing the soaker tube from the T-C duct in a rough manner, which also causes the T-C Duct to flex. Pulling the soaker tube off at an angle can be especially damaging over time to the cell. Pull the soaker tube off straight down and gently.
• Improper disassembly of the T-C ducted temperature and conductivity sensors (SBE 25, 25plus, and 9plus) when removing them for shipment to Sea-Bird for calibration. See Shipping SBE 9plus, 25, and 25plus Temperature and Conductivity Sensors for the correct procedure.

Note: If a Tygon tube attached to the conductivity cell has dried out, yellowed, or become difficult to remove, slice (with a razor knife or blade) and peel the tube off of the conductivity cell rather than twisting or pulling the tube off.

The Thetis system uses on board batteries (BlueFin Robotics, 1.5kW) for power.

The stability of the SeaFET^TM Ocean pH sensor is expected to be 0.005 pH units on the timescale of weeks to months (Martz et al. 2010). At minimum, the SeaFET^TM should be calibrated yearly.  The body of data collected by the community of SeaFET^TM users generally suggests that the stability of the ISFET-based pH measurement offers an improvement by orders of magnitude when compared to glass electrode based pH sensors.

Wherever possible the SeaFET^TM should be deployed in association with a water sampling program in order to collect water for spectrophotometric pH determination or another external measurement technique.  Additionally, coincident measurement of multiple carbonate system parameters, allow the stability of the SeaFET^TM to be assessed.  These approaches have been carried out by a number of researchers over the past several years.

An ISUS should run at approximately 1Hz. Check the amount of storage space left on the internal memory; old data files should be downloaded or deleted from the disk on a regular basis. Additionally, the Messages.log files should be periodically removed. Download and/or delete these files to restore normal operation.

No, Sea-Bird does not perform low or narrow range calibrations on our CTDs. However, CTDs are used successfully in many freshwater environments.

Conductivity calibrations performed at Sea-Bird are valid in the range of 0 – 9 S/m (or 0 – 7 S/m, as specified for some instruments), and the calibration coefficients can be applied in freshwater for accurate calculations of conductivity.

Sea-Bird recognizes that calibration using natural seawater and IAPSO standards for ocean conductivity ranges may result in a small offset and possible slope errors near zero conductivity. For example, the estimated magnitude of offset error is < 0.002 S/m, and of slope error is < 0.002 S/m per 1 S/m change. This is an example of a conservative error estimate for initial accuracy of conductivity sensors used in freshwater, which can be challenging to calculate due to lack of a freshwater standard. However, sensor precision will be near the resolution (0.00004 S/m). Sea-Bird CTDs provide high precision and sensor stability, allowing an accurate measure of conductivity gradients (dC/dz) or water sample differences, regardless of ‘true’ conductivity values.  For these reasons, Sea-Bird CTDs that have been calibrated in seawater can be used successfully in many freshwater systems.

Lastly, note that the Practical Salinity Scale (PSS-78) is defined as valid for salinity ranges from 2 – 42 PSU. For additional references on freshwater algorithms used in the limnology field, see the following literature:

• Millero, Frank J. 2000. Equation of State for Freshwater. Aquatic Geochemistry, 6: 1 – 17.
• Pawlowicz, R. 2008. Calculating the Conductivity of Natural Waters. L&O: Methods 6, 489 – 501.  

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 may be 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.

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 for a few minutes. After scraping off the barnacles and marine growth, rinse the instrument well with fresh water.

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.

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.

For minimizing future growth on the housing, completely wrap the instrument housing with plastic tape. The bio-organisms still grow, but after recovery it is easy to peel off the tape, shells and mussels and all!

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).

Cells that have been contaminated with foreign material generally read low of the actual conductivity. Your zero (in air) conductivity reading is generally unaffected.

The conductivity error due to fouling will generally be proportional to the conductivity value. Conductivity is corrected not as an offset but as a ratio (multiplicative) error compared to a reference.

Salinity is a derivative measurement of temperature, conductivity, and pressure, and should be corrected by adjusting the component measurements. Generally speaking, an error in the conductivity measurement will correlate to a directly proportional error in the salinity measurement.

The pH sensor will be shipped dry but was pre-conditioned in seawater (generally from Pacific Ocean waters near Hawaii). While conditioning and evaluating the pH sensor, only expose it filtered, sterilized natural seawater. Do not use seawater CRMs (Certified Reference Material), synthetic seawater, deionized water, NaCl Solutions, or tap water.

Before pre-deployment testing, you will need to fill the plumbing around the pH sensor with natural seawater. The pH sensor needs time to acclimate to the ionic concentration of region specific waters. Once wet, the time to recondition the sensor so that it will report within its accuracy specification depends on several factors, including the ionic composition of the seawater used and the amount of time the pH sensor was stored dry. This time can range from several hours to up to three days.

When the seawater bridge between Counter Electrode and ISFET is broken for longer than 10 seconds, it will be necessary to re-condition the sensor. The sensor does not require recalibration after being re-conditioned.

To prepare the sensor for deployment, it is recommended that several days prior to deployment, the isolated battery is connected via the float interface and the pH sensor is stored in water that is similar to the deployment site. The sensor should be stored dry to avoid bio-fouling of the ISFET and the battery may be removed during storage. Seawater creates a half cell bridge between the Counter Electrode and ISFET, and power to that circuit is provided by the isolated 9V cell. Without seawater, the battery is unnecessary and may be disconnected.

The primary maintenance procedures that are outlined in the manual are for the bio-wiper (shutter) installation, the internal battery replacement and the bulkhead connector inspection. The shutter replacement is not always necessary; however, having the copper shutter and face plate parts available to swap out as needed is a good idea.

Otherwise, the optics face should be inspected for film/streaks. The wiper may not work effectively if the copper faceplate condition deteriorates and damages the rubber blade. Some environmental conditions can start to “pit” the face plate surface, shredding the wiper blade. Replacing the face plate should be done if the wiper blade is getting damaged by being dragged across it. Otherwise, cleaning the active optics sensor area usually only requires DI water and a lab wipe (i.e. Kimwipe). Superficial scrapes and scratches on the optics face are unlikely to significantly affect the measurement.

Working with the shutter, moving it for inspection and/or removing it to install a new one, requires the instrument to be powered ON… keeping power to the shutter motor and commanding the open/close positions via software command/control. When moving/removing the shutter, it should NOT BE MOVED MANUALLY! There are gears in the ECO shutter motor that can strip easily with the wrong manual motion, unpowered. The manual motion in the wrong direction and speed, can overcome some of the gear ratios at play when they are back-driven.

Terminal emulator programs (as opposed to ECO View) are the most direct platform for working with the ECO’s. However, their use depends on one’s preference for how to interface with the instruments.

SUNAs ordered with the 5mm path length coupler as a factory option will perform much better in low light transmission waters due to the shorter length the light needs to travel leading to less absorption. Equipping your SUNA with the factory bio-wiper option will also perform better and be less susceptible biofouling or buildup of other material that can reduce light transmission.

There are also some maintenance practices and device settings that can give SUNA a better probability of being able to capture enough light for a sample. Enable adaptive integration will trigger the SUNA to increase the lamp on time when light received by the spectrometer is low. It is also important to clean the windows as frequently as possible and monitor lens for scratches. Finally, you want your maximum light spectral counts at the peak wavelength (around 240nm) to be between 45,000 and 55,000 counts in pure or deionized water. This can be viewed in the “Spectra” tab in UCI when sampling or replaying data. If your peak spectrometer output is below 45,000 counts after cleaning the window, you may increase the integration period by 25 to 50 ms if needed (but not more; further changes require a factory recalibration). After adjusting the integration period, always perform a reference spectrum update per the instructions in the SUNA manual.

There are several considerations when determining whether the deck box and CTD underwater unit will be compatible.

(1) In most cases (with the exception being (2), below), instruments with the “-plus” designation are compatible with each other, but the “-plus” variants are not compatible with the variants that do not have “-plus” in their model number (i.e., an SBE9plus CTD must be used with an SBE11plus, and cannot be used with an older SBE11 deck unit).

(2) If you have an SBE9/11plus system with the serial uplink feature installed, then both the deck box and the CTD must have the same hardware configuration from the factory (either enabled or disabled). Otherwise, no telemetry will be received from the CTD by the deck box.

(3) For older instruments that do not have “-plus” in their model number, you need a matching pair of SBE9 and SBE11. There was no standard configuration, and different CTDs and deck units could have telemetry word/rate differences (4/24, 8/24, 12/24, etc.) and power differences (standard low power or high power). You would need to consult the original documentation that shipped with the instruments or send them to Sea-bird service for a repair evaluation to determine compatibility.