Frequently Asked Questions

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 SeaFET and SeapHOx systems are designed to sample at a fixed depth. If you want to run discreet samples at depth intervals, you will need to find a way to move the system to a specific depth before each sample interval and stop the descent / ascent for the entire pumping and sampling cycle to get a valid CTD / pH / Oxygen sample.

If you are able to communicate with the system through the serial I/O during profiling, you can send a sampling command to the sensor at each depth point and allow it to complete its sample cycle. Consult the manual for each model for the length of time required to complete each sample. Once the sensor provides a sample, you can then move it to the next depth point and repeat.

If you aren’t running real-time communications to the SeaFET/SeapHOx, you could also set it to autonomously sample at a time interval that gives you enough time to move the package to a new depth point between sample cycles. The challenges with this approach would be to know exactly when the sensor is sampling without any direct feedback from the 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.

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 nominal control voltage for the relay is 12 VDC. However, between 5 – 30 VDC will work, applied to pin 4 relative to the ground pin 2 on the Deep SUNA V2. The voltage can be applied to the relay any time after external power is applied to the instrument for a recommended 100 milliseconds. Unless the relay is already switched on, there should be a very quiet (but audible) click when the relay connects power to the SUNA V2 electronics, and the instrument should enter its boot up cycle.

The purpose of the relay is to keep external power applied to the SUNA with very low quiescent current draw, so the typical use case involves the SUNA constantly powered. If the application includes the ability to switch power to the SUNA effectively then the relay feature isn’t necessary. Regardless of how power cycling to the SUNA is controlled, there should be a power-off period of at least 30 seconds between power-on cycles to ensure that the capacitors that prevent a hard shutdown are allowed to completely discharge and allow the SUNA to boot up properly during the next power-on cycle.

Though the naming conventions may seem confusing at first glance, the following key should make your C-star configuration and purchasing process much easier!

The letters following the serial number designate the depth rating of the transmissometer and the wavelength of the LED.

Designator key:
P: Plastic housing rated to 600 meters
D: Deep (Aluminium) housing rated to 6000 meters
R: Red LED, wavelength 657nm
G: Green LED, wavelength 532nm
B: Blue LED, wavelength 470nm

Serial number examples:

CST-1236PR – Plastic unit, 600 meter rated, red 657nm

CST-1219DG – Deep unit, 6000 meter rated, green 532nm

When using the SBE45 thermosalinograph (TSG) with an SBE38 remote temperature sensor, you must use an interface box, as the SBE45 has no direct input for the SBE38. The SBE21 TSG, on the other hand, does have a direct input for the SBE38 remote temperature sensor. Check with your sales or support team contacts if you need help identifying your instruments.

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 SeaFET and SeapHOx systems are designed to sample at a fixed depth. If you want to run discreet samples at depth intervals, you will need to find a way to move the system to a specific depth before each sample interval and stop the descent / ascent for the entire pumping and sampling cycle to get a valid CTD / pH / Oxygen sample.

If you are able to communicate with the system through the serial I/O during profiling, you can send a sampling command to the sensor at each depth point and allow it to complete its sample cycle. Consult the manual for each model for the length of time required to complete each sample. Once the sensor provides a sample, you can then move it to the next depth point and repeat.

If you aren’t running real-time communications to the SeaFET/SeapHOx, you could also set it to autonomously sample at a time interval that gives you enough time to move the package to a new depth point between sample cycles. The challenges with this approach would be to know exactly when the sensor is sampling without any direct feedback from the instrument.

The nominal control voltage for the relay is 12 VDC. However, between 5 – 30 VDC will work, applied to pin 4 relative to the ground pin 2 on the Deep SUNA V2. The voltage can be applied to the relay any time after external power is applied to the instrument for a recommended 100 milliseconds. Unless the relay is already switched on, there should be a very quiet (but audible) click when the relay connects power to the SUNA V2 electronics, and the instrument should enter its boot up cycle.

The purpose of the relay is to keep external power applied to the SUNA with very low quiescent current draw, so the typical use case involves the SUNA constantly powered. If the application includes the ability to switch power to the SUNA effectively then the relay feature isn’t necessary. Regardless of how power cycling to the SUNA is controlled, there should be a power-off period of at least 30 seconds between power-on cycles to ensure that the capacitors that prevent a hard shutdown are allowed to completely discharge and allow the SUNA to boot up properly during the next power-on cycle.

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.

This depends on your own expertise and resources. We have extensive experience in integrating and supporting a wide range of auxiliary sensors, but not everything under the sun. We have a large list of commonly used sensors that we routinely offer for sale (see Third Party Sensor Configuration).

When you purchase any of these auxiliary sensors from Sea-Bird, we are able to apply this experience to integrating the sensors with the CTD. The integration includes installing the sensors (with appropriate mounting kits and cables) in a manner that puts each sensor in the best possible orientation for optimum performance. It also includes configuring the CTD system and software to accept the sensors’ inputs and properly display the data, and testing the entire system, typically in a chilled saltwater bath overnight, to confirm proper operation. Having done the integration, we also support the entire system in terms of follow-on service and end-user support with operational and data analysis questions *. There is significant added value in our integration service, and there is some extra cost for this, compared to doing it yourself. However, we do not base our business on selling services, and the prices charged for Third Party sensors carry minimal mark-ups that vary depending on the pricing we are offered by the manufacturers. In some cases we can sell at the manufacturer’s list price, and in others we have to add margin.

*Notes:
1. As described in our Warranty, auxiliary sensors manufactured by other companies are warranted only to the limit of the warranties provided by their original manufacturers (typically 1 year).
2. Read below for information on repairing / recalibrating auxiliary sensors manufactured by other companies:

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.

While the highest range does give you the most flexibility in using the CTD, it is at the expense of accuracy and resolution. It is advantageous to use the lowest range pressure sensor compatible with your intended maximum operating depth, because accuracy and resolution are proportional to the pressure sensor’s full scale range. For example, the SBE 9plus pressure sensor has initial accuracy of 0.015% of full scale, and resolution of 0.001% of full scale. Comparing a 2000 psia (1400 meter) and 6000 psia (4200 meter) pressure sensor:

• 1400 meter pressure sensor ? initial accuracy is 0.21 meters and resolution is 0.014 meters
• 4200 meter pressure sensor ? initial accuracy is 0.63 meters and resolution is 0.042 meters

Sea-Bird currently manufactures only 1 moored CTD that can accept auxiliary sensors, the SBE 16plus V2 SeaCAT (and its inductive modem version, the 16plus-IM V2). These instruments measure conductivity and temperature; a pressure sensor is optional. They have 6 differential A/D channels and 1 RS-232 channel available for auxiliary sensors, which can be plugged into the CTD end cap.

The SBE 37 MicroCAT family includes CTDs that are integrated with a dissolved oxygen sensor at the factory.

Notes:

• The SBE 19plus V2 SeaCAT, intended primarily for profiling applications, can also be used in moored mode. The 19plus V2 also has 6 differential A/D channels and 1 RS-232 channel available for auxiliary sensors. When in moored mode, it functions similar to a 16plus V2 with optional pressure sensor.
• The older versions of these products, the SBE 16 / 16plus / 16plus-IM and SBE 19 / 19plus, also accept auxiliary sensors.

See Product Selection Guide for a table summarizing the features of all our moored instruments.

Sea-Bird makes four main profiling CTD instruments, as well as several profiling CTD instruments for specialized applications.

In order of decreasing cost, the four main profiling CTD instruments are the SBE 911plus CTD, SBE 25plus Sealogger CTD, SBE 19plus SeaCAT Profiler CTD, and SBE 49 FastCAT CTD Sensor:

• The SBE 911plus is the world’s most accurate CTD. Used by most leading oceanographic institutions, the SBE 911plus is recognized for superior performance, reliability, and ease-of-use. Features include: modular conductivity and temperature sensors, Digiquartz pressure sensor, TC-Ducted Flow and pump-controlled time response, 24 Hz sampling, 8 A/D channels and power for auxiliary sensors, modem channel for real-time water sampler control without data interruption, and optional 9600 baud serial data uplink. The SBE 911plus system consists of: SBE 9plus Underwater Unit and SBE 11plus Deck Unit. The SBE 9plus can be used in self-contained mode when integrated with the optional SBE 17plus V2 Searam. The Searam provides battery power, internal 24 Hz data logging, and an auto-fire interface to an SBE 32 Carousel Water Sampler to trigger bottle closures at pre-programmed depths.
• The SBE 25plus Sealogger is the choice for research work from smaller vessel not equipped for real-time operation, or use by multi-discipline scientific groups requiring configuration flexibility and good accuracy and resolution on a smaller budget. The SBE 25plus is a battery-powered, internally-recording CTD featuring the same modular C & T sensors used on the SBE 9plus CTD, an integral strain gauge pressure sensor, 16 Hz sampling, 2 GB of memory, TC-Ducted Flow and pump-controlled time response, and 8 A/D channels plus 2 RS-232 channels and power for auxiliary sensors. Real-time data can be transmitted via RS-232 simultaneous with data recording. The SBE 25plus integrates easily with an SBE 32 Carousel Water Sampler or SBE 55 ECO Water Sampler for real-time or autonomous operation.
• The SBE 19plus V2 SeaCAT Profiler is known throughout the world for good performance, reliability, and ease-of-use. An economical, battery-powered, internally-recording mini-CTD, the SBE 19plus V2 is a good choice for basic hydrography, fisheries research, environmental monitoring, and sound velocity profiling. Features include 4 Hz sampling, 6 differential A/D channels plus 1 RS-232 channel and power for auxiliary sensors, 64 MB of memory, and pump-controlled conductivity time response. Real-time data can be transmitted via RS-232 simultaneous with data recording, The SBE 19plus V2 integrates easily with an SBE 32 Carousel Water Sampler or SBE 55 ECO Water Sampler for real-time or autonomous operation.
• The SBE 49 FastCAT is an integrated CTD sensor intended for towed vehicle, ROV, AUV, or other autonomous profiling applications. Real-time data ? in raw format or in engineering units ? is logged or telemetered by the vehicle to which it is mounted. The SBE 49’s pump-controlled, TC-ducted flow minimizes salinity spiking, and its 16 Hz sampling provides very high spatial resolution of oceanographic structures and gradients. The SBE 49 has no memory or internal batteries. The SBE 49 integrates easily with an SBE 32 Carousel Water Sampler or SBE 55 ECO Water Sampler for real-time operation.

The specialized profiling CTD instruments are the SBE 52-MP Moored Profiler, Glider Payload CTD, and SBE 41/41CP Argo CTD module:

• The SBE 52-MP Moored Profiler is a conductivity, temperature, pressure sensor, designed for moored profiling applications in which the instrument makes vertical profile measurements from a device that travels vertically beneath a buoy, or from a buoyant sub-surface sensor package that is winched up and down from a bottom-mounted platform. The 52-MP’s pump-controlled, TC-ducted flow minimizes salinity spiking. The 52-MP can optionally be configured with an SBE 43F dissolved oxygen sensor.
• The Glider Payload CTD measures conductivity, temperature, and pressure, and optionally, dissolved oxygen (with the modular SBE 43F DO sensor). It is a modular, low-power profiling instrument for autonomous gliders with the high accuracy necessary for research, inter-comparison with moored observatory sensors, updating circulation models, and leveraging data collection opportunities from operational vehicle missions. The pressure-proof module allows glider users to exchange CTDs (and DO sensors) in the field without opening the glider pressure hull.
• Argo floats are neutrally buoyant at depth, where they are carried by currents until periodically increasing their displacement and slowing rising to the surface. The SBE 41/41CP CTD Module obtains the latest CTD profile each time the Argo float surfaces. At the surface, the float transmits in-situ measurements and drift track data to the ARGOS satellite system. The SBE 41/41CP can be integrated with Sea-Bird’s Navis float or floats from other manufacturers. The SBE 41N CTD is integrated with Sea-Bird’s Navis Float with Integrated Biogeochemical Sensors and Navis BGCi + pH Float with Integrated Biogeochemical Sensors.

See Product Selection Guide for a table summarizing the features of our profiling CTDs.

Sea-Bird does not publish prices on the website. Please contact us for pricing:

• Email seabird@seabird.com,
• Phone +1 425-643-9866, or
• Fill out our Quote Request Form

IAPSO standard seawater is available in 250 ml vials. For more information and purchase inquiry, e-mail osil@oceanscientific.co.uk.

Most customers purchase spare conductivity and temperature sensors. These sensors are exposed to ocean conditions and therefore more likely to be broken than an internal sensor. It is also very easy to change them because they are independent sensors that plug into the CTD main housing.

Most customers do not purchase spare pressure sensors for the following reasons:

• The pressure sensor is inside the CTD main housing. It is very well protected against damage of any kind, and reliability of this sensor is extremely good.
• The sensor is expensive.
• It is difficult to change the sensor in the field.

On the product page for each instrument, there are two tabs that provide ordering information:

• Click the Configuration tab to see all the features and options available on our price list. The Configuration tab provides explanatory information, illustrations, and photographs describing each item.
• Click the Accessories tab to see cables, mount kits, and/or spare parts for the products.

Third Party Sensor Configuration lists instruments and integration options for sensors produced by other manufacturers (altimeters, fluorometers, transmissometers, etc.).

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.

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 SeaFET and SeapHOx systems are designed to sample at a fixed depth. If you want to run discreet samples at depth intervals, you will need to find a way to move the system to a specific depth before each sample interval and stop the descent / ascent for the entire pumping and sampling cycle to get a valid CTD / pH / Oxygen sample.

If you are able to communicate with the system through the serial I/O during profiling, you can send a sampling command to the sensor at each depth point and allow it to complete its sample cycle. Consult the manual for each model for the length of time required to complete each sample. Once the sensor provides a sample, you can then move it to the next depth point and repeat.

If you aren’t running real-time communications to the SeaFET/SeapHOx, you could also set it to autonomously sample at a time interval that gives you enough time to move the package to a new depth point between sample cycles. The challenges with this approach would be to know exactly when the sensor is sampling without any direct feedback from the instrument.

The nominal control voltage for the relay is 12 VDC. However, between 5 – 30 VDC will work, applied to pin 4 relative to the ground pin 2 on the Deep SUNA V2. The voltage can be applied to the relay any time after external power is applied to the instrument for a recommended 100 milliseconds. Unless the relay is already switched on, there should be a very quiet (but audible) click when the relay connects power to the SUNA V2 electronics, and the instrument should enter its boot up cycle.

The purpose of the relay is to keep external power applied to the SUNA with very low quiescent current draw, so the typical use case involves the SUNA constantly powered. If the application includes the ability to switch power to the SUNA effectively then the relay feature isn’t necessary. Regardless of how power cycling to the SUNA is controlled, there should be a power-off period of at least 30 seconds between power-on cycles to ensure that the capacitors that prevent a hard shutdown are allowed to completely discharge and allow the SUNA to boot up properly during the next power-on cycle.

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.