- Conductivity, Temperature, and Pressure, at 16 Hz (16 samples/second).
- Pump-controlled, T-C ducted flow to minimize salinity spiking.
- RS-232 serial interface, no memory or batteries -- intended for use on vehicles that can supply power and acquire data.
- Unique flow path, pumping regimen, and (optional) expendable anti-foulant devices, for maximum bio-fouling protection.
- Depths to 350 meters (plastic housing) or 7000 meters (titanium housing).
- Five-year limited warranty.
The SBE 49 FastCAT is an integrated CTD sensor intended for use as a modular component in towed vehicles, ROVs, AUVs, or other autonomous platforms that can supply DC power and acquire serial data. FastCAT’s pump-controlled / TC-ducted flow feature minimizes salinity spiking, and its 16 Hz sampling provides very high spatial resolution of oceanographic structures and gradients.
FastCAT’s temperature thermistor and conductivity cell are the same as used in our premium 911plus CTD system. The strain-gauge pressure sensor is offered in eight full scale ranges from 20 to 7000 dbars. Sophisticated interface circuitry provides very high resolution and accuracy.
FastCAT is an easy-to-use, light, and compact instrument ruggedly made of titanium and other low-maintenance (plastic) materials; it is well suited to even the smallest vehicle. There are straightforward commands for continuous (full rate or averaged) or single sample acquisition. EEPROM-stored calibration coefficients permit data output in ASCII engineering units (degrees C, Siemens/m, decibars, Salinity [PSU], and sound velocity [m/sec]), or the user can select raw data output if desired.
FastCAT must be externally powered, and its RS-232C data logged or telemetered by the vehicle to which it is mounted. As FastCAT does not support auxiliary sensors, where such sensors are required the user's vehicle must be equipped to acquire their signals independently.
FastCAT has two sampling modes:
- Autonomous sampling — FastCAT runs continuously, sampling at 16 scans per second (16 Hz). It can be set to average up to 255 samples, transmitting only the averaged data. Programmable real-time processing (aligning, filtering, and correcting for conductivity cell thermal mass effects) provides high quality data for applications where post-processing is not feasible. FastCAT can be programmed to begin autonomous sampling when power is applied or on command.
- Polled sampling — On command, FastCAT takes one sample and transmits the data.
A standard FastCAT is supplied with:
- Titanium housing for depths to 7000 meters
- Strain-gauge pressure sensor
- Internal pump and T-C Duct
- XSG 4-pin I/O bulkhead connector
FastCAT options include:
- Plastic housing for depths to 350 meters
- MCBH Micro connector in lieu of XSG
- Expendable anti-foulant devices
FastCAT is supplied with a powerful Win 2000/XP software package, Seasoft©V2. Seasoft's modular programs include:
|Conductivity (S/m)||Temperature (°C)||Pressure|
|Measurement Range||0 - 9||-5 to +35||0 to 20 / 100 / 350 /
600 / 1000 / 2000 /
3500 / 7000 meters
|Initial Accuracy||± 0.0003||± 0.002||± 0.1% of
full scale range
|Typical Stability||0.0003 per month||0.0002 per month||0.05% of
full scale range
|Resolution||0.00005 (oceanic waters;
resolves 0.4 ppm in salinity)
0.00007 (high salinity waters;
0.00001 (fresh waters;
full scale range
|Calibration||0 to 9 S/m;
physical calibration over
2.6 to 6 S/m,
plus zero conductivity (air)
|+1 to +32||Ambient to
full scale range
in 5 steps
Input power: 0.75 Amps at 9-24 VDC
Turn-on transient: 750 mA
Sampling and transmitting (includes pump):
350 mA at 9V
285 mA at 12V
180 mA at 19V
Housing Material and Depth Rating:
Standard: 3AL/2.5V Titanium, 7000 meters (22,900 feet)
Optional: Plastic, 350 meters (1150 feet)
Standard titanium housing: In air 2.7 kg (6 lbs), In water 1.4 kg (3 lbs)
Optional plastic housing: In air 1.8 kg (4 lbs), In water 0.5 kg (1 lb)
Do I need to clean the exterior of my instrument before shipping it to Sea-Bird for calibration?
Remove as much biological material and/or anti-foul coatings as possible before shipping. Sea-Bird cannot place an instrument with a large amount of biological material or anti-foul coating on the housing in our calibration bath; if we need to clean the exterior before calibration, we will charge you for this service.
- To remove barnacles, 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.
- To remove anti-foul paint, use a Heavy Duty Scotch-Brite pad (http://www.3m.com/us/home_leisure/scotchbrite/products/scrubbing_scouring.html) or similar scrubbing device.
Can I brush-clean and replatinize the conductivity cell myself? How often should this be done?
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.
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?
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.
How can I tell if the conductivity cell on my CTD is broken?
Conductivity cells are made of glass, which is breakable.
- If a cell is cracked, it typically causes a salinity shift or erratic data.
- However, if the crack occurs at the end of the cell, the sensor will continue to function normally until water penetrates the epoxy jacket. Post-cruise calibration results will reveal whether or not water has penetrated the epoxy jacket.
Inspect the cell thoroughly and make sure that it isn’t cracked or abused in any way.
- (SBE 9plus, 25, or 25plus) If the readings are good at the surface but erratic at depth, it is likely that the problem is in the cable or the connector, not the conductivity cell. Check the connections, making sure that you burp the connectors when you plug them in (see Application Note 57: Connector Care and Cable Installation). Check the cable itself (swap with a spare cable, if available).
- If the readings are incorrect at the surface but good after a few meters, it is likely that the problem is flow-related. Verify that the pump is working properly. Check the air bleed valve (the white plastic piece in the Y-fitting, which is installed on vertically deployed CTDs) to see if it is clogged; clean out the small hole with a piece of fine wire supplied with your CTD.
- If the readings are incorrect for the entire cast, there may be an incorrect calibration coefficient or the cell may be cracked.
- Check the conductivity calibration coefficients in the configuration (.con or .xmlcon) file.
- Do a frequency check on the conductivity cell. Disconnect the plumbing on the cell. Rinse the cell with distilled or de-ionized water and blow it dry (use your mouth and not compressed air, as there tends to be oil in the air lines on ships). With the cell completely dry, check the frequency reading. It should read within a few tenths of a Hz of the 0 reading on your Calibration Sheet. If it does not, something is wrong with the cell and it needs to be repaired.
Should I collect water samples (close bottles) on the downcast or the upcast?
Most of our CTD manuals refer to using downcast CTD data to characterize the profile. For typical configurations, downcast CTD data is preferable, because the CTD is oriented so that the intake is seeing new water before the rest of the package causes any mixing or has an effect on water temperature.
However, if you take water samples on the downcast, the pressure on an already closed bottle increases as you continue through the downcast; if there is a small leak, outside water is forced into the bottle, contaminating the sample with deeper water. Conversely, if you take water samples on the upcast, the pressure decreases on an already closed bottle as you bring the package up; any leaking results in water exiting the bottle, leaving the integrity of the sample intact. Therefore, standard practice is to monitor real-time downcast data to determine where to take water samples (locations with well-mixed water and/or with peaks in the parameters of interest), and then take water samples on upcast.
What are the recommended practices for connectors - mating and unmating, cleaning corrosion, and replacing?
Mating and Unmating Connectors:
It is important to prepare and mate connectors correctly, both in terms of the costs to repair them and to preserve data quality. Leaking connectors cause noisy data and even potential system shutdowns. Application Note 57: Connector Care and Cable Installation describes the proper care and installation of connectors for Sea-Bird instruments. The Application Note covers connector cleaning and cable or dummy plug installation, locking sleeve installation, and cold weather tips.
Checking for Leakage and Cleaning Corrosion on Connectors:
If there has been leakage, it will show up as green-colored corrosion product. Performing the following steps can usually reverse the effect of the leak:
- Thoroughly clean the connector with water, followed by alcohol.
- Give the connector surfaces a light coating of silicon grease.
Re-mate the connectors properly — see Application Note 57: Connector Care and Cable Installation and 9-minute video covering O-ring, connector, and cable maintenance.
- The main concern when replacing a bulkhead connector is that the o-rings on the connector and end cap must be prepared and installed correctly; if they are not, the instrument will flood. See the question below for general procedure on handling o-rings.
- Use a thread-locking compound on the connector threads to prevent the new connector from loosening, which could also lead to flooding.
- If the cell guard must be removed to open the instrument, take extra care not to break the glass conductivity cell.
What is an Anti-Foulant Device? Does it affect the conductivity cell calibration? How often should I replace it? Does it require special handling?
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), 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.
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.
- 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.
What are the recommended practices for storing sensors at low temperatures, and deploying at low temperatures or in frazil or pancake ice?
Large numbers of Sea-Bird conductivity instruments have been used in Arctic and Antarctic programs.
Special accommodation to keep temperature, conductivity, oxygen, and optical sensors at or above 0 C is advised. Often, the CTD is brought inside protective doors between casts to achieve this.
When freezing is possible, we recommend that the conductivity sensor be stored dry. Remove larger droplets of water by blowing through the cell. Do not use compressed air, which typically contains oil vapor. Attach a length of Tygon tubing to each end of the conductivity cell to close the cell ends. See Application Note 2D: Instructions for Care and Cleaning of Conductivity Cells for details.
There are several considerations to weigh when contemplating deployments at low temperatures in general, and in frazil or pancake ice:
- Ensure that the instrument is at or above water temperature before it is deployed. If the cell gets colder than 0 to -2 ºC while on deck, when it enters the water a layer of ice forms inside the cell as the cell warms to ocean temperature. If ice forms inside the conductivity cell, measurements will be low of correct until the ice layer melts and disappears. Thin layers of ice will not hurt the conductivity cell, but repeated ice formation on the electrodes will degrade the conductivity calibration (at levels of 0.001 to 0.020 psu) and thicker layers of ice can lead to glass fracture and permanent damage of the cell.
- For accurate measurements, keep ice out of the sensing region of the conductivity cell. The conductivity measurement involves determining the electrical resistance of the water inside the sensor. Ice is essentially a non-conductor. To the extent that ice displaces the water, the conductivity will register (very) misleadingly low. Some type of screening is necessary to keep ice out of the cell. This is relatively easy to arrange for the Sea-Bird conductivity cell, which is an electrode-type cell, because its sensing region is totally inside a long tube; plastic mesh could be positioned at each end and would have zero effect on accuracy and stability.
The above considerations apply to all known conductivity sensor types, whether electrode or inductive types.
If deploying at low temperatures but no surface frazil or pancake ice is present, rinse the conductivity cell in one of the following salty solutions (salty water depresses the freezing point) to prevent freezing during deployment. But this does not mean you can store the cell in one of these solutions outside . . . it will freeze.
- Solution of 1% Triton in sterile seawater (use 0.5-micron filtered seawater or boiled seawater), or
- Brine solution (distilled seawater or homemade salt solution that is higher than 35 psu in salinity).
Note that there is still a risk of forming ice inside the conductivity cell if deploying through frazil or pancake ice on the surface, if the freezing point of the salt water is the same as the water temperature. Therefore, we recommend that you deploy the conductivity cell in a dry state for these deployments.
Commercially available alcohol or glycol antifreezes contain trace amounts of oils that will coat the conductivity cell and the electrodes, causing a calibration shift, and consequently result in errors in the data. Do not use alcohol or glycol in the conductivity cell.
In general, neither the accuracy of the temperature measurement nor the survival of the temperature sensor will be affected by ice.
For the SBE 43 and SBE 63 Dissolved Oxygen sensor, avoid prolonged exposure to freezing temperature, including during shipment. Do not store the with water (fresh or seawater), Triton solution, alcohol, or glycol in the plenum. The best precaution is to keep the sensor indoors or in some shelter out of the cold weather.
Is it necessary to put my instrument in water to test it? Will I destroy the conductivity cell if I test it in air?
It is not necessary to put the instrument in water to test it. It will not hurt the conductivity cell to be in air.
If there is a pump on the instrument, it should not be run for extended periods in air.
- Profiling instruments (SBE 9plus, 19, 19plus, 19plus V2, 25, 25plus, 49) and some moored instruments (all pumped MicroCATs with integral dissolved oxygen (DO), and pumped MicroCATs without DO with firmware 3.0 and later) do not turn on the pump unless the conductivity frequency is above a specified minimum value (minimum value is hard-wired in 9plus, user-programmable in other instruments). This prevents the pump from turning on in air. See the instrument manual for details.
- If your instrument does not check for conductivity frequency before turning on the pump:
- For moored SeaCATs (16, 16plus, 16plus-IM, 16plus V2, 16plus-IM V2): Disconnect the pump cable for the test.
- For older pumped MicroCATs: orient the MicroCAT to provide an upright U-shape for the plumbing. Then fill the inside of the pump head with water via the pump exhaust tubing; this will provide enough lubrication to prevent pump damage during brief testing.
Can I use a pressure sensor above its rated pressure?
Digiquartz pressure sensors are used in the SBE 9plus, 53, and 54. The SBE 16plus V2, 16plus-IM V2, 19plus V2, and 26plus can be equipped with either a Druck pressure sensor or a Digiquartz pressure sensor. All other instruments that include pressure use a Druck pressure sensor.
- 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.
- The overpressure rating for a Druck (as stated by 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.
What is the maximum cable length for real-time RS-232 data?
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, allowable combinations of cable length and baud rate for Sea-Bird instruments communicating with RS-232 are shown below:
|Maximum Cable Length (meters)||Maximum Baud Rate*|
*Note: Consult instrument manual for baud rates supported for your instrument.
How should I handle my CTD to avoid cracking the conductivity cell?
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.
What are the typical data processing steps recommended for each instrument?
Section 3: Typical Data Processing Sequences in the SBE Data Processing manual provides typical data processing sequences for our profiling CTDs, moored CTDs, and thermosalinographs. Typical values for aligning, filtering, etc. are provided in the sections detailing each module of the software. This information is also documented in the software's Help file. To download the software and/or manual, go to SBE Data Processing.
Which Sea-Bird profiling CTD is best for my application?
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, Navis float with Biogeochemical Sensors, or floats from other manufacturers. The SBE 41N CTD is integrated with Sea-Bird's Navis Float with Integrated Biogeochemical Sensors.
See Product Selection Guide for a table summarizing the features of our profiling CTDs.
How should I pick the pressure sensor range for my CTD? Would the highest range give me the most flexibility in using the CTD?
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
How often do I need to have my instrument and/or auxiliary sensors recalibrated? Can I recalibrate them myself?
- Profiling CTD — recalibrate once/year, but possibly less often if used only occasionally. We recommend that you return the CTD to Sea-Bird for recalibration. (In principle, it is possible for calibration to be performed elsewhere, if the calibration facility has the appropriate equipment andtraining. However, the necessary equipment is quite expensive to buy and maintain.) In between laboratory calibrations, take field salinity samples to document conductivity cell drift.
- Thermosalinograph — recalibrate at least once/year, but possibly more often depending on the degree of bio-fouling in the water.
- DO sensor —
— SBE 43 — recalibrate once/year, but possibly less often if used only occasionally and stored correctly (see Application Note 64), and also depending on the amount of fouling and your ability to do some simple validations (see Application Note 64-2)
— SBE 63 — recalibrate once/year, but possibly less often if used only occasionally and stored correctly and also depending on the amount of fouling and your ability to do some simple validations (see SBE 63 manual)
- pH sensor — recalibrate every 6 months
- Transmissometer — usually do not require recalibration for several years. Recalibration at the manufacturer’s factory is the most practical method.
We often have requests from customers to have some way to know if the CTD is out of calibration. The general character of sensor drift in Sea-Bird conductivity, temperature, and pressure measurements is well known and predictable. However, it is very difficult to know precisely how far a CTD calibration has drifted over time unless you have access to a very sophisticated calibration lab. In our experience, an annual calibration schedule will usually maintain the CTD accuracy to within 0.01 psu in Salinity.
Conductivity drifts as a change in slope as a result of accumulated fouling that coats the inside of the conductivity cell, reducing the area of the cell and causing an under-reporting of conductivity. Fouling consists of both biological growth and accumulated oils and inorganic material (sediment). Approximately 95% of fouling occurs as the cell passes through oil and other contaminants floating on the sea surface. Most conductivity fouling is episodic, as opposed to gradual and steady drift. Most fouling events are small and mostly transitory, but they have a cumulative affect over time. A severe fouling event, such as deployment through an oil spill, could have a dramatic but only partially recoverable effect, causing an immediate jump shift toward lower salinity. As fouling becomes more severe, the fit becomes increasingly non-linear and offsets and slopes no longer produce adequate correction, and return to Sea-Bird for factory calibration is required. Frequently checking conductivity drift is likely to be the most productive data assurance measure you can take. Comparing conductivity from profile to profile (as a routine check) will allow you to detect sudden changes that may indicate a fouling event and the need for cleaning and/or re-calibration.
Temperature generally drifts slowly, at a steady rate and predictably as a simple offset at the rate of about 1-2 millidegrees per year. This is approximately equal to 1-2 parts per million in Salinity error (very small).
Pressure sensor drift is also an offset, and annual comparisons to an accurate barometer to determine offset will generally keep the sensor within specification for several years, particularly as the sensors age over time.
|49||.||1 – 350 m (plastic)||1 – 20 m strain gauge||1 – XSG||0 – RS-232|
|2 – 7000 m (titanium)||2 – 100 m strain gauge||2 – MCBH|
|3 – 10,500 m (titanium)||3 – 350 m strain gauge|
|4 – 600 m strain gauge|
|5 – 1000 m strain gauge|
|6 – 2000 m strain gauge|
|7 – 3500 m strain gauge|
|8 – 7000 m strain gauge|
|9 – 10,500 m strain gauge|
Example: 49.2820 is an SBE 49 with 7000 m housing, 7000 m strain gauge pressure sensor, MCBH connector, and RS-232 communications. See table below for description of each selection:
FastCAT CTD SENSOR - 16 Hz sampling rate, includes RS-232 interface, 2.4 m data/power interface cable, Seasoft software, and complete documentation.
SBE 49 is a profiling CTD, with no memory or internal batteries, often integrated with towed vehicle, ROV, AUV, or other autonomous profiling applications.
SBE 49 can also be used with Sea-Bird's real-time data acquisition systems:
|SBE 49 Housing (depth) Selections — MUST SELECT ONE|
|49.1xx0||350 m plastic housing|
|49.2xx0||7000 m titanium housing|
|49.3xx0||10,500 m titanium housing|
|SBE 49 Pressure Sensor Range (depth) Selections — MUST SELECT ONE|
|49.x1x0||20 m strain gauge pressure sensor||Pressure sensor is installed in end cap, & is not field replaceable / swappable. While highest pressure rating gives you most flexibility in using SBE 49, it is at expense of accuracy & resolution. It is advantageous to use lowest range pressure sensor compatible with your intended maximum operating depth, because accuracy & resolution are proportional to pressure sensor's full scale range. For example, comparing 2000 & 7000 m sensors:
|49.x2x0||100 m strain gauge pressure sensor|
|49.x3x0||350 m strain gauge pressure sensor|
|49.x4x0||600 m strain gauge pressure sensor|
|49.x5x0||1000 m strain gauge pressure sensor|
|49.x6x0||2000 m strain gauge pressure sensor|
|49.x7x0||3500 m strain gauge pressure sensor|
|49.x8x0||7000 m strain gauge pressure sensor|
|49.x9x0||10,500 m strain gauge pressure sensor|
|SBE 49 Connector Selections — MUST SELECT ONE|
|49.xx10||XSG connector on instrument & data I/O cable (801385)||
Wet-pluggable connectors may be mated in wet conditions. Their pins do not need to be dried before mating. By design, water on connector pins is forced out as 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 & require less force to mate, making them easier to mate reliably under dark or cold conditions, compared to XSG/AG connectors. Like XSG/AG connectors, wet-pluggables need proper lubrication & require care during use to avoid trapping water in sockets.
|49.xx20||Wet-pluggable (MCBH) connector on instrument & data I/O cable (801206)|
|SBE 49 Anti-Foulant Option|
|49-3||Anti-foulant devices installed (for moored applications)||
|SBE 49 Spares & Accessories|
|801385||Data/Power interface cable, RMG-4FS to DB-9S & red/black twisted wire leads, 2.4 m (DN 32277)||Included with standard shipment if 49.xx10 (XSG connector) selected; this is spare.|
|801206||Data/Power interface cable, Wet-Pluggable, MCIL-4FS to DB-9S & red/black twisted wire leads, 2.4 m (DN 32366)||Included with standard shipment if 49.xx20 (MCBH connector) selected; this is spare.|
|20200||USB to Serial Port Adapter, FTDI UC232R-10 (connects computers with USB ports to RS-232 instruments)||Many newer PCs & laptop computers have USB port(s) instead of RS-232 serial port(s). USB serial adapter plugs into USB port, & allows a serial device to be connected through adapter. Multi-port adapters are available from other companies; see Application Note 68.|
|17031||4-pin pigtail cable, RMG-4FS with lock sleeve, 2.4 m (DN 30581)||These cables are for interfacing with your system's controller.|
|171368||4-pin pigtail cable, Wet-Pluggable, MCIL-4FS with MCDSL-F, 2.4 m (DN 32363)|
|801542||AF24173 Anti-Foulant Device pair (spare, bagged, labeled for shipping)||Anti-foulant devices fit into anti-foulant device cups at each end of conductivity cell. Anti-foulant devices included with standard shipment; these are spares.
Useful life varies, depending on several factors. We recommend that customers consider more frequent replacement when high biological activity & strong current flow (greater dilution of anti-foulant concentration) are present. Moored instruments in high growth & 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 strongest determining factor in specific deployment environments.
- 801385 To computer COM port with power leads (from XSG connector), 2.4 m, DN 32277
- 801376 To computer COM port with 9V connector (from XSG connector), 2.4 m, DN 32604
- 17031 pigtail (from XSG connector), 2.4 m, DN 30581
- 801206 To computer COM port with power leads (from Wet-pluggable connector), 2.4 m, DN 32366
- 801263 To computer COM port with 9V connector (from Wet-pluggable connector), 2.4 m, DN 32490
- 171368 pigtail (from Wet-pluggable connector), 2.4 m, DN 32363
- 172259 To SBE 55 (RMG/AG connectors), 1.2 m, DN 33191
- 172260 To SBE 55 (Wet-pluggable connectors), 1.2 m, DN 33192
- 17088 To Power & Data Interface Module (PDIM), RMG connectors, 1.1 m, DN 30567
- 171792 To Power & Data Interface Module (PDIM), Wet-pluggable connectors, 1.1 m, DN 32810
- 60037 Hardware & O-ring kit for SBE 49 with titanium housing (document 67111)
- 60052 Hardware & O-ring kit for SBE 49 with plastic housing (document 67205)
- 801542 AF24173 Anti-Foulant Device (pair, bagged, labeled for shipping)
- 50312 Anti-foulant device in-line cap/cup assembly for SBE 49 or 52-MP (document 67123)
- 233186 High-head pressure port plug for muddy/biologically productive environments (Application Note 84)
Compare Profiling CTDs (Conductivity, Temperature, and Pressure)
|SBE||Sampling Rate||Channels for Auxiliary Sensors||Memory||Power||Real-Time Data||Comments|
|SBE 911plus CTD (9plus CTD & 11plus Deck Unit)||24 Hz||
|16 Mb with optional SBE 17plus V2||
(with optional SBE 17plus V2)
|World's most accurate, high resolution CTD, premium sensors, multi-parameter support, water sampler control.|
|SBE 25plus Sealogger CTD||16 Hz||8 A/D;
May require SBE 36 CTD Deck Unit & PDIM
|High-resolution logging CTD with multi-parameter support. Water sampler control with SBE 33 Carousel Deck Unit.|
|SBE 25 Sealogger CTD
||8 Hz||7 A/D||8 Mb||
May require SBE 36 CTD Deck Unit & PDIM
|Replaced by SBE 25plus in 2012. Water sampler control with SBE 33 Carousel Deck Unit.|
|SBE 19plus V2 SeaCAT Profiler CTD||4 Hz||6 A/D;
May require SBE 36 CTD Deck Unit & PDIM
|Personal CTD, small, self-contained, adequate resolution. Water sampler control with SBE 33 Carousel Deck Unit.|
|SBE 19plus SeaCAT Profiler CTD
||4 Hz||4 A/D; optional PAR||8 Mb||
May require SBE 36 CTD Deck Unit & PDIM
|Replaced by SBE 19plus V2 in 2008. Water sampler control with SBE 33 Carousel Deck Unit.|
|SBE 19 SeaCAT Profiler CTD
||2 Hz||4 A/D||1 - 8 Mb||
May require SBE 36 CTD Deck Unit & PDIM
|Replaced by SBE 19plus in 2001. Water sampler control with SBE 33 Carousel Deck Unit.|
|SBE 49 FastCAT CTD Sensor||16 Hz||
May require SBE 36 CTD Deck Unit & PDIM
|For towed vehicle, ROV, AUV, or other autonomous profiling applications. Water sampler control with SBE 33 Carousel Deck Unit.|
|SBE 52-MP Moored Profiler CTD & (optional) Dissolved Oxygen Sensor||1 Hz||1 frequency channel for dissolved oxygen sensor||28,000 samples||Intended for moored profiling applications on device that is winched up and down from a buoy or bottom-mounted platform.|
|SBE 41/41CP CTD Module for Autonomous Profiling Floats (Argo)||OEM CTD for sub-surface oceanographic float that surfaces at regular intervals, transmits new drift position and in situ measurements to ARGOS satellite system. CTD obtains latest temperature and salinity profile for transmission on each ascent. Also available is a Navis Autonomous Profiling Float, Navis BGC Autonomous Profiling Float with Biogeochemical Sensors, and Navis BGCi Autonomous Profiling Float with Integrated Biogeochemical Sensors|
|Glider Payload CTD (GPCTD) and Slocum Glider Payload CTD||OEM CTD for autonomous gliders. Generic Glider Payload CTD (GPCTD) is modular, low-power profiling instrument that measures C, T, P, and (optional) Dissolved Oxygen. Slocum Glider Payload CTD provides retrofit/replacement for CTDs on Slocum gliders. Designs share many features, but there are differences in packaging, sampling abilities, power consumption, and installation (see individual data sheets).|
1. See Application Note 82: Guide to Specifying a CTD.
2. products are no longer in production. Follow the links above to the product page to retrieve manuals and application notes for these older products.