SBE 37-SMP MicroCAT C-T (P) Recorder
The SBE 37-SMP pumped MicroCAT is a high-accuracy conductivity and temperature (pressure optional) recorder with Serial interface (RS-232 or RS-485), internal batteries, Memory, and integral Pump. The MicroCAT is designed for moorings or other long-duration, fixed-site deployments.
Data is recorded in memory and can be output in real-time. Measured data and derived variables (salinity, sound velocity) are output in engineering units.
Memory capacity exceeds 530,000 samples. Battery endurance varies, depending on sampling scheme. Sampling every 2-1/2 minutes, the MicroCAT can be deployed for 2 years (425,000 samples).
FEATURES
- Moored Conductivity, Temperature, and Pressure (optional), at user-programmable 6-sec to 6-hour intervals.
- Integral pump.
- RS-232 or RS-485 interface.
- Internal memory and battery pack (can be powered externally).
- Expendable anti-foulant devices, unique flow path, and pumping regimen for bio-fouling protection.
- 350 m plastic or 7000 m titanium housing.
- Seasoft©V2 Windows software package (setup, data upload, and data processing).
- Field-proven MicroCAT family, with more than 10,000 instruments deployed.
- Five-year limited warranty
COMPONENTS
- Unique internal-field conductivity cell permits use of expendable anti-foulant devices, for long-term bio-fouling protection.
- Aged and pressure-protected thermistor has a long history of exceptional accuracy and stability.
- Optional strain-gauge pressure sensor with temperature compensation is available in eight ranges (maximum depth 7000 m).
- Pump runs for 1 second for each sample, providing improved conductivity response and bio-fouling protection.
OPTIONS
- Plastic (350 m) or titanium (7000 m) housing.
- RS-232 or RS-485 interface.
- No pressure, or strain-gauge pressure sensor in one of 8 ranges.
- XSG or wet-pluggable MCBH connector.
- Wire mounting clamp and guide or brackets for mounting to a flat surface.
ADDITIONAL INFORMATION
Compare features of the numerous SBE 37 MicroCAT models.
Measurement Range
Conductivity | 0 to 7 S/m (0 to 70 mS/cm) |
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Temperature | -5 to +45 °C |
Optional Pressure | 0 to 20 / 100 / 350 / 600 / 1000 / 2000/ 3500 / 7000 m (meters of deployment depth capability) |
Initial Accuracy
Conductivity | ± 0.0003 S/m (0.003 mS/cm) |
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Temperature | ± 0.002 °C (-5 to +35 °C); ± 0.01 (+35 to +45 °C) |
Optional Pressure | ± 0.1% of full scale range |
Typical Stability
Conductivity | 0.0003 S/m (0.003 mS/cm) per month |
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Temperature | 0.0002 °C per month |
Optional Pressure | 0.05% of full scale range per year |
Resolution
Conductivity | 0.00001 S/m (0.0001 mS/cm) |
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Temperature | 0.0001 °C |
Optional Pressure | 0.002% of full scale range |
Miscellaneous
Acquisition Time | 1.9 - 2.9 sec/sample (see manual) |
---|---|
Power Supply & Consumption | 10.6 Amp-hour (nominal) battery pack (derated for calculations); 425,000 samples CTD (see manual) |
Optional External Power | 0.25 Amps at 9-24 VDC |
Memory Capacity | 530,000 samples CTD |
Housing, Depth Rating, & Weight (without pressure) | Plastic, 350 m, 3.4 kg in air, 1.6 kg in water. Titanium, 7000 m, 3.7 kg in air, 2.2 kg in water. |
RS-232 Interface |
SDI-12 / RS-232 Interface |
For older SBE 37-SMP product manuals, organized by instrument firmware version, click here.



Please Note:
Seasoft V2 is a single install bundle with the following stand-alone programs (table below) for use with most of our products (especially SBE numbers products like SBE 37 MicroCATs). While most of our instruments uses one or more of these programs, not all instruments use all programs (eg. Plot39 which is only used by SBE 39 family) .
Each instrument has the list of applicable programs under the product page's software tab. Each software includes Help files with detailed descriptions for use.

What are the major steps involved in deploying a moored instrument?
Application Note 83: Deployment of Moored Instruments contains a checklist, which is intended as a guideline to assist you in developing a checklist specific to your operation and instrument setup.
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.
Replacing Connectors:
- 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, 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.
What are the recommended practices for storing sensors at low temperatures, and deploying at low temperatures or in frazil or pancake ice?
General
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.
Conductivity Cell
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.
Temperature Sensor
In general, neither the accuracy of the temperature measurement nor the survival of the temperature sensor will be affected by ice.
Oxygen Sensor
For the SBE 43 and SBE 63 Dissolved Oxygen sensor, avoid prolonged exposure to freezing temperature, including during shipment. Do not store 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.
Does it matter if I deploy my moored instrument, which includes a conductivity sensor, in a horizontal or vertical position?
Yes, vertical is usually preferable. In the presence of consistent currents and suspended sediment, we have seen instances where a horizontal conductivity cell is scoured by the abrasive effect of the flow. When scouring is particularly intense, the electrodes can be stripped of their electroplated platinum-black coating, driving the calibration toward fresher readings. Sedimentation (silting) in the cell also drives the readings fresh of correct.
Mounting the instrument vertically avoids abrasive flow and sediment build-up while allowing wave motions and Bernoulli pressures to flush the cell.
Note that some moored sensors (SBE 37-SIP, 37-SIP-IDO, 37-SMP, 37-SMP-IDO, 37-SMP-ODO, 37-IMP, 37-IMP-IDO, 37-IMP-ODO, HydroCAT, HydroCAT-EP) have a recommended orientation because of their u-shaped plumbing configuration. Refer to the instrument manual for details.
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, GPCTD) and some moored instruments (all pumped MicroCATs with integral dissolved oxygen (DO), pumped MicroCATs without DO with firmware 3.0 and later, and all HydroCATs and HydroCAT-EPs) 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.
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.
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 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, many 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.
How do instruments handle external power if internal batteries are installed?
Most Sea-Bird instruments that are designed to be powered internally or externally incorporate diode or'd circuitry, allowing only the voltage that has the greater potential to power the instrument. You can power the instrument externally without running down the internal batteries. This allows you to lab test using external power that has higher voltage than the internal batteries, and then deploy using internal power, knowing that the internal batteries are fresh.
For the SBE 25plus, if external power of 14 volts or higher is applied, the 25plus runs off of the external power, even if the main battery voltage is higher.
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
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* |
---|---|
1600 | 600 |
800 | 1200 |
400 | 2400 |
200 | 4800 |
100 | 9600 |
50 | 19,200 |
25 | 38,400 |
16 | 57,600 |
8 | 115,200 |
*Note: Consult instrument manual for baud rates supported for your instrument.
How often do I need to have my instrument and/or auxiliary sensors recalibrated? Can I recalibrate them myself?
General recommendations:
- 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.
- Moored CTD — recalibrate at least once/year, but possibly more often depending on the degree of bio-fouling in the water.
- 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 —
— SBE 18 pH sensor or SBE 27 pH/ORP sensor — recalibrate at the start of every cruise, and then at least once/month, depending on use and storage
— Satlantic SeaFET pH sensor — recalibrate at least once/year. See FAQ tab on Satlantic's SeaFET page for details (How often does the SeaFET need to be calibrated?). - Transmissometer — usually do not require recalibration for several years. Recalibration at the manufacturer’s factory is the most practical method.
Profiling CTDs:
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.
How accurate is salinity measured by my CTD? What factors impact accuracy?
One of the reasons that this is not a simple question is that there are several factors to take into consideration regarding the error margin for practical salinity measurements. Salinity itself is a derived measurement from temperature, conductivity, and pressure, so any errors in these sensors can propagate to salinity. For example, our initial accuracy specification for the SBE 3plus temperature sensor and SBE 4 conductivity sensor on an SBE 9plus CTD is approximately equivalent to an initial salinity accuracy of 0.003 PSU (note that conductivity units of mS/cm are roughly equivalent in terms of magnitude to PSU).
However, another issue to consider is that this accuracy is defined for a clean, well-mixed calibration bath. In the ocean, some of the biggest factors that impact salinity accuracy are 1) sensor drift from biofouling or surface oils for conductivity in particular and 2) dynamic errors that can occur on moving platforms, particularly when conditions are rapidly changing, which will be true for all sensors that measure salinity. Sea-Bird provides recommendations, design features such as a pumped flow path, and data processing routines to align and improve data for the salinity calculation to account for thermal transients and hysteresis, and to match sensor response times. Depending on the environment and the steepness of the gradient, and after careful data processing, this may continue to have an impact on salinity on the order of 0.002 PSU or more, for example. For more details, see Application Note 82.
Lastly, note that salinity in PSU is calculated according to the Practical Salinity Scale (PSS-78), which is defined as valid for salinity ranges from 2 – 42 PSU.
Do I need to remove batteries before shipping my instrument for a deployment or to Sea-Bird?
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.
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 or similar scrubbing device.
I want to change the pressure sensor on my CTD, swapping it as needed to get the best data for a given deployment depth. Can I do this myself, or do I need to send the instrument to Sea-Bird?
On most of our instruments, replacement of the pressure sensor should be performed at Sea-Bird. We cannot extend warranty coverage if you replace the pressure sensor yourself.
However, we recognize that you might decide to go ahead and do it yourself because of scheduling/cost issues. Some guidelines follow:
- Perform the swap and carefully store the loose sensor on shore in a laboratory or electronics shop environment, not on a ship. The pressure sensor is fairly sensitive to shock, and a loose sensor needs to be stored carefully. Dropping the sensor will break it.
- Some soldering and unsoldering is required. Verify that the pressure sensor is mounted properly in your instrument. Properly re-grease and install the o-rings, or the instrument will flood.
- Once the sensor is installed, back-fill it with oil. Sea-Bird uses a vacuum-back filling apparatus that makes this job fairly easy. We can provide a drawing showing the general design of the apparatus, which can be modified and constructed by your engineers.
- For the most demanding work, calibrate the sensor on a deadweight tester to ensure proper operation and calibration.
- Enter the calibration coefficients for the new sensor in:
- the CTD configuration (.con or .xmlcon) file, using Seasave V7 or SBE Data Processing, and
- (for an instrument with internally stored calibration coefficients) the CTD EEPROM, using the appropriate terminal program and the appropriate calibration coefficient commands
Note: This discussion does not apply to the SBE 25 (not 25plus), which uses a modular pressure sensor (SBE 29) mounted externally on the CTD. Swap the SBE 29 as desired, use the CC command in Seaterm or SeatermAF to enter the new pressure range and pressure temperature compensation value, and type the calibration coefficients for the new sensor into the CTD configuration (.con or .xmlcon) file in Seasave V7 or SBE Data Processing.
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.
Family | Model | . | Housing | Pressure Sensor/Range | Connector | Communications | Dissolved Oxygen |
37 | SMP | . | 1 – 350 m (plastic) | 0 – none | 1 – XSG | 0 – RS-232 | 0 – none |
3 – 7000 m (titanium) | 1 – 20 m strain gauge | 2 – MCBH | 1 – RS-485 | ||||
2 – 100 m strain gauge | 2 – SDI-12 (requires MCBH connector) |
||||||
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 |
Example: 37SMP.13100 is an SBE 37-SMP with 350 m housing, 350 m strain gauge pressure sensor, XSG connector, and RS-232 communications. See table below for description of each selection:
PART # | DESCRIPTION | NOTES | ||||||||||||||||||
37SMP |
MicroCAT C and T (pressure optional) Recorder with Serial interface, Memory and internal Pump - Includes mooring clamp, 8 MB Flash memory, serial interface, external power input capability (power plus serial on connector), lithium battery (non-hazardous), AF24173 Anti-Foulant Devices, data/power interface cable (cable may be deleted for credit), Seasoft software, and complete documentation. |
37-SMP MicroCAT includes:
Compare features of the numerous SBE 37 MicroCAT models. |
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SBE 37-SMP Housing (depth) Selections — MUST SELECT ONE | ||||||||||||||||||||
37SMP.1xxx0 | 350 m plastic housing | |||||||||||||||||||
37SMP.3xxx0 | 7000 m titanium housing | |||||||||||||||||||
SBE 37-SMP Pressure Sensor Range (depth) Selections — MUST SELECT ONE | ||||||||||||||||||||
37SMP.x0xx0 | No pressure sensor |
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37SMP.x1xx0 | 20 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x2xx0 | 100 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x3xx0 | 350 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x4xx0 | 600 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x5xx0 | 1000 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x6xx0 | 2000 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x7xx0 | 3500 m strain gauge pressure sensor | |||||||||||||||||||
37SMP.x8xx0 | 7000 m strain gauge pressure sensor | |||||||||||||||||||
SBE 37-SMP Connector Selections — MUST SELECT ONE | ||||||||||||||||||||
37SMP.xx1x0 | XSG connector (includes data/power interface 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.
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37SMP.xx2x0 | Wet-pluggable (MCBH) connector (includes data/power interface cable 801206) | |||||||||||||||||||
SBE 37-SMP Communications Selections— MUST SELECT ONE | ||||||||||||||||||||
37SMP.xxx00 | RS-232 serial interface |
Note: Each interface version of 37-SMP has a separate manual. |
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37SMP.xxx10 | RS-485 (half duplex ONLY) serial interface | Two-wire, RS-485 interface provides communication with individual 37-SMP or with all 37-SMPs attached to RS-485 interface. This allows for coordination of sampling among many instruments. However, note that half-duplex communication is one-direction at a time (i.e., you cannot send commands & receive data at same time). Note: Each interface version of 37-SMP has a separate manual. |
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37SMP.xxx20 | SDI-12 interface (in addition to RS-232 interface); requires MCBH connector | SDI-12 interface is in addition to RS-232 interface. Instrument can be set up via RS-232, using full set of commands, and then a more limited set of commands can be sent via SDI-12 to make small setup changes in the field. Note: Each interface version of 37-SMP has a separate manual. |
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SBE 37-SMP Mooring Clamp Wire Size Selections (Specify clamp to match O.D. of mooring wire jacket) — MUST SELECT ONE | ||||||||||||||||||||
50465.I | Wire guide & mounting clamp for 1/4 in. diameter mooring wire |
Thread for clamping to mooring cable:
Clamp Size Note: Mooring wire is typically specified by wire size, not by outer diameter (O.D.) of the mooring wire jacket. Verify the wire jacket O.D. before selecting the clamp size. The clamp size must be less than or equal to the wire jacket O.D. but larger than the wire diameter. For example, Mooring System Inc.’s specifications for 3x19 wire rope (in 2016) are as follows:
For mounting on a rope, verify the rope outer diameter, and select a clamp smaller than the rope O.D. to account for the rope compressibility (for example, for 5/16 inch rope, select a ¼ inch clamp; a 5/16 inch clamp will be too large). |
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50469.I | Wire guide & mounting clamp for 5/16 in. or 8 mm diameter mooring wire | |||||||||||||||||||
50470.I | Wire guide & mounting clamp for 3/8 in. diameter mooring wire | |||||||||||||||||||
50473.I | Wire guide & mounting clamp for 1/2 in. diameter mooring wire | |||||||||||||||||||
50467.I | Wire guide & mounting clamp for 6 mm diameter mooring wire | |||||||||||||||||||
50471.I | Wire guide & mounting clamp for 10 mm diameter mooring wire | |||||||||||||||||||
50474.I | Wire guide & mounting clamp for 12 mm diameter mooring wire | |||||||||||||||||||
50476.I | Wire guide & mounting clamp for 5/8 in. or 16 mm diameter mooring wire | |||||||||||||||||||
50479.I | Alternative mounting - plastic brackets to provide through-bolt mounting to a flat surface | See document 67218. '.I' designation indicates that brackets are to be installed on instrument at factory. | ||||||||||||||||||
SBE 37-SMP Spares & Accessories | ||||||||||||||||||||
801542 | AF24173 Anti-Foulant Device pair (spare, bagged, labeled for shipping) | ![]() 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. |
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50441 | SBE 37 & 44 lithium batteries (spare), package of twelve 3.6V AA cells (Saft LS 14500) |
One set of batteries is included with standard shipment; 50441 are spares. Batteries are easily accessed by removing 2 screws from connector end cap & pulling out end cap. Shipping restrictions apply for lithium batteries; see SBE 37-SMP manual for details. Click here to buy Saft LS 14500 from Amazon. 801863 is battery holder, without batteries. Battery holder is included with standard shipment; this is a spare.
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801863 | Yellow top battery holder (14V nominal, Version 2) for use with twelve 3.6V AA lithium cells, for pumped SBE 37 (SMP & IMP with firmware version > 4.0 & all SMP-ODO, IMP-ODO, SMP-IDO, & IMP-IDO) | |||||||||||||||||||
801797 | Red top battery holder (7V nominal, Version 1) for use with twelve 3.6V AA lithium cells, for SBE 37 (SM, SMP, IM, IMP with firmware version < 4.0) & SBE 44 |
801797 is battery holder, without batteries. Price for 50442, which includes both battery holder (801797) & batteries (50441), is less than price when ordering battery holder & batteries separately. Sea-Bird is helping to absorb some cost for new battery holders by providing a reduced price. Note: Newer MicroCATs use a battery pack with a yellow cover plate (see above); wiring of that pack is different from this one, and cannot be used with 37-SMP MicroCATs with firmware version < 4.0. |
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50442 | Red top battery holder (7V nominal, Version 1) (PN 801797) and twelve AA lithium cells (PN 50441), for SBE 37 (SM, SMP, IM, IMP with firmware version < 4.0) and SBE 44 | |||||||||||||||||||
233540 | Anti-foulant cap without hose barb, black (for use with SBE 37 [SM, SMP, IM, IMP, SI, SIP] with firmware version < 4.0) |
Anti-foulant cap holds AF24173 Anti-Foulant Device in place. |
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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 37SMP.xx1x0 (XSG connector) and 37SMP.xxx00 or 37SMP.xxx10 (RS-232 or RS-485 interface) 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 37SMP.xx2x0 (MCBH connector) and 37SMP.xxx00 or 37SMP.xxx10 (RS-232 or RS-485 interface) selected; this is spare. | ||||||||||||||||||
802220 | Data/Power interface cable for RS-232 and SDI-12 interface, Wet-pluggable, MCIL-6FS to DB-9S & red/black twisted wire leads, 2.4 m (DN 33733) | Included with standard shipment if 37SMP.xx2x0 (MCBH connector) and 37SMP.xxx20 (SDI-12 interface) 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. | ||||||||||||||||||
233186 | High-head pressure port plug for muddy/biologically productive environments (Application Note 84), for use with SBE 37 [SM, SMP, IM, IMP, SI, SIP] with firmware version < 4.0 | ![]() Note: High-head pressure port plug is not compatible with newer 37-SMPs (firmware version > 4.0), because pressure port plug is behind mount clamp. |
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31632 | Storm Shipping Case (iM2950) - holds up to 4 SBE 37SMPs |
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Cables
RS-232 or RS-485 version
Note: In 2008, a 4-pin bulkhead connector became standard for all 37-SMPs. Previously, a 3-pin connector was standard and a 4-pin connector was optional.
- 801385 To computer COM port with power leads (from 4-pin XSG connector), 2.4 m, DN 32277
- 801376 To computer COM port with 9V connector (from 4-pin XSG connector), 2.4 m, DN 32604
- 801206 To computer COM port with power leads (from 4-pin Wet-pluggable connector), 2.4 m, DN 32366
- 801263 To computer COM port with 9V connector (from 4-pin Wet-pluggable connector), 2.4 m, DN 32490
- 801412 To computer COM port (from 3-pin XSG connector), 2.4 m, DN 32778
- 801366 To computer COM port (from 3-pin Wet-pluggable connector), 2.4 m, DN 32702
Dual SDI-12 / RS-232 version
- 802220 To computer COM port with power leads and leads to SDI-12 (from Wet-pluggable connector), 2.4 m, DN 33733
Mount Kits
Note: Mechanical design changes were implemented along with version 4.0 firmware for pumped SBE 37s without dissolved oxygen. Sea-Bird began selling 37-SMP with version 4.0 firmware in 2011.
Mounted to Flat Surface
- 50264 SBE 37-SI or SM Thru Bolt Mounting Clamp Kit for firmware < 4.0 (document 67096)
- 50479 SBE 37-SIP or SMP Thru Bolt Mounting Clamp Kit for firmware > 4.0 (document 67218)
Mounted to Mooring Cable
For firmware > 4.0 (document 67219 for all sizes)
- 50465 SBE 37-SMP or SIP Cable Clamp Kit, 1/4-inch diameter
- 50469 SBE 37-SMP or SIP Cable Clamp Kit, 5/16-inch or 8-mm diameter
- 50470 SBE 37-SMP or SIP Cable Clamp Kit, 3/8-inch diameter
- 50473 SBE 37-SMP or SIP Cable Clamp Kit, 1/2-inch diameter
- 50476 SBE 37-SMP or SIP Cable Clamp Kit, 5/8-inch or 16-mm diameter
- 50467 SBE 37-SMP or SIP Cable Clamp Kit, 6-mm diameter
- 50468 SBE 37-SMP or SIP Cable Clamp Kit, 7-mm diameter
- 50471 SBE 37-SMP or SIP Cable Clamp Kit, 10-mm diameter
- 50472 SBE 37-SMP or SIP Cable Clamp Kit, 11-mm diameter
- 50474 SBE 37-SMP or SIP Cable Clamp Kit, 12-mm diameter
- 50478 SBE 37-SMP or SIP Cable Clamp Kit, 20-mm diameter
For firmware < 4.0 (document 67094 for all sizes)
- 50261 SBE 37-SM or SI Cable Clamp Kit, 1/4-inch diameter
- 50263 SBE 37-SM or SI Cable Clamp Kit, 5/16-inch or 8-mm diameter
- 50262 SBE 37-SM or SI Cable Clamp Kit, 3/8-inch diameter
- 50269 SBE 37-SM or SI Cable Clamp Kit, 1/2-inch diameter
- 50271 SBE 37-SM or SI Cable Clamp Kit, 5/8-inch or16-mm diameter
- 50267 SBE 37-SM or SI Cable Clamp Kit, 6-mm diameter
- 50337 SBE 37-SM or SI Cable Clamp Kit, 7-mm diameter
- 50268 SBE 37-SM or SI Cable Clamp Kit, 10-mm diameter
- 50260 SBE 37-SM or SI Cable Clamp Kit, 11-mm diameter
- 50270 SBE 37-SM or SI Cable Clamp Kit, 12-mm diameter
- 50410 SBE 37-SM or SI Cable Clamp Kit, 20-mm diameter
Clamp Size Note: Mooring wire is typically specified by wire size, not by outer diameter (O.D.) of the mooring wire jacket. Verify the wire jacket O.D. before selecting the clamp size. The clamp size must be less than or equal to the wire jacket O.D. but larger than the wire diameter. For example, Mooring System Inc.’s specifications for 3x19 wire rope (in 2016) are as follows:
Wire Diameter | Jacket Diameter | Recommended Sea-Bird Clamp |
3/16 inch (5.0 mm) | 0.255 inch (6.5 mm) | 1/4 inch |
1/4 inch (6.5 mm) | 0.330 inch (8.4 mm) | 5/16 inch |
5/16 inch (8.0 mm) | 0.392 inch (9.9 mm) | 3/8 inch |
3/8 inch (9.5 mm) | 0.453 inch (11.5 mm) | 10 mm (0.394 inch) |
7/16 inch (11.1 mm) | 0.5 inch (12.7 mm) | 1/2 inch |
For mounting on a rope, verify the rope outer diameter, and select a clamp smaller than the rope O.D. to account for the rope compressibility (for example, for 5/16 inch rope, select a ¼ inch clamp; a 5/16 inch clamp will be too large).
Spare Parts
Batteries
Note: Mechanical design changes were implemented along with version 4.0 firmware for pumped SBE 37s without oxygen. Sea-Bird began selling 37-SMP with version 4.0 firmware in 2011. Click here for information on differences between red and yellow battery holders, which are not interchangeable.
- 50442 SBE 37 & 44 Red retrofit battery holder (PN 801797) and twelve AA lithium cells (PN 50441) for SBE 37 (SM, SMP, IM, IMP with firmware version < 4.0) and SBE 44 (see MicroCAT Change Notice and Application Note 89)
- 801797 Red retrofit battery holder (7V nominal, Version 1) for SBE 37 (SM, SMP, IM, IMP with firmware version < 4.0) and SBE 44, for use with twelve 3.6V AA lithium cells (see MicroCAT Change Notice and Application Note 89)
- 801863 Yellow battery holder (14V nominal, Version 2) for SBE 37 (SM, SMP, IM, IMP with firmware version > 4.0) and SBE 37 with oxygen (SMP-IDO, IMP-IDO, SMP-ODO, IMP-ODO), for use with twelve 3.6V AA lithium cells
- 50441 SBE 37 and 44 lithium batteries, package of twelve 3.6V AA cells (Saft LS 14500) - Click here to buy Saft LS 14500 from Amazon.
Hardware & O-Ring Kits
Note: Mechanical design changes were implemented along with version 4.0 firmware for pumped SBE 37s without oxygen. Sea-Bird began selling 37-SMP with version 4.0 firmware in 2011.
- 60035 Hardware & O-ring kit for SBE 37-SM or 37-SMP (instruments delivered after 1999; compatible with obsolete 50243 batteries) with firmware version < 4.0 (document 67092)
- 60049 Hardware & O-ring kit for SBE 37-SM or 37-SMP with titanium housing (instruments delivered after 1999; compatible with 50441 AA lithium batteries & 801797 retrofit battery holder) with firmware version < 4.0 (document 67201)
- 60053 Hardware & O-ring kit for SBE 37-SM or 37-SMP with plastic housing (instruments delivered after 1999; compatible with 50441 AA lithium batteries & 801797 retrofit battery holder) with firmware version < 4.0 (document 67206)
- 60056 Hardware & O-ring kit for SBE 37-SMP with firmware version > 4.0 (document 67212)
- 60056 Hardware & O-ring kit for SBE 37-SM or 37-SMP with firmware version > 4.0 (document 67212)
Miscellaneous
Note: Mechanical design changes were implemented along with version 4.0 firmware for pumped SBE 37s without oxygen. Sea-Bird began selling 37-SMP with version 4.0 firmware in 2011.
- 801542 AF24173 Anti-Foulant Device (pair, bagged, labeled for shipping)
- 233186 High-head pressure port plug for muddy/biologically productive environments (for use with SBE 37 [SM, SMP, IM, IMP, SI, SIP] with firmware version < 4.0; not for newer versions or for MicroCATs with oxygen) (Application Note 84)
- 31632 Storm shipping case (iM2950) — holds up to 4 MicroCATs (without oxygen) (photo of MicroCATs in this shipping case)