SBE 37-IMP-ODO MicroCAT CTD-DO Recorder

SBE 37-IMP-ODO MicroCAT C-T-ODO (P) Recorder

Moored Conductivity, Temperature, Optical Dissolved Oxygen, and (optional) Pressure measurements, at user-programmable intervals. Inductive Modem (IM) interface, internal memory, and internal battery pack.


  • Moored Conductivity, Temperature, Pressure (optional), and Optical Dissolved Oxygen measurements, at user-programmable 10-sec to 6-hour intervals.
  • Inductive Modem (IM) interface, internal memory, and internal battery pack.
  • Adaptive Pump Control for high-accuracy oxygen data.
  • Expendable anti-foulant devices, unique flow path, and pumping regimen for maximum bio-fouling protection.
  • Depths to 350 meters (ShallowCAT plastic housing) or 7000 meters (titanium housing).
  • Sea-Bird's field-proven MicroCAT family, with more than 10,000 instruments deployed since 1997.
  • Five-year limited warranty.


The SBE 37-IMP-ODO MicroCAT is a high-accuracy conductivity and temperature (pressure optional) recorder with internal batteries, memory, built-in Inductive Modem, integral Pump, and Optical Dissolved Oxygen sensor. Constructed of titanium and other non-corroding materials for long life with minimal maintenance, the MicroCAT is designed for long duration deployments on moorings. Calibration coefficients are stored in EEPROM, allowing output of C, T, P, DO, and time in ASCII engineering units (raw output available).

The Inductive Modem (IM) system provides reliable, low-cost, real-time data transmission for up to 100 IM-enabled instruments using plastic-coated wire rope (typically 3 x 19 galvanized steel) as both the transmission line and mooring tension member. IM instruments clamp anywhere along the rugged mooring wire. Expensive and potentially unreliable multi-conductor electrical cables with fixed position underwater connectors are not required. IM moorings are easily reconfigured (positions changed or instruments added or removed), by sliding and re-clamping sensors on the cable. IM systems are much less expensive and more power-efficient than acoustic modems, and offer reliable communication over greater distances.

In a typical mooring, an Inductive Modem Module (IMM) or Surface Inductive Modem (SIM) housed in the buoy communicates with underwater IM instruments and is interfaced to a computer or data logger via an RS-232 serial port. The computer or data logger (not supplied by Sea-Bird) is programmed to poll each IM instrument on the mooring for its data, and send the data to a telemetry transmitter (satellite link, cell phone, RF modem, etc.). The MicroCAT saves data in memory for upload after recovery, providing a data backup if real-time telemetry is interrupted.


Conductivity and Temperature sensors are based on our field-proven SeaCAT and SeaCATplus. Electrical isolation of conductivity electronics eliminates any possibility of ground-loop noise. Our unique internal-field conductivity cell permits the use of expendable anti-foulant devices, for long-term bio-fouling protection. The aged and pressure-protected thermistor has a long history of exceptional accuracy and stability.

The oxygen sensor is our field-proven SBE 63 Optical Dissolved Oxygen sensor.

The optional strain-gauge pressure sensor is available in eight ranges, to a maximum depth of 7000 meters. Compensation of the temperature influence on pressure is performed by the MicroCAT's CPU.


The integral pump runs each time the MicroCAT samples, providing the following advantages:

  • Improved conductivity and oxygen response – The pump flushes the previously sampled water from the conductivity cell and oxygen sensor plenum, and brings a new water sample quickly into the system.
  • Improved anti-foul protection – Water does not freely flow through the conductivity cell between samples, allowing the anti-foul concentration inside the system to maintain saturation.
  • Improved measurement correlation – The individually calibrated SBE 63 Optical Dissolved Oxygen sensor is integrated within the CTD flow path, providing optimum correlation with CTD measurements.

With Adaptive Pump Control, the MicroCAT calculates the pumping time for best oxygen accuracy as a function of the previous sample's temperature and pressure (maximizing data quality while minimizing power consumption).


User-selectable operating modes include:

  • Polled – On command, the MicroCAT runs the pump, takes a sample, and transmits data.
  • Autonomous – At pre-programmed intervals, the MicroCAT wakes up, runs the pump, takes 1 sample, stores data in memory, and goes to sleep.
  • Combo or Averaging – The MicroCAT samples autonomously, and the IMM/SIM can request the last stored data or the average of the samples acquired since its last request.


The MicroCAT is supplied with a powerful Windows software package, Seasoft© V2, which includes:

  • SeatermV2© – terminal program for easy communication and data retrieval.
  • SBE Data Processing© – programs for calculation, display, and plotting of conductivity, temperature, pressure (optional), and derived variables such as salinity and sound velocity.


Temperature and conductivity are stored 6 bytes/sample, time 4 bytes/sample, oxygen 6 bytes/sample, and optional pressure 5 bytes/sample; memory capacity is in excess of 380,000 samples (with pressure). The MicroCAT is powered by a 7.8 Amp-hour (nominal) battery pack consisting of twelve AA lithium cells (Saft LS14500) which, when removed from the MicroCAT, can be shipped via commercial aircraft. Battery endurance varies widely, depending on the sampling scheme and deployment pressure and temperature. Sampling every 10 minutes in water temperatures of approximately 10 °C, the MicroCAT can be deployed for almost 6 months (24,000 samples); see the manual for example calculations.


Compare features of the numerous SBE 37 MicroCAT models.

Conductivity 0 to 7 S/m
(0 to 70 mS/cm)
± 0.0003 S/m
(0.003 mS/cm)
0.0003 S/m
(0.003 mS/cm)
per month
0.00001 S/m
(0.0001 mS/cm)
-5 to 45 ± 0.002
(-5 to 35 °C);
± 0.01
(35 to 45 °C)
per month
20 / 100 / 350 /
600 / 1000 / 2000 /
3500 / 7000 m
(meters of
deployment depth capability)
± 0.1% of
full scale range
0.05% of
full scale range
per year
0.002% of
full scale range
Optical Dissolved Oxygen 120% of surface saturation
in all natural waters
(fresh and salt)
larger of ±3 µmol/kg
 (equivalent to 0.07 ml/L or 0.1 mg/L)
 or ±2%
sample-based drift <
1 µmol/kg/100,000 samples (20 °C)
0.2 µmol/kg

Clock Stability: 5 seconds/month

Power Consumption:
Quiescent: 0.0007 Watts
CTD-DO Sample Acquisition (excluding pump):
      Without pressure 0.10 Watts
      With pressure 0.17 Watts
CTD-DO Sample Waiting (not sampling, pump running, excluding pump):
      With pressure 0.016 Watts
Pump: 0.12 Watts
      IM 0.009 Watts listening, 0.13 Watts transmitting
      RS-232 0.06 Watts

Power Supply: 7.8 Amp-hour (nominal) battery pack

Housing Material Depth Rating Weight (with standard mounting clamp & guide)
Plastic 350 m (1150 ft) In air 3.7 kg (8.3 lbs); in water 1.8 kg (4.0 lbs)
Titanium 7000 m (23,000 feet) In air 4.4 kg (9.8 lbs); in water 2.5 kg (5.5 lbs)

The list below includes (as applicable) the current product brochure, manual, and quick guide; software manual(s); and application notes.

For older SBE 37-IMP-ODO product manuals, organized by instrument firmware version, click here.

Title Type Publication Date PDF File
SBE 37-IMP-ODO Brochure Product Brochure Wednesday, March 19, 2014 37IMP-odobrochureMar14.pdf
SBE 37 MicroCAT Feature Comparisons Product Brochure Wednesday, September 17, 2014 MicrocatFeatureComparisonsSept14.pdf
SBE 37-IMP-ODO Manual Product Manual Friday, August 8, 2014 37IMP-ODO_007.pdf
SBE Data Processing Manual Software Manual Tuesday, March 18, 2014 SBEDataProcessing_7.23.2.pdf
SBE 37-IMP-ODO Quick Guide Product Quick Guide Friday, August 8, 2014 37IMP-ODO_referencesheet_006.pdf
AN06: Determination of Sound Velocity from CTD Data Application Notes Tuesday, February 2, 2010 appnote06Aug04.pdf
AN10: Compressibility Compensation of Sea-Bird Conductivity Sensors Application Notes Tuesday, May 7, 2013 appnote10May13.pdf
AN14: 1978 Practical Salinity Scale Application Notes Thursday, January 12, 1989 appnote14.pdf
AN27D: Minimizing Strain Gauge Pressure Sensor Errors Application Notes Thursday, February 13, 2014 appnote27DFeb14.pdf
AN31: Computing Temperature and Conductivity Slope and Offset Correction Coefficients from Laboratory Calibrations and Salinity Bottle Samples Application Notes Monday, February 22, 2010 appnote31Feb10.pdf
AN42: ITS-90 Temperature Scale Application Notes Thursday, February 13, 2014 appnote42Feb14.pdf
AN57: Connector Care and Cable Installation Application Notes Tuesday, May 13, 2014 appnote57Jan14.pdf
AN67: Editing Sea-Bird .hex Data Files Application Notes Monday, October 15, 2001 appnote67.pdf
AN69: Conversion of Pressure to Depth Application Notes Monday, July 1, 2002 appnote69.pdf
AN71: Desiccant Use and Regeneration (drying) Application Notes Wednesday, January 15, 2014 Appnote71Jan14.pdf
AN73: Using Instruments with Pressure Sensors at Elevations Above Sea Level Application Notes Friday, February 28, 2014 appnote73Feb14.pdf
AN83: Deployment of Moored Instruments Application Notes Friday, February 14, 2014 appnote83Feb14.pdf
AN85: Handling of Ferrite Core on Instruments with Inductive Modem Telemetry Application Notes Monday, October 15, 2012 appnote85Oct12.pdf
AN90: Absolute Salinity and TEOS-10: Sea-Bird's Implementation Application Notes Tuesday, September 3, 2013 AppNote90Sep13.pdf
AN92: Real-Time Oceanography with Inductive Moorings and the Inductive Modem Module (IMM) Application Notes Tuesday, December 24, 2013 appnote92Dec13.pdf
Deployment Endurance Calculator is an aid for quickly determining the maximum deployment length for a moored instrument, based on battery capacity. Deployment Endurance Calculator is part of our Seasoft V2 software suite.
Version 1.6 released September 2, 2014
DeploymentEnduranceCalcV1_6.exe for Windows XP/Vista/7

SeatermV2© is a terminal program launcher for setup and data upload of Sea-Bird instruments developed or redesigned in 2006 and later. The common feature of this generation of instruments is the ability to output status responses in XML. SeatermV2 is part of our Seasoft V2 software suite.
Version 2.4.1 released September 2, 2014
SeatermV2_4_1.exe for Windows XP/Vista/7

SBE Data Processing© consists of modular, menu-driven routines for converting, editing, processing, and plotting of oceanographic data acquired with Sea-Bird profiling CTDs, thermosalinographs, and the SBE 16 and 37 families of moored CTDs. SBE Data Processing is part of our Seasoft V2 software suite.
Version 7.23.2 released March 18, 2014
SBEDataProcessing_Win32_V7_23_2.exe for Windows XP/Vista/7

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.
  • 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.

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.

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.

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.

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.

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:

  1. 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.
  2. 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.
  3. 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.
  4. For the most demanding work, calibrate the sensor on a deadweight tester to ensure proper operation and calibration.
  5. 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.

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.

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 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 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.

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.

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 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.

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

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-SIP37-SIP-IDO, 37-SMP37-SMP-IDO37-SMP-ODO37-IMP37-IMP-IDO37-IMP-ODO) have a recommended orientation because of their u-shaped plumbing configuration. Refer to the instrument manual for details.

Family Model . Housing Pressure Sensor/Range Connectors Communications SBE 63 Optical
Dissolved  Oxygen
37 IMP . 1 – 350 m (plastic) 0 – none 0 – none 0 – Inductive Modem 2 – 600 m
      2 – 7000 m (titanium) 1 – 20 m strain gauge     3 – 5000 m
        2 – 100 m strain gauge     4 – 7000 m
        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: 37IMP.13002 is an SBE 37-IMP-ODO with 350 m housing, 350 m strain gauge pressure sensor, and integrated SBE 63 Optical Dissolved Oxygen Sensor with DO sensor rated to 600 m. See table below for description of each selection:


MicroCAT C and T (pressure optional) Recorder with Integrated SBE 63 Optical Dissolved Oxygen sensor (ODO), Inductive Modem, and internal Pump - Includes mooring clamp for jacketed wire, 8 MB Flash memory, lithium battery (non-hazardous), AF24173 Anti-Foulant Devices, Seasoft software, and complete documentation.

37-IMP-ODO MicroCAT includes:

  • Inductive Modem interface
  • Memory
  • internal, integral Pump
  • integrated Optical Dissolved Oxygen sensor

Communicating with 1 or more 37-IMP-ODOs requires use of Sea-Bird Inductive Modem Module (IMM) or Surface Inductive Modem (SIM), which provide serial interface between user’s computer & up to 100 IM instruments coupled to single cable. Purchase IMM/SIM & optional Inductive Cable Coupler (ICC) separately.

Compare features of the numerous SBE 37 MicroCAT models.

SBE 37-IMP-ODO Housing (depth) Selections MUST SELECT ONE
37IMP.1x00x 350 m plastic housing  
37IMP.2x00x 7000 m titanium housing  
SBE 37-IMP-ODO Pressure Sensor Range (depth) Selections MUST SELECT ONE
37IMP.x000x No pressure sensor Pressure sensor is installed in end cap (behind mount clamp), & is not field replaceable / swappable. While highest pressure rating gives you most flexibility in using MicroCAT, 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:
  • 2000 m sensor:
    initial accuracy = 2 m (= 0.1% * 2000 m),
    resolution = 0.04 m (= 0.002% * 2000 m)
  • 7000 m sensor:
    initial accuracy = 7 m (= 0.1% * 7000 m),
    resolution = 0.14 m (= 0.002% * 7000 m)
37IMP.x100x 20 m strain gauge pressure sensor
37IMP.x200x 100 m strain gauge pressure sensor
37IMP.x300x 350 m strain gauge pressure sensor
37IMP.x400x 600 m strain gauge pressure sensor
37IMP.x500x 1000 m strain gauge pressure sensor
37IMP.x600x 2000 m strain gauge pressure sensor
37IMP.x700x 3500 m strain gauge pressure sensor
37IMP.x800x 7000 m strain gauge pressure sensor
SBE 37-IMP-ODO Optical Dissolved Oxygen Sensor Selections MUST SELECT ONE
37IMP.xx002 600 meter  
37IMP.xx003 5000 meter
37IMP.xx004 7000 meter
SBE 37-IMP-ODO Mooring Clamp Wire Size Selections (Specify clamp to match O.D. of mooring wire jacket) — MUST SELECT ONE
37IMP-1a Wire guide & mounting clamp for 1/4 in. diameter mooring wire

37-IMP-IDO shown; mooring clamp detail for 37-IMP-ODO identical

Cable fits loosely through IM coupling core / wire guide, & is clamped only at mounting clamp. See document 67220.

Thread for clamping to mooring cable:

  • 37IMP-1a (1/4 in. diameter): 1/4-28 UNF
  • 37IMP-1b (5/16 in. diameter): 5/16-24 UNF
  • 37IMP-1c (3/8 in. diameter): 3/8-24 UNF
  • 37IMP-1d (1/2 in. diameter): 9/16-12 UNC
  • 37IMP-1e (6 mm diameter): 1/4-20 UNF
  • 37IMP-1f (8 mm diameter): 5/16-24 UNF
  • 37IMP-1g (10 mm diameter): 7/16 -14 UNF
  • 37IMP-1h (12 mm diameter): 1/2-13 UNF
  • 37IMP-1i (16 mm, 5/8 in. diameter): 5/8-18 UNF
37IMP-1b Wire guide & mounting clamp for 5/16 in. diameter mooring wire
37IMP-1c Wire guide & mounting clamp for 3/8 in. diameter mooring wire
37IMP-1d Wire guide & mounting clamp for 1/2 in. diameter mooring wire
37IMP-1e Wire guide & mounting clamp for 6 mm diameter mooring wire
37IMP-1f Wire guide & mounting clamp for 8 mm diameter mooring wire
37IMP-1g Wire guide & mounting clamp for 10 mm diameter mooring wire
37IMP-1h Wire guide & mounting clamp for 12 mm diameter mooring wire
37IMP-1i Wire guide & mounting clamp for 16 mm (5/8 in.) diameter mooring wire
SBE 37-IMP-ODO Storm Shipping Case Option - holds up to 3 SBE 37IMP-ODOs
37IMP-4I Storm Shipping Case (iM2950) instead of wood crate - holds up to 3 SBE 37IMP-ODOs

Case holds only 3 ODO MicroCATs
(photo shows 4 non-ODO MicroCATs)

Storm shipping case with custom foam inserts holds up to 3 ODO MicroCATs — IMP-ODO, SMP-ODO, SIP-ODO.

  • Injection molded case with HPX resin plastic body, recessed wheels, automatic pressure equalization valve, hinged push-button latches, fold-down padded handle, & O-ring seal. Meets airline luggage regulations.
  • Inner dimensions:
    29 x 18 x 10.5 inches (74 x 46 x 27 cm).
  • Outer dimensions:
    31.3 x 20.4 x 12.2 inches (80 x 52 x 31 cm).

Price for 37IMP-4I reflects a credit for deletion of our standard wood crate.

SBE 37-IMP-ODO Spares & Accessories
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.
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-IMP-ODO manual for details.

801863 is battery holder, without batteries. Battery holder is included with standard shipment; this is a spare.
Note: Other MicroCATs use a battery pack with a red cover plate; the wiring of that pack is different from this one, and cannot be used with ODO MicroCATs (37-IMP-ODO or 37-SMP-ODO).

801863 shown with 50441 cells installed
(Note: Cells cannot be shipped
installed in battery holder)

Cells packed in heat-sealed plastic (above),
then placed in bubble-wrap outer sleeve &
strong packaging for shipment (below)

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-IDO, IMP-IDO, SMP-ODO, & IMP-ODO)
801836 37-IM/IMP/IMP-IDO/IMP-ODO Internal Data I/O cable, 0.3 m (DN 33406) For uploading data quickly using internal RS-232 connector.
TBD Storm Shipping Case (iM2950) - holds up to 3 SBE 37IMP-ODOs

Case holds only 3 ODO MicroCATs
(photo shows 4 non-ODO MicroCATs)

Storm shipping case with custom foam inserts holds up to 3 ODO MicroCATs — IMP-ODO, SMP-ODO, SIP-ODO.

  • Injection molded case with HPX resin plastic body, recessed wheels, automatic pressure equalization valve, hinged push-button latches, fold-down padded handle, & O-ring seal. Meets airline luggage regulations.
  • Inner dimensions:
    29 x 18 x 10.5 inches (74 x 46 x 27 cm).
  • Outer dimensions:
    31.3 x 20.4 x 12.2 inches (80 x 52 x 31 cm).
For Surface Inductive Modem (SIM), Inductive Modem Module (IMM), and Inductive Cable Coupler (ICC), see separate listings.



  • 801836 To computer COM port from internal RS-232 connector for fast upload (digital firmware version > 3.0), DN 33406
  • 171887 To computer COM port (from Surface Inductive Modem), 3 m
  • 801583 To computer COM port (from Inductive Modem Module), 0.25 m, DN 33049

Mount Kits

Mount to Mooring Cable (document 67220 for all sizes)

  • 50486  SBE 37-IMP-IDO Cable Clamp Kit, 1/4-inch diameter
  • 50488  SBE 37-IMP-IDO Cable Clamp Kit, 5/16-inch diameter
  • 50489  SBE 37-IMP-IDO Cable Clamp Kit, 3/8-inch diameter
  • 50492  SBE 37-IMP-IDO Cable Clamp Kit, 1/2-inch diameter
  • 50487  SBE 37-IMP-IDO Cable Clamp Kit, 6-mm diameter
  • 50488  SBE 37-IMP-IDO Cable Clamp Kit, 8-mm diameter
  • 50490  SBE 37-IMP-IDO Cable Clamp Kit, 10-mm diameter
  • 50493  SBE 37-IMP-IDO Cable Clamp Kit, 12-mm diameter
  • 50495  SBE 37-IMP-IDO Cable Clamp Kit, 16-mm (5/8-inch) diameter

Spare Parts


  • 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)

Hardware & O-Ring Kits:

  • 60055  Hardware & O-ring kit for SBE 37-IMP-IDO or 37-IMP-ODO (document 67209)


  • 801542 AF24173 Anti-Foulant Device (pair, bagged, labeled for shipping)
  • TBD Storm shipping case (iM2950) — holds up to 3 IDO or ODO MicroCATs (SMP-IDO, SMP-ODO, SIP-IDO, SIP-ODO, IMP-IDO, IMP-ODO) (photo of MicroCATs in this shipping case)