SBE 37-SM MicroCAT CTD Recorder

SBE 37-SM MicroCAT C-T (P) Recorder

Moored Conductivity, Temperature, and (optional) Pressure measurements, at user-programmable intervals. RS-232 or RS-485 interface, internal memory, and internal battery pack.

SUMMARY

  • Moored Conductivity, Temperature, and (optional) Pressure, at user-programmable 6-sec to 6-hour intervals.
  • RS-232 or RS-485 serial interface, internal memory, and internal battery pack (can be powered externally).
  • Expendable anti-foulant devices for 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.

DESCRIPTION

The SBE 37-SM MicroCAT is a high-accuracy conductivity and temperature (pressure optional) recorder with Serial interface, internal battery, and non-volatile Memory. The MicroCAT is designed for moorings or other long duration, fixed-site deployments. Constructed of non-corroding materials to ensure long life with minimum maintenance, it is rated for operation to 350 meters (plastic ShallowCAT housing) or 7000 meters (titanium housing), or pressure sensor full-scale range.

Calibration coefficients are stored in EEPROM, allowing the MicroCAT to output data in ASCII engineering units (decimal or XML format); raw output is also available. The data always includes Conductivity, Temperature, )optional) Pressure, and time; salinity and sound velocity can also be output.

SENSORS AND SENSOR INTERFACE ELECTRONICS

The MicroCAT retains the temperature and conductivity sensors used in our time-proven SeaCAT and SeaCATplus. Electrical isolation of the conductivity electronics eliminates any possibility of ground-loop noise. The MicroCAT’s unique internal-field conductivity cell permits the use of expendable anti-foulant devices. The aged and pressure-protected thermistor has a long history of exceptional accuracy and stability.

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 offset and scale is performed by the MicroCAT’s CPU.

Temperature is acquired by applying an AC excitation to a hermetically sealed VISHAY reference resistor and an ultra-stable aged thermistor (drift rate typically less than 0.002 °C per year). The ratio of thermistor resistance to reference resistance is determined by a 24-bit A/D converter; this A/D also processes the pressure sensor signal. Conductivity is acquired using an ultra-precision Wien-Bridge oscillator.

COMMUNICATIONS AND INTERFACING

The MicroCAT communicates via RS-232 or RS-485 serial interface:

  • RS-232 —Real-time data can be transmitted up to 1600 meters at 600 baud, simultaneous with recording. Data can be uploaded at up to 115.2K baud. The user can upgrade firmware through the external connector, without opening the housing.
  • RS-485 — Multiple MicroCATs can share a common 2-wire cable, minimizing cable complexity for C-T chains.

User-selectable operating modes include:

  • Autonomous — At pre-programmed 6-sec to 6-hour intervals, the MicroCAT wakes up, takes 1 sample, stores data in memory, and goes to sleep.
  • Polled — On command from a computer or satellite, radio, or wire telemetry equipment, the MicroCAT wakes up, samples, and transmits data.
  • Serial Line Sync — In response to a pulse on the serial line, the MicroCAT wakes up, takes 1 sample, stores data in memory, and goes to sleep.

SOFTWARE

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.

DATA STORAGE, FORMAT, AND BATTERY ENDURANCE

Temperature and conductivity are stored 6 bytes/sample, time 4 bytes/sample, and optional pressure 5 bytes/sample; memory capacity is in excess of 530,000 samples. The MicroCAT is powered by a 10.6 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. The pack provides sufficient internal battery capacity for more than 630,000 samples for a typical sampling scheme (battery endurance for RS-232 interface; for RS-485 interface, see RS-485 manual).

ADDITIONAL INFORMATION

Compare features of the numerous SBE 37 MicroCAT models.

  Measurement
Range
Initial
Accuracy
Typical
Stability
Resolution
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)
Temperature
 (°C)
-5 to 45 ± 0.002
(-5 to 35 °C);
± 0.01
(35 to 45 °C)
0.0002
per month
0.0001
Optional
Pressure
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

Clock Stability: 5 sec/month

Quiescent Current: 30 microamps *

Sampling and Communication Current: *
Communication 4.3 milliamps
Sampling
     15 milliamps if transmitting real-time data;
     13 milliamps if not transmitting real-time data

* Power consumption / battery endurance values are for RS-232 interface; for RS-485 interface, see RS-485 manual.

Acquisition Time: 1.8 - 2.6 sec per sample, dependent on sampling mode and inclusion of pressure sensor

Power Supply: 10.6 Amp-hour (nominal) battery pack

Optional External Power: 0.5 Amps at 9 - 24 VDC

Housing Material Depth Rating Weight (without pressure sensor)
Plastic 350 m (1150 ft)  

2.7 kg (6.0 lbs) in air
1.2 kg (2.7 lbs) in water

Titanium 7000 m (23,000 feet) 3.8 kg (8.3 lbs) in air
2.3 kg (5.1 lbs) in water

RS-232 Connector shown. For RS-485: pin 2 is RS-485A, pin 3 is RS-485B)

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

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

Title Type Publication Date PDF File
SBE 37-SM Brochure Product Brochure Wednesday, March 19, 2014 37SMbrochureMar14.pdf
SBE 37 MicroCAT Feature Comparisons Product Brochure Wednesday, September 17, 2014 MicrocatFeatureComparisonsOct14.pdf
SBE 37-SM RS-232 Manual Product Manual Tuesday, March 11, 2014 37SM_rs232_038.pdf
SBE 37-SM RS-485 Manual Product Manual Tuesday, March 11, 2014 37SM_RS485_027.pdf
SBE Data Processing Manual Software Manual Tuesday, March 18, 2014 SBEDataProcessing_7.23.2.pdf
SBE 37-SM RS-232 Quick Guide Product Quick Guide Tuesday, March 11, 2014 37SM_rs232_referencesheet_013.pdf
SBE 37-SM RS-485 Quick Guide Product Quick Guide Tuesday, March 11, 2014 37SM_RS485_referencesheet_012.pdf
AN02D: Instructions for Care and Cleaning of Conductivity Cells Application Notes Monday, March 10, 2014 appnote2DMar14.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
AN27: Strain Gauge Pressure Sensor Error Sources - older instruments with Paine pressure sensors Application Notes Saturday, February 13, 2010 appnote27Feb10.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
AN52: AC Powered Opto-Isolated RS-485 to RS-232 Junction Box P/N 80491 Instructions for Application and Use Application Notes Tuesday, February 9, 2010 appnote52Feb10.pdf
AN56: Interfacing to RS-485 Sensors Application Notes Wednesday, February 11, 2009 appnote56Feb09.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
AN68: Using USB Ports to Communicate with Sea-Bird Instruments Application Notes Friday, October 19, 2012 appnote68Oct12.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
AN84: Using Instruments with Druck Pressure Sensors in Muddy or Biologically Productive Environments Application Notes Tuesday, January 14, 2014 appnote84Jan14.pdf
AN89: Retrofit Battery Pack for SBE 37 MicroCAT and SBE 44 Underwater Inductive Modem Application Notes Tuesday, September 16, 2014 AppNote89Sep14.pdf
AN90: Absolute Salinity and TEOS-10: Sea-Bird's Implementation Application Notes Tuesday, September 3, 2013 AppNote90Sep13.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


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.

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.

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.

Is it necessary to put my instrument in water to test it? Will I destroy the conductivity cell if I test it in air?

It is not necessary to put the instrument in water to test it. It will not hurt the conductivity cell to be in air.

If there is a pump on the instrument, it should not be run for extended periods in air.

  • Profiling instruments (SBE 9plus, 19, 19plus, 19plus V2, 25, 25plus, 49) and some moored instruments (all pumped MicroCATs with integral dissolved oxygen (DO), and pumped MicroCATs without DO with firmware 3.0 and later) do not turn on the pump unless the conductivity frequency is above a specified minimum value (minimum value is hard-wired in 9plus, user-programmable in other instruments). This prevents the pump from turning on in air. See the instrument manual for details.
  • If your instrument does not check for conductivity frequency before turning on the pump: 
    - For moored SeaCATs (16, 16plus, 16plus-IM, 16plus V2, 16plus-IM V2): Disconnect the pump cable for the test. 
    - For older pumped MicroCATs: orient the MicroCAT to provide an upright U-shape for the plumbing. Then fill the inside of the pump head with water via the pump exhaust tubing; this will provide enough lubrication to prevent pump damage during brief testing.

Can I use a pressure sensor above its rated pressure?

Digiquartz pressure sensors are used in the SBE 9plus, 53, and 54. The SBE 16plus V2, 16plus-IM V2, 19plus V2, and 26plus can be equipped with either a Druck pressure sensor or a Digiquartz pressure sensor. All other instruments that include pressure use a Druck pressure sensor.

  • The overpressure rating for a Digiquartz (as stated by Paroscientific) is 1.2 * full scale. The sensor will provide data values above 100% of rated full scale; however, Sea-Bird does not calibrate beyond the rated full scale.
  • The overpressure rating for a Druck (as stated by Druck) is 1.5 * full scale. The sensor will provide data values above 100% of rated full scale; however, Sea-Bird does not calibrate beyond the rated full scale.

Note: If you use the instrument above the rated range, you do so at your own risk; the product will not be covered under warranty.

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.

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.

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 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 should I pick the pressure sensor range for my CTD? Would the highest range give me the most flexibility in using the CTD?

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

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

How often do I need to have my instrument and/or auxiliary sensors recalibrated? Can I recalibrate them myself?

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.

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 (http://www.3m.com/us/home_leisure/scotchbrite/products/scrubbing_scouring.html) 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.

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:

  1. Thoroughly clean the connector with water, followed by alcohol.
  2. 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.

Family Model . Housing Pressure Sensor/Range Connectors Communications Dissolved  Oxygen
37 SM . 1 – 350 m (plastic) 0 – none 1 – XSG 0 – RS-232 0 – none
      2 – 7000 m (titanium) 1 – 20 m strain gauge 2 – MCBH 1 – RS-485  
        2 – 100 m strain gauge      
        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: 37SM.13100 is an SBE 37-SM 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
37SM

MicroCAT C and T (pressure optional) Recorder with Serial interface and Memory - 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-SM MicroCAT includes:

  • Serial interface
  • Memory

Compare features of the numerous SBE 37 MicroCAT models.

SBE 37-SM Housing (depth) Selections MUST SELECT ONE
37SM.1xxx0 350 m plastic housing  
37SM.2xxx0 7000 m titanium housing  
SBE 37-SM Pressure Sensor Range (depth) Selections MUST SELECT ONE
37SM.x0xx0 No pressure sensor

Pressure sensor is installed in end cap, & 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)
37SM.x1xx0 20 m strain gauge pressure sensor
37SM.x2xx0 100 m strain gauge pressure sensor
37SM.x3xx0 350 m strain gauge pressure sensor
37SM.x4xx0 600 m strain gauge pressure sensor
37SM.x5xx0 1000 m strain gauge pressure sensor
37SM.x6xx0 2000 m strain gauge pressure sensor
37SM.x7xx0 3500 m strain gauge pressure sensor
37SM.x8xx0 7000 m strain gauge pressure sensor
SBE 37-SM Connector Selections MUST SELECT ONE
37SM.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.

 
XSG connector on left, Wet-pluggable (MCBH) connector on right

37SM.xx2x0 Wet-pluggable (MCBH) connector (includes data/power interface cable 801206)
SBE 37-SM Communications Selections MUST SELECT ONE
37SM.xxx00 RS-232 serial interface

Note: Each interface version of 37-SM has a separate manual.

37SM.xxx10 RS-485 (half duplex ONLY) serial interface Two-wire, RS-485 interface provides communication with individual 37-SM or with all 37-SMs 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-SM has a separate manual.
SBE 37-SM Mooring Clamp Wire Size Selections (Specify clamp to match O.D. of mooring wire jacket) — MUST SELECT ONE
37SM-1a Wire guide & mounting clamp for 1/4 in. diameter mooring wire

Cable fits loosely through wire guide, & is clamped only at mounting clamp. See document 67094.

Thread for clamping to mooring cable:

  • 37SM-1a (1/4 in. diameter): 1/4-28 UNF
  • 37SM-1b (5/16 in. diameter): 5/16-24 UNF
  • 37SM-1c (3/8 in. diameter): 3/8-24 UNF
  • 37SM-1d (1/2 in. diameter): 9/16-12 UNC
  • 37SM-1e (6 mm diameter): 1/4-20 UNF
  • 37SM-1f (8 mm diameter): 5/16-24 UNF
  • 37SM-1g (10 mm diameter): 7/16 -14 UNF
  • 37SM-1h (12 mm diameter): 1/2-13 UNF
  • 37SM-1i (16 mm, 5/8 in. diameter): 5/8-18 UNF
37SM-1b Wire guide & mounting clamp for 5/16 in. diameter mooring wire
37SM-1c Wire guide & mounting clamp for 3/8 in. diameter mooring wire
37SM-1d Wire guide & mounting clamp for 1/2 in. diameter mooring wire
37SM-1e Wire guide & mounting clamp for 6 mm diameter mooring wire
37SM-1f Wire guide & mounting clamp for 8 mm diameter mooring wire
37SM-1g Wire guide & mounting clamp for 10 mm diameter mooring wire
37SM-1h Wire guide & mounting clamp for 12 mm diameter mooring wire
37SM-1i Wire guide & mounting clamp for 16 mm (5/8 in.) diameter mooring wire
37SM-1j Alternative mounting - plastic brackets to provide through-bolt mounting to a flat surface

See document 67096.

SBE 37-SM Storm Shipping Case Option - holds up to 4 SBE 37SMs
37SM-7 Storm Shipping Case (iM2950) instead of wood crate - holds up to 4 SBE 37SMs

Storm shipping case with custom foam inserts holds up to 4 MicroCATs that do not include dissolved oxygen — IMP, IM, SMP, SM, SIP, SI.

  • 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 37SM-7 reflects a credit for deletion of our standard wood crate.

SBE 37-SM 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-SM manual for details.

In 2008, original battery pack was replaced with red top battery holder, which uses 12 AA lithium batteries instead of 50243.1 battery set. See MicroCAT Change Notice and Application Note 89 for details.

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 (SMP & IMP with firmware > 4.0, and all IDO & ODO MicroCATs) use a battery pack with a yellow cover plate; the wiring of that pack is different from this one, and cannot be used with SBE 37-SM.



801797 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)

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
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. This cap, without a hose barb, is a spare, and is intended for use during deployment.
Note: Do not deploy MicroCAT with barbed anti-foulant device cap(s)!

50087.1 Cell filler/storage device with hose barbs (Application Note 34) This kit includes a syringe & tubing assembly, & 2 anti-foulant device caps with hose barbs. Remove installed anti-foulant device cap(s) & replace them with caps with hose barbs for cleaning & storage only.
  • Cleaning instructions require use of syringe & tubing assembly at intake end of conductivity cell (requiring 1 barbed cap).
  • Storage instructions require looping Tygon tubing from end to end of conductivity cell (requiring 2 barbed caps).
Do not deploy MicroCAT with barbed anti-foulant device cap(s)!
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 37SM.xx1x0 (XSG connector) selected; this is spare.
801206 Data/Power interface cable, Wet-Pluggable, MCIL-4FS to DB-9S & red/black twisted wire leads, 2.4 m (DN 32366) Included with standard shipment if 37SM.xx2x0 (MCBH connector) selected; this is spare.
20200 USB to Serial Port Adapter, FTDI UC232R-10 (connects computers with USB ports to RS-232 instruments) Many newer PCs & laptop computers have USB port(s) instead of RS-232 serial port(s). USB serial adapter plugs into USB port, & allows a serial device to be connected through adapter. Multi-port adapters are available from other companies; see Application Note 68.
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 This pressure port plug extends beyond surface of instrument end cap, and has 4 horizontal vent holes connecting internally to a vertical vent hole. If you are deploying 37-SM in an orientation close to horizontal, with pressure port up, horizontal orientation of vent holes prevents deposit of sediment inside pressure port. Each of the 4 vent holes is larger than single vent hole in standard pressure port plug, significantly reducing possibility that biological growth will cover all holes. See Application Note 84.
31632 Storm Shipping Case (iM2950) - holds up to 4 SBE 37SMs

Storm shipping case with custom foam inserts holds up to 4 MicroCATs that do not include dissolved oxygen — IMP, IM, SMP, SM, SIP, SI.

  • 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).

 

Cables

Note: In 2008, a 4-pin bulkhead connector became standard for all 37-SMs. 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

Mount Kits

Mounted to Flat Surface

  • 50264 SBE 37-SI or SM Thru Bolt Mounting Clamp Kit (document 67096)

Mounted to Mooring Cable
(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 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
  • 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
  • 50271  SBE 37-SM or SI Cable Clamp Kit, 16-mm (5/8-inch) diameter
  • 50410  SBE 37-SM or SI Cable Clamp Kit, 20-mm diameter

Spare Parts

Batteries

  • 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)
  • 50441 SBE 37 and 44 lithium batteries, package of twelve 3.6V AA cells (Saft LS 14500)

Hardware & O-Ring Kits

  • 60023 Hardware & O-ring kit for SBE 37-SM or 37-IM (instruments delivered in 1999 and earlier, with battery pack that requires knob to remove from instrument) (document 67032)
  • 60023.1 Hardware & O-ring kit for SBE 37-SM or 37-IM (instruments delivered in 1999 and earlier) (document 67063)
  • 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)

Miscellaneous

  • 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)