Sea-Bird Electronics            Products            Support            Software            Sales            Service            Search/Sitemap

MicroCAT C-T-ODO (P optional) Recorder
nductive Modem, integral Pump, & integrated Optical Dissolved Oxygen)

[HRule Image]

Print version     Current manual (older manuals)    Reference Sheet     Configuration options & accessories

Intended for deployment in orientation shown (sensor end up) for proper operation.
SBE 37 MicroCAT CTD and Optical Dissolved Oxygen Recorder with Inductive Modem
Titanium housing; plastic housing also available.



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:

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:


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


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.


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)
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
Oxygen 120% of surface saturation in all
natural waters (fresh and salt)
larger of 3 mol/kg
(equivalent to 0.07 ml/L or 0.1 mg/L)
or 2%
sample-based drift <
mol/kg/100,000 samples (20 C)
0.2 mol/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, Depth Rating, & Weight:

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)


       Note: 103 mm dimension is for plastic housing; titanium housing dome is 9 mm smaller


Documentation -- manual, photos, technical papers, application notes, etc.

Sales Information -- options, accessories, cables, mount kits, spares, etc.

Software -- components of Seasoft V2

Links to Other Instruments of Interest

[HRule Image]  

Specifications are subject to change without notice.

Sea-Bird Home     Phone: (+1) 425-643-9866     E-mail: