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MicroCAT C-T (P optional) Recorder
SBE 37-IM 
nductive Modem)

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

SBE 37 MicroCAT CTD with Inductive Modem
Titanium housing; plastic housing also available



The SBE 37-IM MicroCAT is a high-accuracy conductivity and temperature sensor/recorder (pressure optional) with internal battery, non-volatile memory, and built-in Inductive Modem. Calibration coefficients are stored in EEPROM, allowing output of C, T, P, and time in ASCII engineering units (decimal or XML; 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 for changing deployments (positions changed or instruments added or removed), by sliding and re-clamping instruments 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.


The MicroCAT retains the temperature and conductivity sensors used in our time-proven SeaCAT and SeaCATplus. Our 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.


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, 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 300,000 samples for a typical sampling scheme.


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

Dimensions: in millimeters (inches)

Clock Stability: 5 sec/month

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

Quiescent Current: 120 microAmps

Communications Current: 2.5 milliAmps

Communications Time: 0.5 sec/sample

Acquisition Current: 13 milliAmps

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

Housing, Depth Rating, and Weight:

Housing Material Depth Rating Weight (with standard mounting clamp & guide, without pressure)
Plastic 350 m (1150 ft) 2.9 kg (6.4 lbs) in air
1.3 kg (2.9 lbs) in water
Titanium 7000 m (23,000 feet) 4.0 kg (8.8 lbs) in air
2.4 kg (5.3 lbs) in water


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

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Specifications are subject to change without notice.  

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