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MicroCAT C-T (P optional) Recorder
SBE 37-SM
(S
erial interface & Memory)

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Print version     Current manual - RS-232 or RS-485 (older manuals)   Reference Sheet - RS-232 or RS-485    Configuration options & accessories

SBE 37 MicroCAT CTD Moored Recorder
Titanium housing; plastic housing also available

SUMMARY

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 SeaCAT plus. 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:

User-selectable operating modes include:

SOFTWARE

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

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. *

SPECIFICATIONS

  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, Depth Rating, and Weight (without pressure sensor):

Housing Material Depth Rating Weight
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
     

Dimensions: in millimeters (inches)

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

ADDITIONAL INFORMATION / LINKS:

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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