Manual revision 019 Section 2: Description of MicroCAT SBE 37-SMP RS-232
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Section 2: Description of MicroCAT
This section describes the functions and features of the SBE 37-SMP
MicroCAT, including specifications, dimensions, end cap connectors, sample
timing, battery endurance, and external power.
System Description
The SBE 37-SMP MicroCAT is a high-accuracy conductivity and temperature
recorder (pressure optional) with internal battery and non-volatile memory, an
integral pump, and a standard RS-232 serial interface. Designed for moorings
and other long-duration, fixed-site deployments, MicroCATs have non-
corroding titanium housings rated for operation to 7000 meters (23,000 feet)
or pressure sensor full-scale range. An optional plastic ShallowCAT housing
rated for 350 meters (1150 feet) is also available.
Communication with the MicroCAT is over an internal, 3-wire, RS-232C
link. Over 50 different commands can be sent to the MicroCAT to provide
status display, data acquisition setup, data retrieval, and diagnostic tests.
User-selectable operating modes include:
•Autonomous sampling – At pre-programmed intervals, the MicroCAT
wakes up, runs the pump, samples, stores the data in its FLASH memory,
and goes to sleep. If desired, real-time data can also be transmitted.
•Polled sampling – On command, the MicroCAT runs the pump, takes one
sample, and transmits the data. Polled sampling is useful for integrating
the MicroCAT with satellite, radio, or wire telemetry equipment.
•Serial line sync – In response to a pulse on the serial line, the MicroCAT
wakes up, runs the pump, samples, stores the data in its FLASH memory,
and goes to sleep. If desired, real-time data can also be transmitted. Serial
line sync provides an easy method for synchronizing MicroCAT sampling
with other instruments such as Acoustic Doppler Current Profilers
(ADCPs) or current meters, without drawing on their battery or memory
resources.
The MicroCAT can be deployed in two ways:
•Cable installed – The MicroCAT can be remotely controlled, allowing for
polled sampling or serial line sync, or for periodic requests of data from
the MicroCAT memory. If desired, data can be periodically uploaded
while the MicroCAT remains deployed. Additionally, the MicroCAT can
be externally powered.
•Dummy plug installed – The MicroCAT cannot be remotely controlled.
Autonomous sampling is programmed before deployment, and data is
uploaded after recovery.
Calibration coefficients stored in EEPROM allow the MicroCAT to transmit
data in engineering units. The MicroCAT retains the temperature and
conductivity sensors used in the Seacat and Seacat plus family. The
MicroCAT’s aged and pressure-protected thermistor has a long history of
exceptional accuracy and stability (typical drift is less than 0.002 °C per year).
Electrical isolation of the conductivity electronics eliminates any possibility of
ground-loop noise.
For most applications, deploy in orientation
shown (connector end down) for proper
operation – see Optimizing Data Quality /
Deployment Orientation in Section4:
Deploying and Operating MicroCAT
ShallowCAT housing
