Manual revision 001
Section 2: Description of SBE 39
plus
-IM
SBE 39
plus
-IM
9
Section 2: Description of SBE 39plus-IM
This section describes the functions and features of the SBE 39
plus
-IM,
including specifications and dimensions, battery endurance, and mooring
requirements.
System Description
The SBE 39
plus
-IM is a high-accuracy temperature recorder (pressure
optional) with internal battery pack and non-volatile memory. It uses an
Inductive Modem (IM) to transmit data and receive commands over a plastic-
jacketed steel mooring cable (or other insulated conductor), using differential-
phase-shift-keyed (DPSK) telemetry. No electrical cables or connectors are
required. The 39
plus
-IM’s built-in inductive coupler (split toroid) and cable
clamp provide easy and secure attachment to the mooring cable. Designed for
moorings and other long-duration, fixed-site deployments, 39
plus
-IMs have
non-corroding plastic (600 meters) or titanium housings (10,500 meters).
The SBE 39
plus
-IM retains the temperature sensor used in the SBE 39
plus
Temperature Recorder. The 39
plus
-IM’s thermistor has a long history of
exceptional accuracy and stability (typical drift is less than 0.002 °C per year).
Two temperature sensor configurations are offered:
•
Ruggedized model with the thermistor embedded in the titanium end cap
(time constant approximately 25 seconds).
•
(shown in photo) Model with external thermistor in a pressure-protected
sheath (time constant approximately 0.5 seconds) for use when fast
sampling is required.
The SBE 39
plus
-IM is available with no pressure sensor, or with a strain-
gauge pressure sensor in the following ranges: 20, 100, 350, 600, 1000, 2000,
3500, and 7000 meters. Compensation of the temperature influence on
pressure offset and scale is performed by the SBE 39
plus
-IM’s CPU.
Communicating with one or more 39
plus
-IMs requires the use of a Sea-Bird
Inductive Modem Module (IMM) or Surface Inductive Modem (SIM). These
devices provide a standard serial interface between the user’s computer or
other controlling device and up to 100 SBE 39
plus
-IMs (or other IM-
compatible instruments), coupled to a single cable. The user can communicate
with these devices via full-duplex RS-232C. Commands and data are
transmitted half-duplex between these devices and the 39
plus
-IM.
Commands can be sent to the 39
plus
-IM to provide status display, data
acquisition setup, data retrieval, and diagnostic tests. User-selectable
operating modes include:
•
Polled sampling
– On command, the 39
plus
-IM takes one sample and
transmits data.
•
Autonomous sampling
– At pre-programmed 5-second to 6-hour
intervals, the 39
plus
-IM wakes up, samples, stores data in memory, and
powers off (enters quiescent state).
•
Combo sampling
– Autonomous sampling is in progress, and the IMM or
SIM can request the transmission of the last stored data.
•
Averaging sampling
– Autonomous sampling is in progress, and the
IMM or SIM can request the transmission of the average of the individual
data samples acquired since its last request.
Notes:
•
For detailed information on
inductive modem systems, see
Application Note 92: Real-Time
Oceanography with Inductive
Moorings
on our website.
•
Half-duplex communication is
one-direction
at a time (i.e., you
cannot send commands and
receive data at the same time).
For example, if the IMM or SIM
commands a 39
plus
-IM to upload
data, nothing else can be done
while the data is being sent – the
data upload cannot be stopped,
and commands cannot be sent to
other IM instruments on the line.
SBE 39plus-IM with
external thermistor
