Surface Inductive Modem

Surface Inductive Modem (SIM)

Link between the underwater IM instruments and the computer / buoy controller. Communication with the computer / buoy controller is via RS-232.

The Surface Inductive Modem (SIM) is a vital link in Sea-Bird’s inductive modem (IM) telemetry systems, which provide data communications without the need for underwater electrical connections. Each system requires:

  • SIM, housed in a buoy or on land. The SIM provides the link between the underwater IM instruments and the computer / buoy controller. Communication with the computer / buoy controller is via RS-232.
  • Underwater IM instruments. The SIM can link to up to 100 inductively coupled instruments on a jacketed mooring wire. Compatible instruments include:
  • SBE 37 MicroCAT C-T (optional pressure) Recorder — 37-IM, 37-IMP (integral Pump), or 37-IMP-ODO (integral Pump and integrated Optical Dissolved Oxygen).
  • SBE 39-IM Temperature (optional pressure) Recorder.
  • SBE 16plus-IM or 16plus-IM V2 SeaCAT C-T (optional pressure) Recorder, which can acquire additional data from optional auxiliary sensors (oxygen, fluorescence, etc.)
  • Underwater Inductive Modem Module (UIMM) or SBE 44 Underwater IM, which links to a current meter, Doppler profiler, etc. with a standard serial interface.
  • Instruments by other manufacturers with built-in Sea-Bird underwater inductive modems.

FEATURES

  • Communication link between SIM and underwater IM is half-duplex, so talking and listening is sequential.
  • SIM and user’s computer/controller communicate at 1200, 2400, 4800, or 9600 baud; SIM and underwater IM communicate at 1200 baud.
  • Sea-Bird’s field-proven IM telemetry, with more than 3000 Sea-Bird IM instruments deployed since 1997.
  • Five-year limited warranty.

COMPONENTS

An IM system provides reliable, low-cost, real-time data transmission for up to 100 IM-enabled instruments using plastic-coated wire rope (typically 3x19 galvanized steel) as both transmission line and mooring tension member. IM instruments clamp anywhere along the mooring, which is easily reconfigured by sliding and re-clamping instruments on the cable. In a typical mooring, a SIM in the buoy communicates with IM instruments and interfaces to a computer/data logger (not supplied by Sea-Bird) via RS-232. The data logger is programmed to poll each IM instrument for data, and sends the data to a satellite link, cell phone, etc.

OPTIONS

SIM-Direct: In typical cable-to-shore applications), the bottom end of the wire is grounded to seawater, and the top end remains insulated all the way to the SIM connection. A second wire from the SIM connects to seawater ground, completing the circuit.


SIM-Direct: Direct Connection

 

SIM-Coupled: In typical surface buoys it may be preferable to connect the jacketed mooring wire to the buoy with a length of chain, grounding the jacketed wire to seawater at each end. An Inductive Cable Coupler (ICC) connects the SIM to the jacketed wire above the uppermost underwater inductive instrument and below the point where the wire is grounded.


SIM-Coupled: ICC Connection

 

ADDITIONAL INFORMATION

Compare features of Inductive Modem Module (IMM) to SIM.

SIM Sensor Interface to computer or buoy controller: RS-232C; 1200, 2400, 4800, or 9600 baud; 8 data bits; no parity; echoing or no echoing of characters.
Current: 30 mA communicating, 27 mA quiescent state (PwrOff).
With control line, < 10 µA when turned off.
Voltage Input: 7-25 VDC
Underwater Instrument See SBE 37-IM, 37-IMP, 37-IMP-ODO, 39-IM, 16plus-IM, 16plus-IM V2, 44, and UIMM datasheets.
ICC See Inductive Cable Coupler datasheet

 

Communicating with 1 or more IM instruments requires use of Surface Inductive Modem (SIM) or Inductive Modem Module (IMM), which provides standard serial interface (RS-232) between user’s computer & up to 100 IM-compatible sensors coupled to single cable. An Inductive Cable Coupler (ICC) is always required if specifying SIM-COUPLED, & is often required if specifying an IMM.

ICC Version 4a is a 20-turn coupler, while Version 4b is a 100-turn coupler. Other couplers are available for OEM applications (contact Sea-Bird for ordering information). Table below summarizes power requirements for each:

  20-turn ICC
(version 4a)
100-turn ICC
(version 4b)
8-turn ICC
(OEM version)
Direct Cable Connection
(no ICC)
SIM 35 mA 20 mA Not allowed 20 mA
IMM
Low power transmit setting 1
Not allowed 1.2 mA Not allowed 1.3 mA
IMM
Full power transmit setting 1
12 mA 4 mA Not allowed 40 mA
Underwater Inductive Modem (UIM) 2 Not allowed Not allowed 15 mA Not allowed

Notes:
1 IMM power setting is set with SetEnableFullPwrTx= command.
2 Underwater Inductive Modem is a component used by OEMs to integrate Sea-Bird's inductive modem technology with a third-party sensor.

Drawing

The list below includes (as applicable) the current product brochure, manual, and quick guide; software manual(s); and application notes.

PART # DESCRIPTION NOTES
SIM

Surface Inductive Modem

Communicating with 1 or more IM instruments (SBE 16plus-IM, 16plus-IM V2, 37-IM, 37-IMP, 37-IMP-IDO37-IMP-ODO, 39-IM, 44, or UIMM) requires use of Surface Inductive Modem (SIM), which provides standard serial interface (RS-232 or RS-485) between user’s computer & up to 100 IM-compatible instruments coupled to single cable. SIM is housed in buoy or on land. Order SIM-COUPLED or SIM-DIRECT.
Note: IMM can be used in place of SIM.
SIM-COUPLED Surface Inductive Modem PC board (PN 40928) with RS-232/485 interface for use with Sea-Bird Inductive Cable Coupler (formerly SMODEM-1). Includes 3 m serial cable, PN 171887. For typical cable-to-buoy applications, it is often preferable to connect jacketed mooring wire to buoy with length of chain, grounding jacketed wire to seawater at each end. Inductive Cable Coupler (ICC) connects SIM to jacketed wire above uppermost underwater inductive instrument & below point where wire is grounded. Order SIM-COUPLED & Inductive Cable Coupler (ICC); see ICC listing.
SIM-DIRECT Surface Inductive Modem PC board (PN 40870) with RS-232/485 interface for use with direct mooring wire termination to Surface Inductive Modem board (formerly SMODEM-2). Includes 3 m serial cable, PN 171887.

For typical cable-to-shore applications, bottom end of wire is grounded to seawater, & top end remains insulated all way to connection to SIM. Second wire from SIM connects to seawater ground, completing circuit. Order SIM-DIRECT.

 

Many cables, mount kits, and spare parts can be ordered online.

Cables

  • 171887 To computer COM port,3 m

Compare Inductive Modem Instruments

SBE Measures
(C, T, P)
Auxiliary Sensors Memory Power Comments
Internal External
SBE 16plus-IM V2 SeaCAT C-T (P) Recorder C, T, P* 6 A/D; 1 RS-232 64 Mb   Optional pump
SBE 16plus-IM SeaCAT C-T (P) Recorder
C, T, P* 4 A/D; optional RS-232 or PAR 8 Mb   Replaced by SBE 16plus-IM V2 in 2008
SBE 37-IM MicroCAT C-T (P) Recorder C, T, P*   8 Mb    
SBE 37-IMP MicroCAT C-T (P) Recorder C, T, P*   8 Mb   Integral pump
SBE 37-IMP-IDO MicroCAT C-T-ODO (P) Recorder C, T, P* Integrated DO 8 Mb   Integral pump; Replaced by SBE 37-IMP-ODO in 2014
SBE 37-IMP-ODO MicroCAT C-T-ODO (P) Recorder C, T, P* Integrated Optical DO 8 Mb   Integral pump
SBE 39plus-IM Temperature (P) Recorder T, P*   64 Mb   Includes internal USB connector for fast data upload
SBE 39-IM Temperature (P) Recorder T, P*   32 Mb   Replaced by SBE 39plus-IM in 2016
SBE 44 Underwater Inductive Modem (UIM)   1 RS-232 30 Kb buffer Integrates sensor with standard serial interface (current meter, Doppler profiler, etc.) to inductive modem telemetry system
Underwater Inductive Modem Module (UIMM)   1 RS-232 16 Kb Sample Data Memory   Integrates sensor with standard serial interface (current meter, Doppler profiler, etc.) to inductive modem telemetry system; more flexible and economical than SBE 44

C = conductivity, T = temperature, P = pressure, DO = dissolved oxygen
* = optional

Notes:
1. See Inductive Modem Module (IMM) or Surface Inductive Modem (SIM), and Inductive Cable Coupler (ICC) to complete your inductive modem system.
2. See Application Note 92: Real-Time Oceanography with Inductive Moorings and the Inductive Modem Module (IMM) for background information.
3. products are no longer in production. Follow the links above to the product page to retrieve manuals and application notes for these older products.