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.
- 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.
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.
|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-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.||
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:
|Direct Cable Connection
|SIM||35 mA||20 mA||Not allowed||20 mA|
Low power transmit setting 1
|Not allowed||1.2 mA||Not allowed||1.3 mA|
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|
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.
Surface Inductive Modem
|Communicating with 1 or more IM instruments (SBE 16plus-IM, 16plus-IM V2, 37-IM, 37-IMP, 37-IMP-IDO, 37-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.
Compare Inductive Modem Instruments
(C, T, P)
|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