The SBE 39-IM is a high-accuracy temperature (pressure optional) recorder with built-in Inductive Modem. The IM system provides reliable, low-cost, real-time data transmission for up to 100 IM-enabled instruments, using plastic-coated wire rope (typically 3 x 19 galvanized steel) as both the transmission line and mooring tension member. IM instruments clamp anywhere along the rugged mooring wire. Expensive and potentially unreliable multi-conductor electrical cables with fixed-position underwater connectors are not required. IM moorings are easily reconfigured for changing deployments (positions changed or instruments added or removed) by sliding and re-clamping instruments on the cable. IM systems are much less expensive and more power efficient than acoustic modems, and offer reliable communications over greater distances.
In a typical mooring, an Inductive Modem Module (IMM) or Surface Inductive Modem (SIM) housed in the buoy communicates with underwater IM instruments and is interfaced to a computer or data logger via an RS-232 serial port. The computer or data logger (not supplied by Sea-Bird) is programmed to poll each IM instrument on the mooring for its data, and send the data to a telemetry transmitter (satellite link, cell phone, RF modem, etc.). The 39-IM saves data in memory for upload after recovery, providing a data backup if real-time telemetry is interrupted.
The 39-IM's thermistor, the same as used in the SBE 39, has a long history of exceptional accuracy and stability; drift is typically less than 0.002 °C per year. Two thermistor configurations are offered:
Thermistor embedded in titanium end cap (25.0-second time constant), for rugged conditions.
External thermistor in pressure-protected sheath (0.5-second time constant), for fast sampling.
The optional strain-gauge pressure sensor is available in eight ranges, to a maximum depth of 7000 meters. Compensation of temperature influence on pressure is performed by the 39-IM's CPU.
User-selectable operating modes include:
Polled: On command, 39-IM takes one sample and transmits the data.
Autonomous: At pre-programmed 10-second to 8.3-hour intervals, 39-IM wakes up, samples, records data in FLASH memory, and powers off.
Combo or Averaging: The 39-IM samples autonomously, and the IMM/SIM can request the last stored data or the average of the samples acquired since the last request.
DATA STORAGE AND UPLOAD, AND BATTERY ENDURANCE
The 39-IM has a 64 Mbyte non-volatile FLASH memory (32 Mbyte usable). Temperature and time are always stored (total of 7 bytes/sample); pressure adds 4 bytes/sample. Data extraction can be done via the internal RS-232 connector; binary upload capability provides fast upload of large data sets. For example, a 39-IM uploads 466,000 samples of T, P, and time in only 67 minutes — including error checking each block of data. Calibration coefficients are stored in EEPROM, and uploaded data is in ASCII engineering units (°C and decibars).
With its two 3.6-volt, non-hazardous, AA lithium batteries, the 39-IM can acquire more than 400,000 samples of T, P, and time. Because of the low power consumption when not sampling, deployments of 3 years or more are possible.
A standard 39-IM is supplied with plastic housing for depths to 600 meters, internal thermistor, and wire guide and clamp.
- External thermistor in pressure-protected sheath
- Titanium housing for depths to 10,500 meters
- Strain gauge pressure sensor — available in eight pressure ranges, to a maximum depth of 7000 meters
- Net fender / fairing — conical ends are shaped to shed fishing lines and nets
The 39-IM's inherent accuracy, resolution, and stability, combined with a rigorous 11-point temperature calibration, yields a true research-quality tool. Primary temperature standards (water-triple-point and gallium-melting-point cells) and state-of-the-art equipment are maintained in our NIST-traceable calibration facility. Pressure calibrations are referenced to specially maintained (at Sea-Bird) Digiquartz sensors that trace to Paroscientific's pressure standard.
The 39-IM is supplied with a powerful Win 2000/XP software package, Seasoft© V2, for communication, data upload, data conversion, plotting, and export to other programs.