Temperature (& Pressure) RecorderSBE 39-IM (Inductive Modem)
Temperature (& Pressure) Recorder
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Reference Sheet
Configuration options & accessories
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DESCRIPTION
The SBE 39-IM is a high-accuracy temperature (pressure optional) recorder with built-in Inductive Modem. The modem provides reliable, low-cost, real-time data transmission for up to 100 sensors — all 39-IMs or a mix with other IM-capable instruments — using a single, plastic-coated, steel mooring cable. IM instruments clamp anywhere along the inherently rugged mooring cable; expensive and potentially unreliable multi-conductor cables are not required.
IM sensor moorings are easily reconfigured to meet changing deployment scenarios. Because sensor positions can be altered (or sensors added/deleted) by sliding and re-clamping sensors on the wire, there is no need to design and purchase a new cable with different breakout locations. IM systems permit data telemetry from sensors located anywhere along the mooring wire, making them far more efficient and flexible than acoustic modem types that place serious demands on battery capacity and return data from a single underwater position only. At the surface (typically in a buoy), a Surface Inductive Modem (SIM) completes the link between the sensors and a computer or data logger. Data from the sensor string can be stored and transmitted via satellite link, cell phone, or radio telemetry. As insurance against real-time data loss, the 39-IM simultaneously stores data in its non-volatile memory.
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:
The 39-IM's optional Druck pressure sensor employs a micro-machined silicon diaphragm in which the strain elements are implanted with semiconductor fabrication techniques. Unlike metal diaphragms, silicon's crystal structure is perfectly elastic, so the sensor is essentially free of pressure hysteresis. Compensation of temperature influence on pressure is performed by the 39-IM's CPU.
COMMUNICATIONS AND INTERFACING
The bottom of the insulated mooring wire is grounded to seawater, typically via a padeye swaged to its steel core; a padeye at the top completes a conductive loop through the water. A coupling transformer — similar to the one in the 39-IM but clamped to the mooring cable just under the buoy — connects to the SIM (SIM and transformer available separately). Communication with the SIM is via full-duplex RS-232C or half-duplex RS-485. Communication between the SIM and 39-IM is half-duplex using DPSK (differential-phase-shift-keyed) telemetry. Full ocean-depth mooring cables can be used. The system provides a high degree of immunity from fishbite or other cable degradation. Lab diagnostics, setup, and data extraction may be performed by looping any insulated wire through the inductive core and connecting the wire ends to the SIM.
Each 39-IM (or other IM sensor) has a programmable address. Upon receipt of a wake-up command, the SIM sends a tone for 2 seconds, waking all IM sensors on the cable. When a 39-IM receives a command, it replies and then returns to listening. A global power-off command returns all 39-IMs to a quiescent, standby state; they automatically return to quiescent state after no line activity for 2 minutes.
OPERATING MODES
User-selectable operating modes include:
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.
CONFIGURATION
A standard 39-IM is supplied with plastic housing for depths to 600 meters, internal thermistor, and wire guide and clamp.
Options include:
CALIBRATION
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.
SOFTWARE
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.
SPECIFICATIONS
| Measurement Range | Initial Accuracy | Typical Stability | Resolution | |
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Temperature (°C) |
-5 to 35 | ±0.002 | 0.0002 per month | 0.0001 |
| Optional Pressure |
20 / 100 / 350 /
600 / 1000 / 2000 / 3500 / 7000 meters (Expressed in meters of deployment depth capability) |
0.1% of full scale range | 0.05% of full scale range per year | 0.002% of full scale range |
Clock Accuracy: 5 seconds/month
Power Supply/Endurance:
Quiescent Current: 20 microAmps
Communication Current: 0.6 milliAmps
Communication Time: 0.5 seconds/sample
Acquisition Current (per sample):
Memory: 64 Mbyte non-volatile FLASH (32 Mbyte usable)
(T=3 bytes/sample; time=4 bytes/sample, P=4 bytes/sample)
Housing/depth rating:
Weight (without fairing):
| Housing | In Air | In Water |
| Plastic housing (configured with embedded thermistor) * | 1.1 kg (2.4 lbs) | 0.5 kg (1.0 lbs) |
| Titanium housing (configured with embedded thermistor) * | 1.6 kg (3.6 lbs) | 1.0 kg (2.2 lbs) |
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* Other configurations vary. |
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ADDITIONAL INFORMATION / LINKS:
Documentation -- manual, photos, technical papers, application notes, etc.
Sales Information -- options, accessories, cables, mount kits, spares, etc.
Software -- components of Seasoft V2
Links to Other Instruments of Interest
Specifications are subject to change without notice.
Sea-Bird Home Phone: (+1) 425-643-9866 E-mail: seabird@seabird.com
