Strain-Gauge Pressure Sensor 
SBE 29

The SBE 29 pressure sensor, used on our SBE 25 Sealogger CTD (no longer in production as of 2012), is a modular sensor consisting of a mechanical strain-gauge pressure transducer with thermistor temperature compensation. The SBE 29 measures absolute pressure in one of seven full scale pressure ranges from 20 to 7000 meters depth. The sensor elements and their interface electronics are modular and self-contained, providing easy installation, service, and calibration.

The SBE 29 interface electronics provide a pressure-dependent output voltage (+5 to -5) and a temperature-compensation voltage of 0 to +5 VDC (30K ohm thermistor at 25° C). Temperature-corrected pressure in engineering units [Pnum] is computed using the following equation:

Pnum =Vp * 819 - (TC * T/1024)

where

• Vp = pressure signal voltage

• TC = compensation value (from SBE 29 calibration sheet)

• T = temperature [°C] = -Vt * 21.02373 + 40.293 [°C], 
  where Vt = TC signal voltage

Each sensor is calibrated over its full scale range using a dead weight tester. Calibration results are tabulated on a certificate furnished with each sensor.

SPECIFICATIONS

Measurement Range: 20/100/350/1000/2000/3500/7000 meters (expressed in meters of deployment depth capability)

Accuracy: ± 0.1% of full scale range

Typical Stability (per year): 0.05% of full scale range

Power Required: +10 and -10 VDC at 15 mA

Housing Materials:

• Less than 3500 meters -- Anodized aluminum (6061)
• 3500 meters and above -- Anodized aluminum (7075)

Weight: 0.7 kg (1.6 lbs) in air; 0.3 kg (0.7 lbs) in water

ADDITIONAL INFORMATION / LINKS:

Documentation -- manual, photos, technical papers, application notes, etc.

• Print version of this specification sheet / brochure
• Application Notes:
  - 27Druck: (Druck) Strain Gauge Pressure Sensor Error Sources
  - 69: Conversion of Pressure to Depth
  - 71: Desiccant Use and Regeneration (drying)
  - 73: Using Instruments with Pressure Sensors at Elevations Above Sea Level

Sales Information -- options, accessories, cables, mount kits, spares, etc.

• Configuration options & accessories:
  - Details for SBE 29
  - Listing for all products
• Cables
• Mount kits
• Spare parts

Links to Other Instruments of Interest

• SBE 50 Digital Oceanographic Pressure Sensor -- RS-232 (optional 0 -5 volt output) pressure sensor