WET Labs' Beam Attenuation Meter

Beam Attenuation Meter

The beam attenuation meter is specifically designed for Autonomous Underwater Vehicles to accommodate size and drag considerations.

WET Labs’ Beam Attenuation Meter is the next generation transmissometer specifically designed for Autonomous Underwater Vehicles (AUVs), where size and drag are primary considerations.

  • Compact size
  • Rugged construction
  • High precision and stability
  • Digital electronics
  • Protected optics
  • Flush mountable


Length19.56 cm
Height12.45 cm
Width6.35 cm
Weight in air 3.28 kg
Weight in water2.06 kg
Internal air volume 454 cc


Output resolution14 bit
RS-232 output19200 baud
Connector MCBH-6-MP
Power input7.5-15 VDC
Operating current35 mA (532 and 650 nm)
Sample rateto 8 Hz


Rated depth1000 m
Temperature range-2 to 38 deg C
Temperature storage-40 to 70 deg C
Temperature stability0.02% FS/deg C
Long term stability (6hrs)0.02% FS/Hr
Short term noise0.027% FS Std dev over 1 minute


Wavelengths470, 532,  or 650 nm
Optical pathlength10 cm
Acceptance angle~ 1 deg
Precision0.003 m-1 @ 1 Hz (532 and 650 nm)
Linearity99% R2
Specifications are subject to change without notice.


Product Datasheet

BAM datasheet

Monday, December 5, 2016
Product Manual

Transmissometers User Manual

Wednesday, May 17, 2017
Technical Note

Cable and Bulkhead Connector Maintenance

Thursday, March 9, 2017
Technical Note

Functional check and cleaning of transmissometer windows

Thursday, April 27, 2017
Technical Note

Instrument Voltage Ranges (in VDC)

Thursday, June 21, 2012
Technical Note

Information about acceptance angles for beam attenuation meters

Friday, June 22, 2012

Information about acceptance angles for beam attenuation meters.

The acceptance angle of a beam attenuation meter is defined by the detector aperture and the focal length of the lens. Download PDF

An Introduction to In-Situ Absorption and Attenuation Meters

  • Brief introduction to the optical properties we are trying to measure
  • Measurement of absorption and attenuation with an ac9
  • Current developments

Download Presentation

What should I use to lubricate bulkhead connectors?

WET Labs recommends keeping the connectors on your meter lubricated using a good quality silicone spray lubricant, such as 3M Silicone Spray or Loctite 8021 spray. These can be purchased at your local hardware store. Avoid silicone grease. It is messy and attracts contaminants. 

Do not use WD-40. It will destroy connectors.

Do you want WET Labs to review your data?

In order for data questions to be answered in an efficient manner, WET Labs requests:

-  The serial number of the instrument data in question. The most current calibration information
can be verified and the instrument settings upon delivery can be checked.

-  Description of the deployment configuration. Questions to consider:

  •   What are the current instrument settings?
  •   What is the instrument orientation?
  •   Are there possible obstructions?
  •   Is it being used in a mooring, a profiler, or being towed?
  •   What were the deployment date and geographical location?
  •   How far into the deployment was the problem seen?
  •   What power supply and cabling are being used?
  •   What was the instrument condition during the last field service or retrieval?
  •   Do you have any pictures?

-  Raw data files of the physical data in question

  •   examples of good raw data.
  •   examples of questionable raw data .

-  Information about how the raw data was processed.

How do I clean the optical surfaces on my transmissometer?

Functional Checks and Cleaning Methodology for WET Labs Transmissometers Download PDF

IOP Tutorial on Primary Data Processing

Real-Time Coastal Ocean Observing Systems for Ecosystem Dynamics and Harmful Algal Blooms, Villfrance, France- By Andrew Barnard Download PDF Presentation