Integrated Optical Profiler

Transmissometer is a part of an integrated optical profiler, consisting of transmissometer, fluorometer, temperature and pressure gauges.

The underwater part consists of independent measuring, microprocessor and A/C converter modules, mounted together in a housing cage.
On-deck unit provides power supply to underwater part and demodulates information signal and converts it to RS232 standard. Unit is mounted on and powered by the standard CAMAC rack. The PC computer connected via the RS232 controls the measuring process, displays and stores acquired data.

Transmissometer

Conceptually the transmissometer is close to that proposed by Bartz and Zaneveld, (1978), with enhancements in electronics and different design.
As the light source the Siemens CQV30 660 nm LED is used. Light is modulated by local 500 Hz generator. As a detectors two BPYP 07 photodiodes are used. Collimated light passes 25 cm path in water and is directed back to the detector by the prism, travelling totally 50 cm in the water body. The light source is controlled by the second photodiode, electronically coupled with detecting diode. The transmissometer is calibrated against the air as a non-absorbing media, and the appriopriate calibration constats are added to the c definition formula.


  1. Light source
  2. Splitting beam prism
  3. Glass window
  4. Detector photodiode
  1. Compensating photodiode
  2. Condenser lenses
  3. Prism

Technical specification:

light source: Siemens CQV30 660 nm LED
light detector: BPYP 07 photodiode
path: 0.5 m
max. sampling freq.: 5 Hz
accuracy: 5% for c > 2 m-1
  2% for 0.4 < c < 2 m-1
temperature stability: for 0-30 deg less than 0.5 promille per 1 deg

References 

Bartz R., Zaneveld J.R.V., 1978, A transmissometer for profiling and
   moored observations in water. SPIE, 160, Ocean Optics V, 102-108.