Abstract: The invention provides a radiation sensor including a housing, an attenuator with at least one cavity for attenuating optical radiation, and a detector, as well as an optical attenuator including an attenuator body, an entrance with one multi-stage input opening or plural input openings, and means for transferring radiation inside of the attenuator body and then to a detector. The invention further provides methods for using the radiation sensor or the optical attenuator.

Abstract: A small size turbidity sensor for underwater in-situ measurements in the wide range of turbidity values is disclosed that may be integrated into a housing with other underwater sensors. The turbidity sensor incorporates micro focusing devices and light stop that gives no divergence excitation beam with convergence less than 1.5 degrees and the measuring angle between the optical axis of the incident radiation and mat of the diffused radiation 90 ±2.5 degrees. Another embodiment includes internal and external optical calibrators that allows the sensor to work longer without human intervention.

Abstract: The invention provides a radiation sensor including a housing, an attenuator with at least one cavity for attenuating optical radiation, and a detector, as well as an optical attenuator including an attenuator body an entrance with one multi-stage input opening or plural input openings, and means for transferring radiation inside of the attenuator body and then to an detector. The invention further provides methods for using the radiation sensor or the optical attenuator.

Abstract: A turbidity sensor for underwater measurements is provided with a watertight housing, a light emitting diode, a first light focusing device for focusing a light emitted from the diode and passing the focused light into to-be-measured water, a second light focusing device for collecting at least one scattered light resulted form the focused light when passing the water, a photodiode for receiving the collected light thereby generating electronic signals, and an electronic board for processing the electronic signals.