Turbidity; Safety Statement - Valeport Hyperion Operating Manual

Fluorometer

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0901814c - Hyperion Fluorometer

3.4. Turbidity

Valeport's Turbidity technology is essentially two sensors in one. The first is a "classic" nephelometer,

using a 90° beam angle for turbidity levels between 0 and 2000 NTU. The second sensor uses optical

backscatter - OBS (~120° beam angle) for turbidity levels beyond 10 000 NTU. Both sensors output

data simultaneously, at a programmable rate, so there is no need to switch ranges as conditions vary.

Intelligent sampling and the use of a 24 bit ADC eliminates the need to switch gain. The optical head

is very compact, measuring just 20mm diameter and is rated to full ocean depth.

Excitation\Detection:

Linear Range:

Minimum Detection

Level

Valeport's turbidity sensor uses a near Infra Red (NIR) LED operating at 850 nm with a reflector

producing a fairly narrow output beam. As the photo-response of the eye is low at 850 nm the blink

reflex and iris contraction reflex are not activated. NIR LEDs generally produce very low levels of

radiation and pose no threat to the human eye. A photometric test report was commissioned by

Valeport in accordance with BS EN 62471. For this the LED was set to 25 times the operational power

and the sensor was classified as exempt. However, it is best practice to avoid extended exposure to

the LED and it is recommended not to look directly into the sensor windows.

The Turbidity sensor is classified EXEMPT under the standard 62471.

As a Hyperion Turbidity instrument is classified as EXEMPT a hazard label in not required.

850nm

Nephelometer

Optical Backscatter:

(>6,000 NTU has a non-linear monotonic response that allows derivation

of higher values using look-up tables)

0.03 NTU

Never look directly into the Hyperion aperture

0 to >1 000 NTU - linear response

0 to 6 000 NTU - linear response

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