In-Situ TROLL 9500 Operators Manual - Manual (Page 127)

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TROLL 9500 Operator’s Manual 0095110 rev. 007 01/09
be detected. The plate is then pulled up until it is visible again. The
average of the two depths provides an estimate of water clarity or
transparency.
Modern turbidimeters measure the loss in intensity of a light beam
as it passes through a solution containing suspended and dissolved
particles that are large enough to scatter the light. The method is
based upon a comparison of the intensity of light scattered by the
sample with the intensity of light scattered by a standard reference
suspension. The nephelometer is a particular type of turbidimeter
THAT
THE TURBIDITY SENSOR
The optional turbidity sensor of the Multi-Parameter TROLL 9500 is
permanently-installed and factory-calibrated. It may be a turbidity
sensor alone or a pressure/turbidity sensor combination. If your MP
TROLL 9500 was ordered without a turbidity sensor or a pressure
sensor, there will be a permanently installed plug in the pressure/tur-
bidity sensor slot. A turbidity sensor or combination pressure/turbidity
sensor can be added at the factory.
The In-Situ turbidity sensor is comprised of a matched solid-state
detector-emitter pair positioned at right angles. The light source is an
infrared LED, optimized for operation at 870 nanometers (nm). The
optical windows of the detector (photodiode) and emitter (LED) are
SCRATCH
RESISTANT
The In-Situ sensor is an electronic nephelometer which compares
THE
THE TURBIDITY WIPER
The optional wiper accessory helps to keep the turbidity sensor optics
free of bubbles and fouling.
The wiper installs in port 3 of the MP TROLL 9500 like other remove-
able sensors. A positional brace aligns it with respect to the turbidity
sensor and keeps it stable in moving waters.
The wiper pad is adhesive-free, low-abrasion cotton material. The
pad is easily replaced when it becomes too soiled to clean the sensor
optics effectively.
Use of the wiper will significantly impact battery life. Lithium
batteries are recommended.
SECTION 18: TURBIDITY