YSI IQ SensorNet ViSolid Sensor 700 IQ - Manual (Page 14)

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Commissioning ViSolid
®
700 IQ (SW)
3.3.2 General information
The measuring principle of the ViSolid
®
700 IQ (SW) (scattered light
measurement) places specific requirements on the measurement loca-
tion and on the installation of the sensor.
If there is a low level of total suspended solids (< 2000 mg/l SiO2 or
< 1000 mg/l TSS), infrared light penetrates deep into the sample. Thus,
the measuring environment can have a significant effect on the mea-
sured value displayed. Light that is reflected or scattered by the ground
or wall can strike the detector in the sensor and, thus, simulate an
increased level of total suspended solids.
Scattered light can be kept away from the measurement windows to a
great extent by favorable positioning of the sensor. Therefore, an opti-
mum installation position is particularly important for the measurement
of lower values of total suspended solids.
The following factors affect the measurement of the TSS contents:

Inclination of the sensor (see section 3.3.4)
 Sensor orientation around its longitudinal axis (see section 3.3.5)
 Distances from the ground and wall (see section 3.3.6)
 Light-colored, heavily light-scattering surfaces in the measuring ves-
sel (e.g. vessel inner surfaces) or in the measuring environment.
 Unfavorable geometry of the measuring vessel or unfavorable posi-
tioning of the sensor in the measuring vessel.
 Spatial proximity of two optical sensors.
 Very bright ambient light at the measuring location, e.g. direct sun-
light in the open channel
Always maintain a distance of at least 10 cm from the
ground and wall.