YSI VisoTurb 700 IQ - Manual (Page 29)

VisoTurb
®
700 IQ (SW) Measuring
4 - 3 ba76039e01 01/2012
4.2.2 Application offset
In an optimum installation (sufficient distance to the walls, walls made
of dark material), the effect of the measurement environment is
negligibly small. If an optimum installation is not feasible due to local
circumstances, interference effects can be compensated by a
measured value correction.
Note
Depending on the test sample, the optical characteristics of the vessel
inner surface can change greatly with time (biological films, lime
deposits). This can affect the turbidity measurement. Repeat the
application offset from time to time as well as to check the effect of the
surfaces if excessive turbidity values are suspected.
Determining the
correction value
The determination of the correction value can be carried out using
normal drinking water. Two measurements are performed:
The correction value is calculated from the two measurements as
follows (the correction value is usually negative):
Entering the correction
value for the
measurement
The correction value is entered in the setting table of the turbidity
sensor in the Application offset field (see section 3.4.2).
Ideal measurement
environment
An ideal measurement environment for the application offset can be set
up with the following simple accessories:
 Bucket made of black plastic, with a capacity of at least
10 l
 Holding device for the sensor, e. g. laboratory stand
 Shading against direct sunlight (cardboard or similar).
Position the sensor as shown in the following diagram:
1. Measurement in an environment that is as ideal as possible
(reference value).
2. Measurement in the actual measurement environment.
Correction value = turbidity value (ideal) - turbidity value (real)