Endress+Hauser CUS51D Specifications
TI00461C/07/EN/17.19
71438793
2019-01-31
Products Solutions Services
Technical Information
Turbimax CUS51D
Sensor for turbidity and solids content
Application
Turbimax CUS51D is a sensor for all wastewater treatment
applications.
• Turbidity measurement in the outlet
• Solids content in sludge activation and recirculation
• Solids content in sludge treatment
• Filterable matter in outlet of WWTPs
Your benefits
• All sensor principles (90°, 135° and 4-beam pulsed light) are
contained in the sensor head and enable optimum
adaptation to the measuring task.
• The sensor is calibrated in the factory (on the basis of
formazine). All selectable applications (e.g. activated sludge)
are pre-calibrated, thereby enabling quick and easy
commissioning.
• Standardized communication (Memosens technology)
enables "plug and play".
• Intelligent sensor - all characteristics and calibration values
are stored in the sensor.
• Customer calibrations with 1 to 5 points (max.) - can be
performed in the lab or at place of installation.
Function and system design
1
2
3
4
90°
135°
1
2
3
Turbimax CUS51D
Measuring principle
For turbidity measurement a light beam is directed through the medium and is deflected from its
original direction by optically denser particles, e.g. particles of solid matter. This process is also called
scattering.
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1 Deflection of light
1 Light source
2 Light beam
3 Particle
4 Scattered light
The incident light is scattered in many directions, i.e. at different angles to the direction of
propagation. 2 angle ranges are of particular interest here:
• Light scattered at a 90° angle is used primarily for turbidity measurement in drinking water.
• Light scattered at a 135° angle extends the dynamic range for high particle densities.
2 Principle mode of operation of turbidity sensor
1 Light source
2 135° light receiver
3 90° light receiver
If the particle density in the medium is low, a large amount of light is scattered in the 90°channel
and a small amount of light is scattered in the 135° channel. As the particle density increases, this
ratio shifts (more light in the 135° channel, less light in the 90° channel).
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Turbimax CUS51D
1
Ir
FNU
90°
135°
1
2
3
4
5
6
A0030849
3 Signal distribution as a function of the particle density
Ir Relative intensity
FNU Turbidity unit
The CUS51D turbidity sensor has 2 sensor units, which are independent of each other and arranged
in parallel. The application-dependent evaluation of both signals leads to stable measured values.
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4 Arrangement of light sources and light receivers
1, 2 Light sources 1 and 2
3, 5 135° light receiver
4, 6 90° light receiver
The sensor covers a broad range of turbidity and solids measurements thanks to the optical
arrangement with 2 light sources, each with 2 light receivers placed at different angles (90° and
135°).
• As soon as the customer selects an application, e.g. activated sludge, the optical method best
suited for the particular measuring task is automatically activated in the sensor (e.g. 90°
measurements with both light sources).
• The double sensing system (2 light sources with 2 receivers per source) largely compensates for
measured errors caused by fouling (4-beam pulsed light method → 3).
The sensor types available vary in terms of their measuring ranges and therefore the range of
available applications.
Measuring methods
4-beam pulsed light method
The method is based on 2 light sources and 4 light receivers. Long-life LEDs are used as
monochromatic light sources. These LEDs are pulsed alternately and generate 4 scattered light
signals per LED pulse at the receivers.
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Turbimax CUS51D
S
1
E
1-135
E
2-135
S
2
E
1-90
E
2-90
S
E
a
P
This offsets interference influences such as extraneous light, LED aging, fouling of windows and
absorption in the medium. Depending on the chosen application, different scattered light signals are
processed. The signal type, number and calculation are stored in the sensor.
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5 4-beam pulsed light method
S1 S
E
90
E
135
Light source
2
Light receiver for 90° scattered light
Light receiver for 135° scattered light
90° scattered light method
Measurement is performed with a wavelength of 860 Nm (634.3 lbf ft), as described in ISO 7027 /
EN 27027.
The emitted light beam is scattered by the solid particles in the medium. The scattered radiation
generated in this way is measured by scattered light receivers, which are arranged at an angle of 90°
to the light sources. The turbidity of the medium is determined by the amount of scattered light.
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6 90° scattered light method
S Light source
E Receiver
P Particle
135° backscattered light method
The emitted light beam is scattered by the solid particles in the medium. The backscattering
generated is measured by scattered light receivers, which are arranged next to the light sources. The
turbidity of the medium is determined based on the quantity of back-scattered light. It is possible to
measure very high turbidity values with this type of scattered light measurement.
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Turbimax CUS51D
S
1
E
1
P
I
0
I
S
a
Is= I0· C · A· f(a)
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7 Principle of backscattered light method
IoIntensity of transmitted light
IsIntensity of scattered light
A Geometric factor
C Concentration
P Particle
f(α) Angle correlation
Sensor monitoring
The optical signals are continuously monitored and analyzed for plausibility. If inconsistencies occur,
an error message is output via the transmitter. The function is disabled by default.
In addition, the following fault states are detected in conjunction with the sensor check system of the
Liquiline M:
• Implausibly high or low measured values
• Disturbed regulation due to incorrect measured values
Applications
Fields of application
Application
(models)
Formazine Industrial water, WWTP outlet FNU / NTU
Kaolin Filterable matter, industrial water, WWTP outlet, low
SiO
2
TiO
2
Thin sludge Thin sludge, ranging from activated sludge to clear water g/l; ppm; %
Activated sludge Activated sludge basin and similar media g/l; ppm; % X
Waste activated
sludge
Univ. sludge Universal use ranging from clear water to sludge with a high
Digested sludge Contaminated sludge, black - homogeneous g/l; ppm; %
Fields of application/use Unit Compen
sation*
mg/l ; g/l;
concentrations of activated sludge
SiO2, mineral-based solids (sand) g/l; ppm; % X
TiO2, (white media) g/l; ppm; % X
Universal use for sludge in wastewater sector between 5 and
50 g/l (activated sludge, return activated sludge, ...)
concentration of solids, e.g. sludge extraction in thickeners. 0
g/l bis 50 g/l
ppm; %
g/l; ppm; % X
g/l; ppm; % X
* Contamination compensation with 4-beam pulsed light
NOTICE
Multiple scattering in the following applications: formazine, kaolin and thin sludge
If the specific operational range is exceeded, the measured value displayed by the sensor can
decrease despite increasing turbidity or increasing TS content. The indicated operational range is
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reduced in the case of highly absorbing (e.g. dark) media.
In the case of highly absorbing (e.g. dark) media, determine the operational range
‣
experimentally beforehand.
Turbimax CUS51D
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2
3
1
4
5
Measuring system
A complete measuring system comprises:
• Turbimax CUS51D turbidity sensor
• Liquiline CM44x multi-channel transmitter
• Assembly:
• Flexdip CYA112 assembly and Flexdip CYH112 holder or
• Retractable assembly, e.g. Cleanfit CUA451
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8 Measuring system with immersion assembly (example)
1 Flexdip CYH112 holder
2 Liquiline CM44x multi-channel transmitter
3 Protective cover
4 Flexdip CYA112 assembly
5 Turbimax CUS51D turbidity sensor
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