TurbiTechw² LR Instruction Manual
4 The Sensor and Installation
Whilst every attempt has been made to ensure that these instructions are correct, common sense and good
engineering practice should always be used, as every installation can present a new set of challenges and
difficulties. If you are in any doubt please contact Partech or your local distributor for further information.
4.1 TurbiTechw² LR Sensor
All the TurbiTechw² Sensors in the family use an LED infra red light source, which offers long-term
stability, low maintenance and high reliability. All TurbiTechw² Sensors use either Light Scatter or Light
Absorption to perform their measurement.
In simple terms, turbidity means cloudy, hazy or not pure. All drinking water, both raw and treated
contains some degree of turbidity due to dispersed suspended particles such as silt, clay, algae,
organic/inorganic matter or micro organisms.
Turbidity is a measurement quantifying the degree to which light travelling through the water sample is
scattered by the suspended particles. The transmission of light is determined by physical parameters
such as particle concentration, size, shape and chemical properties. The scattering of light increases
with a greater concentration of suspended load. Turbidity is commonly measured in Nephelometric
Turbidity Units (NTU). The nephelometric method compares the light scattered by the sample and the
light scattered by a reference solution.
The TurbiTechw² LR Sensor measures the turbidity of the sample water in NTU's in accordance with
established measurement techniques. The measurement cell has been designed to reduce unwanted
stray light to an absolute minimum resulting in a very accurate zero point. The 7300w² Monitor has the
facility for converting the units to mg/l under some circumstances, further details are provided in the
7300w² Monitor user manual.
The beam from the LED light source is passed through the sample of water contained in the measurement
cell and the amount of light scattered by particles in the sample is measured at 90 degrees to the light
source. The 7300w² Monitor uses an LED light source with an optical feedback loop to maintain constant
light levels. The sample flows through the flowcell continuously while the TurbiTechw² LR Sensor is in
measurement mode. The large bore flowcell reduces the danger of fouling or clogging in raw water
applications.
The TurbiTechw² LR sensor is a dedicated flowcell sensor and uses a wiper type cleaner. In the
intended clean water applications this wiper is more than capable of keeping the optical surfaces
clean. The wiper should be replaced every two years to ensure the cleaning function remains effective.
The TurbiTechw² LR sensor is available in two ranges; 0 to 30NTU & 0 to 500NTU. The range is
dictated by the hardware of the flowcell so cannot be changed by the user. Therefore the range should
be specified when the instrument is ordered.
All the example screens in this manual relate to the 0 to 30NTU sensor. All the menu options and
functionality are identical between the ranges except for the actual numeric value and number of
decimal places of NTUs.
Page 10 of 34
225769IM - Issue - 05 Issue Date 30/04/2019
