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Turbidity sensors are a piece of equipment used to measure the cloudiness or haziness and the concentration of total dissolved/suspended solids of a solution.
A turbidity sensor is an analytical sensor that measures turbidity. They are highly useful and effective instruments to identify the clarity and particle content in a solution, like water. Turbidity sensors are used to reduce waste, improve yields, and analyze water quality in a wide range of industries.
Turbidity sensors measure the amount of light that is scattered by suspended solids in a liquid, such as water. When the concentration of total suspended solids (TSS) and total dissolved solids (TDS) in a liquid increase, the turbidity also increases.
Turbidity sensors are used to measure the cloudiness or haziness (turbidity) of a liquid, usually to determine water quality.
For samples with high amounts of TSS and TDS, the difference in the light intensity from the transmission beam is measured to obtain the turbidity result, while light scattering is more suitable for samples with low amounts of TSS and TDS. Since turbidity sensors use light to detect a solution’s turbidity level, it is important to reduce the amount of external light when using the sensor.
Turbidity sensors must comply with the Environmental Protection Agency (EPA): 180.1, therefore, a tungsten type meter or ISO specified design turbidity meter is used.
When measuring turbidity, most often, you will see the units NTU or JTU.
However, you may also come across alternative turbidity units, such as:
As the optical design of the light, aperture, and photodetector differ between turbidity instruments, samples must be calibrated with an NTU standard or other turbidity standard.
Most modern turbidity sensors work the same; a sample is collected and added into a vial.
The vial is then placed in the instrument where a fixed light beam passes through the sample to measure how much light is transmitted, and how much light is scattered via photodetectors, which are usually set at 90° to the sample.
The type of turbidity sensor you select depends on the application it is being used for. However, for quantitative turbidity measurements, all turbidity probes require calibration, following the regulation by ISO 7027:1999, which has now been revised to ISO 7027-2:2019.
There are three main types of turbidity sensors available:
Nephelometric turbidity sensors detect how light energy scatters through a liquid. The sensor uses a light detector (positioned at a 90° angle), and an LED lamp.
Once the lamp is switched on, the beam shines directly into the sample, where the light scatters when it hits a particle in a defined area. When the light scatters inside the sample, reflection occurs. It is the reflection in the sample that a nephelometric turbidity sensor measures by converting the received light intensity into an electrical signal.
The greater the reflection intensity, the greater the turbidity of the sample, and vice versa. The result is shown on the turbidity sensor’s electronic display in the desired unit.
Nephelometric sensors are used to measure drinking water or other types of water with low turbidity according to ISO 2027/ EN 27027.
Absorption turbidity sensors measure how many particles absorb light (light absorbance) in a solution. Similar to nephelometric sensors, they also contain a light detector and an LED lamp, however, the light detector and lamp are placed directly opposite.
The particles in the solution attenuate the emitted light, which is then converted into an electric signal by the detector, and then into a final turbidity reading.
Advanced absorption turbidity sensors are equipped with a second lamp detector arrangement, which allows for more reliable turbidity measurements. The second light detector can correct light intensity variations, color changes, and reduces lens fouling.
Absorption turbidity sensors are used for water that experiences regular fluctuations in turbidity.
Total solid/suspended solid turbidity sensors use a backscattered light, containing two light detectors and an LED lamp positioned at 90° and 135° angles.
The turbidity of the solution and the amount of TSS present are calculated when the detectors receive the amount of scattered light, which is then displayed by the transmitter in the desired unit (usually g/L or %TS).
Any solid particles in the solution will cause the incident light emitted by the LED lamp to effectively scatter.
Total solid/suspended solid turbidity sensors are used for measuring water with high turbidity.
There are many benefits to using a turbidity sensor:
Turbidity sensors are great, however, they do not come without some limitations.
Applications that use turbidity sensors include:
Turbidity sensors are useful pieces of equipment to measure the cloudiness or haziness of a sample. They are often used to measure water quality in different aquatic environments.
A turbidity sensor consists of a fixed light beam that passes through a sample to measure how much light is transmitted, and how much light is scattered via photodetectors.
Now you have a better understanding of what a turbidity sensor is, all that is left is to identify which turbidity sensor will best suit your needs.
If you have any questions regarding turbidity/water quality or the water testing kits we have to offer, please feel free to reach out to our world-class team at Atlas Scientific, we are always happy to help!
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