YSI EXO Turbidity Sensor

The YSI EXO turbidity sensor is a digital smart sensor featuring welded titanium construction and wet-mateable connectors.


  • 0 to 4000 FNU measurement range
  • T63<2 sec response time
  • 0.3 FNU or ±2% of reading accuracy from 0 to 999 FNU
Your Price $2,030.00

The EXO turbidity sensor is a digital smart sensor featuring welded titanium construction and wet-mateable connectors. For long-term, in situ continuous monitoring of turbidity, the EXO2 sonde has a wiper to clean the turbidity sensor to avoid sensor fouling and maintain accuracy.

Turbidity is the indirect measurement of the suspended solid concentration in water and is typically determined by shining a light beam into the sample solution and then measuring the light that is scattered off of the particles which are present. The suspended solid concentration is an important water quality factor and is a fundamental measure of environmental change. The source of the suspended solids varies in nature (examples include silt, clay, sand, algae and organic matter), but all particles will impact the light transmittance and result in a turbidity signal.

The EXO Turbidity sensor employs a near-infrared light source and detects scattering at 90 degrees of the incident light beam. According to ASTM D7315 method, this type of turbidity sensor has been characterized as a nephelometric near-IR turbidimeter, non-ratiometric. This method calls for this sensor type to report values in formazin nephelometric units (FNU). FNU is the default calibration unit for the EXO sensor, but users are able to change calibration units to nephelometric turbidity units (NTU), raw sensor signal (RAW), or total suspended solids (TSS).

Questions & Answers
How do I change the sensor to read NTU?
The sensor units can be changed using the KorEXO Software and entering the desired parameter code while in the edit template menu.
How often do I need to calibrate this sensor?
The calibration frequency is ultimately up to the end user. Common calibration intervals are bi-weekly, monthly, quarterly, etc.
Is the sensor suitable for marine environments?
Yes, the EXO sonde platform is designed for us in freshwater and marine environments. The only exception is that the ISE sensors for ammonium, nitrate, and chloride are for freshwater use only. When using the EXO sonde and sensors in saltwater applications it is recommended that you use anti-fouling options outlined in this guide: https://www.ysi.com/File%20Library/Documents/Tips/E108-Antifouling-Tips-Book.pdf
What does smart sensor mean?
This simply means that the sensors themselves have on-board memory and maintain calibration settings on the probe versus the sonde. This allows sensors to be switched between sondes without the need to recalibrate.
What benefits does this sensor have over my 6136 turbidity sensor?
The EXO turbidity sensor has an extended range meaning it can measure turbidity from 0 to 4000 FNU.
Does my EXO sensor maintain it's accuracy over 1000 FNU?
The EXO Sensor has an accuracy or +/-5% from 1000-4000 FNU.
Why does the EXO sensor use an internal thermistor?
The turbidity temperature effect is largely from the LED inside the turbidity probe. To accurately measure temperature compensation, the LED temperature should be measured rather than the water temperature.
Can I use my EXO sensor with my 6-series sonde?
EXO sensors are not backwards compatiable with 6-series sondes.
Can this sensor be used to calculate TSS?
Total suspended solids (TSS) can be calculated by entering comparison data from measured turbidity samples and TSS values obtained through lab analysis into YSI Kor Software. Once this has been completed, calculated TSS values can be displayed on the EXO handheld display and/or output in the data string to an external data collection platform (DCP) or data logger.
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