YSI EXO Water Quality Sondes and Buoys

YSI EXO sondes are multiparameter instruments that can be used to gather data on water quality. Each type, however, is a little different, and depending on your application, parameters, and landscape, one might be more advantageous than another. In this post, we’ll describe several popular YSI EXO water quality sondes, cover the basics of how they work for in-situ water quality monitoring, discuss some distinguishing features of the different models, and finally, match up some of the sondes and data buoys that work together well.

YSI EXO1 Water Quality Sonde

The YSI EXO1 water quality sonde gathers data with as many as four sensors, that the user can replace as needed, and an integral pressure transducer. Every port on the instrument automatically recognizes and accepts any type of EXO sensor, making the instrument easy to customize.

Each sensor uses various optical, electrochemical, or physical detection techniques to measure its parameter. Once the YSI EXO1 gathers the data, users can define settings, controlling what happens to the data. For example, the sonde can store the data until the user retrieves it manually, or transmit the data, either straight to an EXO handheld or the user’s computer or online data portal, or simply to a data collection platform (DCP), such as a data logger. Depending on which method works best, you might communicate with your sonde through a field cable with an EXO handheld, or a USB connection, or even a Bluetooth wireless connection.

YSI EXO2 and EXO2S Water Quality Sondes

The EXO2 multiparameter sonde differs from the EXO1 sonde primarily in that it can hold up to seven sensors, each replaceable by the user, and an integral pressure transducer. Every port in the sonde will recognize any EXO sensor automatically and accept it. Just like the other sensors described above, each sensor in an EXO2 water quality sonde uses optical, electrochemical, or physical detection techniques to measure its parameter.

The EXO2 sensor sonde offers the same communications and data logging options as its cousin, the EXO1. However, one distinction with the EXO2 is the central seventh port, which is nonstandard. This port can hold a standard sensor, but it can also accept a central wiper, which keeps the sensors clean. For sondes that stay in use for longer periods of time, this is an extremely useful feature, keeping the unit recording accurate data for longer.

The EXO2 also features an auxiliary port on its top side. This allows the model to connect to other EXO sondes, allowing users to customize and expand even more.

The EXO2s sonde is very similar to the EXO2 sonde. The primary difference is that the EXO2s is the factory-customized version, which is battery-less, and therefore more compact. Obviously, the EXO2s can only be deployed where an external source of power is at hand, and since it is customized in the factory, users must know the intended depth of the sonde at the time they order.

YSI EXO3 Water Quality Sonde

Like the EXO1, EXO2 and EXO2s, the EXO3 sonde is a multiparameter tool that gathers water quality data—in the case of the EXO3, with as many as four user-replaceable sensors and an integral pressure transducer. The EXO3 differs from the EXO1, though, in that it also features the central port for an additional sensor, or, more commonly, an EXO wiper that keeps the sensors clear and functional. In this sense, the EXO3 combines the smaller size and number of ports of the EXO1, and the wiper/extra port of the EXO2, making for a hybrid version.

Just like the other sondes, the EXO3 water quality sonde gathers data on various parameters using various optical, electrochemical, or physical detection techniques. The unit itself is customizable, since each port can carry any kind of EXO sensor, and it’s easy to use because every port automatically recognizes and knows how to work with every sensor. Transmission and communication options for the EXO3 are the same as for the other models, except for the battery-less EXO2s.

Nailing Down the Right Sondes and Buoys

Most Fondriest and NexSens customers use the EXO2 or EXO3 sondes on data buoys because these support the central wiper which keeps sensors clean. The EXO1 does not support a wiper, so it requires more manual maintenance.

Choosing the right data buoy for your YSI EXO water quality sonde is important. Given the larger diameter of the EXO2/EXO3 sondes, there are some mounting considerations to be aware of. Although some buoys are a more natural or automatic “fit” for these sondes, there are different ways to make the sondes and buoys work together.

The CB-40 data buoy will support any water quality sonde on the market including EXO2 and EXO3, but it’s really designed for self-logging deployments with manual data upload.

EXO2 and EXO3 sondes on the CB-50 and CB-150 data buoys need to be mounted on an instrument cage such as the CAGE-EXO. The CB-50 does not have instrument holes, and the CB-150 has instrument holes that are 2-inches in diameter—too small for the EXO2 and EXO3 sondes, hence the need for the instrument cage.

The CB-450 data buoy is the most popular buoy platform for EXO sondes, for good reason. This buoy features instrument holes that are 4-inches in diameter, allowing the sondes to fit through them. The main benefit of deploying a data buoy with the sonde in the instrument hole is that the user can access the sondes for maintenance and recalibration without pulling the buoy out of the water.

Of course, there are other data buoy options with instrument holes that work with the YSI EXO line of water quality sondes. The CB-650, CB-950, and CB-1250 data buoys all have instrument holes that are 4-inches in diameter or larger, so they work the same way as the CB-450 data buoy does.

Find out more about which data buoy and YSI EXO water quality sonde might be best for your deployment. The experienced team at Fondriest and NexSens are here to advise you when you need us.


YSI EXO1 Multi-Parameter Water Quality Sonde

The YSI EXO represents the next generation of water quality instruments from YSI. The EXO1 sonde includes four sensor ports with internal data logging and battery power.

YSI EXO2 Multi-Parameter Water Quality Sonde

The YSI EXO represents the next generation of water quality instruments from YSI. The EXO2 sonde includes six sensor ports and a central anti-fouling wiper option.

YSI EXO2s Multi-Parameter Water Quality Sonde

EXO2s is a customized, batteryless sonde that comes with the same warranty and capabilities as the EXO2, and is ideal for specialized applications.

YSI EXO3 Multi-Parameter Water Quality Sonde

EXO3 is a purpose-built sonde for monitoring major water quality parameters, including: pH, conductivity, temperature, turbidity and dissolved oxygen.