YSI EXO2 Multi-Parameter Water Quality Sonde
Features
- Titanium sensors with wet-mateable, universal sensor ports
- Biofouling protection with central wiper brush and copper-alloy accessories
- Smart QC automatically checks for faults and errors to ensure successful deployments
- Expedited repair and warranty service
- Lifetime technical support
- More
Modern and Efficient Design
The YSI EXO2 represents an advanced sonde platform that offers a wide range of capabilities to those dedicated to monitoring natural aquatic environments such as oceans, estuaries, rivers, lakes, and groundwater. With a highly efficient power management platform, robust construction, and chemistry-free anti-fouling system, The EXO2 allows accurate data collection for up to 90 days between service intervals.
Multi-Port Water Quality Sonde
- Temperature
- Conductivity
- Depth
- Dissolved oxygen
- pH
- ORP
- Total algae (phycocyanin or phycoerythrin along with chlorophyll)
- Turbidity
- Fluorescent dissolved organic matter (fDOM)
- Rhodamine WT
- UV nitrate
- ISE ammonium
- ISE nitrate
- ISE chloride
Outputs Four Calculated Parameters
- Salinity
- Specific conductance
- Total dissolved solids (TDS)
- Total suspended solids (TSS)
Onboard Signal Processing and Memory
All EXO sensors are digital sensors with onboard signal processing and memory. Built-in sensor diagnostic and calibration data allow users to calibrate multiple sensors in one sonde and distribute them to various other sondes in the field. Wet-mateable connectors allow for swaps in wet conditions, while active port monitoring automatically detects each sensor and verifies operation.
EXO2 Specifications
Diameter: 7.62cm (3.00 in)
Length: 71.10cm (28.00 in)
Peripheral Ports: 1 power communication port; 1 auxiliary port for third-party sensors (future functionality; not active yet)
Sensor Ports: 7 (6 ports available when central wiper used)
3-Year Warranty: Sonde; handheld
2-Year Warranty: Cables; conductivity/temperature and optical sensors; electronics base for pH, pH/ORP, ammonium, chloride, and nitrate sensors
1-Year Warranty: Optical DO cap and replaceable reagent modules for pH and pH/ORP sensors
3-Month Warranty: Replaceable reagent modules for ammonium, chloride, and nitrate sensors
Weight: 3.60kg (7.90 lbs)
General Sonde Specifications
Battery Life: 90 days**
Computer Interface: YSIP via USB Signal Output Adapter (SOA) and Bluetooth
Output Options: RS-232 & SDI-12 via DCP-SOA; Modbus & RS-485 via Modbus-SOA
Data Memory: 512 MB total memory; >1,000,000 Logged readings
Depth Rating: 0 to 250m (0 to 820 ft)
Sample Rate: Up to 4 Hz
Operating Temperature: -5 to +50°C (23 to 122°F)
Storage Temperature: -20 to +80°C (-4 to 176°F)
**Typically 90 days at 20˚C at 15-minute logging interval; temperature/conductivity, pH/ORP, DO, and turbidity sensors installed on EXO1; or temperature/conductivity, pH/ORP, DO, total algae, and turbidity sensors installed with central wiper that rotates once per logging interval on EXO2. Battery life is heavily dependent on sensor configuration.
- (1) EXO2 sonde
- (1) Probe guard
- (1) Calibration cup
- (1) Tool kit
- (4) Port plugs
- (4) D-cell alkaline batteries
- (1) USB drive loaded with manual & KOR Software
- YSI EXO Multi-Parameter Water Quality Sonde Brochure
- YSI EXO Multi-Parameter Water Quality Sonde Manual
- YSI EXO Multi-Parameter Water Quality Sonde Quick Start Guide
- YSI EXO Multi-Parameter Water Quality Sonde SmartQC Handbook
- Guide to Monitoring Turbidity at Dredging Sites
- Guide to Monitoring Water Quality on Inland Lakes
In The News
Carbon and Nutrient Monitoring in the Great Lakes Using Satellite Observations
Carbon and nutrients are the foundation of lake food webs and play an important role in the chemical and physical processes that shape aquatic ecosystems and various lake dynamics. Studying these cornerstones can help improve understanding of other lake conditions like harmful algal blooms, hypoxia, and phytoplankton community composition. 
 
The way in which these characteristics are monitored varies, though many rely on a proxy approach wherein parameters are extrapolated from the measurement of a different parameter. An assistant professor at Cleveland State University, Brice Grunert, is working to improve current strategies and take a satellite approach to monitoring the Great Lakes.
Read MoreResearch in the Reserve: Promoting Interdisciplinary Conservation at the Great Bay National Estuarine Research Reserve
On an early winter day in 1973, a helicopter buzzed over Durham, New Hampshire, just a few miles from the Atlantic Ocean. One of the helicopter’s guests, oil magnate Aristotle Onassis, owner of Olympic Refining, looked east of town and saw what he hoped would become the world’s largest oil refinery. Instead, he saw the Great Bay; thousands of acres of green coastal forest, mud flats, salt marshes, and estuarine tidal waters stretching over the land toward New Hampshire's small Eastern coastline. 
 
Onassis likely also saw a group of Durham residents staked out on the bay’s coast, ready for him to pass overhead. While out of place in the natural setting, an obvious message was spelled out in red paper: “Not Here.
Read MoreThree Decades of Research at Acton Lake
A multi-disciplinary team at Miami University, Ohio, has been studying the environmental change at Acton Lake for over three decades. Using three different NexSens buoys over this time, the team has an incredible archive of data that is helping build a picture of Acton’s past, present, and future. 
 
Until recently, a NexSens CB-50 buoy was used alongside other environmental monitoring at Acton Lake. In May 2025, the Miami team deployed a new XB-200 buoy , future-proofing their ongoing monitoring using real-time buoy systems. 
 
Acton Lake, a small hypereutrophic reservoir in southwest Ohio, covers 2.4km² and has a maximum depth of about 8m. The dam was built in 1956, and the lake has a large agricultural watershed.
Read More