Sensors

High-quality data starts with quality sensors. Look for sensors that can perform in harsh environments and for extended periods without drift or biofouling. Sensors that are replaceable in the field will also save you time.

Monitoring Cycle QuickLinks

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It has been stated often that water is our most precious natural resource. Many organizations are working hard to monitor this resource with a variety of equipment. Sensors which measure water quality can provide excellent baseline data about a particular source.

Applications include:

Source water management
Environmental impact assessments
Dredging studies
Pollution monitoring
Surface and groundwater monitoring

However, all sensors are not created equal. Some sensing technologies can drift from calibrated norms more quickly than others while some are more susceptible to biofouling. Use the table below to identify the most appropriate sensors and anti-fouling systems for your monitoring goals.

Parameter	Sensor Type	Drift	Fouling Sensitivity	Anti-fouling Short-term	EDT*	Anti-fouling Long-term	EDT*
Ammonium, Ammonia**	ISE***	High	N/A	N/A	N/A	N/A	N/A
Blue-green Algae - PC	Optical	Low	Med	Standard Wiper	2-4 weeks	AF kits or AF paints	6-12 weeks
Blue-green Algae - PE	Optical	Low	Med	Standard Wiper	2-4 weeks	AF kits or AF paints	6-12 weeks
Chloride (Cl)	ISE***	Low	***	***	***	***	***
Chlorophyll	Optical	Low	Med	Standard Wiper	2-4 weeks	AF kits or AF paints	6-12 weeks
Conductivity	Capacitive Cell	Low	High
Depth	Transducer	Low	Low
DO (% sat)	Optical	Low	Low	Standard Wiper	2-4 weeks	AF kits or AF paints	6-12 weeks
DO (% sat)	Electrochemical	Med	High	6600EDS wiper	2-4 weeks
Free Chlorine	Electrochemical	Low
Level, Vented		Low	Low
Nitrate	ISE***	High	***	***	***	***	***
ORP	Electrochemical	Med	Med	6600EDS or 6600V2 wiper	2-4 weeks	AF kits or AF paints	4-12 weeks
PAR	Photovoltaic detector	Low	High	PAR wipers	2-4 weeks
pH	Electrochemical	Med	Med	6600EDS or 6600V2 wiper	2-4 weeks	AF kits or AF paints	4-12 weeks
Rhodamine	Optical	Low	Low	Standard Wiper	2-4 weeks	AF kits or AF paints	4-12 weeks
Temperature	Thermistor	Low	Low	None required	No limit	None Required	No limit
Turbidity	Optical	Low	High	Standard Wiper	2-4 weeks	AF kits or AF paints	4-12 weeks
* Estimated Deployment Time Long-term monitoting in freshwater has been successful with YSI's land-based monitoring platforms. * ISE (ion selective electrodes) can be used in freshwater only and are not appropriate for continuous immersion.

Check out these water quality instruments from YSI:

600LS (spot sampling level measurements)
600QS (sonde and display logger for quick data collection)
6820 V2 (profiling and logging for accessible sites)
6600 V2-4 (wiped sensors for extended environmental monitoring of remote sites)
Anti-fouling features and techniques

Water Velocity

Considering the scarcity of water resources, flow monitoring is increasingly important. Acoustic Doppler sensors measure water velocity by sending a known sound frequency into the water column and measuring the frequency shift returned from reflections of sediments in the water. Doppler instruments can be used for discrete and continuous monitoring and point and profile measurements.

Applications include:

River and canal discharge measurements
Bathymetry studies
Flood alerts
Pollution monitoring
Tidal/marsh studies

Hydrographic Surveying

Hydrographic surveyors can provide an all-in-one solution for everyday hydrographic use and difficult sites. Acoustic Doppler profilers with bottom tracking provide speed over ground and bathymetry data from a built-in echosounder, keeping you on track and providing crucial coordinate data when you lose GPS (under a bridge, for example).

For quality assurance pirposes, look for equipment that is compatible with HYPACK, a widely used hydrographic surveying package.

Check out these velocity instruments from SonTek/YSI:

FlowTracker (surface water, discharge in wadeable streams)
RiverSurveyor S5 and M9 (discharge in non-wadeable streams and canals)
Argonaut-SW and SL (Shallow water and Side Looker, continuous monitoring of flow)
ADP (3-D water current profiler, mounted on the bottom or fixed to a boat)