Fighting Fouling: Extending Sonde Deployment Times with EXO’s Wiped C/T Sensor

Check out this case study to learn more about how EXO’s latest conductivity sensor is dramatically extending sonde deployment times and reshaping organizations’ SOPs.

For over twenty years, YSI sondes have measured continuous water quality data at field sites around the globe. Along the way, we learned quite a few lessons in developing instrumentation.

Initially, the challenge of using in-situ sensors for long-term autonomous data collection was developing technology that could withstand what Mother Nature could throw at it, technology that could withstand; floods, mudslides, and debris and still continue to record high quality data. It wasn’t long before instruments became much more rugged, with fundamental shifts in the build materials forming a new foundation for our sensing platforms.

Once sensors could survive the harshest of field conditions, the limiting factor for their maintenance and upkeep became battery life. As most field sites lack an external power source and rely on solar panels and batteries alone, it became more and more critical to improve the way our technology operated to reduce power consumption.

An EXO2 water quality Sonde with a Wiped (C/T) Smart Sensor installed.

Our engineers found creative ways to limit the time sensors would be active, allowing them to hibernate until they were ready to take a measurement. They also redesigned the instruments’ internal circuitry to better speed up sensor response times, allowing the equipment to make measurements in less time when they turned on.

These changes helped propel changes in organizations’ operating practices to send folks out for maintenance less frequently, stretching sonde deployment times well past where they were before.

The problem then became sensor fouling.

Now that equipment was measuring water quality in-situ for longer than ever, it was clear that biological growth, sediment, and accumulation of other debris on the sensors over time was wreaking havoc with the data. Huge swings in sensor readings resulted from the slow-buildup of debris on the sensing surfaces. The new focus became (and continues to be) how to actively protect our sensors from the effects of fouling – commonly referred to as “drift”:

Salinity data from a long-term case study.
Note the drift caused by fouling in the Standard (C/T) sensor.

Across the business landscape, companies developed a variety of product enhancements to prevent biofouling from affecting their sensors. Some solutions were more effective than others.

YSI and other sonde manufacturers introduced sensors with automated wipers to clean the sensor surfaces and other passive anti-fouling accessories to prevent biological fouling from latching onto sensor surfaces to begin with. However, for years one sensor eluded all our anti-fouling methods – the conductivity sensor.

While mechanical grooming of most sensors worked exceptionally well in fending off fouling, conductivity sensors saw limited improvement. Why? The reason is pretty straightforward – the measurement is taken inside the probe, far away from the protection of a wiper.

Check out this case study to learn more about how EXO’s latest conductivity sensor is dramatically extending sonde deployment times and reshaping organizations’ SOPs.

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