For the past two weeks, we have been talking about various ways to tackle the common issue – biofouling. This week, we will continue that discussion with tips 4 & 5.
This blog series focus is on helping you, by providing tips on how to fight fouling and how to collect the highest quality data over the course of a long-term sonde deployment period. Using a combination of our suggestions, you’ll be able to significantly reduce the frequency at which your team must travel to field sites to clean and maintain sondes and water quality sensors.
Always Keep Up To Date With New Sensor Technology.
Even with a lot of the anti-fouling tips we’ve described previously, there is one Achilles heel to most anti-fouling solutions: a sondes’ conductivity sensor.
Most conductivity cells are susceptible to interference from fouling in one way or another. Many of these sensors have their electrodes buried deep within the probe, far out of reach of any kind of anti-fouling wiper or copper accessory. When obstacles like small aquatic life, clumps of sediment or even algae build up within these closed-off conductivity cells that interferes with the measurement.
Conductivity sensors are designed with “drive” electrodes to send current through the water towards a receiving electrode. The amount of signal loss between those two electrodes allows us to calculate the conductance of the water. When this path is obstructed, then there is an artificial drop in conductivity readings, directly impacting the quality of your data over the course of a monitoring period.
Because a sonde’s conductivity sensor is typically the only sensor left unprotected from biofouling, it ends up driving maintenance intervals. Left unchecked, fouling on a conductivity sensor not only impacts the conductivity parameter itself, but also dissolved oxygen and depth or level parameters, which use the conductivity reading to compensate for changes in salinity.
Until recently, no conductivity sensor on the market was developed to enable a wiper to clean the electrodes and to maintain a clear path for the measurement. However, just a few months ago, YSI released a new Wiped Conductivity and Temperature probe for the EXO sonde platform.
This new sensor is purpose-built for high fouling, long-term monitoring projects and works with any existing EXO2 sonde. The innovation here is that the conductivity electrodes are no longer buried within the sensor and raised to the same plane as the other sensor faces, allowing the EXO Central Wiper to thoroughly clean the measurement surfaces.
As with all our sensor technology, we put our instruments through intense field testing in sites all around the world. Download our recent “Fighting Fouling - EXTENDING SONDE DEPLOYMENT TIMES WITH EXO’S WIPED (C/T) SENSOR.” In this case, we tested new Wiped Conductivity probe against a standard probe to get data demonstrating its effectiveness against intense sensor fouling. The new probe is in green and the standard probe is shown here in red.
The standard probe began to exhibit signs of artificial data drift in the first week or two due to fouling accumulating on the sensing surfaces and the Wiped probe continues to collect high quality data over the course of the month long deployment. A few weeks into a deployment, and your conductivity data would be off 10-15% in just a few weeks using an unprotected sensor.
So, to reiterate – Tip #4 is to always keep up with new technology. Manufactures are always coming up with new technology that can keep sensor fouling at bay. Whether that’s a new Wiped Conductivity Sensor design or other advances.
Next, Tip #5 – Take Care of Your Instrument and it Will Take Care of You.
A huge thank you to YSI Product Manager, Brandon Smith, YSI Marketing Specialist, Patrick Beatty, YSI Technical Support Team Lead, Tom Moeggenberg and YSI Application Engineer, Tiffany Shirmer for providing the information found in this post.
Additional Blog Posts of Interest:
7 Tips to Fight Fouling and Extend Sonde Deployments | Tip #3
7 Tips to Fight Fouling and Extend Sonde Deployments | Tip #2
7 Tips to Fight Fouling and Extend Sonde Deployments | Tip #1
The EXO Wiped Conductivity & Temperature Sensor Helps Eliminate Biofouling