Choosing a Conductivity/Salinity Logger: 5 Important Considerations

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Paul Gannett Product Marketing Manager

Topics

• Onset Overview

• Typical Conductivity/Salinity Applications

• The 5 Considerations

• Q & A’s

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Choosing a Conductivity/Salinity Logger: 5 Important Considerations

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Who is Onset?

• Leader in portable Data Loggers

• Founded in 1981

• 130 employees

• Designed and assembled in Bourne, MA

• Over 2 million HOBO data loggers sold

Energy Management

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Field Research

Water Management

Onset Markets

• Coastal and estuary research

• Stream restoration

• Water quality monitoring

• Road runoff

• Agricultural runoff

• Monitoring downstream of mines

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Choosing a Conductivity/Salinity Logger:

Typical Applications

• Accuracy

• Mounting

• Ease of deployment and data offload

• Software

• Cost of ownership

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Choosing a Conductivity/Salinity Logger: 5 Important Considerations

• Specified accuracy – percent of reading & minimum error

• The logger’s temperature accuracy – Every 0.5C of temperature error causes 1% error in specific conductance and salinity

• Sensor technology – electrodes in contact with water can corrode, especially in salt water. Non-contact sensors have minimal drift.

• Fouling can cause significant measurement drift (next slide)

• Software (covered later)

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Choosing a Conductivity/Salinity Logger:

Accuracy Considerations

… plan for it

• frequent cleaning

• antifouling materials

– Biocides/copper

– inert materials

• Use field calibration points from the beginning and end of each deployment to compensate for fouling

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Fouling Happens!

Choosing a Conductivity/Salinity Logger:

Accuracy Considerations

• Accuracy

• Mounting

• Ease of deployment and data offload

• Software

• Cost of ownership

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Choosing a Conductivity/Salinity Logger: 5 Important Considerations

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Choosing a Conductivity/Salinity Logger:

Common Mounting Methods

Stilling Well - In ground or attached to a structure such as bridge or dock

Tether Mount Post Mount

• The logger should be placed in a location that has good, continuous water flow, if possible

• Keep the logger at least an inch from metal surfaces

• PVC pipe and zip ties are great for mounting

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Choosing a Conductivity/Salinity Logger:

Mounting Considerations

Features to look for:

• Does the logger sink or float? Loggers that sink are generally easier to deploy.

• The smaller the logger, the easier it is to deploy.

• How will the logger be mounted?

An eyelet makes it easy to hang in wells.

• Can the logger be mounted so that is sheds air bubbles?

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Choosing a Conductivity/Salinity Logger:

Mounting Considerations

• Accuracy

• Mounting

• Ease of deployment and data offload

• Software

• Cost of ownership

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Choosing a Conductivity/Salinity Logger: 5 Important Considerations

Great for the initial deployment

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Easier for ongoing deployments

Choosing a Conductivity/Salinity Logger:

Deployment Considerations - Calibration

Lab Calibration vs Field Calibration

Lab calibration Field calibration