Conductivity & Salinity 

Conductivity scales with dissolved ion content, which makes it one of the fastest screening parameters in the field. Specific conductance, salinity, total dissolved solids and resistivity are all derived from it. A conductivity sensor also supplies the salinity value used to compensate dissolved oxygen in mg/L.

RAECO Rents supplies conductivity and salinity instruments with NIST-traceable calibration included. Free ground shipping and free return shipping are included on every rental.

YSI ProDSS Multiparameter Digital Water Quality Meter
Frequently Asked Questions
Common questions about conductivity & salinity
Which conductivity calibration solution should I use?
Match it roughly to the water you are measuring: 1.0 mS/cm for fresh water, 10 mS/cm for brackish and estuarine, 50 mS/cm for salt water. Never calibrate with a solution below 1.0 mS/cm — you are setting the slope on a linear device, and a weak signal gives poor performance. Note that 1.0 mS/cm equals 1000 uS/cm; mixing those up is a common calibration error.
Do I calibrate conductivity, specific conductance and salinity separately?
No. Calibrating any one of them calibrates the others at the same time. Calibrate specific conductance — temperature-compensated conductivity — for the best combination of ease and accuracy.
Why is my conductivity reading about half what I expect?
The solution is almost certainly not covering the vent holes on the sensor. If the entire sensor is not immersed, the instrument reads roughly half the expected value. Fill the calibration cup properly, then move the sensor gently up and down to dislodge any air bubbles trapped inside the cell.
What cell constant should I see after calibration?
Check the GLP record after accepting a calibration. Around 5.0 to 6.0 indicates the highest accuracy, and the broader acceptable range runs 4.5 to 6.5. A significant jump in cell constant between one calibration and the next usually means either the standard or the sensor has a problem — most often a sensor that needs cleaning.
How do I know when a conductivity sensor needs cleaning?
A clean, dry conductivity sensor reads less than 1 uS/cm in air. If it is dry and reading higher than that, clean it. Use the small brush supplied with the sensor, dipped in clean water and inserted into each opening 10 to 12 times, with a mild detergent if deposits have formed.
Why does a conductivity sensor matter for my other readings?
Because accurate temperature compensation is required for nearly every other parameter, and the salinity value from this sensor feeds the dissolved oxygen mg/L calculation along with the ammonium, nitrate and chloride algorithms. Accepting a questionable conductivity calibration will quietly corrupt your DO data too.
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YSI ProDSS Multiparameter Digital Water Quality Meter
Water Quality Meter

YSI ProDSS Multiparameter Digital Water Quality Meter

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