One of the biggest issues with long term field monitoring of electrical conductivity for salinity measurement is reliability. Electrical contact-type sensors are highly accurate, but the exposed contacts foul quickly and produce poor results, requiring regular cleaning to maintain accuracy. This is why our sealed toroidal type EC sensor has been the preferred choice by Australian hydrographers for over 20 years.
With a new digital output (SDI-12) along with the analogue 4-20mA output, the EC1550 is the most robust and reliable EC sensor on the market. In digital mode, the sensor uses very little power, and with a reading accuracy of 2% (not 2% of full scale as most sensors are specified), the results are consistent and repeatable. Accuracy of readings is typically below 1% between 10-90% of the full-scale range of the sensor, available in a variety of ranges from 0-500µS/cm up to 0-70,000µS/cm.
Electrical Conductivity – EC1550 Salinity Sensor
Electrical conductivity measured in Siemens (S) and represents a fluid’s ability to conduct electricity or pass an electrical flow. Temperature and concentration of free ions in the fluid determine electrical conductivity. Measuring the variables concurrently provides accurate results.
Hence, water’s electrical conductivity will tell us the concentration of salts or solids dissolved in the fluid; a higher concentration means higher conductivity.
The electrical conductivity of Deionized water (pure H2O) is around 5.5 uS/cm (at 25C) whereas seawater is approximately 50,000 uS/cm.
Therefore we can deduct it is the salt which affects electrical conductivity, not the water itself.
Conductivity increases when compounds dissociate into ions when they meet water. For Salt (Sodium Chloride) splitting into Na and Cl. The ions are then free to ‘move about’ and conduct electricity. More free ions equal greater electrical conductivity. Note we are using salt as a basic example, various other dissolved solids alter a fluid’s electrical conductivity and salinity.
For more information, click through to the EC1550 product page.
If you want to stay up to date with all Greenspan announcements and the latest news then follow ESS on LinkedIn.