EC or Electrical Conductivity of water is its ability to conduct an electric current. Salts or other chemicals that dissolve in water can break down into positively and negatively charged ions. These free ions in the water conduct electricity, so the water electrical conductivity depends on the concentration of ions.
Aquaread’s electrical conductivity sensor utilises 4 stainless steel, gold coated rings ( as seen in the image below) to pass a current through a water sample to measure its resistance. The electrical conductivity of the water is the inverse of waters electrical resistance.
Using our EC sensor, you can measure the absolute conductivity (uncompensated), the conductivity compensated to 20 Degrees C or the conductivity compensated to 25 Degrees C (the European standard for conductivity measurement).
Our EC sensors come as standard on many of our probes, below are some examples. To see all of the probes that feature EC please visit the Products section.
The conductivity sensor is included on every Aquaprobe and Aquasonde, it is also included in the AquaPlus optical dissolved oxygen sensor and our Leveline-CTD water level and conductivity logger. Its design is simple and robust and the sensor itself requires little maintenance to keep it operational.
Conductivity measurements vary with temperature, if the temperature increases so too does the conductivity measurement. This causes problems when performing monitoring as the readings fluctuate with both actual changes and temperature related changes.
In order allow comparison of conductivity results and remove the variation by temperature, the concept of a reference temperature was introduced. Generally, the reference temperature used is 25 Degrees Celsius (C), but sometimes the reference temperature of 20 degrees C is used.
All Aquaread conductivity sensors come pre-set to compensate at 25 degrees meaning you will not see any variation in your readings should the temperature of the water change during an event like rainfall. If this does not suit your application however, you are free to change this in the software.
Because the relationship between conductivity and temperature are so important, our temperature sensor is located within the electrical conductivity sensor itself. Meaning you get an accurate compensation, quickly.
Salinity and total dissolved solids (TDS) can be calculated from the EC measurement of water, which helps to indicate the water’s purity. The purer the water the lower the conductivity. To give a real-life example, distilled water is almost an insulator, but saltwater is a very efficient electrical conductor.
Major positively charged ions that affect the conductivity of water are sodium, calcium, potassium and magnesium. Major negatively charged ions are chloride, sulfate, carbonate and bicarbonate. Nitrates and phosphates are minor contributors to conductivity, but they are very important biologically. The natural impacts on EC in water are rain, geology and evaporation. Human impacts include road salt, septic/landfill leachate, impervious surface runoff and agricultural runoff.
An EC sensor makes testing and monitoring the electrical conductivity of water simple. EC water conductivity test equipment can be used in the field to take direct measurements of water.
The probe that is inserted into the water sample applies a voltage between electrodes. The drop in voltage measures the resistance of water, which is converted to conductivity. Conductivity is reciprocal to resistance and is measured as the amount of conductance over a certain distance. The basic unit is mho/cm, or 1 Siemen, but this does not occur in natural water. EC meters use the units milliohms and micromhos. 1,000,000 milliohms/cm (mS) and 100,000 micromhos/cm (µS) each equal 1 mho/cm.
Ocean waters have water electrical conductivity of about 5 mS, tap water has EC in the range of 50 to 800 µS, depending on the source, freshwater streams may fall in the range of 100 to 2000 µS and distilled water has EC of between 0.5 and 3 µS. EC is relative to temperature.
The term “specific conductivity” is used when a value has been corrected to reflect the temperature of the water sample. Aquaread’s water conductivity meter also measures temperature, so gives the value of specific conductivity.
Water conductivity test equipment can be used to build up an understanding of the typical range of conductivity for a particular water body. This can be used as a baseline for regular monitoring and, if there is a significant change in conductivity, this could be an indicator of a discharge or other pollutant entering the water. Conductivity varies with the water source, i.e. ground water, agricultural runoff, municipal wastewater, rainfall. A change in water electrical conductivity can indicate ground water seepage or a sewage leak.
The EC of water has a critical influence on aquatic life. Every kind of organism has a typical range that it can tolerate. In a commercial sense, testing the conductivity of water may be specifically useful for fisheries. Salts and other substances also affect the quality of water for irrigation or drinking, so water conductivity meters can be used when testing the output of water treatment plants.
The water conductivity meter is just one function of Aquaread’s multiparameter water quality monitoring equipment. Use all the parameter readings together to accurately monitor water quality without the need for multiple probes. The EC water testing equipment is suitable for use on surface water, groundwater and wastewater.