It is important to control the concentration
of your nutrient solution. Burning of roots or foliage can occur if the
concentration is too high. If the concentration is too low then deficiency
symptoms can occur. This chapter explains how to successfully use
conductivity as a tool for controlling nutrient concentration.
is Conductivity (EC)?
A “Conductivity Meter” is a device used to help
monitor the concentration of nutrient solutions. It is also known as an EC
meter, CF meter or TDS meter.
‘Conductivity’ represents the ease with which a
solution conducts electricity. Solid substances known as 'salts' (e.g.
sodium chloride, potassium nitrate), yield 'ions' when dissolved in water.
'Ions' permit the flow of electricity through the solution (Fig 11.1a).
Increasing the concentration of ions improves the ease with which the
solution carries an electric current and therefore causes a higher
conductivity. Hence, an EC meter can be used to detect the presence of salts
and their approximate concentration in water.
Not all solutions or liquids conduct
electricity. Water soluble ‘organic’ substances such as sugar, vitamins and
hormones produce very few ions when dissolved in water and consequently
yield zero conductivity. Similarly, many liquids such as petrol, alcohol and
distilled water yield zero conductivity.
This article discusses the following topics:
Units of measure for EC
Using EC to control nutrient concentration
- Maintaining EC electrodes
Buying a conductivity meter