Salinity & Salinity Meters

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Salinity & Salinity Meters




Crops vary as to their sensitivity to sodium and chloride ions. Tomatoes, for example can be grown in saline nutrient solutions; in fact common salt (sodium

chloride) is added to nutrient solutions to increase conductivity. Higher conductivity of nutrient solution provides improved fruit quality, though yield

decreases. On the other hand, plants like lettuce are prone wall stickersto damage by common salt and high salt

concentrations would be disastrous.

Salinity Meters

Growers today, have several types of electronic meters for measuring the salinity of water or nutrient solutions. The more widely used of these are electro-

conductivity (EC) and Total Dissolved Solids (TDS) meters. EC meters measure the ability of an aqueous solution to carry an electric current by measuring the

electric current between two electrodes. A solution that is rich in nutrients has higher electro-conductivity than a solution with less ionic salts. These

meters measure the electro-conductivity in either milliSiemens/cm (mS/cm) or micro Siemens/cm (mS/cm). EC meters are more commonly used by commercial growers

because their measurement more accurately corresponds with the bestNursery decals estimate

of the strength of nutrient solutions.

TDS meters measure the concentration of a solution as the totalX678 weight of dissolved solids.

Widely used by hobbyists, they actually measure the electro-I beam conveyorconductivity of a solution. They

measure the electric current between two electrodes - with a greater concentration of nutrients electric current flows faster than in a solution with a lower

concentration. An in-built conversion factor in the microprocessor logic converts the measured current into parts per million (ppm) of total dissolved

solids. There is no direct relationship between micro Siemens and ppm for mixtures but with an appropriate conversion factor applied to the measured current

a rough estimate of TDS is obtained.

TDS meters can only give a rough estimate of TDS as there are Turnstiles Gatesseveral factors at play including

the presence of air bubbles, probe positioning, temperature etc. TDS measurements are indicative of range and pin point accuracy is not possible. However, in

the majority of typical applications a range indication is good enough.

Meter Ranges

EC and TDS meters are available in different ranges and notph sensor all are suitable for hydroponics applications.

There are TDS meters that measure up to 1999ppm, and EC meters that only measure up to 1990mS. These meters, will not be useful for several crops where the

optimum electro-conductivity exceeds these limits. For use in hydroponics TDS meters should ideally have a rangeconductivity tester from 0 to 10,000ppm while EC meters should have a range from 0 to

19.9mS (19,999mS).

Conclusion

Salinity is an important determinative factor in plant growth and growers need to ensure that the water they use has a low salinity. Both EC and TDS salinity

meters have been in use in hydroponics in different parts of the world in accordance with the regional preferences and practices. Both types of salinity

meters have enabled thousands of growers ensureSealed Lead Acid battery correct water salinity levels for optimizing

plant growth in hydroponics systems. Though much can be said about the need for accuracy, consistency etc. of the measurements, it may be best at times to

let practical experience guide user preferences.

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