Conductometer (EU meter) Is a device designed to measure the conductivity of solutions, steam or condensate. The conductometer is used to analyze the concentration of nutrient solutions. When a particular salt, acid or alkali is dissolved in water, the molecules of this substance are split into electrically charged particles – ions. The amount of current passing through the solution is in direct proportion to the number of ions. Therefore, by the electrical conductivity of the nutrient solution, one can judge its concentration. Pure distilled water is non-conductive. But if mineral salts are dissolved in it, it begins to conduct electricity and electrical conductivity increases proportionally.
EC is the most stable indicator of the total concentration of the nutrient solution. Even a slight increase in the concentration of the nutrient solution can significantly impede its absorption by the plant. Therefore, it is so important to constantly measure the conductivity of the solution. These measurements will allow you to evaluate the concentration of the nutrient solution and prevent it from exceeding its norm or falling below optimal values.
Characteristics of conductometers
Conductivity meters come in various types and shapes. They can be built into complex instruments, together with a pH meter and a TDS meter. Conductometers are of periodic action and constant, designed for continuous monitoring of the state of the solution. They can be highly accurate laboratory or portable for quick and easy analysis.
TDS meters and conductometers – what’s the difference?
Every TDS meter is essentially a conductometer. While EC and TDS are often used interchangeably, there are some important differences. The EU, as applied to water, refers to the measurement of electrical charges in water. TDS refers to the total amount of dissolved salts in water. The valid correct method for measuring TDS is by evaporating water and weighing the dry matter. Since this is almost impossible for the average user to do, it is possible to estimate the TDS level by measuring the EC of the water.
All solutions are electrically charged. Thus, it is possible to estimate the amount of TDS by determining the EC of the solution. However, solutions of different composition have different charges, so it is necessary to convert EC to TDS using a conversion that simulates charge.
To convert EC units to TDS, you need to determine which conversion factor you want to use (NaCl, 442 or KCl) and do the conversion. Most measuring instruments use a NaCl conversion factor that averages 0,5.
Next, you need to understand in what units your EC-meter displays the result. It can be either microsiemens per centimeter (μS / cm) or millisiemens per centimeter (mS / cm). This is not difficult to understand. In most cases, this is indicated on the device itself or in the instructions for it. If there is no such information, then it is easy to understand from the indications. If it is from several hundred to several thousand (210, 520, 1250, etc.), then the unit of measurement will be “μS / cm“. If these are small numbers (0.1, 0.6, 1.25, etc.) in this case – “mS / cm“. In the latter case, it is necessary to multiply the value by 1000, to convert the values into “μS / cm» [eng. μS / cm].
Now all that remains is to multiply the value of the EC-meter (in “μS / cm») By a factor of 0.5 (or other), and you will get the value of the TDS level (ppm).
Example. EC meter reads 0.6 mS / cm… In such cases:
0.6 mS / cm = 600 μS / cm
TDS = 600·0.5 = 300 ppm
If the conversion factor is 0.7 mS / cm, then the following conversion comes out:
TDS = 600·0.7 = 420 ppm
For convenience, you can use our tables to convert EC, TDS (mS / cm, ppm) values.
For a more detailed study of the topic, we recommend visiting the corresponding section of the forum: “EC / TDS / PPM meters”.
