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Total dissolved solids (TDS) differentiates between the different types of ions or other substances (like organic matter) in water or a solution, whereas EC only measures the water’s ability to conduct electricity, not the types of ions. Both TDS and EC can be measured using specialized meters known as EC meters.
In water quality analysis methods, two critical parameters often come up in discussions – electrical conductivity (EC) and total dissolved solids (TDS). While these terms are often used interchangeably, they have distinct differences that are important to understand.
In this article, we look at EC and TDS, exploring what they measure, how they differ, and how to work out conversion rates between these two vital measurements.
Total Dissolved Solids (TDS) refers to the amount of substances that are dissolved in a liquid, typically water.
The amount of substances that have been dissolved in a liquid, known as TDS, includes salts, minerals, metals, calcium, and other organic and inorganic compounds that are not pure water or suspended solids.
The most common way to measure TDS is to examine the specific conductivity to identify the presence of ions (EC) in the water, which is then converted to a TDS estimation with a factor usually ranging from 0.4 to 1.0 and measured in parts per million (ppm) or mg/L. Generally, natural mineral water and tap water can have a TDS value of 300-500 mg/l, while anything above 1200 ppm is typically considered to be an unsatisfactory level of TDS.
Put simply, electrical Conductivity (EC) is a measure of a material’s ability to conduct electricity. In the context of water, EC measures the ability of a liquid to carry an electric current. It indicates the presence of ions, which are charged atoms, in the water.
EC is closely related to TDS as the dissolved substances in the water contribute to its electrical conductivity, however, they are not the same. Generally, water in its natural state has low conductivity because it does not contain impurities. But when water is polluted or has impurities, its conductivity rises. It is important to also note that saltwater can register high conductivity levels due to the charged atoms, or ions, which form when salt dissolves in the water.
The measurement of conductivity is typically expressed in micro Siemens per centimeter (µS/cm) and commonly reads between 30 µS/cm and 2000 µS/cm.
For example, the typical conductivity range of seawater can be up to 50,000 µS/cm.
An interesting fact is that as water warms, its conductivity increases. For this reason, conductivity is normally recorded at 25°C along with its temperature. Another unit of measurement for conductivity is millisiemens per centimeter (mS/cm), which is equivalent to 1000 µS/cm. When a measurement in mS/cm is shown, it typically indicates a high level of conductivity (i.e., 2000 µS/cm or higher).
TDS and EC are closely related, but they are not the same. While TDS measures the total amount of dissolved solids in water, EC measures the ability of those dissolved solids to conduct electricity. In other words, EC provides a quantitative measure of the concentration of ions in the water, whereas TDS gives an overall measure of the dissolved solids.
It is important to note that TDS meters often estimate TDS levels by measuring EC and applying a conversion factor. This estimation is based on the assumption that all dissolved solids contribute to electrical conductivity. However, this conversion factor may vary depending on the sample being tested and may not be entirely accurate.
If you are concerned about the quality of the water you consume, then measuring the TDS and EC levels in your water is crucial. To measure TDS and EC accurately, you will need an EC meter or an EC probe.
To begin, make sure your EC meter or probe is calibrated properly. This step is essential to ensure accurate readings. Next, fill a clean container with the water sample you want to test. It’s important to note that the container should be free from any contaminants that could affect the results. Once you have your sample ready, insert the EC probe into the water. Allow a few seconds for the reading to stabilize on the meter’s display.
The measurement displayed on your EC meter is expressed in units of electrical conductivity, typically microsiemens per centimeter (µS/cm) or millisiemens per centimeter (mS/cm). This reading indicates the EC level of your water sample. To convert this measurement into TDS, you can use a conversion factor specific to your water source. Different conversion factors are available depending on whether you are testing freshwater or seawater.
When using an EC meter or probe, it’s essential to remember that it requires regular maintenance and calibration. This ensures accurate and reliable readings over time. Additionally, it’s worth noting that extreme temperatures can impact the accuracy of your measurements. Therefore, it’s best to conduct tests at room temperature to obtain the most precise results.
Several factors can influence TDS and EC readings to consider. Some of the key factors include:
EC readings are temperature-dependent, meaning that as temperature increases, the electrical conductivity of water also increases. To account for this, measurements are often standardized to a specific temperature, usually 25°C.
The type and concentration of dissolved solids in water directly impact both TDS and EC readings—Different substances have different conductivities, which can affect the overall measurement.
TDS meters require calibration with known standards and the use of appropriate conversion factors to estimate TDS levels. Ensuring the meter is calibrated correctly and using the appropriate conversion factor for the sample being tested is crucial for accurate measurements.
The first step is to establish the exact ratio for transforming TDS into conductivity. This ratio is dependent on the type of salts and minerals present in the liquid. It can be located in specialized tables; if not, 0.67 is often used as a rough estimation.
To measure the TDS, a TDS meter should be employed. Once it is activated, the probe should be placed into the water or solution, and the TDS recorded.
Finally, the TDS should be divided by the conversion factor to calculate the conductivity.
When selecting a TDS or EC meter, it is important to consider the specific requirements of your application. Different meters are designed for different purposes, and choosing the right one will ensure accurate and reliable measurements. Factors to consider include the measurement range, accuracy, ease of use, and the ability to adjust conversion factors.
At Atlas Scientific, we have a range of EC meters and probes to suit the industry or application YOU are specifically working in!
Range: 0.07µs to 50,000µs.
Application/Industry: High-purity water applications.
Additional Notes: As the K0.1 kit can read beyond the range of high-purity water, you can ensure that readings outside the desired range will still be accurate.
Range: 10µs to 100,000µs.
Application/Industry: Different types of environmental monitoring, hydroponics, and measuring both freshwater and saltwater aquariums/aquatic environments.
Range: 10µs to 100,000µs.
Application/Industry: Environmental monitoring, hydroponics, and measuring both freshwater and saltwater aquariums/aquatic environments.
Range: 70µs to 500,000+µs.
Application/Industry: Saltwater and chemical process monitoring.
To browse our full range of probes and EC components, click HERE.
TDS and EC measurements play a crucial role in assessing water quality for various applications. Understanding the composition and conductivity of water is essential to ensure its safety and suitability for consumption, agricultural irrigation, industrial processes, or recreational use.
In drinking water analysis, TDS and EC measurements can help identify potential contaminants, such as excessive salts, heavy metals, or organic pollutants. High TDS levels may indicate water sources with poor quality, which could require additional treatment processes to make the water safe for consumption.
In agriculture, TDS and EC measurements are used to assess the suitability of water for irrigation purposes. Excessive salts or minerals in water can have detrimental effects on crop growth, soil quality, and overall plant health. By monitoring TDS and EC, farmers can make informed decisions about water usage and implement appropriate irrigation strategies.
TDS and EC measurements are also critical in industrial processes that rely on water quality. For example, in manufacturing or chemical industries, high TDS or EC levels can affect the efficiency and lifespan of equipment, as well as the quality of the final products. Regular monitoring and control of TDS and EC levels are necessary to ensure optimal conditions for industrial operations.
Furthermore, TDS and EC measurements are essential in recreational water environments, such as swimming pools or spas. High TDS levels can affect water clarity, taste, and the effectiveness of disinfection methods. Monitoring and maintaining appropriate TDS and EC levels are vital to ensure a safe and enjoyable swimming experience.
In hydroponics and agriculture, TDS and EC measurements are essential to ensure optimal growing conditions for plants. The composition of the nutrient solution directly affects plant growth, nutrient uptake, and overall crop productivity.
Hydroponics, a way to grow plants without the need for soil, depends on a precisely balanced nutrient solution to supply essential elements for plant growth. TDS and EC measurements are used to monitor the nutrient concentration in the solution and adjust it as necessary. By maintaining appropriate TDS and EC levels, hydroponic systems can provide plants with the necessary nutrients for healthy growth and maximize yields.
In traditional soil-based agriculture, TDS and EC measurements are also valuable tools for managing irrigation water and soil fertility. Excessive salts or minerals in water can accumulate in the soil over time, leading to soil salinity issues, soil pollution, and reduced crop yields.
By monitoring TDS and EC, farmers can implement appropriate irrigation practices and nutrient management strategies to prevent soil salinity and optimize crop production.
Additionally, TDS and EC measurements can help diagnose nutrient deficiencies or imbalances in plants. By analyzing the EC of the nutrient solution or soil solution, farmers and hydroponic growers can identify specific nutrient deficiencies or excessive levels, allowing them to adjust the nutrient regimen accordingly.
TDS and EC measurements are also crucial in the field of fishkeeping and aquarium maintenance. Maintaining appropriate water quality is crucial for the health and well-being of aquatic organisms, and TDS and EC play a significant role in achieving this.
In aquariums, TDS and EC measurements help assess the overall water quality and detect potential issues that may affect the fish and other aquatic organisms. High TDS levels could indicate the accumulation of waste, uneaten food, or excessive minerals in the aquarium water.
By monitoring TDS, aquarium enthusiasts can take appropriate actions, such as regular water changes or adjustments in feeding practices, to maintain a healthy aquatic environment.
EC measurements in aquariums can provide insights into the conductivity of the water, which is directly related to the presence of dissolved ions. High EC levels may indicate excessive mineral content or the presence of harmful substances. By measuring EC, aquarium owners can identify potential water quality issues and take necessary steps to improve the aquatic environment.
TDS and EC measurements are particularly important in specialized aquarium setups, such as saltwater aquariums or reef tanks. These systems require specific water parameters to support the delicate balance of corals and other marine organisms. Monitoring and controlling TDS and EC levels help ensure the stability and health of the marine ecosystem within the aquarium.
TDS and EC are important measurements used to assess water quality and determine the concentration of dissolved solids and ions in water. While TDS provides an overall measure of dissolved solids, EC measures the electrical conductivity of water.
TDS meters estimate TDS levels by measuring EC and applying a conversion factor, although this estimation may not be entirely accurate. It is crucial to choose the right meter for your application, considering factors such as measurement range, accuracy, and the ability to adjust conversion factors.
If you would like to know more about TDS or EC measurements or are unsure which meter will best suit the industry that you work in, do not hesitate to contact the world-class team at Atlas Scientific.
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