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TDS Meter

TDS meter used in laboratory

What is TDS meter?

Water quality test pen, also known as TDS meter, TDS tester, or TDS sensor. TDS water quality test pen is a simple portable water quality test tool, used to test the TDS value of water or water conductivity, to determine the degree of water purity or pollution. It also has the function of testing ambient temperature and water temperature. TDS machines can be widely used in the water treatment industry, drinking water industry, family, travel, fieldwork, personal home, etc. as water quality inspection and identification tools.

A TDS meter is a small handheld device used to indicate the total dissolved solids in a solution (usually water). Since dissolved ionized solids (such as salt and minerals) increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that reading.

TDS meters can cost as little as $10, but more advanced models can cost more than $1,000, depending on the level of accuracy and additional features offered. For example, a basic TDS meter may only measure the amount of total dissolved solids in a solution, while a more advanced model may be able to check salinity, temperature, and more.

What is TDS?

The drinking water we get today is flushed with dangerous chemicals from different water treatment plants. As a result, the natural minerals present in the water are taken away. In this case, a proper filtration process must be used to remove the contaminants and make the water safe to drink. The main contaminant present in the water is the total dissolved solids (TDS) that remain in the water after the normal filtration process. Contaminants larger than 2 microns are called TDS. Fine filters typically remove 0.45 microns of particles of varying sizes and origins. After the filtration process, the remaining contaminants in the water consist of charged atoms and ions. Moderate to high levels of TDS in water not only change the taste of the water but also pose many health hazards.

TDS refers to total dissolved solids. TDS usually consists of inorganic salts and small amounts of organic matter. Inorganic salts consist of positively charged cations (calcium, magnesium, potassium, and sodium) and negatively charged anions (carbonates, nitrates, bicarbonates, chlorides, and sulfates.) The TDS level is the amount of total dissolved solids in the water. TDS in water is the amount of total dissolved solids in tap water. When water falls to the ground as rain, it dissolves the minerals present in the rocks and soil it passes over or through. As it dissolves these minerals are retained in the water in varying concentrations. This is a very natural process that helps make the water taste "right" by slightly raising the pH of the water. The most common minerals found in water are calcium, sodium, and magnesium.

Some areas of the country have high levels of these dissolved minerals in the water, making it "hard", while other areas have lower levels. According to the Water Quality Association, water in the range of 120 mg/L (or ppm) and above is considered hard, and 180 mg/L is considered very hard. Water in the range of 80 to 100 mg/l is ideal, as this range is not too hard and contains the right amount of dissolved minerals for optimal taste. At TDS levels below 17 mg/L, (as minerals are removed) it becomes "soft" with a lower pH and higher acidity.

In addition to inorganic materials, such as minerals, TDS also contains small amounts of organic materials from sources such as sewage, leaves, and waste.

However, the TDS meter does not measure contaminants. The TDS meter reading is only the amount of total dissolved solids in the water, it does not tell you exactly what those solids are and if they are harmful to your health. For example, there are no harmful contaminants in the water but your TDS tester may have a high reading. Some healthy minerals, such as potassium, magnesium, and calcium, can actually cause spikes in your TDS meter. Therefore, any water filter with a remineralized can cause your TDS meter to read high, even if the remineralized adds the quality minerals you want. On the other hand, your TDS level may be low even if there are many harmful contaminants in your drinking water. Your water may contain heavy metals or other contaminants that a TDS sensor cannot identify. This is why you should not rely on a TDS meter to determine the quality of your water. You need to know not only how many solids are dissolved in your water, but also what those solids are and whether they are harmful to your health.

Why is it necessary to measure TDS?

TDS tester

Water with TDS levels above 1000mg/L is not suitable for drinking. High levels of TDS in water can cause many health problems. The presence of potassium, sodium, and chloride can increase the TDS level in the water. However, the presence of toxic ions such as lead, nitrates, cadmium, and arsenic in water can lead to many serious health problems. This is especially important for children because their defenses are not fully developed and are therefore more sensitive to contaminants. The purer the water, the healthier the body. If you're concerned about the quality of your tap water but aren't sure if you need a water filter, you may have heard of using a TDS meter (also known as a TDS tester) to check for contaminants. TDS meters are often easy to use and relatively affordable.

What is the acceptable level of TDS in water is one of the important questions on many people's minds. The following table shows the acceptable TDS levels.
TDS levels in parts per million (ppm)Palatability quotient
Between 50-150Very good for drinking
The presence of TDS in water is not an indicator of any single contaminant, so many government agencies do not typically regulate it as a health concern. However, high TDS levels can affect the taste and odor of water. The U.S. Environmental Protection Agency has set a maximum recommended level of 500 milligrams per liter (mg/L).

TDS levels in water can be determined with the help of a TDS meter. the TDS test helps determine the total amount of dissolved solids in the water. However, it does not identify any individual compounds or sources. Therefore, some additional testing must be done to determine the contaminants present in the water.

In addition, people can determine whether TDS levels in water are healthy or harmful based on the types of salts and compounds released in the water. TDS is made up of a variety of salts, minerals, and organic compounds, including calcium, chloride, sulfate, magnesium, potassium, carbonate, and bicarbonate. While some of these may provide some minerals to the body, most are considered harmful and must be filtered before consumption.

The following table provides the allowable range of TDS in drinking water and the reasons why the TDS levels mentioned in the water are not drinkable.
TDS level (mg/L)Reason
Less than 50Unacceptable because it lacks essential minerals.
50-150Drinkable. TDS level for areas where water is contaminated with sewage or industrial waste.
150-250Good. This water is ideal for people with cardiovascular disease.
250-350Good. This water is ideal for people with cardiovascular disease.
500-900Less acceptable
900-1200Least acceptable. Avoid drinking water with a TDS level of 900.
1200-2000Water is not acceptable.

Why should labs use a TDS meter to check TDS levels?


PPM meter

Even after passing through a water filter, lab water can contain high TDS, giving it a salty, pungent taste.

A. Taste

High TDS levels can change the taste of water, making it salty, bitter or metallic. High TDS levels also indicate the presence of toxic minerals that are harmful to health.

B. Hardness

High TDS can harden water, cause spots on labware, and in severe cases, cause instrumentation to fail. Checking the TDS level of your water can help you avoid these problems in advance.

Methods of reducing or removing TDS from water

TDS is reduced in the same way as salt, calcium hardness, nitrate, and cyanuric acid.
A. Reverse Osmosis (RO)
Reverse osmosis removes TDS by forcing water under pressure through a synthetic membrane that contains microscopic pores that allow only molecules smaller than 0.0001 microns to pass through. Since the molecules of dissolved metals and salts are larger than the water molecules, the water is squeezed through the membrane, leaving the metals and salts behind.
B. Distillation
This process involves boiling water to produce water vapor. The water vapor rises to a cold surface, where it is condensed back into liquid form. The dissolved salt cannot evaporate and remains in the boiling solution.

C. Deionization (DI)

In this process, water passes through the positive and negative electrodes. The ion-selective membrane allows positive ions to separate from the water and move toward the negative electrode. The end result is high-purity deionized water. However, the water first passes through a reverse osmosis unit to remove non-ionic organic contaminants.

How to buy TDS meter?

ANTITECK provide lab equipment, lab consumable, manufacturing equipment in life sciences sector.
If you are interested in our TDS meter or have any questions, please write an e-mail to, we will reply to you as soon as possible.

    AntiTeck Life Sciences Limited

    A1-519, XingGang GuoJi, Yingbin Road, Huadu, Guangzhou, China, 510810
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