What is the relationship between the resistance value of ultrapure water machine and water purity?

       The ultra-pure water machine is that the tap water is pretreated by a precision filter element and an activated carbon filter element to filter particles such as sediment and adsorb odors, so that the tap water becomes cleaner, and then the water is purified and desalinated through a reverse osmosis device. When the water tank is stored, the water quality can reach the national standard, and the waste water in the reverse osmosis device is discharged at the same time. The reverse osmosis pure water is deeply desalted through the purification column to obtain ultrapure water. Then, if the user has special requirements, ultraviolet sterilization or microfiltration, ultrafiltration and other devices are added to the laboratory ultrapure water to remove the residual bacteria in the water. , particles, heat sources, etc.

In the process of taking ultrapure water by the ultrapure water mechanism, the resistance value is one of the measurement ranges of water purity. By measuring the resistance value of the water, we can know the level of ion content in the water, so as to judge the purity of the water quality, which is related to the measurement of the conductivity of pure water. Different, ultrapure water generally indicates the purity of water quality by resistance value.

1. Resistance unit

The unit of resistance value is called ohm, and the symbol is Ω. The resistivity of ultrapure water is usually larger, which is generally expressed by MΩ, and the other conductivity is reciprocal relationship.

5μS/cm=0.2MΩ.cm;

1μS/cm=1MΩ.cm;

0.5μS/cm=2MΩ.cm;

0.2μS/cm=5MΩ.cm;

0.1μS/cm=10MΩ.cm;

18.25MΩ.cm=0.055μS/cm.

2. Principle of ultrapure water purity

According to Ohm's law, when the water temperature is the same, the resistance value R of the water is inversely proportional to the vertical cross-sectional area F of the electrodes, and proportional to the distance L between the electrodes. Therefore, when measuring the conductivity, the greater the resistance value of water, the worse the conductivity, and the smaller the resistance value, the better the conductivity.

The resistivity of water is related to the ion content and salt content in the water, so the higher the purity of the water, the less the ion content, and the greater the resistivity. Therefore, the resistance value usually reflects the purity of ultrapure water. Ultrapure water has low ion content, and the resistance value is usually >10MΩ.cm, and the theoretical resistance value of pure water is 18.25MΩ.cm.