Waterguide - Chemical free hardness measurement

Hardness measurement without chemical?

Ion-selective hardness measurement is a technique used to determine the concentration of specific ions, such as calcium and magnesium, in a liquid, typically water. It operates using a specialized sensor that exploits the unique selectivity of certain membranes for these ions. Here's a simplified description of how it works:


Ion-Selective Membrane:

The core of this measurement is an ion-selective membrane that only allows certain ions to pass through. In the case of hardness measurement, it selectively allows calcium and magnesium ions to move through the membrane.


Ion Diffusion:

In a solution, ions move from areas of higher concentration to lower concentration due to diffusion. As calcium and magnesium ions attempt to diffuse through the ion-selective membrane, a dynamic equilibrium is established.


Voltage Generation:

The movement of calcium and magnesium ions across the membrane generates a voltage difference, known as the membrane potential. This voltage is directly related to the concentration of these ions in the sample solution.



The generated electrical voltage is measured and interpreted. Higher concentrations of calcium and magnesium ions result in higher voltages, while lower concentrations lead to lower voltages.


Water Hardness Determination:

The measured voltage is used to determine the water hardness. This information is used to represent the hardness level of the water.


The ion-selective hardness sensor, in conjunction with a reference electrode, provides a practical and accurate way to assess the hardness of water, which is essential in various applications, such as water treatment, industrial processes to ensure that water is suitable for specific uses.

What Herco offers:

At Herco we provide Volume-controlled duplex softener from the Ecotrol-D series which could be upgraded with such hardness sensors for quality control (switching criterion when exceeding set point total hardness).

Feel free to explore more details on our website or reach out to us directly. Our team would be glad to assist you with tailored services.

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