Definition

A measurement of a water sample's ability to conduct electric current, reported in microsiemens per centimetre (μS/cm). Conductivity is directly proportional to dissolved ion concentration (calcium, magnesium, sodium, chloride, sulphate). It is the decisive parameter for steam humidifier selection: electrode humidifiers require 125–1,250 μS/cm, whereas resistive humidifiers operate across the full range — including RO/DI water — independent of water quality.

Detailed Explanation

Electrical conductivity is the ability of water to carry an electric current, expressed in μS/cm. Pure water itself is almost non-conductive (≈ 0.055 μS/cm at 25 °C); nearly all measured conductivity comes from dissolved ions. RO water is typically a few to a few tens of μS/cm, while mains waters generally range from a few hundred μS/cm to above a thousand μS/cm depending on the source.

Because ion mobility changes by about 2% per degree, conductivity is reported corrected to 25 °C (the Turkish drinking-water regulation uses 20 °C). The regulation gives an indicator value of 2,500 μS/cm (20 °C) for conductivity.

Why It Matters

In an electrode steam humidifier the current flows through the water between the electrodes and heats it that way, so conductivity is an operating requirement. The suitable band varies by product; Neptronic's report comparing electrode and resistive humidifiers gives it as about 125–1,250 μS/cm. Below the band (RO/DI water included) the unit cannot reach its capacity; above it, frequent draining, foaming and rapid build-up occur.

In a resistive steam humidifier the current flows through the heating elements, not the water. Conductivity is therefore not an operating requirement; the unit produces steam with any water, RO and DI included. Here conductivity is only an indirect indicator: the more dissolved salts, the more deposits build up in the tank and the more draining is needed.

Worked Example

A mains water with a conductivity of 500 μS/cm (25 °C) has a TDS of roughly 250–350 mg/L using TDS ≈ conductivity × 0.5–0.7. If the same water passes through RO and 95–99% of the dissolved salts are rejected, conductivity drops to about 5–25 μS/cm. This is far below the electrode unit's band; a resistive unit runs normally on this water.

Engineering Note

Field measurements should use a temperature-compensated (ATC) conductivity meter, noting the reference temperature of the result. Because mains-water conductivity can change with the season and the source, measurements taken at different times should be compared where possible instead of relying on a single reading.

How Nem Kontrol Teknolojileri Applies It

As Neptronic's authorised distributor in Türkiye, Nem Kontrol Teknolojileri asks the customer for a recent water analysis from an accredited laboratory when selecting a steam humidifier and compares the values with Neptronic's feedwater requirements. The resistive Neptronic SKE4 runs on any water, RO and DI included; water quality only affects maintenance frequency. Pre-treatment systems are designed and installed by specialist water-treatment companies.