Walchem Conductivity Sensors (Contacting and Electrodeless / Toroidal)

Walchem conductivity sensors come in two technologies: contacting sensors that measure through electrodes, and electrodeless (toroidal) sensors that measure through an encapsulated coil without touching the solution. Contacting sensors cover cooling towers, boilers, reverse osmosis equipment and other non-oily applications; electrodeless sensors are used in oily cleaner baths, chromate solutions, rinse tanks and fume scrubbers. As the Walchem distributor in Turkey, Mikron Proses (Üsküdar, Istanbul) supplies the sensors, flow cells and matching controllers and provides application consulting for cell constant selection, commissioning and calibration support.

Tell us the solution, temperature and expected conductivity and we will select the sensor → Send us your requirement

Comparison of sensor types

Sensor type	Cell constant / range	Materials	Limits	Typical use
Contacting, cooling tower	K = 1.0, up to 30,000 µS/cm	Polypropylene body, graphite or 316 stainless steel electrodes	Up to 10 bar; high-pressure inline version of stainless steel and PEEK up to 20 bar	Cooling tower blowdown control
Contacting, general purpose	K = 0.01, 0.1, 1.0, 10.0 (0-300 to 0-300,000 µS/cm)	316 stainless steel, PTFE	Polypropylene fitting 0-100 °C, 6.9 bar; stainless steel fitting 0-120 °C, 13.8 bar	RO systems and boiler condensate monitoring
Contacting, boiler	K = 1.0 (up to 30,000 µS/cm) or K = 10.0 (up to 300,000 µS/cm)	316 stainless steel, PEEK	Up to 17.2 bar, 0-205 °C	Boiler blowdown control
Electrodeless (toroidal)	500 µS/cm to 2000 mS/cm (passive); narrow active ranges 0.1-1 to 100-1000 mS/cm	CPVC or PEEK, no metal electrode	PEEK sensors 0-88 °C	Oily baths, chromates, rinse tanks, scrubbers

Contacting (electrode) sensors

Contacting sensors measure conductivity through electrodes. The low-pressure types have a polypropylene body with graphite or 316 stainless steel electrodes and work up to 10 bar; the high-pressure inline types are built from stainless steel and PEEK. Boiler sensors of 316 stainless steel and PEEK are rated up to 17.2 bar and 0-205 °C. Standard sensors with a cell constant of 1.0 cover 0-30,000 µS/cm, and a cell constant of 10.0, available for W100 and W600 controllers, extends boiler measurement up to 300,000 µS/cm. Sensors with cell constants 0.01 and 0.1 cover the low ranges of 0-300 and 0-3,000 µS/cm, for example in RO systems and boiler condensate.

Electrodeless (toroidal) sensors

Electrodeless sensors use encapsulated, non-contacting toroidal technology and are immune to thin coatings and to the contamination and calibration problems that direct contacting sensors are prone to, which is why they are used in oily cleaner baths, chromates, rinse tanks and fume scrubbers. CPVC or PEEK construction is available for inline or submersion mounting; passive sensors cover 500 µS/cm to 2000 mS/cm, and active sensors are supplied in narrower ranges (0.1-1, 1-10, 10-100 and 100-1000 mS/cm).

Temperature compensation and controller choice

Temperature is measured with a thermistor (10K or 100K) or a Pt1000 RTD, and the conductivity is normalized to 25 °C with a range multiplier table (181.3% at 0 °C, 22.9% at 180 °C). W100 and W600 controllers use passive sensors with a cable of up to 6 m, whereas the older W400 and WebMaster controllers need active sensors with built-in electronics and allow cables up to 76 m. Suitable controllers include the W100P panel-mount controller, the W600 and the Intuition series. For background see the boiler water conductivity guide, the toroidal conductivity sensor guide, the cooling tower automation guide and the Walchem brand page.