Contacting Conductivity Sensors SC42/SC4A(J)

Why measure Conductivity?

It can be used as a fairly inexpensive and low maintenance indicator of water quality.  Good quality water with little contaminants will have a low conductivity.  There is far less maintenance than pH and minimal calibration. Conductivity is used in Boiler feedwater, RO, and Demineralizer applications.

Since conductivity, up to a point, increases with an increase in the concentration of the ions in the process, we can use it to correlate to a % concentration value of solutions such as acids or bases.  Again, since conductivity is non-specific, % concentration can only be measured on ONE chemical at a time and not a mixture of contributing chemicals.

There are two basic sensor styles used for measuring Conductivity: Contacting and Inductive (Toroidal, Electrodeless).

When Contacting Sensors are used, the conductivity is measured by applying an alternating electrical current to the sensor electrodes (that together make up the cell constant) immersed in a solution and measuring the resulting voltage. The solution acts as the electrical conductor between the sensor electrodes.

The accuracy of conductivity measurements can be influenced by the following factors:

  • Polarization.
  • Contamination: Deposits or coating on the electrode surface of a 2-pole cell have a similar effect to polarization errors, i.e. the conductivity reading is lower than usual. These effects can also be prevented with a 4-pole conductivity cell.
  • Cable resistance: The cable resistance can induce error in the measurement and must be taken into account.
  • Temperature: Conductivity measurements are temperature dependent, if the temperature increases, conductivity increases.

Series (2)

  SC42 Large Bore SC4A SC42 Small-Bore
Model Code SC42 Large Bore SC4A(J) SC42 Small Bore
Cell Constants 0.01/cm; 0.1/cm; 1.0/cm 0.02/cm; 0.1/cm 0.02/cm; 0.1/cm; 1.0/cm
Ranges 0.02-2,000 µS/cm; 0.2-20,000 µS/cm; 2.0-200,000 µS/cm 0.04-400 µS/cm; 0.2-2,000 µS/cm 0.04-400 µS/cm; 0.4-2,000 µS/cm; 4.0-5,000 µ/cm
Temperature Element Pt1000 Pt1000 Pt1000
Pressure Rating 10 bar/142 PSIG 10 bar/142 PSIG 7 bar/100 PSIG
Maximum Temperature 150°C/302°F 110°C/230°F 100°C/212°F
Installation Connections Requires FD40, FS40 or FF40 Holder 3/4" NPT Fitting; 1", 1.5" or 2" Tri-Clamp; Retractable 3/4" NPT Fitting; 1", 1.5" or 2" Tri-Clamp
Integral Cable NO YES YES
Materials Of Construction 316 Stainless Steel 316 Stainless Steel or Titanium 316 Stainless Steel or Titanium
Design Sytle 2-Electrode 2-Electrode 2-Electrode

Process liquid analyzers such as pH meters, conductivity meters, ORP meters, and density meters play an important role at electrolysis plants in the control of concentrations of various process solutions. This requires both precision and stability under harsh conditions that include highly corrosive substances, high temperatures, and many impurities.


Seawater leak detection is the post-condensation water quality management processes. Damage to the ion exchange resin, which deionizes the supplied water, is also monitored during this process, and both of these applications are executed by a conductivity analyzer. (AN10D01P01-01E)

Application Note

To defray energy costs, many industrial plants have their own boilers to generate steam to produce a portion of their energy needs. In addition to generating power, the steam may also be used directly in plant processes or indirectly via heat exchangers or steam jacketed vessels. 

Application Note

The term "cooling tower" is used to describe both direct (open circuit) and indirect (closed circuit) heat rejection equipment. Cooling towers are heat-transfer units, used to remove heat from any water-cooled system. The cooled water is then re-circulated (and thus, recycled) back into the system. Since the process water is re-circulated, the mineral concentration increases as a result of the evaporation. (AN10B01B20-01E)

Industry:Refining, Food and Beverage, Power, Oil and Gas, Pulp and Paper, Chemical


There are a number of suppliers of oil and fat products used for edible purposes. These products include, but are not limited to olive oil, peanut oil, soybean oil, sunflower oil, lard, shortening, butter, and margarine. The raw materials for these products include animal by-products, fleshy fruits (palm and olive), and oilseeds. 

Industry:Food and Beverage


Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure.

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