551 Four-Electrode High Performance Inline with Nut Lock Adapter Sensors

The 551 Four Electrode Conductivity sensor is designed for sample line installations. The sensor mounts with Barben's 1 inch NPT Nut Lock union adapter. This allows for threadless installation and removal of the sensor for cleaning and calibration.


551 Conductivity

  • Quick change 1 inch NPT Nut Lock Adapter installation
  • Conductivity measurements up to 2 Siemen (Dependent on cell constant)
  • Kynar Body and PEEK insulator
  • Self compensating for corrosion and scale build up (analyzer dependent)
  • Well suited for sample line installations
  • Electrode options in 316 Stainless, Titanium, and Hastelloy

As the name suggests, four electrode sensors add an additional pair of electrodes to the two electrode sensor design. This second pair of electrodes provides sensor diagnostics which can then be used to compensate the measurement if scale or particulate build-up occur on electrodes. Four electrode conductivity sensors can withstand coating and scale which might otherwise foul a traditional two electrode sensor. Typical applications include the following:
  • Leak Detection
  • Condensate Return
  • Salinity
  • Chemical Concentration
  • Clean-In-Place


Sensor Technology - How it works

4 Electrode Tech

Four-electrode sensor designs keep a constant current through two of the electrodes and let the drive voltage change. If fouling occurs then the drive voltage can be increased to compensate the measurement.

Pros Cons
  • Compensation for coating and build-up
  • Wide measurement range
  • Sensor diagnostics if fouling is too great (analyzer dependent)
  • No polarization affect
  • Not as accurate as two electrode sensors at low conductivity
  • Susceptible to corrosion
  • Limited availability of analyzers (ABB, Rosemount, Mettler Toledo, Knick)
  • Conductive field can be distorted by pipe walls and flow cells


Conductivity Chart