When installing conductivity sensors it is very important that the electrodes be in continuous contact with the fluid. Anything that interferes with this contact can affect the measurement.
All Signet contacting conductivity/resistivity sensors are constructed of stainless steel with an inner plate and an outer plate. An AC voltage is applied across the two plates. As fluid passes between the plates, the resistance of the fluid can be measured. This value is used to calculate the conductivity of the fluid. Cable Lengths
• Signet sensors have cable length restrictions (See Fig. 1)
• Exceeding the maximum cable length will introduce measurement errors.
• Sensors with extended cable lengths can be ordered from Signet. This eliminates the possibility of poor
connection points or high resistance connections that can affect the accuracy of the system.
• If extending the sensors cable length is required to be done in the field, Signet strongly recommends the
3-8050-1 (159 000 753) universal junction box be used in conjunction with the proper Signet cable as listed in
the catalog. Avoiding Entrapped Air Any air that is trapped inside the sensor when a new system is installed MUST be displaced. Air bubbles reduce the surface area of the electrode that is in direct contact with the fluid. 
• To avoid bubbles from being trapped, make sure that one of the holes in the outer electrode is facing upward.
(Fig 3a and 3b).
• Fig 3a shows the preferred method of installing a sensor. The holes in the sensor body allow air
bubbles to escape. The sensor is also positioned so that fluid is flushed through the center of the sensor. This is
most important in measuring very low conductivity fluid. Fig 3b is also suitable for low conductivity water and all
other Signet conductivity sensors.
• Fig 3c and 3d are suitable for installing sensors with a cell constant of 10 and 20. It is not recommended to install
a low conductivity cell into a flow stream using the 3c and 3d configuration.
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