Model Q45C4 Conductivity Monitor
from Analytical Technology

The Q45C4 4 electrode conductivity monitor is the answer for monitoring almost any water based process. Drinking water, plating bath solutions, cooling water, process wash water or virtually any other aqueous system can be monitored accurately and reliably. The unique drive/control scheme used in the 4 electrode system allows a single sensor configuration to be used in conductivity ranges from 0-200 uS to as high as 0-2,000 mS (0-2.5). The "auto-ranging" feature enables the monitor to display the actual conductivity value during "overshoot" conditions. For chemical making applications, a concentration display can be selected for a limited number of acids and bases. If your application involves very low conductivity/resistivity measurement, ATI can provide the Q45C2 system that is used in process waters with conductivities below 20 uS.

Monitor Features

Benefits of a 4 Electrode Sensor

Q45C Conductivity monitors are designed to use a rugged 4 electrode sensor that provides wide range conductivity measurement without the need for multiple sensors. Virtually all conductivity applications ranging from 0-200 uS up to 0-2,000,000 uS (0-2.5) can be reliably measured using this unique and flexible system. What can be accomplished with a single 4 electrode sensor with increasing cell constants. The "one sensor fits all" approach to conductivity measurement eliminates the need to inventory multiple sensor types, as well as the confusion in matching cell constants to conductivity ranges.

The 4 electrode sensors not only provide wide range measurement capability, but also excellent resistance to electrode coatings that can degrade measurement accuracy. Changes in electrode condition are compensated for in the electronic transmitter, so even partially fouled sensors continue to produce accurate measurements. And should the sensor become so fouled that it requires cleaning, the monitor will display a "fouled sensor" indication to ensure that operating personnel are alerted.

Sensors for the Q45C4 system are available in a variety of mounting configurations: convertible system with 1" NPT threads for pipe or tank mounting, 1 1/2" or 2" sanitary style fittings in 316SS and insertion style for 1 1/4" NPT hot tap assemblies that allow the sensor to be removed from service without shutting down the process.

How a 4 Electrode Sensor Works

In a traditional 2 electrode sensor, each electrode performs two functions. First, the electrodes are used to generate a "drive potential" through the aqueous solution. Second, the electrodes are used to measure the level of current flow as the conductivity of the solution varies. It is this dual role that limits a 2 electrode sensor to a narrow functional conductivity range.

A 4 electrode sensor splits the two functions between two set of electrodes. One set of electrodes is used to generate the drive potential through the aqueous solution. The other set of electrodes is used to measure the current that flows between the two drive electrodes. Because these two functions are separate, the 4 electrode sensor does not suffer the polarization effects that limit a 2 electrode sensor to a narrow functional range. This allows a single 4 electrode sensor to operate reliably over the entire 0-2.5/cm conductivity range.

Sensor Features

4 Electrode Style Sensor: Allows the sensor to be used over 0 to 2,000,000 uS range.
PEEK Sensor Construction: Electrode holders made of PEEK, a high performance thermoplastic that provides outstanding mechanical strength and chemical resistance. High structural integrity ensures accurate conductivity measurement.
Multiple Mounting Styles: Sensors available in 1" NPT convertible style, insertion style and 1 1/2" or 2" sanitary styles.
Titanium Electrodes: The four electrodes used in the sensor are made of titanium for greater chemical resistance.
Sensor Diagnostics: Sensor diagnostics are used to alarm the user in the event of loss of sensor seal integrity or integral temperature sensor failure. Automatic foulant rejection circuitry is used to compensate for the effects of sensor fouling. As the two drive electrodes become coated by the process solution, a feedback mechanism involving the two sensing electrodes detects the decrease in drive potential and automatically reestablishes the proper drive potential. When the degree of coating reaches a limit where compensation is no longer possible, the diagnostics actuate and alarm to signal that the sensor requires cleaning.
Multiple Sealing Materials: Multiple sealing materials are used to preserve sensor integrity over a wide range of chemical processes and varying temperature.