Four-electrode sensor for conductivity measurements
04 December 2007
Emerson Process Management has introduced the Rosemount Analytical PUR-Sense Model 410VP conductivity sensor, an easy to install four-electrode contacting sensor designed for sanitary applications in the food & beverage and life sciences industries. The sensor is manufactured from FDA compliant materials, meets 3A and EHEDG hygienic standards, and is available with a range of sanitary process connections.
The Model 410VP PUR-Sense sensor offers the industry’s widest conductivity measurement range, providing exceptional linearity between 0.1 µSiemen/cm to 600 mSiemen/cm.
Typical applications for the Model 410VP include monitoring the concentration of high conductivity fluids such as clean-in-place solvents and low conductivity rinses. It can also be used for monitoring eluents in chromatographic separations, and for the detection of liquid interfaces, all with the same sensor.
The Model 410VP is compatible with the Emerson Model 1056 Intelligent Analyser. An alternating current is injected through the outer electrodes and the analyser measures the voltage across the inner electrodes. During operation, the current is continuously altered to keep the voltage constant. Thus, the injected current is directly proportional to the conductance of the solution. Because the voltage measuring circuit draws almost no current, series capacitance and cable resistance, which cause considerable error in two-electrode measurements at high conductivity, are essentially eliminated.
Electrolytic conductivity readings are typically corrected for temperature. The Model 410VP uses an integrated Pt1000 RTD that makes contact with the process liquid through a stainless steel capsule flush with the sensing face, so temperature response is fast.
The Model 410VP is designed for fast, easy, and trouble free start-up. It has an accurate factory-determined calibration constant, which eliminates the need for troublesome calibrations against liquid standards and ensures maximum accuracy. It is available with four sanitary connections; 1.5” tri-clamp, 2” tri-clamp, Ingold G1-1/4, or Varivent Process Connection. All wetted plastics and elastomers (G 1-1/4 version only) are compliant with 21CFR177, and all wetted surfaces have a 16 microinch (0.4 micrometer) Ra finish.
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