Capacitive Level Sensors
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Capacitive Level Sensors The sensing means is based on our capacitive proximity sensing technology. Electrodes embedded in the front of the sensor detect changes in the capacitance as the fluid nears the sensor face. Once the trigger point is reached (either calibrated at Gems™ or set by the user once after installation) the sensor switches creating the desired output. Because they are adjustable they can be used to sense aqueous and non-aqueous fluids, regardless of color. Capacitive Level Switch Operating Principle A capacitor is a two terminal device that consists of two conducting bodies separated by a non conducting (dielectric) material. A simple capacitor consisting of two plates is shown below. A simplified expression for the capacitance of this arrangement is: To create a more usable geometry for sensors the plates (or electrodes) can be arrayed in a variety of ways. Though this complicates the above expression for capacitance, the overall relationship between the variables remains the same. Shown below, the electrodes are arrayed on the same plane. This can be accomplished in numerous ways. The electric field is projected away from the electrodes. If the dielectric remains constant, the capacitance also remains constant. If the dielectric changes, the capacitance naturally also changes. In capacitive proximity sensors, these two electrodes are coupled together, and integrated in a high frequency oscillator. In the “no target” state the oscillator is tuned to be resting. As a target enters the electric field, increasing the capacitance, oscillation begins. When the amplitude reaches a high enough level, a change in signal state is triggered. |