National’s Continuous Liquid Level Indicators use hermetically sealed magnetic reeds and precision resistors to form a linear resistance network. A magnetic float closes the reeds in such a manner as to tap the voltage off the array very much the way a potentiometer does, only without parts that wear out. An excitation voltage is applied across the sensor, and a meter or computer reads the voltage and displays the result, usually scaled in gallons or as percentages of tank capacity. The signal is always within ¼” of actual liquid level. It changes by ¼” increments as the tank level changes.
Repetitive Accuracy to within ¼” is constant throughout the length of the unit which is directly proportional to the depth of the tank. The signal will change every ¼” of float travel, and built in circuit redundancy stands up to shock, vibration, and physical extremes. The strongest asset this TLI (tank level indicator) has is its lack of wear parts. The float is the only moving part, and it is self-cleaning by nature.
Direct Contact Measurements are made without periodic calibrations or adjustments. Where the float is, is where the signal comes from, a simple and very strong potentiometric sensor. The signal is not affected by humidity, pressure, or temperature fluctuations.