All float-operated liquid level transmitters operate on the basic buoyancy principle, "the buoyant force acting on an object is equal to the mass of liquid displaced by the object." As a result, floats ride on the liquid surface partially submerged and move over the same distance at which the liquid level moves.
The TR420 Transmitter employs a series of magnetic reed switches inside the vertical sensor stem that are actuated by a magnet within the moving float. Each probe segment contains 64 discrete resistors. Multiple segments are plugged together to achieve the desired length probe. The resultant probe segments form a resistive daisy chain (series circuit). These segments have been configured as a voltage divider where the magnetic reed switches are the tapping point in the circuit. As each switch closes, the voltage divider varies in proportion to the corresponding switch position and provides a proportionate voltage signal.
That signal is electronically conditioned through the transmitter controller board to provide the proportional output in mA or volts DC (depending on the model selected).
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TR420
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