Low level gamma energy is emitted in a controlled pattern from a source housing, through the vessel walls, to an ion chamber-based detector (maximum of four detectors) placed on the other side of the vessel.
As the material in the vessel fills, the amount of gamma energy reaching the detector is partially blocked, creating a shadow-like impression on the detector.
The microprocessor-based electronics mounted in the detector convert the gamma energy into a digital communication signal that is sent via a standard three-wire instrument cable to the level transmitter.
The transmitter includes a menu-driven local display and an isolated 4-20 mA DC output signal for operator interface and level indication. All signal processing and system diagnostics are performed within the transmitter.