Noninvasive Photon uses scintillation technology to measure point level, continuous level, or fluid interface in tanks and batch reactors. Gauge includes strip source holder with small photon sources that span measuring range; point or rod-shaped scintillation detector; mounting hardware; and microprocessor control unit. Explosionproof enclosure clamps to outside of vessel; control unit is housed in NEMA 4x enclosure. Transmission or backscatter modes permit level measurement on any size vessel. System has two isolated 4-20 mA analog outputs and 2 RS232/422 serial ports.