As the lamps deteriorate, the LM100 lamp monitor tracks the lamp output through the UW254 underwater germicidal detector. A warning threshold can be set to turn on a warning indicator and activate a relay for external control. If the lamps continue to deteriorate, a second threshold (the error threshold) can be set which when crossed will turn on an error indicator and set a second relay which can also be used for external control. Both thresholds are programmable from 0% to 100% levels. The input of the LM100 lamp monitor accepts a 4 to 20ma detector (two wire). In addition to the display and alarms, the monitor has a 4 to 20ma output which represents the 0% to 100% on the display. This output can be used for remote monitoring or sent to a data collection system. The uw254 underwater germicidal detector is supplied with a 30' cable, and uses 9-25VDC.