The invention provides an optical drop detection system (10), for a low-flow metering device of the type having a drop generator 12, 24, (19), the system comprising at least one optical transmitter (26) which produces a plurality of light beam pulses (28) of microsecond duration and at millisecond intervals, and at least one optical receiver (33) positioned to register receipt of the light pulses (28) transmitted through the path of drops (18) generated by the drop generator (12, 24, 19) and to record the number of pulses which hit a given drop and which do not register on the receiver (32), the frequency and strength of the pulses being calibrated so that a single drop is impinged upon by a plurality of pulses, and further comprising automatic feed-back means for adjusting the parameters of interaction between the at least one optical transmitter (26) and the at least one optical receiver (32) to produce and maintain a predetermined minimum and a predetermined maximum number of hits per drop.