Drops passing through the drop tube
either interrupt or reduce the light falling on the photo cell and generate
an impulse which is amplified to operate the electro magnetic counter and
also a low resistance marker. About 1.5 mts length of cable with suitable
non reversible connectors connect the photo head and the marker to the
electronic unit. A counter on off switch enables the counting to be started
and ended when desired.
The unit also provides power
(approximately 6 volts D.C.) for operating an external low resistance marker
or relay, to enable the number of drops and time between successive drops
to be recorded on graph ,or to trigger an ancillary equipment or apparatus.
The apparatus works from 220 volts
A.C. mains, and is housed in steel cabinet attractively finished. The photo
head and marker are boxed separately.