TM 9-4940-568-34
3-7
e.
System Operation. The microprocessor
central unit operates as the control center of
the system. The length cable is connected to
the boom nose. During telescoping the length
cable spools off a drum which turns the length
potentiometer using a gear assembly. The
length potentiometer is a variable resistor
which varies linearly with the boom length. An
angle sensor is built into the central unit which
senses the boom angle (pendulum turns a
potentiometer, similiar to length sensor). The
load cell provides the signal to calculate the
load on hook. The proximity switch located on
the hoist drum switches to a different
calibration factor during spooling off the hoist
rope. This will allow a steady load calculation
and compensates for the difference in the lever
arm. All together the signals get processed in
the central microprocessor unit where actual
and rated load are compared. Once the actual
load exceeds the rated load, the system
de-energizes a relay and disables the
applicable crane functions.
