LINK Systems System 1100 Tonnage Monitor - Manual (Page 47)

THEORY OF OPERATION
___________________________________________________________________
3-10
Figure 10.
Without the delay time, the tonnage display would be updated three
times in a single stroke, retaining only the last (40 ton) peak for
a time long enough to be read. Each time the signal goes above the
threshold the timer is reset.
The threshold level to which a signal has to rise to turn off the
automatic zero circuit is about 5% of rated channel tonnage. On
some machines, particularly larger geared machines, clutch
engagement or braking can introduce torques that strain the machine
frame as much or more as load signals equal to 5% of rated channel
tonnage. These extraneous signals will produce nuisance readings
on the tonnage displays.
The threshold level can be changed to 10% of rated channel tonnage
in the THRESHOLD screen located in the Config menu (section 2.8.4).
This is only recommended for machines that don't perform draw
operations or other operations using air cushions or nitrogen
cylinders for material clamping. Air cushions or nitrogen
cylinders may exert forces too low to reach the 10% threshold
during the first part of tooling contact. The automatic zero
circuit will then continue to operate until the tooling closes
enough to exert forces that cross the 10% threshold, shifting the
baseline by a few percent of rated tonnage and introducing errors
of a few percent of rated tonnage into the peak tonnage indicated.
When clutch and brake engagement cause nuisance readings, the
recommended procedure is to employ automatic zeroing by position,
as discussed next in this manual.