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1 General Description
The Montalvo X-3000ce-UW PID analog controller provides precise automatic control
of web tension. The progressive PID regulator automatically compensates for roll
diameter. The X-3000ce-UW is used in a closed loop, of which the load cell roller and
brake (or other tension-affecting device) are a part.
To properly set up and operate the X-3000ce-UW and to take advantage of all its
available features, it is important to have a general understanding of the controller
and its place in the tensioning system (please refer to the diagram on the following
page). A typical pneumatic system is displayed; however, the same principles apply to
any other closed-loop control system. The control outputs of 4 to 20 mA and 0 to 10
volts DC enable the X-3000ce-UW to interface with a variety of output devices to
control web tensioning brakes, clutches, and motors.
Load Cell Function
Two load cells (also called transducers) are normally used. The signals from the load
cells are summed together to indicate total web tension across the entire web. Each
load cell contains two strain gauges connected in a series. The two load cells are
connected so that the four strain gauges form a Wheatstone bridge configuration
supplied with + 2.5 VDC. The web tension transfers a force to the load cell roll,
changing the resistance values in the bridge. The resulting voltage change is
amplified and calibrated to display actual web tension.
Converter Function
The I/P converts the 4 to 20 mA regulator output to a proportional 0 to 75 PSI (0 to 6
bar) to control the brake. Other converters may be used, depending on the
application.
Brake Function
One or more brakes may be controlled, converting the pneumatic output pressure
from the I/P into torque. This torque in turn changes the web tension.
Auto Mode Function (Closed Loop)
The operator sets the desired tension with the auto setpoint potentiometer. The
controller compares actual tension to the auto setpoint, and adjusts output until the
actual tension and setpoint are equal. Because the web itself is part of the feedback
loop, the X-3000ce-UW can quickly compensate for speed and diameter changes,
and for other factors that affect tension during the process.
