ABB TP858 3BSE018198R1 Module base
And in the textiles industries, machinery
applications include nonwovens production
as well as finishing operations like bleaching,
desizing, dyeing, and printing.
In all web processing areas, PRT load cells are
used on the full range of winding machinery,
from unwinders to slitter-rewinders.
The Pressductor difference
Like ABB’s other load cells based on Pressductor
Technology, PRT load cells rely on electromagnetic
changes in the transducer, not on physical
movement, to sense fluctuations in web tension.
The Pressductor Technology operating principle
provides exceptional improvements in load cell
performance characteristics, including reliability
(notably absence of drift), durability, repeatability,
and wider measurement range.
Machined from a solid block of steel, the load cells
are rugged and stiff, affording high overload
protection as well as an extended measurement
range above the nominal load. And they do not
contribute to machine vibration, even at high
speeds.
Since the transducer action – the magnetic flux
– takes place inside a steel core, environmental
factors like dirt or fluids can’t degrade
performance and reliability. These stainless
steel load cells don’t require any physical seals.
Furthermore, low transducer impedance
– less than a couple of ohms – helps eliminate
susceptibility to radio-frequency and
electromagnetic interference.

Selecting and sizing load cells
Calculating the forces exerted on load cells in
a specific application allows you to determine the
ideal load cell size specification. Force calculations
and load cell sizing are typically conducted
in collaboration with ABB; this page provides an
overview of the considerations that play a role
in this stage of the specification process.
The orientation of PRT load cells on the end of
the roll shaft can be adjusted to perform measurements in the most advantageous direction for each
application.
In sizing PRT load cells, both the web tension and
the weight of the roll and bearings (tare weight)
should be considered. If the load cell is oriented
vertically or diagonally with respect to the force
of gravity, the tare force will contribute to the total
force level sensed by the PRT load cell system.
If the load cell is oriented horizontally, the tare
force will be perpendicular to the measurement
axis, and so will not be sensed.
Calculating the forces
The PRT load cell measures bi-directionally
along its measurement axis (see illustration).
Once the load cell is oriented and the measurement
axis determined, the force components exerted
on the load cells of a roll are easily calculated as
functions of the web tension, tare force, and
deflection angles. Since most systems involve
two load cells, the calculated forces are divided
by 2 to obtain the forces exerted on each individual
load cell. The illustrations on this spread show
three scenarios, involving horizontal, vertical
and diagonal measurement axes.