ABB TP867 Control I/O Unit Base
When horizontal, the measurement force (FRtot)is a function of just the tension in the web (T) and
the deflection angles (α and β). Since the weight of
the roll and bearings (Tare) is not sensed, the load
cells can be sized to measure low tension levels
even on a comparatively heavy roll. However, the
perpendicular force (FVtot) – which does include
Tare – should not exceed the overload rating.
When the measurement force (FRtot) is vertical,
it includes the weight of the roll and bearings (Tare),
and the load cell must be sized accordingly. In effect,
the weight of the roll and bearings are using up
some of the measurement range of the load cell.
A diagonal load force orientation requires a more
complex calculation. Here, the forces sensed in both
the measurement direction and the perpendicular
direction include a portion of the tare as well as
the web tension, and the angle formed by the
measurement axis and the horizontal axis (γ)
enters into the calculation.
Application hint
Two 10 % application guidelines are useful
in selecting load cell sizes:
1. The proportion of web tension that is actually
sensed by the load cell should be at least 10 %
of total web tension. For operational conditions
producing values below 10 %, consult ABB.
2. During normal operation, the sensed force
should not be less than 10 % of the load cell’s
capacity.

Four standard sizes measure web tension from
0.1 to 100 kN. With its extended-capacity feature,
the PRT load cell is capable of measuring tension
reliably over a 30:1 range. Superior overload
characteristics in all force directions (up to 500 %)
eliminate overload failures for all practical
purposes.
Exceptionally high spring constant virtually
eliminates load cell contributions to machine
vibration, even at very high machinery speeds.
The performance of the load cells is unaffected
by environmental factors like dust, corrosion
and radio or electromagnetic interference.
Extended-Range Operation Beyond their nominal capacity,
PRT load cells have an extended range of measurement
– so they can be sized for normal, as opposed to maximum,
tension levels. As a result, they can process a wider variety
of materials.
1 Values indicate the total capacity of the load cells when
taking into account their permissible extended capacity.
In the extended range, above the nominal load, some small
decline in measurement accuracy may be experienced.
2 Maximum permitted loads without affecting load cell calibration.
3 At nominal load.
4 Accuracy class is defined as the maximum deviation, and is
expressed as a percentage of the sensitivity at nominal load.
This includes linearity deviation, hysteresis and repeatability error.
5 Corrosion resistance properties similar to AISI 304.
6 Applies for 20 to 80 °C (68 to 176 °F).