Tecsis news: "Crossover from weighing technology"
"Single Point"- bending beam as economically priced
force sensor
Although implemented in millions of bench scales the bending
beam platform load cell is a fairly unknown measurement element
to the mechanical engineer. These so called "Single Point"-load
cells are now used in the automation industry as force sensors.
The measuring element remains unchanged. Only the calibration
adjustment process is now based on the unit "Newton" instead of
"Kilogram".
In the function as a force sensor the transducer frequently offers
decisive advantages. Besides the unbeatable low price (due to
high quantities in weighing technology), the easy force transmission
and the compact dimensions are advantages in the application.
Designated force transducers generally need costly engineering
to achieve optimal force readings. This charge is reduced in many
applications using the "off-center load compensated" bending
beams. This compensation referrs to the maximum allowed
platform size which can be up to 400x400 mm depending on the
capacity.
A non centrical loaded platform will due to the special compensation
still give correct readings.
Bigger sized platforms can possibly be measured with cells
connected in parallel considering the increasing measurement
uncertainty. The accuracy as per the specification is at ±0,025%
of the nominal load.
The following example of an abrasive belt machine demonstrates
the achievable accuracy. The abrasive belt runs over the "single
point" measured platform. Applying grinding forces of 1.000 N
(nearly 100 kg) will result in a maximum signal deviation of 0,25 N
or 25 g. Even if the grinding area changes on the platform the
sensor signal will remain the same.
Available capacities are beginning from 0,6 kg up to 1.000 kg.
Like all the other force transducers from tecsis the bending beams
are made to work in the industrial environment: Temperatures
-20°...60°C and IP65 protection.
Available output signals are mV/V resp. amplified analogue outputs
4..20 mA or 0..10V. The amplifying circuit is located directly in
the cable or in a DIN-rail enclosure resp. in a rugged aluminum
field housing.
Connected to a smart panel meter digital outputs like serial I/O
(RS232, RS485) or fieldbus (Profibus, CAN-Open) can be provided .
The application fields of the bending beam force transducers are
versatile and interbranch. Apart from scale manufacturing these
sensors can be found for example in low cost web-tension
measurement or they are used for leak testing in the food industry.
_____________________________________________________
tecsis GmbH
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November 2002
