Load Cells Overview

A load cell is a transducer that is used to convert a force into an electrical signal and offers measurement of tension, compression and shear forces. The majority of today's designs use strain gauges as the sensing element, whether foil or semiconductor, and feature low deflection and high frequency response characteristics, which are especially beneficial for both materials testing and high‐speed load measurement applications, particularly where peak forces are being monitored.

Load cells are available in many physical shapes and forms to suit particular applications and forms of loading. Typical designs include S Type Load CellsS-Beam / Z-Beam and Shear Beam Load CellsRing-Torsion Load CellsThrough Hole and Pancake Load CellsButton Load CellsSingle Point Load CellsMiniature Load CellsPlatform Load Cells and Digital Load Cells.

These designs can be used in either compression, tension and compression / tension configurations and many are available as standard, low profile or miniature load cell designs:

Compression Load Cells such as the Sherborne Sensors SS3 are typically Shear Beam, Single Point, Pancake or Platform designs and often have an integral button design. 

Sherborne Sensors SS3 Compression Load Cell

Tension Load Cells such as the Sherborne Sensors SS4000 include ‘S’ beam and ‘Z’ beam and are typically used in applications where force is measured with the load cell suspended.

Compression/Tension Load Cells such as the Sherborne Sensors SS 5000 are used for applications where the load can vary from tension to compression.

Sherborne Sensors SS5000 Load Cell

Load cells can be used in a wide variety of applications, including:

Aerospace – flight control force measurement, internal engine forces and ejector seat force measurements.

Paper Mill – bearing force load cells to monitor and maintain correct roller tension.

Marine – hoist loads, platform retention, towing forces and mooring loads and systems       

Civil Engineering – bridge lifting/weighing, vehicle/crane load monitoring and earthquake force monitoring.

Pharmaceutical Industry – to control the compressive forces during tablet manufacture during many millions of cycles.

  

Understanding Load Cell Designs

Beam Sensor Type Load Cells        

Beading Beam type load cells are one of the most popular load cell designs due to their simplicity and relatively low cost. The design consists of a straight beam which is anchored to a base at one end and has a load applied to the opposite end.

The shape of a Bending Beam Type load cell can either be cantilevered, single point or pancake / ring.  

Cantilever Design

A cantilever bending beam type load cell has strain gauges mounted onto the top and bottom to measure tension and compression forces, which are then typically covered by rubber bellows to protect the gauges.

Sherborne Sensors Cantilever Load Cell Design

Binocular, Single Point Design

A single point load cell design (often called a binocular bending beam design) has good moment immunity which results in very small errors of change in the force application point. For this reason the design is popular for low force commercial weighing applications.

 

Ring / Pancake Design

Ring or Pancake design load cells are round, flat, bending beam sensors. These designs consist of bonded foil strain gauges which are encapsulated in a stainless steel housing. A typical example of a Ring or Pancake design load cell is the Sherborne Sensors VC 7600:

Sherborne Sensors VC7600 Load Cell

A Compression only Ring or Pancake design is typically mounted in way that both limits the movement of the load and directs the load toward the centre of the pancake.

When used in Compression-Tension applications, the Ring or Pancake design have a threaded hole running completely through the centre of the sensor which allows accessories such as eyed bolts to be added to the load cell.

Shear Beam Sensors

Shear beam sensors are design to measure the shear effect caused by a load. Shear cannot be measured by a bending beam sensor because shear stresses change across the cross section of the load cell.

Shear load cell designs are typically I-beam constructions which produce a uniform shear over the cross section of the load cell. When compared to bending beam load cells, a shear beam load cell will display better handling of side loads and dynamic forces, as well as a faster return to zero.

 

Direct Stress Load Cells

Direct Stress load cells (often called Canister or Column Load Cells) are bending beam sensors which are mounted inside a rugged column. The beam sensor is mounted upright with two of the four strain gauges mounted in the longitudinal direction and the other two mounted transversely. Depending on the application, the shape of the column may be square, circular, or circular with flats machined on the sides to accommodate the strain gauges.






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