A load cell is a transducer which converts force into a
measurable electrical output. Although there are many varieties
of load cells, strain gage based load cells are the most
commonly used type. Before strain gage-based load cells became
the method of choice for industrial weighing applications,
mechanical lever scales were widely used. Mechanical scales can
weigh everything from pills to railroad cars and can do so
accurately and reliably if they are properly calibrated and
maintained. The method of operation can involve either the use
of a weight balancing mechanism or the detection of the force
developed by mechanical levers. The earliest, pre-strain gage
force sensors included hydraulic and pneumatic designs. In 1843,
English physicist Sir Charles Wheatstone devised a bridge
circuit that could measure electrical resistances. The
Wheatstone bridge circuit is ideal for measuring the resistance
changes that occur in strain gages. Although the first bonded
resistance wire strain gage was developed in the 19