A load cell is a transducer that is used to convert a
force into electrical signal. This conversion is indirect and happens in two
stages. Through a mechanical arrangement, the force being sensed deforms a
strain gauge. The strain gauge measures the deformation (strain) as an
electrical signal, because the strain changes the effective electrical
resistance of the wire.
Explanation:
A load cell usually consists of strain gauges connected in a
Wheatstone bridge configuration. Load cells of one strain gauge (Quarter Bridge)
or two strain gauges (half bridge) are also available. The electrical signal
output is typically in the order of a few milli-volts and requires
amplification by an instrumentation amplifier before it can be used. The output
of the transducer is plugged into an algorithm to calculate the force applied
to the transducer.
Strain gauge load cells are the most common;
there are other types of load cells as well. In industrial applications,
hydraulic (or hydrostatic) is probably the second most common, and these are
utilized to eliminate some problems with strain gauge load cell devices.
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