Force conversion into an electrical signal by a load cell is usually carried out indirectly and in two stages.
The first stage conversion is done through a mechanical arrangement in which the force being sensed deforms the strain gauge.
This strain gauge then converts the deformation (strain) to electrical signals. One can also get load cells with one or two strain gauges.
The electrical signal generated by strain gauge is in the order of a few millivolts which needs further amplification by an instrumentation amplifier.
The output of the transducer is fed to an algorithm calculator to calculate the force applied to the transducer.