The internal strain gauge is used with a set of mechanical adapters that allow it to measure forces on many different surfaces, such as internal and external corners (notch adapters), flat surfaces (flat adapters), other surfaces (point and chisel point adapters), and many others.  The basic unit can measure weight by using a mechanical adapter that has a hook at its end (hook adapters), and a hanging weigh pan that is suspended from the hook. The weight measurement is made in tension, and the pan must be suspended vertically in order that gravity can have its full effect.  Force gauges must be able to tare (zero out) forces in order to display only the desired force.  


The display can be set to read out in several different units, such as the standard unit for force measurement, the Newton (N), or in Grams (g), or Kilograms (Kg), or Pounds (lb), or any one of many others.  The conversion factor for Newton to grams is 1.0N = 101.97g.
The results of measurements can be stored and downloaded later to a printer or an external computer running analytical software.  The depth of the internal storage has grown steadily as the cost and density of semiconductor memory has improved dramatically.


But the real claim to fame is the variety of measurements that can be made with external adapters, each of which has its own strain gauge, and been designed to function with the force gauge.  Torque measurements, where circular forces are measured, require special adapters that convert torque to a proportional voltage.  Many special functions require the use on an external test stand to facilitate measurements, such as materials testing (things such as hardness, ultimate strength, yield point, spring constant, etc.), pharmaceutical testing (pill yield point, hardness), food texture analysis, and others.  The applications in physical therapy and ergonomics are almost boundless.
The better units are capable of high-go-low testing with adjustable limits.  Some do statistical analysis internally and display the results graphically.  Most are capable of detecting peak values and average values.
These are important devices in almost every QC and Testing operation.