Full Bridge Strain Gauge - 5 vs. 4 solder tabs ( Transducer Applications)

To measure such small changes in resistance, Advanced Sensors Technology strain gage sensor configurations are based on the idea of a Wheatstone bridge. The three types of strain gage configurations, quarter-, half-, and full-bridge, are decided by the number of active elements in the Wheatstone bridge, the orientation of the strain gages, and the directions of principal strains.  All full-bridge configurations have four corners, two for power and two for signal. 

So why are some strain gages designed with four solder tabs and others with five solder tabs?

In this video we explain about full-bridge strain gage configurations that have four active strain gages and are available in different types with 4 or 5 solder tabs.

https://www.youtube.com/watch?v=Sb9E036s7qU