In Search of the “Perfect” Zero
Whenever you encounter instability or “drift” in your strain gage readings, the first place to investigate is your instrumentation. This can be done easily by removing the strain gage input and substituting a clever circuit known as a star bridge. By design, a star bridge cannot produce drift over time and therefore any drift seen when this bridge is connected can be directly blamed on the instrument. Another beneficial use of a star bridge is to determine true instrument zero (zero reading for zero input). A star bridge loads the instrument power output and signal input with a normal bridge resistance value, but it cannot produce any output.
For the star bridge circuit diagram and more information see Micro-Measurements Application Note VMM-7: In search of the Perfect Zero.