I have an experiment composed of 16 strain gages, mounted on a steal beam. The steal beam is horizontally placed under a compression cylinder for a stress test. the test took around two hours to complete and composed of different stages and levels, the maximum load achieved on the was of 160KN. The stress machine is a YLE compression machine with National instruments PXI modules for data acquisition
After retrieving the measurement results, most of the gages have stopped changing in value and become somehow saturated as shown in figure 1 while the remaining strain gages did not preserve a linear variation, the installation used a quarter bridge and the results were calibrated at the start.
The strain gages used in this experiment is the Vishay strain gages general purpose linear module 125BT
So the questions are: - How did the strain gages get saturated? and how to choose the best strain gage? -what are the causing errors/noise which can cause such behavior? Does the amplifier gain limits affects the resulting values? if so why didn't it affect all of them? -what are the most common errors and noise generated when installing and using strain gages (the strain gages where soldered to a 10m shielded cable and connected to the machines inputs)