You have a 120 Ω quarter bridge 2 wire set up with Sg=2.10 and an unknown lead wire resistance. A 59880Ω calibration resistor is switched in parallel to the gage only and a recording instrument is set to give a -100 mm deflection for this calibration.
a) The calibration resistor is removed. The structure is loaded and a deflection on the recording instrument is 123 mm. what is the actual strain?
b) If the calibration had been across the gage and lead wires, what additional information would be required to determine the actual strain? For this case develop an expression between the recorded deflection and the actual strain.