dA more recent method requires the use of a direct writing oscillograph and proximity indicators. The proximity indicators are calibrated to show the shaft deflection magnitude. The shaft is marked by cementing a steel shim at a known angular location - usually corresponding to No. 1 rotor arm. As the shim passes a proximity device, a characteristic mark will appear on the oscillograph record. This mark then can be used to locate the angular position of the maximum shaft deflection. This method has the advantage that - once set up - the deflection at every point around the shaft can be quickly and accurately measured and a written record is generated automatically.