rotordynamics

4. Instrumentation and Measurement
Several methods are used to locate and measure the unbalance. The most common method requires dial indicators and a stroboscope. Dial indicators are mounted, with the indicator stems in contact with the shaft, at locations where deflection measurements are desired. The shaft is marked and numbered with equally spaced segments. By using the stroboscope speed control, the scope is adjusted to flash at a number on the shaft and the dial indicator reading corresponding to that number is recorded. Dial indicator readings are recorded at each numbered location. The largest reading and its location are used in balancing techniques discussed later in this bulletin.
4.1 - A 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 a...