Vibration Recorder For Electrically Measuring and Recording Small Mechanical Movements

The vibration recorder makes it possible to obtain oscillographic measurements and records of rapid mechanical movements as small as five or ten-thousandths of an inch. From two to five millimeters deflection will be obtained on the oscillograph for every one-thousandth of an inch variation of the apparatus undergoing investigation. This instrument has been successfully used to record permanent data of vibrations of a rotating turbine wheel, the mechanical movements or whipping of a rotating shaft and transient oil pressures due to an explosion produced by opening up a high-voltage switch in a scaled vessel. The vibration recorder is a balanced circuit comprising a test coil and a dummy coil, connected to two windings of a differential transformer. When the circuit is balanced there will be zero flux set up in the differential transformer, and the oscillograph vibrator which is connected to a third winding will have a zero deflection. Deflections produced on the oscillograph vibrator are obtained when the circuit is unbalanced by mechanical vibrations in front of the test coil. By suitable calibration curves, these deflections on the oscillograph are used as a measure of the mechanical movements which cause them.