Homemade moving magnet type vibrometer

Abstract

To measure the vibrations at the handle of the power tillers in field operation, we designed and constructed a small moving magnet type vibrometer (accelerometer) which consists of a pick up, amplifier and oscillograph.
The pick up consists of a permanent magnet pendulum, coil and damping plate (see Fig. 1). The natural frequency of the magnet pendulum is 21cps. The overdamping is given by the damping plate and the damping oil filled in the pick up case. The size of the pick up is 66×54×54 (mm) and its weight is about 500g.
The oscillogram (Fig. 3) of the vibration of the pick up gained by the vibration testing machine means the wave is the acceleration curve.
The characteristics curve of this vibrometer is shown in Fig. 4. The performance of this vibrometer shows a good result when the acceleration is rapid, but it is not good when the acceleration is slow.