Velocity Measurement. Electromagnetic Linear-Velocity Transducer. An electromagnetic linear-velocity transducer is composed of a stationary coil with a permanent-magnet core moving within the coil. The core is attached to the object whose velocity is to be measured.
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Electromagnetic Linear-Velocity Transducer
An electromagnetic linear-velocity transducer is composed of a stationary coil with a permanent-magnet core moving within the coil. The core is attached to the object whose velocity is to be measured.
When the core moves, magnetic lines of the field created by the core cross the turns. An electromotive force induced in the turns is proportional to the speed of the core
For series operation, the blue and green leads are tied together and the output is taken from the black and red leads. With the coils wired in series, the output is summed, producing the maximum sensitivity.
Besides a high sensitivity, the transducer exhibits excellent noise immunity, attributed to the coils being wound in series opposition. Noise generated on one coil will be equal in magnitude but opposite in polarity to the other coil.
Parallel operation is achieved by tying the black and blue leads together, and the green and red leads together. The two connections create the terminals for the output. This configuration cuts the
sensitivity in half, and reduces the source impedance by a factor of 4. The benefits of this arrangement are: lower output, for use in high speed applications; lower output impedance, for compatibility with electronics with a low input impedance, and higher frequency response for a given load impedance
The Doppler effect (or Doppler shift), named after Austrianphysicist Christian Doppler who proposed it in 1842, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession
slide down as it passes, and continue lower than its stationary pitch as it recedes from the observer
Change in frequency