A velocity receiver (velocity sensor) is a sensor that responds to velocity rather than absolute position. For example,
dynamic microphones
A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public ...
are velocity receivers. Likewise, many
electronic keyboard
An electronic keyboard, portable keyboard, or digital keyboard is an electronic musical instrument, an electronic derivative of keyboard instruments. Electronic keyboards include synthesizers, digital pianos, stage pianos, electronic organs an ...
s used for music are velocity sensitive, and may be said to possess a velocity receiver in each key. Most of these function by measuring the time difference between switch closures at two different positions along the travel of each key.
There are two types of velocity receivers, moving coil and piezoelectric. The former contains a coil supported by springs and a permanently fixed magnet and require no output signal amplifiers. Movement causes the coil to move relative to the magnet, which in turn generates a voltage that is proportional to the velocity of that movement.
Piezoelectric sensor
A piezoelectric sensor is a device that uses the piezoelectric effect to measure changes in pressure, acceleration, temperature, strain, or force by converting them to an electrical charge. The prefix ''piezo-'' is Greek for 'press' or 'squeeze'. ...
velocity receivers are similar to a piezoelectric
accelerometer
An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is accele ...
, except that the output of the device is proportional to the velocity of the transducer. Unlike the moving coil variety, piezoelectric sensors will likely require an amplifier due to the small generated signal.
Transducers
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