Electromagnetic log


An Electromagnetic Log, sometimes called an "EM Log", measures the speed of a vessel through water.
It operates on the principle that:
1 when a conductor passes through an electromagnetic field, a voltage is created and
2 the amount of voltage created increases as the speed of the conductor increases.
The process is
  1. the EM Log creates an electromagnetic field.
  2. a voltage is induced in the water; the magnitude of the voltage varies depending upon the speed of the water flow past the sensor.
  3. the EM Log measures the voltage created and translates this into the vessel's speed through water.

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