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Hydraulic motors are finding their way into more and more places in recent years and there is a good reason why. They are far more compact and can produce more torque in a much smaller sized unit. Electric and fuel powered motors are also noisy and produce heat. Also, both of these types of motors often require some type of transmission system to regulate torque.

The Problems of High Pressure Hydraulic System

However hydraulic motors do have their own shortcomings that have to be dealt with. For instance, they require a source of high pressure hydraulic fluid be ran to them for the motor to operate. High pressure hydraulic fluid presents its own problems in handling and moving it.

A Tightly Sealed System

For instance, due to the torque sensor the a hydraulic motor contains and is powered by high pressure hydraulic fluid they need to be tightly sealed. This by nature prevents the use of a standard speed sensor that uses a cable that is connected to a gear in the motor.

The Hall Effect

So what is the answer? The answer is to use speed sensors that use magnets to gage the speed of a hydraulic engine from the outside. So how can a magnet gage the speed of something? When an electrical current is ran perpendicular to a magnet, the current will be effected when the magnet is in the presence of a ferrous metal such as iron or steel. Its called the “Hall effect”

Counting Gear Teeth or Turbine Blades

So a magnetic sensor is used to count the rotations of a gear or a turbine blade that is in the hydraulic motor or the hydraulic fluid line. Every time a tooth of the gear or a blade on the small turbine passes the magnetic hydraulic motor speed sensor, an electric pulse is created that is then sent by wire to a speed gage.