- High Cost Service Applications
- Heavy Loads
- Corrosive or Washdown
- Temperature Extremes
- Wet or Dirty Environments
- Electrically Noisy Environments
Speed sensors, magnetic rely on a magnet as the sensing element or sensed target to capture rotational or linear speed. They are typically used as gear tooth speed sensors or incorporated into stroboscopes or tachometers. The technology types for magnetic speed sensors include magnetoresistive, inductive, variable reluctance, and Hall effect. In a magnetoresistive sensor the resistance of the sensing element is a function of the direction and magnitude (proximity) of an applied magnetic field. In an inductive sensor an oscillator circuit generates an RF EMF that radiates from a ferrite core and coil assembly. The field is directed at the sensor face. When a metal target enters the field, eddy currents are induced into the surfaces of the target. This causes a reduction in the amplitude of the oscillator circuit (change in inductance). Variable reluctance speed sensors are typically self-generating, meaning they require no external power. When a magnetic surface is passed in close proximity to the sensor, a small voltage is induced. In a Hall effect sensor a current is passed through a semiconductor material. When a magnetic field is applied perpendicularly to the surface of the semiconductor, a voltage is developed. This Hall voltage is proportional to the applied field intensity, driving the magnetic
Important performance specifications to consider when searching for speed sensors, magnetic include rotary speed range, linear speed range, and accuracy. Rotary speed and linear speed are two mutually exclusive ranges. In rotary speed sensors, the speed is measured in revolutions per minute, useful for gear speed or belt speeds. In linear speed sensors, the speed is measured in inches per second, useful for linear speed applications - web processes, robotic arm movement. The accuracy is measured as a percent of the full-scale range of the sensor range. It is a comparison of the speed sensed and the actual speed. The lower the percentage, the more accurate the device. Important electrical specifications to consider when searching for speed sensors, magnetic include power requirements and output. Power requirements can be self-generating, DC powered or AC powered. Common outputs include resistance, voltage, current, frequency, switch output, serial, and parallel.