The Hall sensor detects the movement of ferromagnetic materials such as gear teeth. The tooth of a gear wheel moving in and out of the magnetic field of the sensor influences this magnetic field in different degrees. The sensor element measures the change of the Hall voltage. This allows the changes in the magnetic field to be converted into an electric variable, reflecting the rotational movement of the gearwheel after the appropriate filtering and conditioning of the output signal.

Hall sensors are suitable for the non-contact rotational speed detection of small gearwheels at high resolution. Type SH rotational speed sensors are found in the most varied applications in general machine construction, in vehicles and in mobile operating machines and in hydraulic drives.

In the differential Hall sensor, two Hall generators are arranged close to each other. The individual Hall generators operate along the same principle as the magnetic field dependent semi-conductor in single Hall sensors. Both Hall elements of the sensor are biased with a permanent magnet. The sensor detects the movement of ferromagnetic materials such as gear teeth. If one element is faced with a ferro-magnetic tooth and the other with a gap, the result is a one-sided amplification of the induction. The difference developed between both elements changes the polarity as soon as the gearwheel moves. These changes are evaluated filtered and digitized for the output stage.

Differential Hall sensors are designed specially for the rotational speed detection in machines and equipment where an extremely high resolution is required in a wide frequency range. When properly installed, differential Hall sensors allow greater installation distance than Hall sensors even at low frequencies.

Magnetoresistive sensor elements are magnetically controllable resistors. The sensor element is often designed with 4 magnetic field sensitive resistors interconnected to form a measuring bridge. The measuring bridge is energized by a bridge voltage. The sensor element is biased with a permanent magnet. A magnetic field influences each of the bridge resistors differently depending on their angle. This causes a voltage difference that is then amplified and evaluated.

The sensor detects the movement of ferromagnetic materials such as gear teeth. A tooth or a gap moving past the sensor changes the magnetic field. This causes changes in the internal bridge resistance values. The changes are converted into a square-wave output signal which reflects the changes in the magnetic field. Magnetoresistive sensors are sensitive to changes in the external magnetic fields. For this reason the sensed objects should not have different degrees of magnetization.

Magnetoresistive sensors are designed specially for rotational speed and zero speed detection. Magnetoresistive sensors are also capable of detecting high frequencies and finer gear teeth. Unlike Hall sensors, magnetoresistive sensors are not limited by a lower frequencies, provided that the sensors are properly installed.

Magnetoresistive sensor elements are magnetically controllable resistors. The sensor element is often designed with 4 magnetic field sensitive resistors interconnected to form a measuring bridge. The measuring bridge is energized by a bridge voltage. The sensor element is biased with a permanent magnet. A magnetic field influences each of the bridge resistors differently depending on their angle. This causes a voltage difference that is then amplified and evaluated.

The sensor detects the movement of ferromagnetic materials such as gear teeth. A tooth or a gap moving past the sensor changes the magnetic field. This causes changes in the internal bridge resistance values. The changes are converted into a square-wave output signal which reflects the changes in the magnetic field. Magnetoresistive sensors are sensitive to changes in the external magnetic fields. For this reason the sensed objects should not have different degrees of magnetization.

Magnetoresistive sensors are designed specially for rotational speed and zero speed detection. Magnetoresistive sensors are also capable of detecting high frequencies and finer gear teeth. Unlike Hall sensors, magnetoresistive sensors are not limited by a lower frequencies, provided that the sensors are properly installed.

Oscillatory sensors comprise a high frequency oscillator which includes a coil and a capacitor. The coil is wound around a core open to one side. It is within this open side that the alternating field generated by the coil can be influenced. If a metallic object is placed or moves near the coil face, induction causes eddy currents or demagnetization. This also causes energy to be drawn from the field and the resonant circuit to be attenuated. The oscillation amplitude in the oscillator circuit thus becomes smaller.

Inductive oscillatory sensors are suitable for rotational speed and zero-speed detection in normal industrial environments. They allow detection of keyways, bolts, screw heads and similar shaft-mounted objects and where only one or a few pulses per revolution can be detected.