Geartooth Sensing

Geartooth Sensing

As useful as they are, hall effect sensors are not always the correct sensor for an application. There might not be sufficient space for a magnetic target, or for both magnetic target and hall effect sensor in certain applications. It then becomes necessary to use a different sensing method. A Geartooth Sensor is often used to sense machine speed or position when it is not feasible to add a magnetic target to an application.  A Geartooth Sensor is typically able to utilize something which already exists on the application at the point of measurement, such as (but not limited to) teeth on a gear, bolt head(s), key stock, holes, etc.

Detecting an un-magnetized steel target presents some challenges. Usually the target must be low carbon steel. In other words, the target must have a high iron content. Stainless steel and cast iron are two examples of “steel” which a Geartooth Sensor typically will not detect or will not detect consistently. Contained within the Geartooth Sensor are a magnet and a hall effect transistor. When a high iron target is in front of the Geartooth Sensor, the iron attracts the magnetic field inside the sensor. The magnetic field is pulled across the hall effect transistor which triggers the Geartooth Sensor. When the high iron target is taken away from in front of the sensor, the magnetic field returns to normal and stops triggering the sensor.

Geartooth Sensors do not have the same sensing distance as a Hall Effect Sensor. The sensing distance between a Hall Effect Sensor and a Magnetic Target depends on the magnetic field strength (gauss) of the magnets contained within the Magnetic Target.

Since the target of the Geartooth Sensor is not magnetized, the sensing distance between the sensor and target is greatly reduced, unless the target is ferromagnetic material. The tip of a magnetized screwdriver is an example of ferromagnetic material. A Geartooth Sensor is able to detect Magnetic Targets since the sensor contains a hall effect transistor. It doesn’t matter to the hall effect transistor where the source of a magnetic field is – whether within the sensor or external. When it senses a magnetic field, the Geartooth Sensor is triggered.