Hall sensors for extended position measurement

June 06, 2011 // By Christoph Hammerschmidt
Automotive and industrial IC supplier Micronas AG presents a new generation of Hall sensors for linear position measurement with their HAL 38xy family. The device is particularly suited for applications where relatively long distances have to be measured in confined construction spaces, for example in transmission clutches.

The HAL 38xy family is based on the 3D Hall technology which features two vertical and one horizontal Hall plate. Accompanying Micronas' market launch of this new generation is a first spin-off, the HAL 3855. The HAL 3855 is strictly speaking a 2D position sensor, as it needs only two components of a magnetic field in order to enable a linear position measurement. If an axially magnetized magnet is moved parallel to the surface of the sensor housing, the sensor detects every change in the magnetic field components By and Bz. The internal digital signal processing of the HAL 3855 puts the measured values in relation to each other and so delivers the displacement information at the output side by way of an analog signal.

As the displacement or position information gained is on principle subject to variations, the HAL 3855 has the ability to linearize the output signal using 32 support points with 16 bit resolution. The sensor features a high-temperature capable EEPROM which operates within a temperature range of -40 to +170°C with absolute reliability, delivering a substantially higher linearity at lower system costs compared with classic linear Hall sensors.

The HAL 3855 features numerous diagnosis functions such as over- and under-voltage detection, and it is capable of detecting a break in the supply lines or the loss of the magnet. Thermal monitoring at the output protects the sensor from overload.

Because of these properties, the new Hall sensor is particularly suitable for applications in the automobile and the industrial market where longer distances are to be measured in confined construction spaces, for instance as clutch travel sensor to detect the traveling range of the clutch. Other potential applications for the HAL 3855 include exhaust gas recirculation systems (where the sensor determines the valve position) or determining the position of the gear selector.

Accompanying the new generation of Hall sensors, Micronas also supplies the complete tool box including