Digital position sensors
Providing a highly accurate position digital signal using a low cost zero-Gauss principle
MMT digital position sensors provide an accurate digital output signal from a toothed ferromagnetic target with a contactless principle. They are based on a very simple patented principle that eliminates the influence of temperature and tolerance variations. The main features of this sensor are:
· Extended temperature range operation (-40°C, 150°C) · Zero speed, true power-on sensor · Extended air gap operation (typically 0 to 3.5 mm) · Low cost, 0 Gauss principle				Exploded view of the basic MDPS
MMT digital position sensor with its target			The advantage of MMT technology is that the probe alternatively sees a positive and negative field according to the position of the target: the magnetic signal varies around the “0 Gauss“ point. This offers the possibility to use a low cost digital Hall probe with a good efficiency as there is no offset caused by temperature variations.
Basic Principle
Flux lines in MDPS
The basic working principle is explained above: a molded magnet is glued on a return flux yoke. A Hall effect switch is inserted in a cavity designed on one side of the magnet faces. This side of the sensor faces the ferro-magnetic target that has to be detected. The field distribution created by the magnet exhibits a “0 Gauss” point (shown by a red cross on the drawings). When the target comes in front of the tooth, that point moves and the field through the switch is alternatively positive and negative. When an ASIC is used, it is possible to specify the commutation point level and thus to avoid the trimming. The point is calculated by the ASIC by taking into account the minimum and maximum value of the induction. Thanks to this method, one may use large air gaps (typically 2 to 4 mm) with a very good reliability. Measurements and calculations specify a typical error of ± 0.2 ° when the air gap varies between 2 and 3 mm, for example.
Main applications
MMT digital position sensors are particularly well suited for low cost applications that require high accuracy and low sensitivity to temperature or production tolerances. That is typically the case in automotive applications as crankshaft sensing, where the temperature variation range is wide and where tolerances are a major cost issue. Our digital position sensors are mainly used in the following applications:					Encapsuled digital position sensor Patents for these technologies are granted or pending in USA, Europe, Korea and Japan.
Crankshaft sensing	· Crankshaft speed and position sensor · Camshaft position sensor · Gear tooth position sensor for automatic gearboxes · Brushless motor rotor position sensor · End of stroke sensor
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