319
Proximity Sensors
1
Proximity Sensors,
Capacitive Sensors
1
.2
Proximity Sensors,
Magnetic Field Sensors
1
.3
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Introduction to Magnetic Field Sensors
Unlike inductive or capacitive proximity switches, magnetic field sensors
react to the presence of a magnetic field, regardless of whether this field
is generated by an electromagnet or a permanent magnet. Compared
with close-range sensors, they usually have longer operating distances.
Special technical characteristics of magnetic field sensors
•
Long operating distance - longest operating distance among close-
range sensors
•
Variable operating distance - the required operating distance can be
adjusted based on the magnet selected and installed
•
Coding character – sensor reacts solely to magnetic fields
Operating Distance and Responsiveness
The possible operating distance of a magnetic field sensor depends on
the size and magnetic flux density of the actuating magnet. Permanent
magnet DM60 is used as a base for determining the rated operating dis-
tance (Sn). The magnet has a diameter of 31 mm and a height of 15 mm
with a remanence B r of 380 to 400 mT.
When the magnet passes laterally over the surface of the sensor, a po-
larity-dependent response curve is produced.The response curve repre-
sents the detection range of the sensor. The result is a bipolar alignment
of the magnet: two symmetric curves.
Unipolar alignment of the magnet results in a central detection range with
side curves. These side curves are responsible for maintaining a specific
minimum distance between the magnet and the sensor to ensure safe
switching behavior.
Mounting Conditions for Magnetic Field Sensors
Due to the passive character of magnetic field sensors, unlike inductive
or capacitive sensors, they can be flush mounted without affecting the
operating distance. In contrast, the mounting conditions of the actuating
magnet affect the operating distance.
If the magnet is applied to a magnetizable carrier, the obtainable operat-
ing distance increases slightly.
If the magnet is inserted flush into a magnetizable carrier material, the op-
erating distance is considerably reduced by the magnetic "short circuit"
through the carrier material.
Introduction to Magnetic Field Sensors
