Specifications

68 Control and Automation Solutions Guide
Overview
Proximity sensing is used in many
applications to control position,
to sense an object, and to control
speed. It can be achieved by
sensing a magnetic eld or light.
Using light for proximity sensing is a
good way to isolate components from
the environment and from each other.
Infrared (IR) light is usually used for this
purpose. In addition, digital IR proximity
sensors can be employed to sync
the transmitter and receiver, thereby
rejecting noise from DC IR sources.
Maxim’s MAX44000 is a good example
of using an IR LED to sense the proximity
of an object. It pulses the LED at a low
duty cycle, reducing heat dissipation and
eliminating problems due to detection of
sunlight.
Hall-eect sensors are also used for
proximity sensing. The Hall eect is
the production of a voltage across a
current-carrying conductor in the vicinity
of a magnetic eld. Sensors based on
this principle detect a change in the
magnetic eld, thus allowing speed,
position, and direction to be deduced.
This signal can then be digitized for
control purposes. The robustness and
reliability of Hall-eect sensors have
proven valuable in many industrial
applications.
Diagnostics and protection are crucial
elements of Hall-eect sensor interface
electronics. Maxim’s MAX9921/
MAX9621 Hall-eect sensor interface
products combine dual Hall-eect
sensor connectivity with diagnostics
and protection features to improve
the reliability of Hall-eect sensors
in position-sensing applications.
Proximity Sensing