Proximity Sensor: Inductive, Hall Effect

1. OVERVIEW
Proximity Sensors
• Inductive
• Hall Effect

2. Proximity Sensors
• A proximity sensor is a sensor able to detect the presence of nearby objects without any
physical contact.
• A proximity sensor emits an electromagnetic field or a beam of electromagnetic radiation ,
and looks for changes in the field or return signal.
• The object being sensed is often referred to as the proximity sensor's target.
• Proximity sensors can have a high reliability and long functional life because of the absence
of mechanical parts and lack of physical contact between sensor and the sensed object.

4. Inductive Proximity Sensor
• It is based on the principle “change of inductance due to the presence of metallic object.”
• Inductive sensors are solid state sensing devices which require no physical contact to
actuate them.
• The sensing range of an inductive switch is dependent on the type of metal being
detected.
• Common applications of inductive sensors include metal detectors, traffic lights, car
washes, and a host of automated industrial processes.

5. Working Principle
• It basically consists of a wound coil located next to a
permanent magnet packaged in a simple rugged housing.
• When the sensor is brought in close proximity to a metallic
material, there is a change in the position of flux lines
of magnet.
• The change in the flux lines induces a current pulse
whose amplitude and shape are proportional
to rate of change of flux.
• This is effective for fractions of a millimeter (mm).

9. Inductive Sensor used in the Sensoric Lab

10. Sensing Distance
Nominal Switching Distance (Sn): The characteristic
sensing distance without any deviations in temperature,
voltage or manufacturing process.
Actual Sensing Distance (Sr) : The actual sensing distance
is determined at rated line voltage and an ambient
temperature of 293K. Maximum permissible distance is
±10% of the nominal distance.
Useful Switching Distance (Su) : Useful sensing distance
within a predetermined voltage and temperature.
Maximum permissible sensing distance ±10% of actual
sensing distance.
Working Switching Distance (Sa) : The sensing distance
at which the sensor operates within permissible operating
conditions. Sa is between 0 and smallest useful sensing
distance Su.

11. Characteristics of Inductive Sensors
• Detects only conductive materials.
• Operating distance up to 50mm.
• Switching frequency up to 5kHz.
• Max. ambient temperature 200°C.
• High noise immunity.

12. Hall Effect Sensor
The magnetic field intensity (e.g. produced by either permanent or electromagnets mounted
on a object) determine the generated output voltage. They act on the principle of Lorentz
Force.
Hall Effect: When a object carrying current I is placed in a magnetic field B, then an electric
field E is induced in the object in direction perpendicular to both I and B.

14. Working
When a beam of charged particles passes through a magnetic
field, forces act on the particles and the beam is deflected from a
straight path.
The flow of electrons through a conductor is known as a beam of
charged carriers.
When a conductor is placed in a magnetic field perpendicular to
the direction of the electrons, they will be deflected from a
straight path.
As a consequence, one plane of the conductor will become
negatively charged and the opposite side will become positively
charged.
The voltage between these planes is called Hall voltage.