OVERVIEWProximity Sensors• Inductive• Hall Effect

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.

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.

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 metallicmaterial, there is a change in the position of flux linesof magnet.• The change in the flux lines induces a current pulsewhose amplitude and shape are proportional to rate of change of flux.• This is effective for fractions of a millimeter (mm).

Inductive Sensor used in the Sensoric Lab

Sensing DistanceNominal 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.

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.

Hall Effect SensorThe 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.

WorkingWhen 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.