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Hall Effect Sensor Variants - Unipolar, Bipolar, Omnipolar, Linear Hall Sensor

This page covers Hall Effect Sensor Variants (i.e. types) viz. Unipolar Hall Sensor, Bipolar Hall Sensor, Omnipolar Hall Sensor and Linear Hall Sensor. It mentions difference between Unipolar, Bipolar, Omnipolar and Linear Hall Sensor types (i.e. variants).

What is Hall Effect Sensor?

Introduction:
• When current is flowing through the length of a conductor, and a magnetic field is applied across the width of conductor, the field generates a force which causes electrons/holes to accumulate asymmetrically on the opposite sides. This is known as "Hall Effect".
• Hall effect sensor components contain amplifier circuitry in addition to sensing element. It uses open collector output and a comparator/schmitt trigger to provide some hysteresis.

hall effect current sensing

• The figure-1 depicts hall effect current sensing >>.
• There are four variants of hall effect sensor viz. unipolar hall sensor, bipolar hall sensor, omnipolar hall sensor and linear hall sensor.

Unipolar Hall Sensor

Following are the features of Unipolar Hall Sensor:
• It is activated when external magnetic field exceeds certain threshold value.
• This hall sensor switches OFF when applied magnetic field diminishes or removed.
• Unipolar sensors can be activated either by north pole or south pole of the magnet.

Bipolar Hall Sensor

Following are the features of Bipolar Hall Sensor:
• Proximity to one magnetic pole will switch this sensor ON.
• Proximity to the opposite pole will switch this sensor OFF.
• The sensor remains in its present state (either ON or OFF) in the absense of magnetic field.

Omnipolar Hall Sensor

Following are the features of Omnipolar Hall Sensor:
• Proximity to strong magnetic field of either polarity will switch it ON.
• Removal of magnetic field will switch it OFF.
• Omnipolar sensor can be constructed using pair of unipolar sensors mounted in the opposite directions with their outputs (i.e. open collector) wired together.
• This component functions similar to reed switch but it requires power supply.

Linear Hall Sensor

Following are the features of Linear Hall Sensor:
• Its output voltage varies in proportion to external magnetic field.
• When no magnetic field is detected, the output is half of the supply voltage.
• In response to one polarity, the output can drop almost to zero. The opposite polarity can increase the output almost near to supply voltage.
• It is also known as analog hall sensor.
• The output from linear sensor is usually supplied from emitter of internal NPN transistor and not the collector.



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