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Inductive Sensors

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Selection Guide For Proximity Switch:- For a large number of production & processing facilities, various mechanical operations demand proper sensing & measurement needs, which can be handled by Proximity Switches. BEE Proximity Switches are in operation all over India since early eighties. Selection of an appropriate model of Proximity Switch for a specific application has always been a treacherous task for new user. This guide should help all such users.

In general, proximity switches are considered for position & level sensing, motion detection and counting applications. Some of the situations are listed below

When actuating or return forces are extremely low.

Where low power switching is required.

When the item being detected can not be
physically contacted.

Where direct connections to electronic control
systems are desired.

When high switching frequencies are required.

As motion detectors & output indicators.

When long & reliable service life is  necessary.

In electronic counters.

Where severe vibrations or movements exist.
As anti-collision detectors.
Where splashing coolants or other liquids
are present.

Input to Electronic equipments from
hazardous areas Etc.

This critical element of sensing, automation & control is available from BEE in following basic types which are devised based on type of object & object sensing principle.

Inductive Proximity Switches for sensing Metallic objects (Ferrous / Non-ferrous)

Capacitive Proximity Switches for sensing Metallic as well as Non-metallic objects like liquids,

Optical Proximity Switches for sensing all types of objects from large distances.

Magnetic Proximity Switches for high speed sensing of metallic objects (Applications such
as Gear Wheel Speed Sensor)

Ultra-Sonic Proximity Switches usually for Liquid Level Sensing applications.Sensor)

Why each of these parameters are used for selection are explained below

Object Material:- This information will enable you to choose proper sensor from five types which have been mentioned above. Usual materials & sensor used are mentioned below; MS- Inductive

Object Size:- The sensing distances offered by Proximity Sensors are specified for object sizes which shall be at least of the size of the sensing face of the particular sensor. This parameter is necessary for Inductive Sensors.

Object Texture :- This parameter is to be considered while selecting Optical Sensor. It is required that the object be as bright as possible. Also operational hazards like coolants & dust which are likely to damage the texture have to be considered. In such situations, optical sensor will not probably work.

Object Distance From Possible Mounting Position:- With this parameter, one can choose an appropriate model simply by browsing through sensing distance column in specification chart.

Mounting Space Available :- With this information, one can choose appropriate dimensions.

Ambient Temperature:- Before choosing a model, we should know the temperature variations which can affect the working of the sensor if the model is not of  appropriate temperature rating.

Object Movement Speed with Respect to the Sensor:-A wrong model with reference to this parameter can malfunction at high operating speed. Hence this parameter should be noted and converted in Hz to select sensor with proper frequency response.

Surrounding Conditions:-As explained earlier, dust, dirt & cooling oils can change object texture and this can affect the performance of an optical sensor or capacitive sensor. This will not affect the performance of Inductive sensor though.

Output Load Requirement:-Sensor are available with various output configurations & load current capacities. User should know their output circuit in order to select an appropriate load current capacity & configuration. For certain applications linear current or voltage signal is required and such models are also available.

Available Supply Voltage with Variations:-This is crucial. For DC proximity switches, well rectified, filtered & regulated supply is absolutely necessary. If the sensor is to be operated on line voltage then two wire AC type sensor is to be selected. For hazardous area applications the supply voltage has to be essentially low (8.5 V DC) in order to control the switching power to minimum values as per IS-5780 : 1980.

Consult our Engineers before choosing a model for hazardous area applications and flameproof enclosures.

Once the above data is collected, appropriate model can be easily chosen from given chart where each of these parameters are specified for each model.

Given below are some standard applications and type of sensors generally used industry-wide;

Application Description

Sensor Generally Used

Anti-collision detector on Cranes.

Optical Sensor of Retro-reflective type
Diameter 80mm. With Power Supply Unit  

End Limits detectors for Stacker-Reclaimers
in cement plants.

Inductive Proximity Switch.

Bucket movement speed sensor for bucket elevators
in cement plants.  

Magnetic Sensor Probe MSP-50 / MSP-75

Liquid Level Sensing.

Ultra-Sonic Proximity Sensor.

Bottling Plants : For sensing presence of bottle
on the conveyor.

Capacitive / Optical Sensor.

Pharmaceutical Industries : For sensing
non-metallic objects such as tablets.
Capacitive Sensor.

Gear Wheel Speed Sensing.

Magnetic Hall Effect Sensor.
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