Sensors-
Sensors are used for detecting and often measuring, the magnitude of Variation.
They convert mechanical, magnetic, thermal, optical, and chemical variations into electric voltages and currents.
Sensors are usually categorized by what they measure, and they play an important role in modern manufacturing process control.
Proximity Sensor: -
Proximity Sensor - Proximity sensors or switches, such as that shown in the figure, are pilot devices that detect the presence of an object (usually called the target) without physical contact.
These solid-state electronic devices are completely encapsulated to protect against excessive vibration, liquids, chemicals, and corrosive agents found in the industrial environment.
When we use Proximity sensors
• The object being detected is too small, lightweight, or soft to operate a mechanical switch.
• Rapid response and high switching rates are required, as in counting or ejection control applications.
• An object must be sensed through non-metallic barriers such as glass, plastic, and paper cartons.
• Hostile environments demand improved sealing properties, preventing proper operation of mechanical switches.
Figure 1: Photo courtesy: maker lab-electronics.com
Connection of NPN Prox sensor With the PLC.
Figure 2: Photo courtesy ATO.COM
Connection of PNP Prox sensor With the PLC.
Figure 3: Photo courtesy: ATO.COM