How to select Inductive Proximity Sensors M24 Unshielded.
M24 inductive proximity switch, proximity switch, as the name suggests, when there is an object approaching, the switch automatically on, or off. Automatic control, all kinds of mechanical equipment, machine tools, industrial control, numerical control, production lines and other equipment are inseparable from him. There are several types of proximity switches. Choose according to specific use. For example, to detect the proximity of non-magnetic objects, such as the production line to detect whether the product is in place. You can use light control. If detecting the proximity of living objects, people or animals, the pyroelectric proximity switch is selected. If testing liquid, flakes, granules, etc., will choose capacitive proximity switch (all objects close to bow | capacitance change, high sensitivity, easy to misjudge) if the detection of conductive metal door – class, as long as a conductor. Go with the vortex proximity switch. For example, equipment doors are equipped with proximity switches (vortex type). You can detect if it is shut down. And Hall proximity switches, detecting magnets… And some special proximity switches. Working principle: PNP sensor, when the sensor does not act, the voltage of the 4 terminals is 0V, when the sensor acts, due to the existence of external resistance, the voltage of the 4 terminals is 24V.
For NPN sensor, when the sensor does not operate, the voltage of terminal 4 is 24V. When the sensor operates, the voltage of terminal 4 is 0V due to the existence of external resistance. For the two-wire system of proximity switch, equivalent to a switch, and can induce the proximity of metal or non-metal, the general principle is Hall effect, the three-wire system is equivalent to two output terminals, a normally closed, a normally open, when there is an object close, the state will change, generally we only use one end can, the two-wire system than the three-wire system of the pressure drop is much larger, So when using to pay attention to the small voltage of the load is how much, the two-line switch must be used after the load (relay line ring, PLC digital module, etc.), otherwise it will be burned off short circuit. Proximity switchinside is a magneto resistor, when it is close to the metal resistance value becomes smaller conduction, the two-wire circuit must take it to allow the current load, before it is connected to the power supply, do not allow no load power supply.
