Questions You Should Know about Inductive Sensors Manufacturer

How do inductive proximity switches work?

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An inductive proximity sensor can detect metal targets approaching the sensor, without physical contact with the target. Inductive proximity sensors are roughly classified into the following three types according to the operating principle: the high-frequency oscillation type using electromagnetic induction, the magnetic type using a magnet, and the capacitance type using the change in capacitance.

Inductive proximity switches are used to detect the presence of metallic objects without actually contacting the object. Their high-speed switching and small size make them indispensable in automation applications. Inductive proximity switches consist of a coil driven by an oscillator. The oscillator creates an electromagnetic field which appears at the active face of the switch. If a metal target enters this area, the electromagnetic field is reduced and the switch turns on or off. Some typical inductive sensor applications are: counting metallic objects, monitoring the position of elements in a machine, sensing the presence of metallic parts like screws, etc., and measuring the rotational speed of axial detecting cams.

What is the difference between inductive and capacitive sensors?

Capacitive proximity sensors are non-contact devices that can detect the presence or absence of virtually any object regardless of material. They utilize the electrical property of capacitance and the change of capacitance based on a change in the electrical field around the active face of the sensor.

The primary difference is sensing material. Inductive sensors only detect metallic objects while capacitive sensors will detect materials such as wood, paper, liquids, cardboard, etc.

How do I know what size proximity sensor I need?

It depends on two factors: mounting space and sensing distance. Each application has a specific space available for the sensor and each application has a requirement for how close the sensor can be mounted to the sensed object.

What is the difference between shielded and unshielded?

With a shielded proximity sensor, the face of the sensor may be mounted flush with metal whereas an unshielded sensor may NOT be mounted flush with metal (otherwise the sensor will always be ON). In many applications, flush mounting is a requirement. Also, unshielded proximity sensors allow for greater sensing distances.

What output do I need? NPN or PNP?

PNP sensors are sometimes called “sourcing sensors” because they source positive power to the output. NPN sensors are sometime called “sinking sensors” because they sink ground to the output.

This is determined by the device you are connecting the sensor to. Most PLC modules allow NPN or PNP sensors to be connected. This is determined by how the sensor is wired to the PLC.

How do I choose between normally open (N.O.) and normally closed (N.C.)?

N.O. sensors do not pass power to the PLC until an object is detected. N.C. sensors always pass power to the PLC until an object is detected. The majority of proximity sensors are Normally Open (NO); however, some sensors offer the option of Normally Close (NC).

When do I want quick disconnects (Q/D) versus embedded cable output?

There is a slight cost increase to purchase a sensor and a Q/D cable compared to only purchasing a sensor with a pre-attached (potted-in) cable. However, the Q/D output allows easy replacement of a failed sensor. This is important in minimizing machine or operation downtime.

What is the difference between 2-wire, 3-wire, and 4-wire sensors?

2-wire sensors: allows either NPN or PNP outputs (do not have to select). 3-wire sensors: standard sensors. When ordering, you must choose between NPN and PNP output. 4-wire sensors: Allow either N.O. or N.C. outputs (do not have to select). Must still select NPN or PNP output.

Do proximity sensors operate on AC voltage or DC voltage?

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The majority of proximity sensors operate on 10VDC – 30VDC. There are other proximity sensor series that operate on 20VAC – 253 VAC.

Can my sensor be installed in a wash-down area?

Yes. some proximity sensors carry an IP67 or IP68 enclosure rating. This rating allows temporary submersion of the sensor into water.

What does switching frequency mean to my application?

This is how fast your sensor can sense an object, reset, and sense another object. For example, if a sensor has a switching frequency of 100Hz or 100 cycles per second, the sensor can sense a maximum of 100 objects per second. This is very critical in many applications such as gear rotation measurement.

Can the sensor be put into a vibrating environment?

Yes. Frequency range of 10Hz – 55Hz, maximum amplitude of 1mm. Duration in any axis a maximum of 30 minutes.

What is the temperature range of the sensors?

Most sensors operate between -25°F and 70°F. However, check the specifications for exact ranges.

If I wire my proximity sensor wrong, will it damage it?

Possibly. All sensors contain polarity reversal, short-circuit and transient noise protection. However, the transient protection is only effective under 30V DC.

Hello, i wanna create an automatic trash sorting machine, the important part is the metal detecting, I wanna use a proximity inductive sensor but I don't know which one will be best? also if I should choose an NPN or PNP? most of the sensors are of 4mm detecting distance, is it enough? in the project I ll use an ultrasonic and an LDR sensor as well plus the proximity inductive sensor, is an Arduino uno enough or should I get the Mega? this is my first post so I apologize for the too many questions, thanks in advance.

These are designed for rotary encoders by counting the passing teeth of a sprocket wheel.

A metal detector for treasure hunters may be a good starting point.

Well back in the 60's in my first job we used to use them as replacement for reed / magnetic switches for extra reliability.

Then one wakes week break, there was just a skeleton staff in the building and all the development engineers were away. I was given the project of seeing if they could be used for measuring frequency of rotating objects, and what were the limitations. When they came back my boss was impressed as to how I had investigated not only counting teeth, but counting a single rod and a single hole.

Yes that might be a good start, but this same company made some of the first metal detectors, so I have lots of experience with large 3 coil detectors. Out first product was for measuring stainless steel strands from meshes that got into pharmaceuticals. We had a large tub of "the contraceptive pill" to test with. Then it used to be used to prop the door open.

Stainless steel is quite hard to detect.

can you tell me how the rest of the circuit will determine if I should get npn or pnp, I just spoke with a seller and we ordered a npn sensor, it will arrive in 3 days, for the trash part, the machine will be like any trash can just bigger, there will be an opening where the trash will be thrown, then there will be like a small box where the sensors are, the trash arrives there, the inductif sensor detects if it s metal, in this case a servo motor will move the box with a specified angle and place the metal into there place, for the paper and plastic process, we ll use an LDR sensor to try to differentiate between these 2.

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