Cylindrical inductive sensors M4 to M30

A cylindrical inductive sensor detects a metal object without contact and passes a switching signal to the control system. The threaded housing lets you set the working gap with nuts; however, a matching thread alone is not enough to choose a replacement.

Choose LANBAO cylindrical sensors · TECHNOLINE standard sensors

Principle · Selection · Mounting · Wiring · Example · Questions

How the switching signal is generated

A coil in the sensing face generates an alternating electromagnetic field. A metal target in the field induces eddy currents, which change the energy balance of the oscillator. The electronics evaluate this change and switch the output. A gap remains between the target and the face: the sensor must not be used as a mechanical stop.

The result depends on the material, size and position of the target. A small screw or a thin edge may require a smaller working gap than a large steel surface. For aluminium or stainless steel, do not use the range specified for a standard steel target without checking the correction factor of the specific model.

Choose the housing size together with the mounting space

The designation M12 describes the housing thread, not automatically the connector M12. Also check the thread pitch, overall length and the space needed to replace the sensor without removing surrounding parts.

Flush mounting and working distance

Flush sensor is designed to be mounted with its face level with the surrounding metal according to the installation drawing. Non-flush sensor needs free space around the active part. Embedding an unsuitable model in a metal bracket can cause permanent switching or reduce the usable gap.

PNP, NPN and NO/NC logic

In a standard three-wire DC version, a PNP output supplies a positive potential when active, while an NPN output pulls it to 0 V. The type must match the PLC input. NO means an output activated by the presence of the target; NC uses the opposite logic. Take wire colours and pin numbers from the wiring diagram of the specific order code.

The LED on the sensor confirms the local state, not correct signal processing in the PLC. During commissioning, check the supply, output voltage, input indicator and the input value in the program at the same time.

Example: counting metal parts

A conveyor moves at 0.6 m/s and the part pitch is 60 mm. The passing frequency is f = v / p = 0.6 / 0.06 = 10 Hz. But that alone is not enough: with an effective detection length of 12 mm, the pulse lasts approximately t = 0.012 / 0.6 = 20 ms. The input filter and the PLC program must be able to capture such a pulse. Verify the length of the actual detection zone by measuring on a real part.

Check before ordering

• Size and material of the target, its minimum and maximum distance.
• Flush/non-flush mounting, available space and the manufacturer's tightening torque.
• Supply, PNP/NPN, NO/NC, number of wires and pinout.
• Speed of the process, input filtering and how the PLC reads the signal.
• Temperature, degree of protection, chemical influences and cable suitability for movement.

Frequently asked questions from practice

Can I replace a M12 sensor with any other M12?

Also compare the length, mounting, range for the actual metal, electrical output and connector wiring. The same thread only ensures part of the mechanical compatibility.

Why does the sensor react to steel, but to aluminium only at close range?

Different metals may have a different correction factor. If materials alternate, consider a Factor 1 version and check its properties for the targets in question.

Can a reliable gap be determined from Sn alone?

The design must include the tolerances of the bracket and target, temperature and a margin against impact. Use the manufacturer's data and verify the worst operating condition.

Choosing a specific sensor

Choose LANBAO cylindrical sensors · TECHNOLINE standard sensors

For the connection, also check sensor cables and connectors. An overview of principles and other versions can be found in the category Inductive sensors.

Technical documents: ifm: mounting cylindrical and rectangular sensors. This guide describes the selection procedure; binding parameters and wiring are defined by the documentation of the ordered model.