Correction factor, inductive sensors, Metal Object Detection, Presence check

How can steel and stainless steel sheet metal strips be reliably detected?

wenglor received this request in the context of an application in which sheet metal strips made of steel or stainless steel – in thicknesses between 0.5 and 1.5 mm – need to be reliably detected. This is primarily a simple attendance check: metal strips here or not there.

The challenge is to detect both materials in a process-compatible, contact-free manner and regardless of surface properties . Since both stainless steel and highly polished metals can appear, optical sensors are often ruled out due to possible reflections.

The ideal solution: Inductive sensors for metal object detection

For applications where it is only necessary to check whether a metal part is present, inductive sensors are among the most cost-effective and at the same time most reliable technologies.

Why inductive sensors?

They react exclusively to metals – regardless of colour or gloss.
Highly polished or reflective surfaces do not affect the function, as no optical principle is used.
They work wear-free and insensitive to dust, oil or vibration.
Ideally suited for sheet metal strips, metal tabs, stamped parts, clips or other flat metal objects.

An important point:
The sensing distances given in the data sheet always refer to steel (Fe360).
In the case of other metals – especially stainless steel – this distance is reduced by a so-called correction factor.

When steel and stainless steel alternate: correction factor 1 sensors

If the application is to detect both steel and stainless steel sheets with exactly the same switching behavior, wenglor recommends special inductive sensors with correction factor 1.

Advantages of this sensor generation:

Identical sensing distance to all metals
(e.g. steel, stainless steel, copper, aluminium, brass)
Robust against magnetic direct and alternating fields
Particularly resistant, partly with Teflon coating
Designed for harsh industrial environments (e.g. welding areas)

Depending on the model, detection ranges between 4 and 50 mm are available – this allows the sensor technology to be flexibly aligned to the space available in the application.

Conclusion

For the reliable detection of steel and stainless steel sheet metal strips, inductive sensors are the optimal choice.

For easy steel/stainless steel detection: standard inductive sensor
For identical detection regardless of the metal type: correction factor 1 sensor

This provides the customer with a robust, maintenance-free and easy-to-integrate solution for a permanently process-reliable presence check of their sheet metal strips.