What is a non-ferrous detector and a ferrous detector?


10 February 2022

Difference between ferrous product to be detected and non-ferrous product to be detected

Ferrous products:  any steel
Non-ferrous products: any metal except steel (brass, copper, etc.)

  • Caution, non-ferrous does not mean any material (wood, plastic, etc.), it refers to metals

Difference between ferrous sensors and non-ferrous sensors

There are sensors which can detect:

Ferrous metals as a preference (steel, iron)
The sensing distances for these products vary according to the metals to be detected: maximum for ferrous metals and dependent on a Km coefficient typical of each metal (value between 0 and 1: Km = 1 for steel) 
This coefficient reduces the sensor detection range. For example while Km = 1 for cast iron, it is only 0.25 for copper.
This is the conventional inductive sensor

Both ferrous (steel, iron) and non-ferrous (brass, aluminum, copper, etc.) metals
The sensing distance for these sensors is the same for both ferrous and non-ferrous materials. The Km coefficient is always 1
They are called Ferrous/Non-Ferrous sensors.
The Schneider part numbers are: XS1M18KPM40x, XS1M30KPM40x 18 and 30 diameter sensors respectively and XS7C40KPM40

Selective, either ferrous materials or non-ferrous materials
The Schneider part numbers are: XS1M18PAS40x insensitive to ferrous materials, XS1M18PAS20x insensitive to non-ferrous materials
They are called selective Ferrous/Non-Ferrous sensors.

Difference in detection principles 
For both sensors, an LC oscillator creates an electromagnetic signal.

The difference in detection principles for the two types of sensor lies in:

Attenuation of the oscillation amplitude for ferrous materials, it is significant for ferrous materials and insignificant for non-ferrous materials
Variation in oscillation frequency for selective or non-selective ferrous/non-ferrous materials. For high-frequency operation (in the region of one MHz), both types of material (ferrous and non-ferrous) have the same effect on the oscillation frequency variation.
Km coefficient depending on the different metals for inductive sensors