Correction factors for inductive sensors

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Correction factors for inductive sensors – Factor 1

What is meant by 'reduction factor' or 'correction factor' in the context of inductive sensors? Explanation: Inductive sensors respond to metals. The distance between the forward surface of the sensor and the measurement object is referred to as the sensing range. This distance depends on the material of the metal to be sensed. Steel, for instance, is detected significantly better than copper. For this reason, manufacturers specify correction factors or reduction factors in their data sheets. The actual sensing range for individual metals is obtained by multiplying the nominal sensing range by the specified factors. The following table shows the correction factors for the various metals:

Material	Factor	Exemplary sensing range
Steel	1,00	6,00 mm
Cast iron	0,93 ... 1,05	5,58 ... 6,30 mm
Stainless steel	0,60 ... 1,00	3,60 ... 6,00 mm
Nickel	0,65 ... 0,75	3,90 ... 4,50 mm
Brass	0,35 ... 0,50	2,10 ... 3,00 mm
Aluminium	0,30 ... 0,45	1,80 ... 2,70 mm
Copper	0,25 ... 0,45	0,45 ... 2,70 mm

Inductive factor 1 sensor using steel, aluminium and copper as examples.

Inductive standard sensors using the example of steel, aluminium and copper.

Factor 1 sensors have the same sensing range for all metals.
Patrick Targonski, Product Manager at autosen

The Factor 1 sensors were developed to address this problem. Factor 1 sensors have the same sensing range for all metals. Instead of the single coil in a ferrite core to be found in conventional inductive sensors, the oscillators in Factor 1 sensors have two air-core coils that are electrically linked with each other. These can be specifically influenced depending on the metal concerned, making it possible to maintain a constant sensing range for all metals. However, while the double coil has the great advantage of having the same reduction factor for all metals, this is at the price of some disadvantages. For one thing, the increased technical outlay causes higher costs. Also, double switching of the sensor can occur under certain circumstances. With small objects that traverse Factor 1 sensors from the side, the double coil can lead to a double switching impulse. Here is an overview of the advantages and disadvantages of Factor 1 sensors in comparison with inductive sensors: