Page 107 - Sensors and Control Systems in Manufacturing

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2Sn Cha p te r T w o

Sn
Core
Shield

FIGURE 2.49 Standard
range fi eld plot. FIGURE 2.50 Extended range core and coil.

it emanates straight from the sensing face. Figure 2.49 shows the
typical standard-range sensing-field plot.
An extended range coil and core assembly does not have the fer-
rite around the perimeter of the coil (Fig. 2.50). This unshielded device
accordingly has an extended range. Figure 2.51 illustrates a typical
extended sensing-field plot.

2.6.3 Sensing Distance
The electromagnetic field emanates from the coil and core at the face
of the sensor and is centered around the axis of the core. The nominal
sensing range is a function of the coil diameter and the power that is
available to operate the electromagnetic field.
The sensing range is subject to manufacturing tolerances and
circuit variations. Typically, it varies by 10 percent. Similarly, tem-
perature drift can affect the sensing range by 10 percent. Applied to
the nominal sensing switch, these variations mean that the sensing

FIGURE 2.51 2Sn
Extended range
fi eld plot.
Sn