Sensors and device axes

As already explained in the Sensors section (see p. 8 ff.), switching point sensors only supply a trigger signal when a measurement point is picked up. This causes the position measuring systems of the coordinate axes to be read out and the point coordinates on the surface of the measuring object to be determined. This requires movement in the axes (dynamic measuring principle). These sensors can work in one, two or three dimensions (Fig. 57).

Measuring point sensors have their own internal measuring range (Fig. 3) in one, two or three dimensions. Its size can be several millimetres. The measured value is defined as the distance of the measured point of the respective axis to the internal sensor zero point. An object point is determined by superimposing the measured values of the sensor and the coordinates of the sensor position read out in the measuring machine. The prerequisite is that the object point is within the measuring range of the sensor. It is therefore also possible to determine a point when the coordinate measuring machine is stationary (static measuring principle). However, the measurement of several points required to determine features also requires movement of the machine axes.

Other sensor principles (e.g. image processing and X-ray tomography) allow the measurement of several points in a separate two- or three-dimensional measuring range practically simultaneously without moving the sensor in the machine axes. These sensors can therefore be referred to as line, flat or volume sensors. Small object features can thus be captured all at once. This is referred to as measurement "in the image" (Fig. 58). In X-ray tomography, the volume of the object is captured completely. For dimensional measurement, the material transitions (surfaces) are extracted. This can be done as a surface or in cross sections (linear) with any spatial position.