The selection of the sensor for multi-sensor applications must always be made taking into account the measuring task. Economic aspects such as measuring time and costs also play a role. The structure of the sensors consisting of mechanics, optics, electronics and software is very different. This leads to very different properties, the basic understanding of which is necessary for optimal use.

An essential criterion for differentiating between sensors is the physical principle of transmission of the primary signal. In this respect, the majority of sensors commonly used today can be assigned to the categories of tactile and non-contact. Tactile sensors obtain information about the position of a measurement point by contacting the measuring object with a probe tip, usually a stylus tip. The resulting deflection of the probe tip can be determined electrically or optically. Optical sensors capture the position of a measurement point by reflecting light off the surface of the workpiece. In the X-ray tomography sensor, an object area is penetrated by X-rays and the three-dimensional geometry of the measuring object is reconstructed from the radiographic images. From this, the position of the measurement points is deduced.

The sensors can have their own measuring range (measuring sensors) or only detect when a threshold value is exceeded (switching sensors). The direction of action of the sensors can be reduced to one or two coordinate axes (1D, 2D sensors) or include all three axes (3D sensors). The measured values of the respective non-measuring axes are given by the sensor position (e.g. position of the measuring axis of the sphere center with 1D styluses or position of the object plane with image processing). Sensors can measure single points (point sensors), contours (line sensors) or surface areas (area sensors).