Sorting through proximity and distance sensor technology choices
of the material and can vary from 1 for metals and water to 0.4 for polyvinyl chloride (PVC), 0.6 for glass and 0.5 for ceramics. Magnetic Magnetic proximity sensors respond to the presence of a magnet. Magnetic proximity sensors from SICK use two detection technologies: ■ Giant magneto resistive (GMR) sensors are based on resistors that change their value in the
presence of a magnetic field. A Wheatstone bridge is used to detect the change in resistance and produce an output signal. The MZT7 cylinder sensors, like the MZT7-03VPS-KP0 designed for use with T-slot cylinders, use GMR technology to detect piston positioning in pneumatic drives and in similar applications. ■ LC technology uses a resonant circuit that resonates with a small amplitude. If an external magnetic field approaches, the resonant amplitude increases.
The increase is detected by a signal evaluator and an amplifier produces the output signal (Figure 6). The MM08- 60APO-ZUA has an Sn of 60 mm and an Sa of 48.6 mm.
Ultrasonic sensors
For objects up to 8 m away, designers can turn to ultrasonic sensors like the UM30 family from SICK. These sensors have integrated temperature compensation to improve
Figure 6: In a magnetic proximity sensor, the field probe can use GMR or LC technology. (Image source: SICK)
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