Position, Displacement, and Level



The measurement of position and displacement of physical objects is essential for many applications: process feedback control, performance evaluation, transportation traffic control, robotics, security systems, just to name the few. By position, we mean determination of the object’s coordinates (linear or angular) with respect to a selected reference. Displacement means moving from one position to another for a specific distance or angle. In other words, displacement is measured when an object is referenced to its own prior position rather than to an external reference.

A critical distance is measured by proximity sensors. In effect, a proximity sensor is a threshold version of a position detector. A position sensor is often a linear device whose output signal represents a distance to the object from a certain reference point. A proximity sensor, however, is a somewhat simpler device, which generates the output signal when a certain distance to the object becomes essential for an indication. For instance, many moving mechanisms in process control and robotics use a very simple but highly reliable proximity sensor, the end switch. It is an electrical switch having normally open or normally closed contacts. When a moving object activates the switch by a physical contact, the latter sends a signal to a control circuit. The signal is an indication that the object has reached the end position where the switch is positioned. Obviously, such contact switches have many drawbacks, for example, a high mechanical load on a moving object and a hysteresis.


Output Signal Permanent Magnet Ground Penetrating Radar Displacement Sensor Liquid Level 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


  1. 1.
    Barker MJ, Colclough MS (1997) A two-dimensional capacitive position transducer with rotation output. Rev Sci Instrum 68(8):3238–3240ADSCrossRefGoogle Scholar
  2. 2.
    Peters RD U.S. Patent No. 5,461,319 Symmetric differential capacitive pressure transducer employing cross coupled conductive plates to form equipotential pairs.Google Scholar
  3. 3.
    De Silva CW (1989) Control sensors and actuators, Prentice Hall, Englewood Cliffs, NJGoogle Scholar
  4. 4.
    Linear application handbook (1990) Linear Technology, AN3–9Google Scholar
  5. 5.
    CN-207 Hall Effect IC Applications, Sprague (1986)Google Scholar
  6. 6.
    Halg B (1992) A silicon pressure sensor with a low-cost contactless interferometric optical readout, Sens Actuators A 30:225–229CrossRefGoogle Scholar
  7. 7.
    Dakin JP, Wade CA, Withers PB (1987) An optical fiber pressure sensor, SPIE fiber optics ’87: fifth international conference on fiber optics and opto-electronics, vol 734, pp 194–201Google Scholar
  8. 8.
    Lee CE and Taylor HF (1991) Fiber-optic Fabry-Perot temperature sensor using a low-coherence light source, J Lightwave Technol 9:129–134ADSCrossRefGoogle Scholar
  9. 9.
    Wolthuis RA, Mitchell GL, Saaski E, Hartl JC, Afromowitz MA (1991) Development of medical pressure and temperature sensors employing optical spectrum modulation, IEEE Trans Biomed Eng 38:974–980CrossRefGoogle Scholar
  10. 10.
    Spillman WB Jr (1981) Multimode fiber-optic hydrophone based on a schlieren technique. Appl Opt 20:465ADSCrossRefGoogle Scholar
  11. 11.
    van Drecht J, Meijer GCM (1991) Concepts for the design of smart sensors and smart signal processors and their applications to PSD displacement transducers. In: Transducers’91. International conference on solid-state sensors and actuators. Digest of technical papers, ©IEEE, pp 475–478Google Scholar
  12. 12.
    Noffz GK, Bowman MP (1996) Design and Laboratory Validation of a Capacitive Sensor for Measuring the Recession of a Thin-Layered Ablator. NASA Technical Memorandum 4777Google Scholar
  13. 13.
    In-Depth Ablative Plug Transducers, (1992) Series #S-2835, Hycal Engineering, 9650 Telstar Avenue, P.O. Box 5488, El Monte, CAGoogle Scholar
  14. 14.
    Brown RC, Andreussi P, Zanelli S (1978) The use of wire probes for the measurement of liquid film thickness in annular gas-liquid flows, Can J Chem Eng 56:754–757CrossRefGoogle Scholar
  15. 15.
    Graham J, Kryzeminski M, Popovic Z (2000) Capacitance based scanner for thickness mapping of thin dielectric films. Rev Sci Intrum 71(5):2219–2223ADSCrossRefGoogle Scholar
  16. 16.
    Brusch L, Delfitto G, Mistura G (1999) Level meter for dielectric liquids. Rev Sci Instrum 70(2)Google Scholar
  17. 17.
    Steven Kirsch ST (1985) Detector for electro-optical mouse. U.S. Patent No. 4,546,347, 8 OctGoogle Scholar
  18. 18.
    Olson LT (1988) Inertial mouse system. U.S. Patent No. 4,787,051, 22 NovGoogle Scholar
  19. 19.
    Solhjell E (1996) Mouse and trackball design with contact-less roller sensor. U.S. Patent No. 5583541, 10 DecGoogle Scholar
  20. 20.
    Azevedo SG, Gavel DT, Mast JE, Warhus JP (1995) Landmine detection and imaging using micropower impulse radar (MIR). Proceedings of the workshop on anti-personnel mine detection and removal, 1 July 1995, Lausanne, Switzerland, pp 48–51Google Scholar
  21. 21.
    Dowla FU, Nikoogar F (2007) Multi-pulse multi-delay (MPMD) multiple access modulator for UWB. U.S. Patent No. 7,194,019, 20 MarGoogle Scholar
  22. 22.
    Young D et al. (1996) A micromachined variable capacitor for monolithic low-noise VCOs. Solid-state sensor and actuator workshop. Hilton Head, SCGoogle Scholar
  23. 23.
    McEwan TE (1994) Ultra-wideband radar motion sensor. U.S. Patent No. 5,361,070, 1 NovGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.San DiegoUSA

Personalised recommendations