Linear variable differential transformer

Linear variable differential transformer

The linear variable differential transformer (LVDT) is a type of electrical transformer used for measuring linear displacement. The transformer has three solenoidal coils placed end-to-end around a tube. The centre coil is the primary, and the two outer coils are the secondaries. A cylindrical ferromagnetic core, attached to the object whose position is to be measured, slides along the axis of the tube.

An alternating current is driven through the primary, causing a voltage to be induced in each secondary proportional to its mutual inductance with the primary. The frequency is usually in the range 1 to 10 kHz.

As the core moves, these mutual inductances change, causing the voltages induced in the secondaries to change. The coils are connected in reverse series, so that the output voltage is the difference (hence "differential") between the two secondary voltages. When the core is in its central position, equidistant between the two secondaries, equal but opposite voltages are induced in these two coils, so the output voltage is zero.

When the core is displaced in one direction, the voltage in one coil increases as the other decreases, causing the output voltage to increase from zero to a maximum. This voltage is in phase with the primary voltage. When the core moves in the other direction, the output voltage also increases from zero to a maximum, but its phase is opposite to that of the primary. The magnitude of the output voltage is proportional to the distance moved by the core (up to its limit of travel), which is why the device is described as "linear". The phase of the voltage indicates the direction of the displacement.

Because the sliding core does not touch the inside of the tube, it can move without friction, making the LVDT a highly reliable device. The absence of any sliding or rotating contacts allows the LVDT to be completely sealed against the environment.

LVDTs are commonly used for position feedback in servomechanisms, and for automated measurement in machine tools and many other industrial and scientific applications.

See also

RVDT
Dot convention

External links

* [http://www.rdpe.com/ex/hiw-lvdt.htm How LVDTs Work (interactive)]
* [http://www.lvdt.co.uk/howtheywork.html How LVDTs Work]
* [http://www.josephtierney.com/lvdt.jpgLVDT Image]
* [http://www.allaboutcircuits.com/vol_2/chpt_9/4.html Phasing Explanation]


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Linear Variable Differential Transformer — Vue en coupe d un LVDT. Un courant est généré dans la bobine primaire A, entraînant un courant induit dans la bobine secondaire B Un LVDT (de l anglais Linear Variable Differential Transformer) est un capteur électrique passif (inductif) de… …   Wikipédia en Français

  • Rotary variable differential transformer — A rotary variable differential transformer (RVDT) is a type of electrical transformer used for measuring angular displacement.More precisely, a Rotary Variable Differential Transformer (RVDT) is an electromechanical transducer that provides a… …   Wikipedia

  • Variable capacitor — Rotary variable capacitor A variable capacitor (also known as a variable air condenser ) is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C… …   Wikipedia

  • LVDT — linear variable differential transformer …   Medical dictionary

  • LVDT — • linear variable differential transformer …   Maritime acronyms and abbreviations

  • LVDT — • linear variable differential transformer …   Dictionary of medical acronyms & abbreviations

  • LVDT — Linear Variable Differential Transformer Vue en coupe d un LVDT. Un courant est généré dans la bobine primaire A, entraînant un courant induit dans la bobine secondaire B Un LVDT (de l anglais Linear Variable Differential Transformer) est un… …   Wikipédia en Français

  • LVDT — • Linear Variable Differential Transformer ( > IEEE Standard Dictionary ) NASA • Linear Velocity Displacement Transformer ( > IEEE Standard Dictionary ) • Linear Voltage Differential Transformer NASA …   Acronyms

  • LVDT — agricult. abbr. Linear Variable Differential Transformer electr. abbr. Linear Variable Differential Transformer lun. sc. abbr. Linear Variable Differential Transformer nucl. abbr. Linear Variable Differential Transformer nucl. abbr. Linear… …   United dictionary of abbreviations and acronyms

  • Seismometer — Seismometers (from Greek Seism the shakes and Metro I measure ) are instruments that measure and record motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions, and other seismic sources. Records of… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”