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What is a LVDT (Linear Variable Differential Transformers) ? What are some LVDT applications?

What is a LVDT (Linear Variable Differential Transformers)

A Linear Variable Differential Transformer or an LVDT, is an electromechanical device used to convert mechanical motion or vibrations, specifically rectilinear motion, into a variable electrical current, voltage or electric signals, and the reverse.

LVDTs were invented by George Hoadley in 1936 and advanced by Herman Schaevitz in 1946.



The LVDT operation does not require electrical contact between the moving part (probe or core assembly) and the coil assembly, instead relying on electromagnetic coupling by measuring a specific signal value based on the cores position.

What are some LVDT applications?

The LVDT is a natural contender for high-temperature applications when compared to other displacement technologies such as potentiometers, magnetostrictive transducers, and capacitive sensors. Using off-the-shelf materials and components, LVDTs generally operate from −60 to 200°C. A change in materials and assembly techniques can expand the temperature range from −200 to 500°C.

For example, an LVDT made from an alloy of cobalt, nickel, and chromium with mineral insulation continues to function in sulfidation environments with high concentrations of H2-H2S and temperatures up to 425°C. Other wide-temperature LVDTs find use in aerospace, power generation, down-hole oil and gas exploration, nuclear fuel-rod gaging, steam-valve control systems, blast furnaces, and aircraft engine, landing gear, wheels and breaks, and flap controls — environments where other technologies do not survive.


Besides high temperatures, LVDTs can also handle extreme pressure as found at the bottom of the sea in search of oil and natural gas deposits. Depending upon the temperature, salinity, oxygen levels, and the depths of the oil and gas fields, the LVDT’s hermetic seal and non-contacting operation is the only technology that delivers accurate and reliable performance.

Even at operating pressures up to 7,500 psi (500 Bar), LVDTs still maintain a mean-time-between-failure (MTBF) rate of 5 million hr. That translates into years of trouble-free operation in deep-sea well heads, subsea control valves, chokes, safety cable extension monitoring on subsea towers, remote-operating vehicles (ROVs), and drilling platform stabilizers.

What are the AMETEK LVDT benefits?

At AMETEK, our Linear Variable Differential Transformers (LVDTs) are designed for accurate measurement of position in aircraft and missile systems. They are tested to meet the most stringent environmental requirements for many systems in the military industry.

The AMETEK LVDT performance specifications include:

  • Single or dual-voltage output devices designed for high accuracy and reliability
  • Welded or hermetically sealed construction to withstand harsh environments
  • Full range motions for +0.01 inches to +6.0 inches
  • Wide range of operating frequencies to match aircraft and missile systems requirements
  • Case and fitting configurations can be custom designed to fit actuator and control surface requirements
  

 

 





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