Linear Position Sensors - LVDT and LVIT

Linear Variable Differential Transformers (LVDT) and Linear Variable Inductance Sensors (LVIT) both have analog output, but use different physical principles in linear position sensing applications. Which is correct for your application?

The LVDT is composed of a primary transformer and two identical secondary transformers. The transformers are coupled in series by using a movable cylindrical shape of a high magnetic permeability magnetic material as the core. Through a particular range of core motions, the output voltage of the differentially connected secondary transformer changes linearly with the movement of the core.

  • LVDTs does not require any mechanical contact with the measuring body. This non-contact operation means that the LVDT position sensor will not wear and will not be affected by mechanical overload, with excellent repeatability and resolution, as well as long life and high reliability.

  • However, LVDT’s stroke-to-length ratio is relatively poor, which requires the sensor to be long when measuring a few inches of position.

LVIT sensors operate on the coil inductor to induce different current values when the magnetic field is changed. LVIT has excellent repeatability, good resolution and linearity. Its structural and non-contact operation allows to withstand large shock and vibration environments. Its internals can also contain electronic equipment such as ambient temperature compensation.

  • Compared to other technologies, LVIT installation cost is lower than other technologies.
  • The biggest limitation of LVIT technology is that it has only direct current (DC) output, but LVDT can be designed as alternating current (AC) or direct current (DC).