LVDT Linear Position Sensors

A linear variable differential transformer, or LVDT, is a series of inductors in a hollow cylindrical shaft and a solid cylindrical core. The LVDT produces an electrical output proportional to the position of the core. The LVDT may be used in many different types of measuring devices that need to convert changes in physical position to an electrical output, including LVDT position sensors. The lack of friction between the hollow shaft and the core prolong the life of the LVDT and enable very good resolution. In addition, the small mass of the core allows for good sensitivity in dynamic tests.

The LVDT is constructed with two secondary coils placed symmetrically on either side of a primary coil contained within the hollow cylindrical shaft. Movement of the magnetic core causes the mutual inductance of each secondary coil to vary relative to the primary, and thus the relative voltage induced from the primary coil to the secondary coil will vary as well. LVDTs typically have a plunger that rides on the object whose position is being measured. To remain in contact with the object, LVDTs will use some sort of force to keep the plunger extended as far as possible. This can be a pneumatic force, a spring or an electric motor. They can be used with either AC or DC power.

LVDTs may also be calibrated by varying the position of the core and measuring the corresponding output voltages. Then a calibration curve or calibration constant may be determined and applied to arrive at the engineering units of position.

LVDT position sensors have one key specification: the range they are to measure. Accuracy is measured as a percentage of the full scale of measurement. Outputs for LVDT position sensors can be analog voltage, analog current, digital, or even a parallel or serial computer output.

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Part Numbers for LVDT Linear Position Sensors