Top 10 Reasons to use LVDT Position Sensors

1. Frictionless Measurement

No rubbing parts, no wear, no error due to stiction, no resistance.

Because the low-mass LVDT core can float freely within the housing of the LVDT, there is no friction between the core and the housing. This is ideal for measurements of vibration or of systems where friction can cause a change in a dynamic response, and for measurements of structural deflection or creep where stiction can cause inaccuracies. Clearance between the core and housing also offers some tolerance for misalignment.

This cutaway image of an LVDT shows how the core can float freely in the center of the LVDT, without touching any of the side walls. If the core does touch the side wall due to vibration or misalignment, it is perfectly okay. In this image the LVDT core is linked to the mechanical indicator of a gate valve to provide position feedback - a very common LVDT application.

2. Infinite Mechanical Life

You may never have to replace this sensor, even after decades and millions of cycles.

Because the LVDT has no moving parts and no friction, it has nearly infinite mechanical life as no components wear. Used to make measurements in inaccessible locations like nuclear plants, embedded in structures for strain monitoring, or installed in choke vales on the seabed, LVDTs are depended on to continue their operation many years, even decades, after installation.

3. Seperable Core & Coil

Highly corrosive, subsea, and pressurized environments? LVDTs can do that.

A non-magnetic barrier can separate the LVDT coil from the core, allowing the LVDT to make measurements in corrosive or pressurized environments. Frequently used in level systems, pumps, and valves, the LVDT core can be exposed to media at high pressure and temperatures while the housing and coils can be separated by a sleeve or tube made of glass, metal, or other non-magnetic materials.

Because the core and coils can be separated and sealed from each other, LVDTs can be designed to operate in highly pressurized and harsh environments.

4. Excellent Repeatability

LVDTs do not drift or get noisy over time... even after decades.

Often specified at 0.01% of full range or better, LVDTs exhibit excellent repeatability for any point within its range. For example, in dimensional testing or roller position where repeatability is of paramount importance, LVDTs deliver extremely consistent output at a given position. This is in contrast to most pressure sensors, for example, whose output at any given pressure drifts over time due to metal fatigue and linear potentiometers whose output can become very noisy over time due to wear, vibration, or foreign matter intrusion. This is of critical importance for structural monitoring and product thickness measuring applications where often very small movements are measured over many years.

The chart shows how the output of how a position sensor changes over time at a given point. A cycling, aging potentiometer will eventually experience wear between the wiper and the resistive element, degrading the quality of the electrical contact that creates noise and inconsistent results in the output signal. The inductive, frictionless operation of an LVDT give it superior repeatability for its entire service life. With no components that wear, the LVDT Position Sensor provides consistent output at a given position during decades of operation.

5. Infinite Resolution

Even the most infinitesimal movements are measured accurately by LVDTs.

Without stiction and the principle of being a variable transformer, the LVDT inherent makes a position measurement of infinite resolution only limited by the associated electronics. In practice, LVDTs can detect extremely small changes in position. Particularly valuable to measure parameters like dimensional quality, TIR measurements, and thermal expansion, LVDTs are capable of detecting changes on the sub-micron level.

6. Null Repeatability

From -300°F to 1000°F , LVDTs always give you a consistent reference point

Inherent of symmetric coil design, the null point of the LVDT (the center of the LVDTs electrical range where the output is nearest to zero) is extremely repeatable. This consistent reference point becomes valuable in applications where temperature varies widely as the null point is impervious to drifts and serves as a consistent point from which calibrations are based.

Across temperature swings, the LVDTs null point does not shift which always gives users a fixed reference point for the center of the LVDTs measuring range if re-calibration is necessary.

7. Insensitivity to Cross-Axial Core Movement

Neither vibrations nor zig-zags will compromise measurement quality.

The LVDT output responds very effectively to movement along the axis of measurement and is insensitive to movement along the other two axes. Ideal for applications where the measured member spins the core, causes slight misalignment, or where cross-axial vibration takes place, the LVDT delivers consistent measurements only along the intended axis.

The LVDT is only sensitive to movement along the measured axis - so if the core moves in any other direction the LVDT output does not change.

8. On-Board Electronics Unnecessary

LVDTs can take a serious beating while in use, and the signal conditioner can be far away in safety.

AC LVDTs can have their associated electronics mounted externally, so there is no need to have a printed circuit board (PCB) or other sensitive electronic components inside the housing. With the absence of a PCB, the LVDT can operate in areas with extremes in high temperatures, vibration, and pressures.

Because the LVDT does not require on-board electronics, the sensor itself can operate in very harsh environments with temperature and pressure extremes, and the signal conditioning electronics can be housed remotely outside of the harsh area.

To learn more about LVDT signal conditioning, visit our signal conditioning tutorial! To learn more about our NTC-6000, you can download a datasheet from its product page!

9. Absolute Output

LVDTs never forget where they are, even after months of power-down.

Even through power cycles, LVDTs always deliver the true position unlike incremental sensors that must be re-homed after each power down. The true-position output through power cycles makes the LVDT ideal for long-term measurement applications like structural monitoring or critical measurement applications like a safety valve where errant readings due to loss of power can be very costly. It also allows the LVDT to be periodically awakened to make an accurate measurement then be put back to sleep where power budgeting is important.

10. Customization for Nearly Any Application

You name it, we'll make it!

With a little engineering know-how, LVDTs can be customized for nearly any application or requirement. From small changes like custom wire lengths, pinouts, mounting features like flanges and construction materials for radiation or high temperature, to full developments for reliability targets, dual or triple redundancies, custom outputs, or corrosive environments, an LVDT can be made deliver reliable position feedback in nearly any application.

Why Use an LVDT?

LVDT position sensors are ideal for so many applications! Here is the Top 10 list of reasons why.