LVDT vs Potentiometer: Which Position Sensor Should You Use?

The Short Answer

An LVDT is contactless, so it does not wear out and holds accuracy over millions of cycles in dirty environments. A potentiometer — including the string potentiometer version — costs a fraction as much and works perfectly well for light-duty or long-stroke applications where you can accept a finite wiper life.

Choose on three questions: How many cycles? How long is the stroke? How harsh is the environment? Everything else follows.

How the Two Actually Measure

LVDT (Linear Variable Differential Transformer). A magnetic core slides inside a coil assembly with no physical contact. Position becomes a differential AC voltage, demodulated into 0–10 V or 4–20 mA. Resolution is theoretically infinite because the output is a continuous analogue function, not a series of steps.

Potentiometer. A wiper slides along a resistive track. Position becomes a voltage divider ratio. Cheap, simple, and it needs only three wires. But the wiper touches the track every millimetre of every stroke, and that contact is a consumable.

A string potentiometer is the same resistive element packaged with a spring-loaded cable and drum — you pull the cable out and the drum turns the potentiometer. It buys you a long measuring range (up to several metres) in a very small body.

Head-to-Head Comparison

Where Each One Genuinely Wins

Pick an LVDT when

• Cycle count is enormous. Presses, valves, fatigue testers, packaging machines — anything cycling millions of times. A wiper is a wear item; a core is not.
• The environment is hostile. Oil mist, coolant spray, steam washdown. Our PTL-ARTSD is IP68-rated at 0–50 mm with ±0.25 % FS, running 0–10 V or 4–20 mA straight into a PLC.
• You need stable accuracy over years without recalibration. No contact means no drift from track wear.
• Vibration is severe. Nothing to rattle loose inside the measuring element.
• The stroke is short. Under ~250 mm, the LVDT is compact and the price gap is modest.

Pick a potentiometer (or string pot) when

• The stroke is long. Beyond about 300 mm, an LVDT becomes a long, costly tube. A draw wire or string pot covers 0–1500 mm in a body you can hold in one hand — the DWS1A reaches 1.5 m with a voltage divider output; the SKD covers 0–400 inch with 4–20 mA or 0–10 V.
• Duty cycle is light. A test rig that moves twice an hour does not need a contactless sensor.
• Budget is the constraint. For high-volume OEM equipment, the cost difference is decisive.
• You want the simplest possible integration. Three wires, ratiometric output, no conditioner, no carrier frequency.

The Hybrid Case: Draw Wire Sensors

A draw wire sensor is a string pot with a better mechanical package — stainless cable, precision drum, spring return, sealed housing. It is the standard answer for long-stroke linear measurement in industrial equipment: lifters, cranes, valve position, press brake depth, telescopic masts.

The trade-off versus an LVDT is honest: you gain range and lose contactless life. Practical advice — if the draw wire sees more than a few million cycles, or the cable runs through abrasive dust, budget for replacement cable kits and plan the mounting so the cable exits cleanly.

For a detailed sizing walkthrough, see our draw wire sensor selection guide.

Cost Reality Check

Rough relative positioning across the same measuring range:

• String potentiometer / OEM draw wire: baseline
• Industrial draw wire with 4–20 mA and IP67: 1.5–2.5×
• DC LVDT with integrated electronics: 3–5×
• AC LVDT plus matched signal conditioner: 4–7×

The gap narrows when you account for total cost of ownership — a failed potentiometer mid-production costs far more than the sensor. But for low-cycle applications, paying LVDT prices is simply overspending.

A Decision Table You Can Actually Use

Frequently Asked Questions

Is an LVDT more accurate than a potentiometer? Usually, yes — but the gap is smaller than marketing suggests. Typical industrial LVDT: ±0.25 % FS. Typical string pot: ±0.35 % to ±0.5 % FS. The bigger difference is stability: the LVDT's accuracy does not degrade with wear, while a potentiometer's does.

Can I replace a potentiometer with an LVDT directly? Mechanically often yes, electrically not always. A potentiometer gives a ratiometric voltage divider; an LVDT gives either an AC signal needing demodulation or a conditioned DC/current output. Check your input card before ordering.

Do LVDTs need a special cable? AC LVDTs do — the excitation and signal share a cable, and capacitance matters. DC LVDTs run on standard shielded cable.

Which lasts longer? An LVDT has no wearing element, so its life is limited by bearings, seals and cable, not by the sensing principle. A potentiometer's life is quoted in cycles (often 1–10 million) and drops sharply with vibration and contamination.

Still Deciding?

Send us the stroke, cycle rate, environment and the input your controller provides. We will tell you which of the 149 models fits — including when the cheaper one is the right answer.

LVDT position sensors → · Draw wire & string potentiometers →