Modern LVDTs operate at lower excitation voltages and use excitation frequencies between 2.5 kHz – 10 kHz, which makes them resistant to electrical noise and radio frequency interference. They also consume much less power than legacy LVDTs that ran on 120 V and 60 Hz, which drew high current. This lower power consumption is critical in applications where measurements are taken infrequently, and the sensors are paired with battery-powered electronics.

Traditional AC-operated LVDTs require an external signal conditioner to provide excitation voltage and convert the raw AC output into a usable analog or digital signal. However, modern LVDTs are now available with internal signal conditioning modules, eliminating the need for external excitation while retaining many of the advantages of traditional AC-operated LVDTs. More details can be found at: NewTek LVDT Signal Conditioning.

Typically, each signal conditioner drives a single LVDT. Applications with multiple LVDTs require a dedicated signal conditioner for each sensor or a multi-channel conditioner designed to manage multiple LVDTs simultaneously.

The NewTek NTC-6000 signal conditioner is primarily intended for use with a single sensor. However, multiple NTC-6000 units can be networked via RS-485 for coordinated operation in systems with several sensors.  NTC-6000s can also synchronize with one another, phase locking the excitation signal to prevent cross-talk or drift when multiple LVDTs and cables operate close to each other.

AC-operated LVDTs require an external signal conditioner to provide excitation and process the output. The conditioner demodulates the low-amplitude AC signal and produces standard DC outputs such as voltage ranges, 4-20mA current, or RS-485 digital output.

Modern LVDTs that incorporate signal conditioning and processing functions enable the direct generation of custom analog voltages, currents, or digital outputs from the sensor. DC-operated LVDTs are often available with loop-powered 4-20mA current output, which are less sensitive to electrical noise and reduce voltage drops over cable runs in excess of 100 ft compared to traditional analog voltage signals.

LVDT sensitivity, usually given in mV/V per unit of displacement, indicates how much the output voltage changes when the core moves a specific distance. For example, a sensitivity of 50 mV/V/mm means that for each millimeter of core movement, the output changes by 50 mV for every volt of excitation. The actual sensitivity depends on the specific LVDT model, and the signal conditioner used, so it is always important to refer to the data sheet.

Demodulation converts the AC voltage output of the LVDT into a usable DC signal that reflects position. This step is usually performed by an external signal conditioner for AC-LVDTs or internally in modern DC-LVDTs with built-in conditioning. It is not necessarily for operators to implement this themselves.

Stable excitation frequency is essential for accurate, dependable, and repeatable measurements. Modern LVDT signal conditions and DC-LVDTs with internal electronics actively stabilize and track the excitation, minimizing the impact of frequency drift.

LVDTs are highly precise, but have a few sources of error:

• Linearity: This happens when the sensor’s output voltage is not proportional to the core displacement over the full range. It is exceedingly small for modern LVDTs at <0.25% of full scale.
• Hysteresis: This is the difference in output when approaching a position from opposite directions. LVDTs have exceptionally low hysteresis due to their frictionless, non-contacting design.
• Thermal drift: LVDT’s do have a very small linear thermal sensitivity caused by copper’s resistance change over temperature. For users needing extreme accuracy, temperature compensation and ratiometric signal conditioning, help minimize these effects. Many sensors, like NewTek models, use special materials and winding techniques to reduce the impact of temperature on winding resistance and magnetic properties.   Importantly, the LVDT’s null point remains consistent over temperature so re-scaling at temperature is a simple way to achieve superior accuracy.

Total stroke is the full travel distance the LVDT core can physically move inside the sensor. Useable stroke is the portion of that movement where the output remains accurately linear, typically 70 to 90 percent of the total stroke. Modern LVDTs, such as NewTek’s precision models, can achieve +0.25% full scale linearity or better within the usable stroke.

While known for their long-term stability and reliability, LVDTs typically can be calibrated every 1- 3 years, depending on applications and industry standards. Calibration is usually a routine verification to ensure continued accuracy rather than a response to sensor drift or failure.

Many LVDTs are built with materials and winding techniques that minimize thermal drift, reducing shifts in zero or sensitivity caused by temperature changes. In addition, modern signal conditioners can adjust the output based on measurement temperature.

NewTek’s HT-1000 high-temperature series, for example, uses a ratiometric output that cancels many thermal errors, resulting in extremely low thermal sensitivity over a wide temperature range. Their NTC-600 DS Ratiometric Signal Conditioner compensates for temperature-induced resistance changes in LVDT winding resistance, maintaining accurate, stable measurements even as the environment changes.

If a housing and core are misaligned for a high-cycle or high-vibration application, it can introduce gain errors, reduce linearity, decrease overall accuracy, and increase potential wear. Using alignment sleeves or guide rods help ensure the core moves along the intended axis while proper mounting prevents unwanted stress or off-axis motion.

The null voltage is the output of the LVDT when the core is exactly at the center of its measurement range. It serves as the zero point or reference position, from which all positive and negative displacements are measured. Essentially, it establishes a baseline for accurate and consistent position readings.

LVDTs have an exceptionally long life and high MTBF, making them one of the most durable position sensing technologies in the industry. Because LVDTs operate without mechanical contact between the moving core and stationary coils, there are no wear mechanisms such as friction, wiper degradation or contact erosion. Most have a mechanical life of tens of millions of cycles. Many NewTek LVDTs are rated for >50 million strokes without degradation. This translates into an electrical life of millions of hours.

With proper design and certification, LVDTs can be used in radiation-prone or explosive environments. Radiation-resistant LVDT position sensors, such as NewTek Radiation Resistant LVDT Position Sensors, are built using heat-resistant materials, radiation-tolerant insulation and specialized coatings.  These designs can withstand total integrated radiation doses up to 100 Mrad, making them suitable for nuclear power facilities, research reactors, and space-related applications.

Intrinsically safe position sensors, such as the NewTek NT-HL-750, are engineered for operation in hazardous and explosive locations. Constructed with stainless steel housing and hermetically sealed to IP-67, these sensors can safely be used in areas containing flammable gases, vapors, dust, and other dangerous substances

LVDT sensors are highly immune to EMI and RFI due to their transformer-based, differential design compared to resistive sensors like potentiometers. With proper shielding and quality signal condition, these sensors can deliver stable, accurate, noise-free measurement even in electrically noisy applications such as heavy industrial machinery, power generation systems, and aerospace applications.

With the right model and configuration, LVDTs are suitable for use in oil, hydraulic, and even underwater environments.

Vented LVDT designs, such as NewTek’s M-375 series, are specially engineered for hydraulic cylinder applications.  When embedded in hydraulic systems, these sensors tolerate direct exposure to hydraulic fluids while withstanding high pressures, elevated temperatures, shock, and vibration, ensuring reliable and accurate position feedback.

NewTek can make high-pressure, water-resistant LVDTs designed for deep subsea environments.  Their robust housings resist extreme hydrostatic pressure and corrosive seawater conditions, making them suitable for offshore and underwater operations. For deeper and harsher environments, these LVDTs incorporate exotic electrical materials, ceramics, and specialized core materials, supporting temperatures up to 1000°F (538°C).

Hermetically-sealed and hazardous-rated LVDTs, such as the NT-HL-750 series, are built for oil, gas and petrochemical applications. With stainless steel housings and IP-67 sealings, they provide reliable performance in hostile liquid environments where contamination, pressure and exposure are critical concerns.

DC-operated LVDTs typically function at temperatures up to 85°C, making them suitable for standard industrial environments. AC-operated LVDTs can withstand temperatures of up to 200°C and even higher. High-temperature LVDTs constructed with advanced materials, high-temperature insulation and ceramic components can operate at temperatures exceeding 1000°F. These are used in rugged environments such as power plants, engine control systems, and autoclaves. On the low-temperature extreme, AC-LVDTs can be engineered for cryogenic operation, allowing reliable displacement measurement in environments involving liquid nitrogen, liquid helium or space and aerospace applications.

Maintaining proper coaxial alignment between the LVDT core and body is helpful for accurate measurements and long-term reliability, but not critical as some core misalignment does not negatively affect measurement quality. Ideally, the core should move along the centerline of the coil assembly to ensure balanced magnetic coupling. Proper installation and guidance help prevent misalignment, allowing the core to move smoothly and ensuring consistent sensor operation.

The choice depends on your application and mechanical requirements. A captive core design is mechanically attached to the LVDT body, typically with a spring mechanism. This configuration is easier to install, lowers the risk of losing the core and lets the core return to its original position automatically. It is suitable for short stroke measurements and direct contact applications.

In a free-floating design, the core moves freely within the sensor bore without being attached to the body. Because there is no mechanical contact with the sensor body, this design can provide reduced mechanical interference. It is often used in high-precision systems and applications where minimal mechanical interference is required.

Read Free-Core vs. Spring-Loaded LVDTs.

Proper mounting plays a key role in minimizing side loading, which occurs when the LVDT core is subjected to lateral or off-axis forces. Methods may include:

• External guides, linear bearings, or bushings keep the core moving strictly along its axis.
• Flexure mounts allow slight movement or angular alignment.
• Pivot mounts accommodate small misalignments without transferring side forces to the LVDT.
• Flexible couplings, bellows, or spring-loaded connectors connect the LVDT to the moving part, preventing side loads from reaching the core.
• Mounting blocks securely hold the LVDT without causing mechanical deformation to the housing.

Particularly in fast dynamic applications, the mass and friction of the LVDT core can influence measurement accuracy, response time, and system performance. Low-mass cores reduce inertia, allowing sensors to respond quickly in dynamic applications. Low-friction cores minimize mechanical resistance, improving repeatability and measurement accuracy. Using low-mass, low-friction cores help maintain high precision, faster response, and reduced wear, ensuring reliable long-term performance.

The vibration and shock tolerance of an LVDT depends on its design and conditions of the application. Most standard LVDTs can handle typical industrial vibration and  shock, especially when properly mounted and mechanically guided. In high-vibration or high-shock environments,  ruggedized LVDTs are available and designed specifically to withstand these conditions to maintain accuracy and longevity.

Core overtravel occurs when the LVDT core moves beyond its specified stroke range. When this happens, linearity will be heavily degraded and the measurement output will have significant error  (See Figure 2 of our LVDT Tutorial).   For almost all NewTek LVDTs, core overtravel will cause no damage to the sensor and the sensor will resume normal operation when the core is reinserted.

The mass of the LVDT core can affect the dynamic response. A low-mass core improves the LVDT’s ability to track rapid motion, extending its usable frequency range, and maintaining measurement accuracy. A heavier core adds inertia to the measured object, which may hinder or influence the movement or vibration the user is attempting to measure.

The bandwidth, or frequency response, of an LVDT refers to the range of motion frequencies that the sensor can accurately track. It indicates how fast the core can move while still producing a reliable, linear output. DC LVDTs usually have a set frequency response/bandwidth, while an AC LVDT’s can be user-controlled by changing the excitation frequency and using appropriate accompanying electronics.

LVDTs can measure fast motion or vibration if they have a low-mass core, sufficient bandwidth to track rapid movements, proper mounting to maintain coaxial alignment and minimize friction, and suitable signal conditioning to accurately process high-frequency signals.

Phase lag is the signal delay between the excitation frequency and the corresponding output signal from the LVDT. It is measured in degrees or radians, and this delay is typically very small.   In modern signal conditioners, even a high phase lag does not influence measurement quality, however in some legacy fully analog signal conditioning circuits a high phase lag can introduce error.

While LVDTs themselves do not generate much noise, sometimes the output can have attenuated noise if placed in an environment with heavy electrical machinery.  Signal filtering is sometimes implemented with LVDTs to reduce noise or smooth the output signal. To maintain both accuracy and speed:

• Choose a filter cutoff frequency higher than the maximum motion frequency.
• Match the filtering settings to the dynamic requirements of the system to avoid unnecessary signal delays.

Before choosing an LVDT, it is important to understand the temperature range the sensor will experience during operation. Temperature can significantly affect the performance and reliability of the sensor.

In standard environments, almost all LVDTs operate between -20°C to 85°C. In harsher environments below -20°C or above 85°C, AC-operated LVDTs are usually the better choice as they can manage more extreme or rapidly changing temperatures. They are often used in industrial, aerospace, or outdoor environments. DC-operated LVDTs, on the other hand, are typically designed for moderate temperature ranges and are commonly used in lab equipment, automation, and controlled environments.

The physical size of the LVDT matters when fitting it into a system. For installations in tight or difficult-to-access spaces, a smaller, more compact unit is usually required. Compact LVDTs are lighter in weight and often feature a low-mass core, which helps meet size and weight restrictions if applicable. Advances in coil design and computer-controlled winding machines have made it possible to manufacture smaller, lighter LVDTs while maintaining accuracy and reliability. In addition, AC-operated units, which do not include built-in electronics, tend to be more compact than DC-operated versions. Miniature LVDT Position Sensors are specifically designed to meet restrictive space requirements.

Standard LVDTs work well in typical conditions, but extreme environments, such as high ambient pressures and elevated temperatures, require sensors built for rugged operation. Some options include:

• Hermetically sealed LVDTs that withstand higher temperatures and prevent dust and dirt from entering the sensor windings.
• Custom and specialized LVDTs feature stainless-steel housings that provide resistance to high pressures, corrosion, and chemicals, making them suitable for subsea applications up to 7500 ft. and 5000 psi external pressure

Applications with harsh environments such as elevated temperatures, pressures, vibration, and shock should consider an AC-operated LVDT as it does not contain internal electronics affected by these conditions

LVDTs can either have built-in or remote processing.   The best choice depends on the application. Some applications benefit from built-in signal conditioning, which simplifies integration, while more complex systems may use external signal processors for amplification, demodulation, filtering, and conversion to specific output format. Choose an LVDT with output compatible with your system requirements (analog voltage output, analog current output, digital output).

Easy installation is a major advantage in many applications as it reduces setup time, minimizes alignment errors, and simplifies maintenance. Even though LVDTs can operate for decades at a time reliably, easy access does still have advantages.  Factors that make for easy installation:

• Compact and integrated design: Fewer external components and less wiring needed.
• Simple mounting options: Threaded housings, flanges, or mounting brackets for quick mechanical attachment.
• Plug-and-play Electrical Connections: Standard connectors or pre-wired cables reduce wiring mistakes.

Selecting a USA manufacturer can help mitigate supply chain risks caused by regulations, shutdowns, or import/export restrictions. US-based suppliers often provide better technical support, are accessiable, reliable documentation, and warranties, giving them strong consideration when selecting an LVDT.

Ensure the LVDT has the appropriate certifications for your application. For hazardous areas that can contain explosive  solids or gasses, look for approvals such as UL, CSA, Intertek, ATEX, or IECEx approvals to ensure safe, compliant, and reliable operation.  Always adhere to local regulations for installation of electrical equipment in classified areas.

Most LVDT failures in the field fall into a few categories: mechanical (core or coil damage), electrical (open/short circuits), environment (temperature, vibration, contamination), or installation-related (extreme misalignment or side loading). Proper sensor selection, correct installation, and regular maintenance can reduce these failure risks.

Noisy output from an LVDT output can result from several factors including mechanical misalignment or friction, electrical interference from nearby equipment, improper shielding, ground loops, and incorrect signal conditioning. Reviewing the installation, mounting alignment, wiring, shielding, grounding and considering filtering can significantly reduce noise and improve signal quality.

A zero shift occurs when the LVDT output gradually drifts away from its calibrated zero position. This can happen due to temperature changes, mechanical stress, corrosion, long-term vibration, or contamination.  When a zero-shift is noticed, recalibration about the null point will “reset” the output of the LVDT.

Asymmetrical output occurs when the LVDT produces unequal signal levels for equal displacements on either side of the null (zero) position. This can lead to inaccurate or distorted measurements. The most common culprit is core damage caused by extreme misalignment or years of heavy vibration.  Ensuring proper alignment, correct wiring, and regular calibration can help maintain a balanced and accurate LVDT output.

Swapping the lead wires reverses the polarity of the LVDT output signal and the LVDT will produce an inverted output, but it does not harm the sensor and will operate properly if simply re-calibrated or re-scaled.

Proper grounding and shielding are important to prevent electrical noise, interference, and unstable signals in an LVDT system. Best practices include using shielded twisted-pair cables for the excitation and signal wires, grounding the shield at one end, typically at the signal conditioner or instrumentation, separating signal and power wiring, and maintaining proper system grounding.  Sometimes grounding the LVDTs housing helps, and sometimes it actually introduces noise.  Always run grounds to one point to avoid ground loops.

The maximum cable length depends on the LVDT design, excitation frequency, signal conditioning, and the environment of the application. Long cables can degrade the signal due to capacitance, resistance, and noise pickup. Using high-quality shielded cables, proper grounding, and placing signal conditioning close to the LVDT helps maintain signal integrity over long runs. NewTek LVDT Cable Assemblies area available in standard lengths from 6 ft to 100 ft in increments of 10 ft.