How to Select the Right Displacement Sensor for Hydraulic Systems

• June 2, 2025

How to Select the Right Displacement Sensor for Hydraulic Systems

Displacement sensors are essential components in hydraulic systems, enabling precise monitoring and control of linear movement, position, and feedback, typically within hydraulic cylinders. By continuously measuring the position of moving components such as pistons, these sensors convert mechanical motion into electrical signals, allowing control systems to make real-time adjustments. In industries ranging from construction to manufacturing, selecting the right displacement sensor is key to achieving accuracy, efficiency, and safety in system performance.

Accurate displacement sensing in hydraulic systems enables:

• Improved system performance through precise motion control and positioning
• Predictive maintenance by monitoring trends in component movement and wear
• Enhanced automation and feedback control with closed-loop systems
• Reduced downtime due to faster and more accurate fault detection

 

Types of Displacement Sensors

There are several types of displacement sensors, but only a few are rugged and precise enough for the demanding nature of hydraulics:

1. Linear Variable Differential Transformer (LVDT)

• Advantages: Non-contact, high accuracy, excellent repeatability, and long life
• Best For: Harsh environments and applications that require continuous feedback
• Considerations: Requires signal conditioning and slightly more complex installation

2. Magnetostrictive Sensors

• Advantages: High resolution, non-contact, resistant to wear and contamination
• Best For: Embedded cylinder applications in mobile or industrial hydraulics
• Considerations: Typically more expensive than other options

3. Potentiometer

• Advantages: Cost-effective, easy to install, good for general-purpose applications
• Best For: Budget-conscious applications with moderate precision requirements
• Considerations: Contact-based, subject to wear over time

4. Laser Displacement Sensor

• Advantages: High-speed, non-contact, excellent for long-range or precise measurements
• Best For: External monitoring of hydraulic mechanisms, especially where fast dynamic changes occur
• Considerations: Sensitive to surface reflectivity, dirt, and ambient lighting; not ideal for embedded applications

5. Inductive Displacement Sensors

• Advantages: Non-contact, very robust, resistant to oil, dust, and electromagnetic interference
• Best For: Short-range measurements in contaminated or enclosed hydraulic environments
• Considerations: Limited measurement range; typically used for proximity or small displacement

6. Eddy Current Sensors

• Advantages: High precision, non-contact, unaffected by oil or dust, ideal for conductive targets
• Best For: Monitoring small displacements in metallic hydraulic components like pistons or valves
• Considerations: Requires metal targets; limited range; more expensive than inductive types

7. Confocal Displacement Sensors

• Advantages: Ultra-high precision, sub-micron resolution, excellent for reflective and transparent surfaces
• Best For: Laboratory-grade diagnostics or quality control of hydraulic components
• Considerations: Sensitive to vibrations and surface conditions; high cost; not ideal for rugged field environments

 

Hydraulics Applications and Sensor Selection

Choosing the right distance sensor depends on the specific hydraulic application and its operating conditions. Here are some common use cases and suitable sensor types:

• Industrial Presses:
  LVDTs are ideal for press applications that require high accuracy and repeatability. Their non-contact design ensures reliable performance in high-force environments where precise closed-loop control is essential.

• Agricultural Machinery:
  Linear potentiometers offer a cost-effective solution for tracking the position of hydraulic components like lift arms or rams. They provide sufficient accuracy for many farming tasks while keeping equipment costs low.
• Mobile Equipment (e.g., Excavators):
  Magnetostrictive sensors, embedded directly into hydraulic cylinders, provide rugged, non-contact position feedback. Their durability and resistance to vibration make them ideal for heavy-duty mobile hydraulics operating in harsh outdoor environments.

Key Factors When Choosing a Position Sensor for Hydraulic Systems

When selecting a displacement sensor for a hydraulic application, consider the following:

1. Measurement Range

Choose a sensor with a range that matches the stroke length of your hydraulic cylinder. Avoid over-sizing, as it can reduce accuracy and increase cost.

2. Environmental Conditions

Hydraulic environments are often dirty, wet, and prone to vibration. Look for sensors with:

• IP-rated enclosures (IP67 or higher)
• Shock and vibration resistance
• Temperature tolerance suited to the application

3. Mounting Style

• External mounting is easier for retrofits.
• Embedded sensors (like in-rod magnetostrictive types) offer better protection and aesthetics.

4. Signal Output Requirements

Match the sensor’s output to your control system. Common output types include:

• Analog (0-10V, 4-20mA)
• Digital (SSI, CANopen, IO-Link)
• Pulse-based interfaces

5. Durability and Maintenance

Non-contact sensors like LVDTs and magnetostrictive types require less maintenance, making them ideal for critical applications or hard-to-reach locations.

 

Which Displacement Sensor Fits Your Hydraulic Operation? 

For most hydraulic applications, magnetostrictive sensors are the preferred choice due to their non-contact design, high accuracy, and excellent resistance to wear and harsh environments. They are especially well-suited for use inside hydraulic cylinders in both mobile equipment and industrial machinery.

LVDTs are another excellent option, particularly in applications that demand extreme precision and long-term stability, such as industrial presses or test rigs. Their robust construction and non-contact operation make them ideal for continuous feedback in high-cycle systems.

For simpler or cost-sensitive applications, such as those found in agricultural machinery, linear potentiometers offer a reliable and affordable solution. While they are contact-based and subject to wear, they provide adequate performance where ultra-high precision or long life is not critical.

 

Choosing the right displacement sensor for hydraulic applications means balancing precision, environment, budget, and integration requirements. LVDTs and magnetostrictive sensors lead in durability and accuracy, while potentiometers serve well in cost-sensitive, less demanding setups.

Need help choosing the right displacement sensor?

If you’re unsure which sensor fits your needs, contact MeasureX or email sales@measurex.com.au to speak with our experts about your requirements, and we’ll help you find the best solution or provide flexible and customised options for your application.