LVIT Linear Position Sensor ME-7 Series

What Is the ME-7 and How Does It Install?

The ME-7 Series LVIT (Linear Variable Inductance Transducer) from Alliance Sensors Group is an embeddable in-cylinder position sensor designed to mount directly into the end cap of industrial and mobile hydraulic cylinders and pneumatic actuators. Engineered as a more robust, lower-cost alternative to magnetostrictive sensors, the ME-7 uses a 7 mm diameter inductive probe inserted into a target tube mounted inside a gun-drilled blind hole in the cylinder rod — sensing the rod’s position without any permanent magnet on the piston.

The sensor head measures 1.89 inches (48 mm) in diameter with an O-ring and back-up ring in a machined groove, allowing it to mount in the same end cap cavity used by magnetostrictive sensors. Radial set screws lock the sensor in place, just as they would for the magnetostrictive unit being replaced. With measuring ranges from 25 mm to 900 mm (1 to 36 inches) and a 5,000 psig operating pressure rating (7,500 psig proof), the ME-7 covers the full spectrum of industrial and mobile hydraulic cylinder strokes.

Why Replace a Magnetostrictive Sensor with the ME-7?

No Magnet Ring — Simpler Cylinder Assembly, Fewer Failure Points

Magnetostrictive sensors require a permanent magnet ring assembled to the piston inside the pressurized cylinder bore. This ring must be properly oriented, securely attached to survive shock and vibration, and protected during cylinder assembly to avoid damage or contamination. The ME-7 eliminates this component entirely. Position sensing is accomplished through the inductive interaction between the probe and the target tube in the gun-drilled rod — no magnets, no waveguides, and no delicate internal components. For cylinder manufacturers, this means fewer parts to procure and assemble, and one less failure mode inside the cylinder.

Higher Shock and Vibration Tolerance Than Magnetostrictive Technology

Magnetostrictive sensors use a precision waveguide and time-of-flight measurement principle that is inherently sensitive to mechanical shock. The ME-7’s inductive coil has no waveguide to fracture or deform — it uses a simple, mechanically robust coil design that withstands 1,000 g shock and continuous vibration across the 5–2,000 Hz range. In mobile hydraulic equipment, industrial presses, and heavy machinery where cylinders experience repeated impact loading, the ME-7 provides a sensing element that survives conditions that damage or destroy magnetostrictive alternatives.

Lower Total Cost of Ownership

The ME-7’s lower sensor cost, eliminated magnet ring, simplified cylinder assembly, and longer service life in high-shock environments combine to reduce total cost of ownership compared to magnetostrictive installations. For cylinder manufacturers building in volume, the per-cylinder savings from removing the magnet ring and simplifying the assembly process compound across production runs. For end users, the reduced failure rate in harsh service means fewer cylinder teardowns for sensor replacement — each of which carries labor, downtime, and hydraulic fluid disposal costs that far exceed the sensor’s purchase price.

Key Applications for the ME-7

Industrial Hydraulic Cylinders

In factory automation, metal forming, injection molding, and general industrial hydraulics, the ME-7 provides closed-loop position feedback from inside the cylinder. The embedded installation protects the sensor from external damage, contamination, and tampering. Cylinder manufacturers integrate the ME-7 during production, delivering a position-sensing cylinder to the end user with no external sensor installation required.

Mobile Hydraulic Equipment

Construction, agriculture, forestry, mining, and material handling equipment all subject hydraulic cylinders to severe mechanical environments. The ME-7’s shock and vibration resistance exceeds what magnetostrictive sensors tolerate, and the absence of an internal magnet ring eliminates piston impact failures that are common in mobile applications. The compact 48 mm head and favorable stroke-to-length ratio minimize space consumed inside the cylinder end cap — important in mobile equipment where cylinder envelopes are tightly constrained.

Pneumatic Actuators

For pneumatic cylinders requiring position feedback in automation and packaging systems, the ME-7 provides the same embeddable installation and contactless sensing in lower-pressure service. The sensor’s operating pressure rating far exceeds pneumatic system pressures, providing ample mechanical margin.

ME-7 vs. MR-7: Embedded vs. Port-Mounted Installation

Both the ME-7 and MR-7 use the same 7 mm LVIT probe technology, the same measurement ranges, and the same contactless inductive sensing principle. The difference is how they mount to the cylinder:

ME-7: Embeds into a 48 mm cavity in the cylinder end cap, sealed with O-ring and back-up ring, retained by radial set screws. Requires cylinder disassembly to install or remove.

MR-7: Threads into an SAE J1926-8 or ISO M18 O-ring port boss from outside the cylinder. Can be installed and removed without opening the cylinder.

For new cylinder builds where the manufacturer controls the end cap design, the ME-7’s embedded installation provides a cleaner package with no external protrusions. For retrofit applications where the sensor must be serviceable without cylinder teardown, the MR-7’s port-mount design is the better choice. For subsea service, see the SS-7 in 316 stainless steel with subsea connector.

Electrical Output and Field Calibration

Analog Output Options for Direct System Connection

The ME-7 provides DC-in/DC-out operation with multiple analog outputs: 0–5 V, 0.5–4.5 V, or 0–10 V voltage outputs, and 4–20 mA current output. Reverse-acting outputs are available for applications requiring inverted feedback. All outputs connect directly to PLCs, motion controllers, and hydraulic control systems without external signal conditioning.

SenSet™ Field Programmability

The ME-7 includes ASG’s SenSet™ feature, allowing the analog output to be scaled after installation to match the actual range of motion of the cylinder rod. This is particularly valuable for cylinder manufacturers who use the same sensor model across cylinders with different stroke lengths — a single ME-7 part number can be stocked and then SenSet-adjusted to each cylinder’s specific stroke during final test, simplifying inventory and reducing lead times.

Key Specifications

Measuring ranges: 25 mm to 900 mm (1 to 36 inches) full scale

Linearity error: ±0.15% FSO typical, ±0.25% FSO maximum

Resolution: 0.025% of full scale output

Update rate: 300 Hz nominal

Operating pressure: 5,000 psig (350 bar) max, 7,500 psig (520 bar) proof

Shock: 1,000 g, 11 msec

Vibration: 5–20 Hz at 0.5 inch p-p; 20–2,000 Hz at 4.2 g p-p

Sensor head: 1.89 inch (48 mm) diameter with O-ring and back-up ring

Housing material: aluminum or 300 series stainless steel

Operating temperature: -20°C to 85°C (-40°C to 105°C extended range)

Temperature coefficient: ≤0.015% FS/°C

Terminations: IP67-rated cable (1 m or 1 ft)