Positioning sensor selection comes down to technology (each has different trade-offs in stroke length, accuracy, environment tolerance), output type (must match the controller input), and the mechanical interface to the machine. Substituting technology — replacing an LVDT with a magnetostrictive of the same stroke, for example — changes the accuracy, response, and mounting characteristics.
Specs to confirm before ordering:
- Technology: magnetostrictive (long stroke, sub-mm accuracy, oil/hydraulic compatible), LVDT (medium stroke, very high accuracy in short range), draw-wire (long stroke, lower cost, mechanical), linear potentiometer (medium stroke, simple, wears with cycles), magnetic-tape absolute (modular, long lengths)
- Stroke / measuring length
- Linearity and resolution
- Output: analog 0–10 V or 4–20 mA, digital SSI, CANopen, Profibus, Profinet, EtherCAT, Start/Stop pulse
- Supply voltage
- Operating temperature range
- Pressure rating for magnetostrictive sensors in hydraulic cylinders (often 350 bar / 5000 psi)
- Mechanical interface: rod-style (with magnet on slide), profile-style (with magnet on slider), flange-mount, draw-wire body mounting
- IP rating
Common gotchas: magnetostrictive sensors require a specific magnet style and orientation paired with the rod or profile — substituting magnet brands within a single OEM works, across brands it usually does not. LVDT sensors use AC excitation and require an LVDT signal conditioner; using a raw LVDT output without the matched conditioner gives no useful signal. Draw-wire sensors have a maximum extension speed; pulling the wire faster than rated damages the spring return mechanism. Linear potentiometers wear at the wiper contact and develop "dead spots" after extended high-cycle use; cycle-rated models extend life but are not infinite.
Typical applications: hydraulic cylinder position feedback on injection molders and presses (magnetostrictive), precision gap measurement on machine tools (LVDT), boom or arm position on mobile equipment (draw-wire), gate position monitoring on hydraulic gates (linear pot), and machine-axis position feedback (magnetic tape with absolute reader). On legacy installations, in-kind replacement preserves the controller's expected output and the mechanical mounting.
For obsolete positioning sensors, send the OEM part number for a sourcing quote.
