Selecting and integrating encoders, linear position sensors, and inclinometers in industrial automation, mobile machinery, and safety-critical systems. Covers absolute vs. incremental feedback, output formats, environmental ratings, and installation patterns that prevent commissioning surprises.
What’s Covered
Three feedback classes you need to choose between
Position and motion sensors fall into three behavior classes, and the choice between them determines almost every downstream design decision.
- Incremental, outputs pulses as motion occurs. Position is computed by counting pulses from a reference. Compact, fast, and inexpensive, but the count is lost on power loss until a homing sequence reestablishes the reference.
- Absolute, outputs a unique position code at every shaft angle or stroke position. Power loss does not lose position. Required for safety-critical applications and for systems that cannot tolerate a homing sequence at every startup.
- Analog, outputs a voltage or current proportional to position. Common for short-stroke linear sensors and inclinometers. Resolution is set by the analog signal chain rather than digital encoding.
Rotary and linear encoders
Durham Instruments stocks the Leine & Linde encoder lineup with optical and magnetic variants spanning compact 30 mm units (300 series), general industrial models (380, 470, 500), heavy-duty (600, 700, 800), and extreme-duty for steel mills and paper plants (900, 1000 EXTREME). Bearing-less designs (2000 series) handle very large shaft diameters where a conventional shaft encoder cannot fit.
| Specification | Why it matters | What to confirm |
|---|---|---|
| Resolution (PPR or bits) | Determines smallest detectable motion increment | Match resolution to control-loop dynamics, not catalog maximum |
| Mechanical interface | Shaft / hollow-shaft size, mounting flange, stator coupling | Verify against the application’s shaft diameter and mounting space |
| Output | Compatibility with drive, PLC, or DAQ | HTL, TTL, SinCos, SSI, BiSS, EnDat, PROFINET, EtherCAT, CANopen |
| Environmental rating | Survival in dust, washdown, oil mist | IP rating, temperature range, sealing class |
| Diagnostics & safety | Predictive maintenance, functional safety | Self-check features (Leine & Linde Advanced Diagnostic System), SIL/PL ratings |
Browse the full encoder catalog for current part numbers, accessories, and gateway options (CANopen, PROFIBUS, PROFINET).
Linear position sensors
Linear position covers stroke ranges from a few millimeters to several meters and uses different technologies depending on length, accuracy, and environment:
- LVDT, frictionless, high-accuracy, suited to short-stroke laboratory and aerospace applications
- Magnetostrictive, long-stroke, non-contact, robust in hydraulic cylinders and industrial automation
- Linear potentiometers, simple, low-cost, suitable where contact wear is acceptable
- Linear encoders, high resolution and accuracy on machine-tool and automation applications
For LVDT integration, pair with the right signal conditioner (LVM-110, SCM100, LDM-1000), LVDT excitation, demodulation, and linearization are not generic functions.
Tilt sensors and inclinometers
Inclinometers measure angle relative to gravity. Durham Instruments distributes Jewell Instruments tilt sensor lines covering MEMS, servo / fluid-damped, capacitive, and conductive technologies. Ranges from ±1° (high-accuracy leveling) to ±90° (mobile equipment slope monitoring) cover most industrial applications.
| Technology | Strength | Typical use |
|---|---|---|
| MEMS (JMI, JDI, DMH) | Compact, robust, broad temperature range | Mobile machinery, vehicle tilt, industrial automation |
| Servo / fluid-damped (LCF, LSO) | Highest accuracy and stability | Geotechnical monitoring, structural inclination, calibration reference |
| Conductive (AAL, D-series) | Cost-effective, simple integration | Tip-over protection, slope alarms, basic platform tilt |
| eCompass (ECG, ECS) | Tilt + heading combined | Mobile mapping, antenna pointing, aim assistance |
Output options include analog voltage (0–5 V, ±5 V), 4–20 mA loop, and digital (RS232, RS485, USB, CAN, Ethernet). Browse the full tilt sensors and inclinometers catalog.
Integration: outputs, fieldbus, and safety
Modern industrial controls increasingly demand digital communication and functional safety compliance. The encoder or position sensor must speak the same protocol as the drive or controller, and where the application is safety-related, the device must carry the appropriate SIL or Performance Level rating.
- Match output to controller, TTL or HTL incremental for general-purpose drives; SSI / BiSS / EnDat for absolute servo applications; PROFINET / EtherCAT / CANopen for fieldbus integration
- Plan diagnostics for predictive maintenance, Advanced Diagnostic System (ADS) and similar features detect bearing wear, optical degradation, and signal anomalies before failure
- For safety-relevant applications, specify a device with documented SIL2 / SIL3 or PLd / PLe rating and verify the rating end-to-end including drive and controller
Installation that survives the duty cycle
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Couple correctly
Use a shaft coupling that absorbs misalignment without back-driving radial load into the encoder bearings. For hollow-shaft encoders, the stator coupling absorbs the same role.
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Respect mounting torque
Over-torque distorts housings; under-torque allows movement that produces fretting and intermittent signals.
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Cable management
Provide service loops, prevent flex over short radii, and route away from drive cables and high-current conductors.
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Verify zero or home position
For absolute systems, confirm the zero offset matches the mechanical reference. For incremental systems, confirm the homing sequence and the tolerance window.
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Document the configuration
Resolution, output format, scaling factor, gear ratio (for systems with downstream gearing). Configuration drift across maintenance cycles is one of the most common sources of “the encoder broke” tickets.
FAQ
When should I use absolute vs. incremental encoders?
Absolute encoders maintain position through power loss and are required for safety-critical applications and machines that cannot tolerate a homing cycle on startup. Incremental encoders are simpler, less expensive, and ideal where homing is acceptable and continuous position retention is not required.
Are MEMS inclinometers accurate enough for industrial applications?
Modern industrial-grade MEMS inclinometers from Jewell Instruments achieve sub-degree accuracy across wide temperature ranges and are appropriate for the vast majority of automation and mobile equipment applications. For sub-arc-minute accuracy or geotechnical work, servo / fluid-damped inclinometers remain the right choice.
What output should I choose for a long cable run?
For analog outputs over distance, 4–20 mA is preferred over voltage. For digital outputs, differential signaling (HTL, RS422, EnDat, BiSS) tolerates much longer cables than single-ended TTL. Confirm cable specs match the protocol.
Can encoders be calibrated in the field?
Encoders themselves are typically not user-calibrated; their accuracy is set by the disc and read-head geometry at manufacture. Field service consists of verifying mechanical alignment, electrical signal integrity, and configuration parameters. Persistent inaccuracy usually indicates mechanical or coupling issues rather than electronic drift.
Does Durham Instruments support fieldbus integration?
Yes. Durham Instruments stocks gateways for CANopen, PROFIBUS, and PROFINET and supports selection of encoders with native fieldbus interfaces. Contact our team with your controller platform.
Specifying position or tilt sensing?
Send the duty cycle, environment, and controller platform, Durham Instruments will return a fit-for-purpose recommendation, including conditioning and installation guidance.