SSI Magnetostrictive Linear Position Sensor — 25-bit, 1µm Resolution, OEM China

Both formats transmit the same position value over the SSI link, but use different binary encoding. Binary: each bit represents a power of 2 (standard binary). At position transitions, multiple bits change simultaneously, which can cause reading errors if the controller samples mid-transition. Gray code (reflected binary): adjacent position values differ by only 1 bit, eliminating multi-bit transition errors at any clock frequency. Gray code is the recommended and most common format for magnetostrictive sensors and absolute encoders. Binary is useful when the downstream controller expects binary format and cannot perform Gray-to-binary conversion. SEGMENsensor sensors ship in Gray code by default; binary available on request via DIP switch.

Use shielded twisted-pair cable (2×2×0.25 mm², individually shielded pairs, overall shield). Connect Clock+ and Clock– from the drive SSI output to the sensor CLK pair; connect the sensor DATA pair to the drive SSI Data input. Ground the cable shield at the controller end only (single-point grounding). Maximum cable length at 100 kHz clock: 50 m with 0.25 mm² wire. In the drive or controller, configure: absolute encoder type = SSI, bit count = 25, code = Gray, position range = sensor stroke in counts (2^25 = 33,554,432 counts per full-scale). Refer to SEGMENsensor connection diagram supplied with the sensor.

SSI is a universal standard supported by most industrial servo drives and motion controllers with absolute encoder input modules. SEGMENsensor SSI sensors use standard RS-422 physical layer and 25-bit Gray code, compatible with all major servo platforms. For PLC connection, use an SSI input module (available from most major PLC vendors). Confirm SSI parameters in the drive manual: clock frequency, bit count, and code format. SEGMENsensor provides parameter files and connection notes for common drive and controller platforms on request.

SSI magnetostrictive sensors provide 25-bit resolution over the full stroke. For a 1,000 mm stroke, 25-bit resolution = 1000 mm ÷ 33,554,432 = 0.03 µm theoretical resolution. In practice, the sensor's physical resolution is 1 µm (the magnetostrictive pulse timing precision), so displayed resolution is 1 µm regardless of stroke. Accuracy (linearity) is ±0.05 mm — this is the maximum deviation of actual measured position from true position, and is the relevant specification for machine positioning applications. Resolution and accuracy are different: 1 µm resolution with ±0.05 mm accuracy means the sensor can detect 1 µm changes in position, but the absolute position value may differ from true position by up to 0.05 mm.

Yes, in many applications. SSI magnetostrictive sensors offer advantages over linear encoders in harsh environments: no optical scale (immune to contamination), absolute output (no homing), long stroke capability (up to 4 m), and sealed stainless steel housing (IP67). Linear encoders offer higher accuracy (submicron) for precision machine tools. Choose magnetostrictive when: stroke > 500 mm, contamination is a concern, absolute position at power-up is required, or the mechanical coupling for an encoder is impractical. Choose a linear encoder when accuracy < ±0.01 mm is required (e.g., grinding machines, precision lathes).

The SSI data transmission time depends on the clock frequency and bit count: at 1 MHz clock with 25 bits, one transmission takes 25 µs. At 100 kHz clock, one transmission takes 250 µs (4,000 readings/second). Most servo drives use 100 kHz–1 MHz SSI clock. Between transmissions, the sensor performs a new measurement and latches the result. SEGMENsensor sensors perform a new magnetostrictive measurement approximately every 100 µs (10 kHz measurement rate), so the position data is refreshed at up to 10 kHz regardless of the SSI clock rate. For servo control loops requiring >1 kHz position feedback, confirm the sensor's measurement refresh rate — not just the SSI transmission rate.

MOQ 10 pcs for standard SSI magnetostrictive sensors (stroke 100–2000 mm, 25-bit Gray code, M12 5-pin connector, IP67). Samples 1–2 pcs accepted. Standard lead time: 3–4 weeks. Custom stroke (specify in 1 mm increments), binary output, non-standard connector, profile rod variant, or private label OEM: add 2–3 weeks. CE and RoHS documentation with every order. Factory: Segmen Industrial Development Co., Ltd., Registration No. 91440300MAEUXXQU04, Shenzhen, Guangdong, China.