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Magnetic Encoder Signal Reading Methods
1. Incremental Encoder Signal Reading
A/B Phase Pulse Analysis:
A high-speed counter is used to capture square wave pulses with a 90° phase difference.
Direction Determination:
Phase A leads phase B → forward motion
Phase B leads phase A → reverse motion
Z-Phase (Zero Position) Synchronization:
An index pulse is output per rotation for mechanical origin calibration.
A home search is triggered during system initialization, resetting the counter.
2. Absolute Encoder Signal Reading
Digital Communication Protocol Processing:
Synchronous Serial Interface (SSI): The controller sends a clock pulse, and the encoder outputs binary position data on the falling edge of the clock.
Bidirectional Communication Protocol (BiSS, EnDAT): Supports real-time configuration and diagnostics, transmitting position, temperature, and fault codes via differential signals.
Parallel Output Direct Reading (less commonly used): Directly connect the encoder output pins to a PLC digital input module to read Gray code.
3. Hybrid Encoder Dual Signal Processing
Master-Slave Switching Logic: Absolute position signals are used by default, automatically switching to incremental pulse backup when an abnormality is detected. Cross-check mechanism: Compares the difference between two signals and triggers an alarm if the threshold is exceeded (e.g., in wind turbine pitch control systems).
4. Hardware Interface Connection
| Signal Type | Interface Requirement | Noise Countermeasure |
| Incremental Pulses(A/B/Z phases) | Differential receiver IC(e.g., AM26LS32, SN75175) | • Twisted-pair shielded cable• 120Ω termination resistor |
| Absolute Serial Data(SSI/BiSS/EnDAT) | RS422/485 transceiver circuitwith clock synchronization | • Ferrite beads on signal lines• Common-mode choke |
| Analog Output(1Vpp sinusoidal) | Precision ADC with>12-bit resolution | • RC low-pass filter(cutoff ~ low-pass filter(cutoff ~10× signal freq) |
| Fieldbus Communication(PROFIBUS, EtherCAT) | Protocol-specific PHY chipand controller | • Double-shielded cables• Galvanic isolation |
5. Key Software Processing Steps
Noise Filtering Algorithm: Moving Average or Kalman Filter to Eliminate Jitter
Position Compensation: Pre-stored calibration tables (e.g., eccentricity compensation) to correct position offsets in real time.
Fault Diagnosis: Monitor signal loss, overspeed, and overheating flags to trigger safety shutdowns.
6. Oscilloscope Diagnostic Techniques
Signal Quality Check: Observe the symmetry of the A/B phase pulses and the sharpness of the rising and falling edges (>45°). Interference Identification: Background glitches indicate poor grounding or shielding failure.
Z-Phase Signal Verification: Ensure that the signal only appears once per revolution and that the pulse width is >20μs.
7. Safety Precautions
Electrostatic Discharge (ESD) Protection: Wear a grounding wrist strap during operation to prevent CMOS circuit breakdown.
Power Isolation: Use a DC/DC isolation module to block ground loop interference.
Surge Protection: Connect a TVS diode in parallel at the signal line input to protect against lightning strikes and surges from inductive loads.
