Incremental Quadrature (TTL/RS422) Scales
Incremental quadrature is the most common signal type for DRO scales. These scales output digital A and B phase signals that are 90° out of phase, allowing direction detection and position measurement.
Signal Characteristics
- A and B phases: Square wave signals 90° out of phase
- Index pulse (Z): Optional reference pulse once per revolution/cycle
- Voltage levels: TTL (0-5V) or RS422 differential
- Resolution: Typically 1µm, 5µm, or 10µm per pulse
Common Pinouts
Standard 9-pin D-sub (most glass scales)
- Pin 1: +5V power
- Pin 2: 0V (ground)
- Pin 3: A+ (or A for single-ended)
- Pin 4: A- (differential only)
- Pin 5: B+ (or B for single-ended)
- Pin 6: B- (differential only)
- Pin 7: Z+ (index, if present)
- Pin 8: Z- (differential index)
- Pin 9: Shield/case ground
Compatible Scales
- Most Chinese glass scales (Ditron, Easson, etc.)
- Heidenhain incremental scales
- Mitutoyo AT2xx series
- Magnetic scales (Newall, Fagor, etc.)
- Rotary encoders
TouchDRO Compatibility
All TouchDRO adapters support quadrature signals:
- TDA-4xx: Native support, auto-detection
- DIY kits: Primary supported signal type
- Glass scale adapters: Designed specifically for this signal type
Wiring Notes
- Use shielded cable for long runs
- Connect shield to adapter ground, not scale ground
- Differential (RS422) signals are more noise-resistant
- Single-ended (TTL) works for shorter distances
Troubleshooting
- No movement: Check power and ground connections
- Wrong direction: Swap A and B signals
- Erratic readings: Check for noise, use differential if available
- Missing counts: Verify signal levels and cable integrity