When FG40KK-1200G-90G-NG is replaced in an existing drive system, EncoderWorks can configure a custom compatible replacement solution around the 1200 PPR count, A/B 90° phase relationship, inverted channels, NG reference pulse, KK dual-terminal-box wiring, EMC grounding, and coupling preload. The key failure boundary is not simply pulse loss; it is loss of reference repeatability, wrong counter scaling, or unstable direction detection after the encoder has been mechanically and electrically changed. Typical production lead time: 15 working days.
This configuration belongs to the FG 40 heavy-duty incremental encoder platform. It provides 1200 pulses per revolution with square-wave output, a basic 0° channel A, a 90° pulse channel B, inverted signal channels, and an NG reference pulse with inverted signal. The KK version should be treated as a dual terminal-box or redundant-style layout, not as a single-terminal-box K encoder. Replacement work should focus on controller scaling, A/B phase accuracy, N pulse position, shield bonding, terminal-box routing, cable-gland sealing, and shaft coupling alignment.
System Limits
The first system limit is counter scaling. A 1200 PPR encoder will not produce the same speed or position calculation as 1000, 1024, 2048, or 2500 PPR versions. If the controller parameter remains set for another pulse count, the feedback can look electrically stable while the drive calculates the wrong travel, speed, or machine position.
The second limit is the NG reference pulse. The N and /N signals must remain repeatable at the expected mechanical position. If the reference pulse polarity, terminal assignment, or timing changes, the machine may count normally but fail during homing, zero return, synchronization, or position recovery after shutdown.
The third limit is mechanical and EMC installation. Shaft coupling misalignment, axial preload, radial load, weak shield bonding, or signal wiring routed close to inverter and motor cables can degrade edge quality. With a KK layout, separated signal paths or redundant terminal-box wiring must also be preserved.
Wiring & Installation
Before replacement, record the wiring for A, /A, B, /B, N, /N, supply voltage, GND, shield, and any diagnostic or error signal used in the cabinet. Confirm how both terminal boxes are used: redundant feedback, separated routing, service isolation, or signal distribution.
During installation, mount the coupling without force and do not strike the shaft or housing. Keep angular error, axial offset, and parallel displacement within the machine coupling tolerance. Route signal and supply wiring away from inverter output, motor, brake, contactor, and solenoid cables. Use low-impedance grounding, maintain shield continuity, tighten cable glands, and seal the terminal boxes before startup. After commissioning, verify pulse count, direction, N reference repeatability, counter scaling, terminal-box separation, and signal stability over the full operating speed range.
Custom Compatible Solution
EncoderWorks can configure the replacement around the installed drive and counter system:
- Match 1200 PPR square-wave incremental output with A/B 90° phase relationship and inverted channels
- Preserve NG reference pulse behavior, KK dual-terminal-box layout, supply voltage, output level, and counter input compatibility
- Adapt the FG 40 mechanical envelope, flange or foot mounting requirement, shaft interface, coupling alignment, and cable-gland layout
- Review counter scaling, shield grounding, EMC routing, terminal separation, bearing load, cable sealing, and reference-pulse repeatability
Key Data
| Item | Data |
|---|---|
| Model | FG40KK-1200G-90G-NG |
| Encoder type | Heavy-duty incremental encoder |
| Series | FG 40 |
| Connection structure | KK dual terminal box / redundant-style version |
| Pulses per revolution | 1200 PPR |
| Pulse category | Standard pulse rate |
| Signal output | Square wave A/B, 90° phase |
| Inverted signals | Yes |
| Reference pulse | NG, with inverted signal |
| Supply voltage | 12–30 VDC |
| Output type | Push-pull line driver |
| Max frequency | 200 kHz |
| Standard shaft | 11j6 × 30 mm |
| Optional shaft | 14j6 × 30 mm |
| Key checks | Counter scaling, NG reference pulse, A/B phase, dual terminal-box wiring, EMC grounding |
