FG4KK-1200G-90G-NG is a redundant nickel-disk FG 4 replacement case, where EncoderWorks can configure a custom compatible replacement solution only if the 1200 PPR scaling, KK dual-terminal-box structure, duplicated scanning systems, A/B 90° phase relationship, inverted signal pairs, N marker behavior, shielded twisted-pair routing, and coupling preload are preserved together. The main failure boundary is a redundant feedback system that runs normally on one channel but reports direction mismatch, speed deviation, or reference disagreement when both terminal-box outputs are compared. Typical production lead time: 15 working days.
This configuration belongs to the FG 4 optical incremental encoder platform for heavy-duty industrial environments. The 1200 PPR value is a preferred nickel-disk pulse rate, so the replacement focus is not extreme frequency loading but stable scaling, repeatable phase behavior, and redundant-channel consistency. The KK version uses two terminal boxes and two scanning/evaluation systems, not a single K terminal-box layout. Both output paths must be checked separately for terminal assignment, shield bonding, supply integrity, controller input compatibility, and marker-pulse interpretation.
System Limits
The first system limit is 1200 PPR redundant scaling. Both channels must be interpreted with the same pulse count, edge-counting mode, and speed-conversion factor. If one counter input is configured differently, the system may show speed deviation or position disagreement even when both signal sets are electrically clean.
The second limit is marker-pulse behavior. In a KK redundant version, the two marker pulses are not simply identical terminal duplicates; their mechanical relationship must be considered during commissioning. If the controller expects a defined marker offset and one channel is rewired or reinterpreted, homing, zero recovery, or channel comparison may fail.
The third limit is terminal-box EMC and mechanical preload. A-/A, B-/B, and N-/N should be routed as paired shielded conductors on both terminal boxes. Loose glands, moisture, long exposed shield drains, inverter-side routing, coupling misalignment, axial preload, or radial load can create edge jitter that appears as redundant-channel disagreement.
Wiring & Installation
Before replacement, document both KK terminal boxes separately. Record the basic channel, 90° channel, marker pulse, inverted signals, supply voltage, GND, shield connection, LED-check or diagnostic output if used, and the controller or safety input connected to each system. Confirm whether the two channels are compared by a drive, PLC, or safety circuit.
During installation, fit the coupling smoothly and do not strike the shaft or housing. Keep the encoder centered, control angular and parallel offset, and avoid axial preload. Route both sets of A-/A, B-/B, and N-/N through shielded twisted pairs, keep the cable away from inverter output, motor, brake, and contactor wiring, and maintain terminal-box sealing on both sides. After commissioning, verify pulse count, speed scaling, direction, N marker behavior, redundant-channel agreement, terminal-box sealing, and signal stability through the full operating range.
Custom Compatible Solution
EncoderWorks can configure the replacement around the installed redundant feedback system:
- Match 1200 PPR square-wave incremental output with 0°/90° channel behavior and inverted signal pairs
- Preserve KK dual-terminal-box structure, redundant channel separation, N marker behavior, supply range, and output level
- Adapt the FG 4 mechanical envelope, shaft interface, flange or foot mounting requirement, coupling alignment, and cable-gland layout
- Review 100 kHz / 150 kHz frequency margin, shielded twisted-pair routing, EMC grounding, terminal-box sealing, bearing load, and redundant-channel agreement
Key Data
| Item | Data |
|---|---|
| Model | FG4KK-1200G-90G-NG |
| Encoder type | Heavy-duty optical incremental encoder |
| Series | FG 4 |
| Connection structure | KK redundant dual terminal boxes |
| Pulses per revolution | 1200 PPR |
| Pulse disk class | Preferred nickel-disk pulse rate |
| Signal output | Square wave, 0° and 90° channels |
| Inverted signals | Yes, Option G |
| Marker pulse | Option N with inverted marker signal |
| Redundant structure | Two scanning/evaluation systems |
| Supply voltage | 12–30 VDC |
| Output type | Differential line driver / push-pull style output |
| Frequency range | 0–100 kHz standard, up to 150 kHz if specified |
| Standard shaft | Ø11j6 × 30 mm |
| Optional shaft | Ø14j6 × 30 mm |
| Key checks | 1200 PPR scaling, marker-pair offset, KK channel agreement, terminal-box shielding, coupling preload |
