FG4KK-1024G-90G-NG should be handled as a redundant 1024 PPR FG 4 feedback encoder, where EncoderWorks can configure a custom compatible replacement solution around the 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. The main failure boundary is a machine that accepts one clean feedback channel but reports channel disagreement, direction mismatch, or reference-position error when the redundant 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 1024 PPR value is a preferred nickel-disk pulse rate, so the replacement task is not an extreme high-frequency case; it is mainly a redundant scaling, terminal-box, phase, and marker-consistency task. The KK version uses two terminal boxes and two scanning/evaluation systems, not a single K terminal-box layout. Both signal 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 1024 PPR redundant scaling. Both feedback paths must use the same pulse count, edge-counting mode, speed-conversion factor, and direction logic. If one counter input is set differently, the machine may show speed deviation or position disagreement even though both A/B pulse trains look stable on an oscilloscope.
The second limit is A/B/N channel consistency. Each terminal box must preserve the expected A, /A, B, /B, N, and /N relationship. If one phase pair is swapped, one inverted signal is omitted, or one marker input is interpreted differently, the controller may detect direction mismatch, homing error, or zero-reference disagreement.
The third limit is EMC and mechanical preload. A-/A, B-/B, and N-/N should be routed as paired shielded conductors on both redundant channels. Loose cable glands, moisture inside either terminal box, long exposed shield drains, inverter-side cable routing, coupling misalignment, axial preload, radial load, or shaft shock can create edge jitter that appears as redundant-channel instability.
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 read by one drive, two independent counters, or a safety comparison 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 speed range.
Custom Compatible Solution
EncoderWorks can configure the replacement around the installed redundant feedback system:
- Match 1024 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-1024G-90G-NG |
| Encoder type | Heavy-duty optical incremental encoder |
| Series | FG 4 |
| Connection structure | KK redundant dual terminal boxes |
| Pulses per revolution | 1024 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 | 1024 PPR scaling, KK channel agreement, N marker behavior, dual terminal-box shielding, coupling preload |
