FG4KK-2048G-90G-NG should be handled as a 2048 PPR glass-disk redundant 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, controller scaling, and coupling preload. The main failure boundary is a redundant feedback system that produces stable pulses on both outputs but reports speed deviation, direction disagreement, or reference mismatch because the two terminal-box signal paths are not matched. Typical production lead time: 15 working days.
This configuration belongs to the FG 4 optical incremental encoder platform for heavy-duty industrial environments. The 2048 PPR value belongs to the preferred glass-disk pulse-rate group, so replacement should be checked for both glass-disk signal stability and redundant-channel consistency. The KK version uses two terminal boxes and two scanning/evaluation systems, not a single K terminal-box layout. Both feedback paths must be verified separately for terminal assignment, shield bonding, supply integrity, counter input compatibility, phase sequence, and marker-pulse interpretation.
System Limits
The first system limit is 2048 PPR redundant scaling. Both feedback paths must use the same pulse count, edge-counting mode, speed-conversion factor, and direction logic. If one counter is configured for 2000, 1024, 4096, or another pulse rate, the machine may show speed deviation or position disagreement even when both A/B outputs look electrically stable.
The second limit is dual-box A/B/N 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 stability. At 2048 PPR, counter frequency margin is wider than with 4096, 5000, or 8192 PPR versions, but shield discontinuity, loose cable glands, moisture inside either terminal box, inverter-side routing, coupling preload, shaft runout, or radial load can still appear as redundant-channel jitter.
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, and verify the 2048 PPR scaling on both paths.
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 2048 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-2048G-90G-NG |
| Encoder type | Heavy-duty optical incremental encoder |
| Series | FG 4 |
| Connection structure | KK redundant dual terminal boxes |
| Pulses per revolution | 2048 PPR |
| Pulse disk class | Preferred glass-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 | 2048 PPR redundant scaling, dual-box signal matching, A/B phase, N marker behavior, terminal-box shielding |
