FG4KK-2500G-90G-NG is a special-pulse redundant FG 4 feedback encoder, where EncoderWorks can configure a custom compatible replacement solution only if the 2500 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 confirmed as one matched feedback boundary. The main failure point is a redundant system that appears stable on one channel but reports speed deviation, direction mismatch, 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. Unlike 2048, 4096, 5000, or 8192 PPR versions listed as preferred glass-disk pulse rates, the 2500 PPR value should be treated as a special pulse-rate request. Replacement work should therefore verify pulse-disc availability, controller scaling, frequency margin, terminal assignment, shield bonding, supply integrity, phase sequence, and marker-pulse interpretation on both redundant paths.
System Limits
The first system limit is 2500 PPR redundant scaling. Both feedback paths must use the same pulse count, edge-counting mode, speed-conversion factor, and direction logic. If one counter remains configured for 2048, 2000, 4096, or another value, the machine may show speed deviation or position disagreement even when both A/B signals look clean.
The second limit is special pulse-rate confirmation. Because 2500 PPR is not one of the listed preferred FG 4 glass-disk pulse rates, the replacement should not be treated as a routine catalog pulse selection. Pulse count, disk execution, output frequency margin, and controller input bandwidth must be checked together before commissioning.
The third limit is KK terminal-box 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 disagreement, homing error, or zero-reference mismatch. Shield discontinuity, loose cable glands, moisture, or coupling preload can also 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 both channels are read by one drive, two independent counters, or a safety comparison circuit, and verify the 2500 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 2500 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 special pulse-rate feasibility, 100 kHz / 150 kHz frequency margin, shielded twisted-pair routing, terminal-box sealing, bearing load, and redundant-channel agreement
Key Data
| Item | Data |
|---|---|
| Model | FG4KK-2500G-90G-NG |
| Encoder type | Heavy-duty optical incremental encoder |
| Series | FG 4 |
| Connection structure | KK redundant dual terminal boxes |
| Pulses per revolution | 2500 PPR |
| Pulse disk class | Special pulse rate on request |
| 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 | 2500 PPR scaling, special pulse-rate confirmation, KK channel agreement, N marker behavior, terminal-box shielding |
