FG4K-2000G-90G-NG is best replaced as a 2000 PPR glass-disk FG 4 encoder with a standard radial terminal box, where EncoderWorks can configure a custom compatible replacement solution around the A/B 90° phase relationship, inverted signal pairs, N marker pulse, shielded terminal wiring, counter scaling, and coupling preload. The main failure boundary is a machine that receives clean pulses but calculates the wrong speed, loses direction stability, or fails reference recovery because phase, marker, or terminal wiring has changed. Typical production lead time: 15 working days.
This configuration belongs to the FG 4 optical incremental encoder platform for heavy-duty industrial environments. It uses 2000 pulses per revolution, square-wave output, a 0° basic channel, a second channel electrically shifted by 90°, inverted outputs for industrial transmission, and an N marker pulse with inverted marker signal. The K version uses a standard radial terminal box with terminal-strip wiring, not a redundant KK dual-terminal-box structure. Replacement work should focus on controller scaling, 100 kHz standard frequency margin, 150 kHz special-order boundary if applicable, A/B phase accuracy, marker-pulse repeatability, shield bonding, cable-gland sealing, and shaft coupling alignment.
System Limits
The first system limit is 2000 PPR scaling. If the controller is configured for 1024, 1200, 2048, 4096, or another pulse count, the speed and travel calculation will be wrong even when the A/B signals are electrically stable. Edge-counting mode, speed conversion, direction detection, and input frequency margin should be checked before commissioning.
The second limit is 90° phase and marker behavior. The controller must receive A with /A, B with /B, and N with /N as stable paired signals. If the 90° channel phase sequence changes, direction can reverse; if the N marker polarity or timing changes, homing and zero recovery may fail.
The third limit is terminal-box EMC and mechanical preload. Long exposed shield drains, loose cable glands, moisture in the terminal box, or inverter-side cable routing can introduce false edges. Coupling misalignment, axial preload, radial load, or shaft shock can shorten bearing life and create rotational modulation in the pulse train.
Wiring & Installation
Before replacement, record the radial terminal-box wiring for the basic channel, 90° channel, marker pulse, inverted signals, supply voltage, GND, shield, and LED-check or diagnostic output if used. Confirm whether the installed system was designed for the standard 100 kHz frequency range or a specified 150 kHz version.
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 A-/A, B-/B, and N-/N through paired shielded conductors, bond the shield through the terminal box with a short low-impedance path, and keep the cable away from inverter output, motor, brake, and contactor wiring. After commissioning, verify pulse count, speed scaling, direction, N marker repeatability, terminal-box sealing, and signal stability through the full operating speed range.
Custom Compatible Solution
EncoderWorks can configure the replacement around the installed drive and counter system:
- Match 2000 PPR square-wave incremental output with 0°/90° channel behavior and inverted signal pairs
- Preserve N marker pulse behavior, K radial terminal-box layout, supply range, output level, and controller input compatibility
- 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 marker-pulse repeatability
Key Data
| Item | Data |
|---|---|
| Model | FG4K-2000G-90G-NG |
| Encoder type | Heavy-duty optical incremental encoder |
| Series | FG 4 |
| Connection structure | K standard radial terminal box |
| Pulses per revolution | 2000 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 |
| 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 | 2000 PPR scaling, 90° phase, N marker, terminal-box shielding, coupling preload |
