EncoderWorks develops a concise custom compatible solution for FGH4K-2828G-90G-NG/20P, focused on preserving 2828 PPR incremental hollow-shaft feedback where the pulse count is not a common standard value. The replacement fails when the encoder mounts correctly, but the controller is configured with a nearby standard pulse count, causing speed, position, or reference behavior to drift even though the A/B signals look normal. Typical production lead time: 15 working days.
Where the System Fails First
The controller reads FGH4K-2828G-90G-NG/20P as an incremental hollow-shaft encoder with A/B square-wave channels shifted by 90° and an NG reference pulse with inverted signal. The FGH 40 manual states that standard and special pulse rates are available, including customer-specific pulse counts, while square-wave versions use a current-limited, short-circuit-proof push-pull line driver. The supply range is 12–30 VDC, with maximum frequency listed as 200 kHz unless otherwise specified.
This replacement fails when 2828 PPR is rounded, replaced by 2800, 2048, 2500, or another easier catalog value. The machine may still count pulses, but the scaling error accumulates into wrong speed feedback, wrong travel distance, or unstable synchronization.
A stable replacement must first reproduce the original 2828 PPR count, A/B 90° phase relationship, NG reference behavior, and hollow-shaft mechanical boundary before the encoder can be judged compatible.
Hollow-Shaft and Scaling Boundary
The /20P code indicates a 20 mm hollow shaft with feather key. The manual warns against hammer impact during installation, requires careful adapter-shaft alignment, and specifies 0.05 mm maximum radial runout of the adapter shaft. It also states that the link rod must rotate freely around the link rod heads; otherwise bearing damage may occur.
For FGH4K-2828G-90G-NG/20P, the unique checkpoint is non-standard pulse scaling. EMC grounding, shielding, and torque bracket freedom still matter, but the first commissioning error is often parameter substitution: the replacement encoder is mechanically close, yet the controller scaling no longer matches the original machine calculation.
Installation Notes
- Confirm the controller is set to the exact non-standard pulse count
- Check A/B phase order against actual shaft rotation
- Test the NG reference pulse during slow rotation
- Mount the hollow shaft without hammer impact
- Keep the torque bracket and link rod free from preload
- Tighten cable glands and terminal-box entries before operation
- Keep shield bonding short, continuous, and low-resistance
- Route signal cables away from inverter and motor power wiring
Key Data
- Model: FGH4K-2828G-90G-NG/20P
- Type: Incremental hollow-shaft encoder
- Pulse rate: 2828 PPR
- Signal format: G, 90° A/B square-wave
- Reference pulse: NG, with inverted signal
- Supply voltage: 12–30 VDC
- Output: Push-pull line driver
- Max frequency: 200 kHz
- Hollow shaft: 20P
- Protection: IP65 standard
- Standard temperature: 0°C to +70°C
- Main replacement focus: non-standard counter scaling, NG reference behavior, shield grounding, hollow-shaft alignment
