EncoderWorks builds a concise custom compatible solution for FGH4K-1024G-90G-NG/20P, focused on preserving 1024 PPR incremental feedback while keeping the 20P hollow-shaft mounting, NG reference pulse, and EMC grounding path stable. The replacement fails when the controller count is correct, but the reference channel, A/B phase order, shield bonding, or torque bracket freedom is not restored in the real machine. Typical production lead time: 15 working days.
Where the System Fails First
The controller reads FGH4K-1024G-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 lists 1024 PPR as a standard pulse rate and defines the square-wave output as a current-limited, short-circuit-proof push-pull line driver. The normal supply range is 12–30 VDC, with maximum frequency listed as 200 kHz unless otherwise specified.
This replacement fails when 1024 PPR is treated as only a safe, low-frequency counter value. In many field systems, the first fault is not counter overload; it is a missing, noisy, or wrongly phased reference pulse. Homing may become inconsistent even when the A/B channels look stable.
A stable replacement must first reproduce the original 1024 PPR scaling, A/B phase relationship, NG reference behavior, and shield grounding path before the encoder can be judged compatible.
Hollow-Shaft and Reference Boundary
The /20P code indicates a 20 mm hollow shaft with feather key. The manual warns against hammer impact during mounting and requires careful adapter-shaft alignment; the maximum radial runout of the adapter shaft is 0.05 mm. The link rod must also rotate freely around the link rod heads, otherwise bearing damage may occur.
For FGH4K-1024G-90G-NG/20P, the unique checkpoint is standard-count reference reliability. If the cable shield is weak, the cable gland is loose, or the grounding strap is not connected to a nearby bare-metal point, the machine may show intermittent zero-reference errors rather than complete encoder failure.
Installation Notes
- Set the controller counter value before startup
- Check A/B phase order against actual rotation direction
- Test the NG reference pulse during slow rotation
- Mount the hollow shaft without hammer impact
- Keep the torque bracket 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-1024G-90G-NG/20P
- Type: Incremental hollow-shaft encoder
- Pulse rate: 1024 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: reference pulse grounding, phase order, hollow-shaft alignment, EMC cable routing
