EncoderWorks develops a concise custom compatible solution for FGH4K-100G-90G-NG/20P, focused on preserving 100 PPR incremental hollow-shaft feedback where low-speed counting, reference-pulse reliability, and EMC grounding are more important than high-frequency counter margin. The replacement fails when the controller scaling is changed correctly, but the A/B phase order, NG reference pulse, shield path, or torque bracket freedom is not restored in the field installation. Typical production lead time: 15 working days.
Where the System Fails First
The controller reads FGH4K-100G-90G-NG/20P as an incremental hollow-shaft encoder with A/B square-wave signals shifted by 90° and an NG reference pulse with inverted signal. The FGH 40 manual defines the square-wave output as a current-limited, short-circuit-proof push-pull line driver, with 12–30 VDC supply and a maximum frequency of 200 kHz unless a different value is specified.
This replacement fails when 100 PPR is treated as too simple to verify. Low pulse count reduces counter load, but it also makes each missed edge more visible in speed or position calculation. If the controller depends on one reference pulse per revolution, a weak NG signal or wrong phase relationship can create homing errors even when the encoder appears electrically healthy.
A stable replacement must first reproduce the original 100 PPR count, A/B 90° phase relationship, NG reference behavior, and shield grounding path before the encoder can be judged compatible.
Hollow-Shaft and Low-Pulse Boundary
The /20P structure indicates a 20 mm hollow shaft with feather key. The manual warns against using a hammer 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-100G-90G-NG/20P, the unique checkpoint is low-pulse feedback accuracy, not frequency overload. The signal may look slow and easy to count, but poor grounding, cable routing near motor power, or a preloaded torque bracket can still create drift, false reference behavior, or unstable low-speed feedback.
Installation Notes
- Set the controller counter value before startup
- Check A/B phase order against actual machine rotation
- 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, motor, brake, and contactor wiring
Key Data
- Model: FGH4K-100G-90G-NG/20P
- Type: Incremental hollow-shaft encoder
- Pulse rate: 100 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: low-speed counter scaling, NG reference stability, shield grounding, hollow-shaft alignment
