EncoderWorks develops a concise custom compatible solution for FGH4KK-1024G-90G-NG/20P, focused on preserving 1024 PPR incremental hollow-shaft feedback through the KK dual terminal-box structure. The replacement fails when the counter value is correct, but the NG reference pulse, A/B phase order, terminal-box shield path, or torque bracket freedom is not restored with the same field behavior. Typical production lead time: 15 working days.
Where the System Fails First
The controller reads FGH4KK-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 describes the square-wave output as 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 a higher value is requested.
This replacement fails when the machine accepts the A/B pulses but loses repeatable zero or index behavior. At 1024 PPR, the first field problem is usually not counter overload. It is a reference-channel, phase-order, shielding, or terminal-box contact issue.
A stable replacement must first reproduce the original 1024 PPR scaling, NG reference pulse behavior, A/B 90° phase relationship, and KK terminal-box 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 installation and requires careful adapter-shaft alignment. It also specifies 0.05 mm maximum radial runout of the adapter shaft and states that the link rod must rotate freely around the link rod heads to avoid bearing damage.
For FGH4KK-1024G-90G-NG/20P, the unique checkpoint is reference-pulse reliability through a dual terminal-box layout. A loose terminal, weak shield bond, poor cable-gland sealing, or preloaded torque bracket can cause intermittent homing errors even when the encoder output appears normal.
Installation Notes
- Set the controller counter value before startup
- 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 terminal-box entries and cable glands before operation
- Keep shield bonding short, continuous, and low-resistance
- Route signal cables away from inverter and motor power wiring
Key Data
- Model: FGH4KK-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
- Connection style: KK dual terminal-box structure
- Protection: IP65 standard
- Standard temperature: 0°C to +70°C
- Main replacement focus: reference pulse reliability, KK terminal-box shielding, phase order, hollow-shaft alignment
