EncoderWorks supports a concise custom compatible solution for FGH4KK-1200G-90G-NG/20P, focused on preserving 1200 PPR incremental hollow-shaft feedback through the KK dual terminal-box wiring structure. The replacement fails when the controller scaling is correct, but the NG reference channel, A/B phase order, shield bonding, or torque bracket freedom is not restored with the same low-resistance grounding behavior. Typical production lead time: 15 working days.
Where the System Fails First
The controller reads FGH4KK-1200G-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 1200 PPR as a standard pulse rate. For square-wave pulse versions, the output stage is a current-limited, short-circuit-proof push-pull line driver, with 12–30 VDC supply and 200 kHz maximum frequency unless otherwise specified.
This replacement fails when 1200 PPR is treated as a moderate counter load and the wiring enclosure is ignored. The pulse frequency is usually manageable, but the dual terminal-box layout adds more places where shielding, cable glands, terminal seating, and grounding can become the first fault source.
A stable replacement must first reproduce the original 1200 PPR scaling, 90° A/B phase relationship, NG reference behavior, and KK terminal-box shield path before the encoder can be judged compatible.
Hollow-Shaft and Grounding 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 FGH4KK-1200G-90G-NG/20P, the unique checkpoint is standard-pulse stability through dual terminal-box grounding. The shield path should stay short and continuous, cable routing should avoid inverter and motor power wiring, and the grounding strap should connect to a nearby bare-metal grounding point. If this boundary is weak, the fault usually appears as speed jitter, reference inconsistency, or intermittent counter noise.
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, motor, brake, and contactor wiring
Key Data
- Model: FGH4KK-1200G-90G-NG/20P
- Type: Incremental hollow-shaft encoder
- Pulse rate: 1200 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: dual terminal-box grounding, 1200 PPR scaling, NG reference stability, hollow-shaft alignment
