FGHJ4KK-1024-90G-NG/25K Encoder with Isolated Clamping-Bore Feedback

For FGHJ4KK-1024-90G-NG/25K, EncoderWorks can configure a custom compatible replacement solution only if the 1024 PPR nickel-disk scaling, J isolated-bearing construction, KK redundant dual terminal-box layout, /25K clamping hollow-shaft bore, A/B 90° phase relationship, N marker behavior, torque bracket freedom, adapter-shaft run-out, and shielded signal transmission remain matched. The main failure boundary is a hollow-shaft drive that receives pulses but shows speed deviation, direction error, marker disagreement, redundant-channel mismatch, bearing-current damage, or pulse jitter because the pulse count, clamping bore, terminal-box mapping, torque support, or isolation path has changed. Typical production lead time: 15 working days.

This model belongs to the FGHJ 4 isolated hollow-shaft incremental encoder platform. The 1024 PPR value should be treated as a preferred nickel-disk pulse rate. The /25K suffix changes the mechanical replacement boundary because the hollow shaft uses a clamping-bore interface rather than the /20P feather-key interface used on many related variants. The model code also differs from 1024G-90G-NG versions, so the exact original terminal assignment must be confirmed before production instead of assuming a fully identical inverted-output set.

System Limits

The first system limit is 1024 PPR reference scaling. If either controller path is configured for 1000, 1200, 2048, or another pulse value, both outputs may appear electrically stable while speed, travel, and synchronization values become wrong. Edge-counting mode, gear ratio, direction logic, and machine conversion factors should be confirmed on both redundant paths.

The second limit is KK redundant terminal-box agreement. Each terminal box must preserve the original A/B/N channel assignment and the available inverted outputs exactly as expected by the controller or comparison circuit. If one 90° phase channel is swapped, one inverted output is assumed but not present, one shield reference differs, or the N marker signal is wired differently between boxes, the machine may fail during homing, direction reversal, or redundant-channel comparison.

The third limit is the /25K clamping hollow-shaft interface. The bore must clamp evenly on the prepared shaft without forcing the encoder body into position. Incorrect clamp tightening, shaft undersize, shaft oversize, adapter-shaft eccentricity, axial movement, or torque-arm binding can load the bearings and appear as pulse jitter or marker instability. Because this is an isolated-bearing version, the isolation path must also remain intact so shaft currents do not pass through the encoder bearings.

Wiring & Installation

Before replacement, document both terminal-box connections separately. Record supply voltage, GND, shield connection, A/B/N signal sequence, the exact inverted outputs present in the installed unit, and any LED-check or diagnostic output used by the control system. Confirm that both counter inputs are scaled for 1024 PPR and that the system expects the same 0°/90° phase sequence and N marker behavior.

During mechanical installation, clean the customer shaft, clamping surface, centering area, bolting faces, and fastening threads. Slide the hollow-shaft unit into position without hammering, align the adapter shaft carefully, and tighten the /25K clamp only after the encoder is correctly seated. The torque bracket should remain free at the link heads and should not transmit bending load into the bearings.

For signal stability, route feedback wiring away from inverter, motor, brake, contactor, and power cables. Use shielded cable, keep signal-pair routing consistent, and maintain continuous shield bonding. The isolation requirement should be preserved so potential differences or shaft currents do not bypass the insulated bearing arrangement. After commissioning, verify pulse count, direction, N marker repeatability, redundant-channel agreement, clamp stability, shielding continuity, isolation boundary, and stable operation through the required speed range.

Custom Compatible Solution

EncoderWorks can configure the replacement around the installed FGHJ 4 isolated hollow-shaft and redundant terminal-box interface:

• Match 1024 PPR square-wave incremental output with 0°/90° channel behavior and the required installed signal set
• Preserve J isolated-bearing construction, KK dual terminal-box structure, N marker behavior, supply range, output level, and redundant-channel compatibility
• Adapt the FGHJ 4 /25K clamping hollow-shaft bore, shaft fit, clamp position, torque bracket geometry, sealing boundary, and cable-entry orientation
• Review 100 kHz / 150 kHz frequency margin, terminal-box mapping, shielded routing, bearing isolation, clamp tightening, and redundant-channel agreement

Key Data

Related Models

1. FGHJ40SS-2048G-90G-NG/20P Hollow-Shaft Encoder with Isolated Dual-Plug Feedback
2. FGHJ4S-1024G-90G-NG/20P Hollow-Shaft Encoder with Isolated Plug Feedback
3. FGHJ40S-1024G-90G-NG/20P Hollow-Shaft Encoder with Isolated EMC Plug Feedback
4. FGHJ4KK-2048G-90G-NG/20P Hollow-Shaft Encoder with Isolated Dual-Box Feedback