FG4SS-1200G-90G-NG should be treated as a redundant dual-plug FG 4 encoder, where EncoderWorks can configure a custom compatible replacement solution only if the 1200 PPR nickel-disk scaling, SS dual 15-pole plug layout, duplicated scanning systems, A/B 90° phase relationship, inverted signal pairs, N marker behavior, shielded plug wiring, and coupling preload remain matched on both feedback paths. The main failure boundary is a machine that runs from one plug channel but reports speed deviation, direction disagreement, or reference mismatch when both redundant plug outputs are compared. Typical production lead time: 15 working days.
This configuration belongs to the FG 4 optical incremental encoder platform for heavy-duty industrial environments. The 1200 PPR value is a preferred nickel-disk pulse rate, so the replacement focus is stable redundant speed scaling, plug pin assignment, phase sequence, and marker consistency rather than high-frequency glass-disk overload. The SS version should be handled as a redundant dual 15-pole industrial plug encoder, not as a single S plug encoder or a KK dual-terminal-box unit. Both plug-connected paths must be checked separately for pin mapping, shield connection, supply integrity, counter input compatibility, A/B phase sequence, and marker-pulse interpretation.
System Limits
The first system limit is 1200 PPR redundant scaling. Both feedback paths must use the same pulse count, edge-counting mode, speed-conversion factor, and direction logic. If one counter is configured for 1000, 1024, 600, or another pulse value, the machine may show speed deviation even when both square-wave signals look electrically stable.
The second limit is dual 15-pole plug mapping. Each plug must preserve the expected A, /A, B, /B, N, and /N relationship. If one phase pair is swapped, one inverted signal is omitted, or one marker input is interpreted differently, the controller may detect direction mismatch, homing error, or zero-reference disagreement.
The third limit is plug shielding and mechanical preload. The SS plug format is not the same installation boundary as KK terminal boxes. Plug seating, cable strain, shield bonding, moisture protection, pin contact condition, and lateral cable stress should be checked on both plug assemblies. Coupling misalignment, axial preload, radial load, or shaft shock can reduce redundant-channel stability and appear as comparison jitter.
Wiring & Installation
Before replacement, document both 15-pole plug connections separately. Record the basic channel, 90° channel, marker pulse, inverted signals, supply voltage, GND, shield connection, LED-check or diagnostic output if used, and the controller or safety input connected to each plug. Confirm whether both channels are read by one drive, two independent counters, or a safety comparison circuit, and verify 1200 PPR scaling on both paths.
During installation, fit the coupling smoothly and do not strike the shaft or housing. Keep the encoder centered, control angular and parallel offset, and avoid axial preload. Route both sets of A-/A, B-/B, and N-/N through paired shielded conductors, keep the cables away from inverter output, motor, brake, and contactor wiring, and avoid lateral cable stress at the plugs. After commissioning, verify pulse count, speed scaling, direction, N marker behavior, redundant-channel agreement, plug seating, shield continuity, and signal stability through the full operating speed range.
Custom Compatible Solution
EncoderWorks can configure the replacement around the installed redundant plug interface:
- Match 1200 PPR square-wave incremental output with 0°/90° channel behavior and inverted signal pairs
- Preserve SS dual 15-pole industrial plug structure, redundant channel separation, N marker behavior, supply range, and output level
- Adapt the FG 4 mechanical envelope, shaft interface, flange or foot mounting requirement, coupling alignment, and plug cable layout
- Review 100 kHz / 150 kHz frequency margin, shielded twisted-pair routing, plug pin mapping, bearing load, and redundant-channel agreement
Key Data
| Item | Data |
|---|---|
| Model | FG4SS-1200G-90G-NG |
| Encoder type | Heavy-duty optical incremental encoder |
| Series | FG 4 |
| Connection structure | SS redundant dual 15-pole industrial plugs |
| Pulses per revolution | 1200 PPR |
| Pulse disk class | Preferred nickel-disk pulse rate |
| Signal output | Square wave, 0° and 90° channels |
| Inverted signals | Yes, Option G |
| Marker pulse | Option N with inverted marker signal |
| Redundant structure | Two scanning/evaluation systems |
| Plug capacity | Up to 13 outputs per S plug format |
| Plug protection boundary | IP55 |
| Supply voltage | 12–30 VDC |
| Output type | Differential line driver / push-pull style output |
| Frequency range | 0–100 kHz standard, up to 150 kHz if specified |
| Standard shaft | Ø11j6 × 30 mm |
| Optional shaft | Ø14j6 × 30 mm |
| Key checks | 1200 PPR scaling, dual 15-pole plug mapping, A/B phase, N marker behavior, redundant-channel agreement |
