The FG4K is a discontinued heavy-duty encoder series, and official successor models have since been introduced. However, versions featuring a “V” suffix remain relatively easy to misinterpret during replacement selection. In particular, if the internal electronic pulse-doubling function associated with Option V is not properly understood, the pulse count shown in the model number can easily be miscalculated, leading to unnecessary delays and added costs in procurement, commissioning, and field replacement.
Basic Specifications of the FG4K Series
The FG4K series features a standard 115 mm flange and is commonly supplied with 11 mm or 14 mm solid shaft diameters. Differences between individual models lie primarily in output pulse rates, with common values including 1024, 2000, 2048, 2400, 2500, and 4096 PPR.
Certain models in this series carry a “V” suffix, such as:
FG4K-2000G-90G-NG-VFG4K-2048G-90G-NG-VFG4K-2400G-90G-NG-VFG4K-2500G-90G-NG-V
According to official documentation for Option V, the basic channel and $90^\circ$ channel are replaced by internal signal channels operating at twice the pulse count of the physical pulse disk. The two output channels maintain a $90^\circ$ phase displacement with a strict 1:1 duty ratio.
Demystifying the "V" Suffix Pulse Count
The most common misunderstanding involves how to read the pulse count in the model string. Taking the FG4K-2500G-90G-NG-V as an example, it should NOT be interpreted as a 2500 PPR physical disk whose output is further doubled by Option V to deliver 5000 PPR to the PLC.
Instead, Option V utilizes a lower-resolution, mechanically robust pulse disk internally and applies electronic doubling to achieve the final rated output specified in the model code:
- A 2500G-V model uses an internal pulse disk of approximately 1250 lines, electronically doubled to output 2500 PPR.
- Similarly, 2000G-V, 2048G-V, and 2400G-V models correspond to internal disk counts of 1000, 1024, and 1200 lines respectively, with Option V generating the final output rate.
Official manuals explicitly state that Option V is recommended when pulse rates exceeding 1414 PPR are required on standard incremental encoders. This confirms that Option V was designed to overcome the physical line-density limits of heavy-duty pulse disks while avoiding custom disk development costs—not to multiply the rated model number again.
Key Considerations for Field Replacement
When selecting a replacement encoder (whether an original successor or a direct equivalent):
- Do not apply a multiplication factor: The actual target output for replacing an
FG4K-2500G-90G-NG-Vremains 2500 PPR, not 5000 PPR. - Verify total signal architecture: Ensure full compatibility across the required A/B/N channels, inverse signals ($\bar{A}/\bar{B}/\bar{N}$), electrical interface (12-30V HTL / Line Driver), and mechanical mounting dimensions (115 mm flange and shaft diameter).
Custom Replacement Solutions
High-reliability, custom replacement solutions for legacy FG4K encoders are widely available. Originally developed by SIVIDI at the request of steel and metallurgical enterprises, these customized solutions match the original electrical interface, heavy-duty vibration resistance, and mechanical installation footprints directly. Users do not need to calculate internal disk ratios manually—providing the complete original nameplate model number is generally sufficient to specify a fully compatible drop-in replacement.
Because these heavy-duty encoders are frequently sourced across international supply chains, avoiding model misinterpretation prior to ordering prevents costly downtime and freight expense. Clarifying the logic of Option V ensures a seamless field replacement from day one.
