FG4K-2500G-90G-NG-V is a discontinued incremental encoder, and original spare units are no longer readily available. Although newer products were later introduced for the FG 4 series, some versions differ from the older configuration in the way the signals are generated. For this reason, selecting a replacement based only on the mechanical dimensions and the “2500 PPR” value may not fully match the requirements of the existing equipment.
This model uses a K-type terminal box and has a rated pulse output of 2500 PPR. It also includes a second pulse channel with a 90° phase shift, a marker pulse, and the corresponding inverted signals. In the model code, G indicates inverted output signals, 90 indicates the second pulse channel shifted by 90°, and N indicates one marker pulse per revolution.
The most easily overlooked technical feature of FG4K-2500G-90G-NG-V is the final “V”. Here, V indicates Option V electronic pulse doubling. This does not mean that the 2500 PPR value should be doubled again. Instead, the encoder internally uses electronic multiplication so that the 0° and 90° output channels have twice the pulse count of the internal pulse disk. For this model, 2500 PPR is already the final rated output pulse count.
The purpose of Option V is therefore related to how the pulse signals are generated internally, rather than requiring the user to apply another ×2 calculation to the model number. The doubled 0° and 90° channels still maintain a 90° phase relationship and a 1:1 duty ratio, and they can be processed externally in the same way as conventional incremental signals.
For this reason, a conventional 2500 PPR encoder should not automatically be treated as equivalent to FG4K-2500G-90G-NG-V. A proper replacement needs to reproduce the required 0° / 90° phase relationship, marker pulse, inverted signals, and the output structure associated with Option V.
The original FG 4 series uses a 12–30 VDC supply range, while the customized product uses 10–30 VDC. For equipment where the original spare part is no longer available, the customized solution is developed to retain the required 2500 PPR output and the relevant Option V signal characteristics rather than simply matching the pulse number alone.
