The optical hollow shaft encoder FGH 8 is supplied with a large hollow shaft bore up to 80 millimeters in size. Thanks to the stable, ribbed cast aluminium design and the flat style construction it is easily possible to attach other devices such as speed switches and absolute encoder or a combination of these without a coupling or flange. The device is available with radial shaft seals and high ingress protection class rating up to IP56 (IP66) for use in permanently oily/wet environments. The precision nickel pulse disk offers up to 4096 pulses. The electronics are integrated in the encoder or rather in the scanning head. A redundant version is available with two identical scanning and evaluation electronics. The encoder is insensitive to the effects of mechanical stress factors such as vibration, axial bearing play and thermal expansion.