Heidenhain: Angle Encoders (ERA 4000, ERA 4282 C, ERA 7000 & ERA 8000 Series)

The term angle encoder is typically used to describe encoders that have an accuracy of better than ± 5“ and a line count above 10000. In contrast, rotary encoders are encoders that typically have an accuracy of more than ± 10“. Angle encoders are found in applications requiring precision angular measurement to accuracies within several arc seconds.

Examples:

Absolute angle encoders without integral bearing

The angle encoders without integral bearing (modular angle encoders) ERP, ERO and ERA consist of two components—a scanning head and a graduation carrier, which must be aligned with each other during mounting. The eccentricity of the shaft as well as installation and adjustment therefore have a decisive effect on the achievable accuracy.

Modular angle encoders are available with various graduation carriers

Angle encoders without integral bearing are designed for integration in machine elements or components. They are designed to meet the following requirements:

Because angle encoders without integral bearing are supplied without enclosure, the required degree of protection must be ensured through proper installation.

ERA 4000 Series

The ERA 4000 modular angle encoders are supplied as two components: the scale drum and the scanning head.

The scanning heads of the ERA 4000 series feature very compact dimensions. The scale drums of the ERA 4000 are available in different versions to suit the particular application. The ERA 4x80 versions are available with various grating periods depending on the accuracy requirements. The appropriate scanning heads are shown in the table at right. Special design measures are required to protect the ERA from contamination. The ERA 4480 angle encoders are also available for various drum diameters with a protective cover. A special scanning head (with compressed-air inlet) is needed for versions with protective cover. The protective cover suited to the scale drum diameter must be ordered separately.

Special design features of the ERA modular angular encoders assure comparatively fast mounting and easy adjustment.

Mounting the ERA 4x00 scale drum

The scale drum is slid onto the drive shaft and fastened with screws. The scale drum is centered via the centering collar on its inner circumference. The drum does not need to be adjusted. HEIDENHAIN recommends a slight oversize of the shaft on which the scale drum is to be mounted. For mounting, the scale drum may be slowly warmed on a heating plate over a period of approx. 10 minutes to a maximum temperature of 100 °C.

Mounting the ERA 4202 scale drum

The scale drum is centered over three positions at 120° increments on its circumference and fastened with screws. The benefits of three-point centering and the solid design of the scale drum make it possible to attain a very high accuracy when the encoder is mounted, with relatively little mounting effort. The positions for centering are marked on the scale drum

Mounting the scanning head

In order to mount the scanning head, the spacer foil is held against the circumference of the scale drum. The scanning head is pressed against the foil, fastened, and the foil is removed. ERA 4000 encoders with 20 μm grating period also feature an eccentric bushing for fine adjustment of the scanning field.

Mounting the protective cover

The ERA 4480 modular angle encoders with protective cover are available in various diameters. This cover provides additional protection against contamination when compressed air is applied.

The scale drum and the scanning unit are mounted as described above. The separate spacer foil supplied with the protective cover is placed around the scale drum. It protects the scale drum when mounting the protective cover, and ensures that a constant scanning gap is maintained. Then the protective cover is slid onto the scale drum and secured. The spacer foil is removed. For information about the compressed-air inlet see General mechanical information.

ERA 7000 and ERA 8000 Series

(Mechanical design types and mounting)

The ERA 7000 and ERA 8000 series of angle encoders consist of a scanning unit and a one-piece steel scale tape. The steel scale tape is available up to a length of 30 m. The tape is mounted on: the inside diameter (ERA 7000 series) or the outside diameter (ERA 8000 series) of a machine element.

The ERA 74x0C and ERA 84x0C angle encoders are designed for full-circle applications. Thus, they are particularly suited to hollow shafts with large inside diameters (from approx. 400 mm) and to applications requiring an accurate measurement over a large circumference, e.g. large rotary tables, telescopes, etc. In applications where there is no full circle, or measurement is not required over 360°, circle segments are available.

Model No.: AK ERA 4280, AK ERA 4480, AK ERA 4880, AK ERA 7480, AK ERA 8480, MSB ERA 7400 C, MSB ERA 7401 C, MSB ERA 8400 C, MSB ERA 8401 C, MSB ERA 8402 C, TTR ERA 4200 C, TTR ERA 4202 C, TTR ERA 4400 C, TTR ERA 4800 C