Frequently Asked Questions

Yes, each EM1 or EM2 encoder module is designed to match a disk CPR (Cycles Per Revolution) or linear strip CPI (Cycles Per Inch) and cannot be used with any other disk or linear strip resolution.

US Digital's optical encoder disks and linear strips are fabricated from Mylar film that is nominally 0.007" thick. The Mylar film has two sides; only one side of the film has the encoder disk pattern, which is referred to as the artwork side of the disk. The artwork side is the top of the disk when viewing the inscription correct read up.

TIR is the Total Indicted Runout of an object as it turns on an axis in a complete rotation. With a rotary optical encoder, the TIR of the Disk pattern, as it is rotated one revolution, is an important value used to calculate the positional accuracy of the encoder signals. TIR is a cyclic value that does not accumulate over multiple rotations.

Our encoders have not been tested in a vacuum. We believe the encoders will perform just fine in this environment. Regardless, it would be best if you verified this with your own tests.

Our encoders have not been tested in a radioactive environment. We believe the encoders will perform just fine in this environment. Regardless, it would be best if you verified this with your own tests.

US Digital encoders are fairly robust to dusty environments. The encoders look at multiple sets of window and bar pairs. Thus a speck of dust at any one window will be averaged by the other sets of windows and bars. Because of this averaging effect, several windows can be covered completely, and the module will still not lose a count. The phased array differential modules that read the disks have plenty of signal margin. An impressive demonstration of this is to color the disk completely black with a Sharpie pen. The encoder will continue to work without errors.

US Digital has found that almost all solvents (besides water) will attack some of the encoder module parts. This includes alcohol and freon-based cleaners. US Digital has not qualified any solvent to be compatible with the encoder modules.

A long cable distance typically requires a differential line driver and differential line receiver to transmit digital signals reliably. Most US Digital encoders have an optional differential output circuit option (line driver) selected during part number configuration. If the US Digital encoder does not offer a differential output option, you can select an EA Incremental Encoder Adapter to provide a differential interface.

Maximum electrical noise immunity is achieved using differential line driver outputs and receivers along with twisted pair shielded cable assemblies. Each encoder differential output pair should use the same twisted pair in the cable assembly. Routing encoder communication cables away from electrical noise sources such as motor leads will also minimize exposure to noise sources.