| EM1 Optical Incremental Encoder Module |
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 Download the PDF version of this Data Sheet.
(257K) Press Release (Released on December 6, 2001) Encoder
Selection ChartEncoder
FAQ
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Description: The EM1 is a three channel optical incremental encoder module. It is designed to detect linear or rotary position when used together with an encoder disk or linear strip. Each module consists of a lensed LED source and a monolithic detector IC enclosed in a small plastic package. This module uses phased array technology to provide superior performance and greater tolerances over traditional aperture mask type encoders. Each module provides digital quadrature and index channel outputs. They use a single supply +5V supply; +12 volt versions will also be available. The EM1 features internal single ended line drivers that swing from rail to rail while sourcing or sinking up to 8mA of current. The resolution of the modules and encoder disks and linear strips must match. They can easily be mounted by using 4-40 screws through the mounting holes. Agilent encoder disks are not compatible with the EM1. Only US Digital encoder disks are compatible with the EM1. The EM1 is designed to fit all of US Digital's current and future incremental encoders. The suggested mating connector is AMPMODU# 103977-4 or AMP# 640442-5. For open collector and higher voltage applications, add the PC3 device, or for differential cable driver outputs, add the PC4 device. Encoder disks, linear strips, quadrature decoder chips, counter chips, computer interface boards, mating connectors and mating cables are also available. US Digital warrants its products against defects and workmanship for two years. See complete warranty for details. Mechanical Specifications:
 Recommended Operating Conditions:
Encoding Characteristics: Over recommended operating range. Values are for the maximum error over a full rotation.
Timing Diagram:
Shaft Rotation for Shaft Encoders: H1: A leads B in a clockwise rotation; B leads A in a counterclockwise rotation. H3, H5D, H5S, HD25, S1, S2, S5D, S5S and SP-16: B leads A in a clockwise rotation; A leads B in a counterclockwise rotation. Shaft Rotation for Kit Encoders: E3, E5D, E5M, E5S and E6M: A leads B in a clockwise; B leads A in a counterclockwise rotation. E2: B leads A in a clockwise rotation; A leads B in a counterclockwise rotation. Definitions: CPR (N): The number of Cycles Per Revolution. Compatibility: Our new encoder module uses a single track with multiple windows to detect index. At first glance, it may appear that using multiple windows to detect a single ¼ cycle index may not be as accurate as a single window detection method. In reality, this new method yields a stronger signal, excellent positional accuracy, and insures a single index pulse per revolution. Here's how it works: the index pattern consists of I and I-not photodiodes (sensors). There are two to five times as many I-not sensors as I sensors. Except for the index pattern area, the index track of the disk is transparent allowing light to expose all of the index sensors. Because there are more I-not sensors, the differential index amplifier detects not-index. When the index pattern of the disk exactly lines up with matching detector sensors, only the I sensors receive light. All of the I-not sensors are blocked. The detection pattern is a complex sequence. The number of bits is proportional to the resolution. For example: a 1-inch disk with 1024 CPR uses a 32-bit index sequence. The sequence is arranged so that even through the transition into and out of the correct index phase, only the exact index alignment can bias the index detector into the asserted state. The sequence has similarities to a combination lock. Only the exact code in the correct sequence will work. Nothing else comes close. This new method yields plenty of index signal and phase accuracy for even the highest resolution modules. These modules are designed to be closely compatible with Agilent encoder modules. The EM1 modules and disks have the following differences. Why does US Digital use one track rather than two to generate the index channel? A single “combination-lock” type index track provides a stronger internal index signal at higher resolutions and requires less LED current. This enables US Digital to provide the index channel even at the highest resolutions. Can I use Agilent encoder disks with US Digital modules? If you do not use the index channel, the non-index Agilent compatible disks will work just as well. US Digital will continue to manufacture both versions with no cost difference. What resolutions are planned for the EM1 module? The resolution is set by a single mask when fabricating the monolithic detector chip. New resolutions are in process and will be added to our datasheets as they become available. Check this page for the most current list of available resolutions. We encourage you to inquire about any resolutions we do not already stock, that may be beneficial to you. Ordering Information: Part #: Type: Resolution: 1" Disk (CPR) Price: Ordering Notes:
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