EM2 Transmissive Optical Encoder Module

EM2 Features

  • Two-channel quadrature with index
  • High-resolution version of EM1
  • Single 5V supply
  • Rotary versions up to 10,000 CPR
  • Linear versions up to 2,000 CPI
  • Internal decoupling capacitor
  • Outputs source/sink 5 mA

See more info below

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EM2 Product Description

The EM2 is a transmissive optical encoder module designed to offer 2x or 4x higher resolution than the EM1 encoder module. This module is designed to detect rotary position when used with a US Digital encoder disk. The EM2 consists of a lensed LED source and a monolithic detector IC enclosed in a small polymer package identical to the EM1. The EM2 uses phased array detector technology to provide superior performance and greater tolerances over traditional aperture mask-type encoders.

The EM2 provides digital A & B quadrature outputs with a third output index channel. Each EM2 module is resolution-specific and is matched to the resolution of an encoder disk. The EM2 operates with a single 5V supply and provides single-ended outputs capable of sinking and sourcing 5mA. An internal 0.1 µF decoupling capacitor is designed into the EM2 to provide enhanced noise immunity.

For open collector and higher voltage applications, add the PC3 cable driver, or for differential cable driver outputs, add the PC4 cable driver. Encoder disks, quadrature decoder chips, counter chips, computer interface boards, mating connectors, and cables are also available.

Download the EM2/EM1 comparison chart.

Product Specifications

View here or download the specifications


1000 EM2-0-1000-* - - LIN-1000-*-*
2000 EM2-1-2000-I (1") / EM2-0-2000-I / EM2-0-2000-N (LIN) HUBDISK-1-2000-*-IE - LIN-2000-*-*
2048 EM2-1-2048-I HUBDISK-1-2048-*-IE - -
2500 EM2-1-2500-I HUBDISK-1-2500-*-IE - -
3600 EM2-2-3600-I - HUBDISK-2-3600-*-IE -
4000 EM2-1-4000-I (1") / EM2-2-4000-I (2") HUBDISK-1-4000-*-IE HUBDISK-2-4000-*-IE -
4096 EM2-1-4096-I (1") / EM2-2-4096-I (2") HUBDISK-1-4096-*-IE HUBDISK-2-4096-*-IE -
5000 EM2-1-5000-I (1") / EM2-2-5000-I (2") HUBDISK-1-5000-*-IE HUBDISK-2-5000-*-IE -
7200 EM2-2-7200-I - HUBDISK-2-7200-*-IE -
8000 EM2-2-8000-I - HUBDISK-2-8000-*-IE -
8192 EM2-2-8192-I - HUBDISK-2-8192-*-IE -
10000 EM2-2-10000-I - HUBDISK-2-10000-*-IE -


Temperature -25 100 C  
A/B Output Frequency 0 360 kHz 2000, 2048, 2500 CPR (1")
3600, 4000, 4096, 5000 CPR (2")
1000 CPI (Linear)
0 720 kHz 4000, 4096, 5000 CPR (1")
7200, 8000, 8192, 10000 CPR (2")
2000 CPI (Linear)
Disk RPM 0 (21.6 x 10^6) / CPR RPM 2000, 2048, 2500 CPR (1")
3600, 4000, 4096, 5000 CPR (2")
0 (43.2 x 10^6) / CPR RPM 4000, 4096, 5000 CPR (1")
7200, 8000, 8192, 10000 CPR (2")
Linear Strip Speed 0 360 in./sec. 1000, 2000 CPI (Linear)
Disk/Linear Strip Radial Position Tolerance ± .005   inch  


  • Specifications apply over the entire operating temperature/voltage range.
  • Typical values are specified at Vcc = 5.0V and 25C.
Supply Voltage 4.5 5.0 5.5 V Ripple < 100 mVpp
Supply Current   72 85 mA no load
Low-level Output     0.5 V IOL = 5 mA
  0.25   V no load
High-level Output 2.0     V IOH = -5 mA
  4.0   V no load
Output Current Per Channel -5   5 mA  
Load Capacitance      100  pF  
Output Rise Time   50   nS ± 5 mA load 
Output Fall Time   50   nS ± 5 mA load
Electrostatic Discharge     ± 4 kV IEC 61000-4-2



  • Specifications apply over the entire operating temperature/voltage range.
  • Values are for the worst error over full rotation.
  • Refer to the timing diagram below.
Symmetry X, Y 108  190 252 °e
Quadrature  Z 45  90 135 °e
Index Pulse Width Po 45  90 135 °e
Ch. I Rise After Ch. B or Ch. A Fall t1    -40   ns
Ch. I Fall After Ch. B or Ch. A Rise t2    25   ns


CPI: The number of Cycles (C) of the A or B output Per Inch of linear strip movement.

CPR: The number of Cycles (C) of the A or B outputs Per Revolution.

Index (I): The index output goes high once per revolution, coincident with the low states of channels A and B, nominally 1/4 of one cycle (90 °e).

One Shaft Rotation: 360 mechanical degrees.

One Electrical Degree (°e): 1/360th of one cycle.

One Cycle: 360 electrical degrees (°e). Each cycle can be decoded into 1 or 4 states, referred to as X1 or X4 resolution multiplication.

PPR: The number of resolvable Positions Per Revolution of the encoder disk with x4 quadrature decoding.

Quadrature (Z): The phase lag or lead between channels A and B in electrical degrees, nominally 90 °e.

Symmetry: A measure of the relationship between (X) and (Y) in electrical degrees, nominally 180 °e.


Mounting Screws 3.5-4 in-lbs


Pin Description
1 Ground
2 Index
3 A channel
4 +5VDC power
5 B channel


Title Date Description Download
EM1 & EM2 Update - PCN 4199 1/14/2014 Based on our continuous process improvement program, US Digital is changing the current marking method for our EM1 and EM2 encoder modules to a serialization method. This change will allow for each module to have a unique code; the current marking method is based on a date code system that includes all encoder modules produced within a specific week / year. The serialization system will be based on a hexadecimal system. Download

Additional Information

Product Notes

  • US Digital® warrants its products against defects in materials and workmanship for two years. See complete warranty for details.



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