E3 Optical Kit Encoder

E3 Features

  • Quick, simple assembly, and disassembly
  • Rugged screw-together housing
  • Accepts .010 in. axial shaft play
  • Small size
  • 64 to 10,000 cycles per revolution (CPR)
  • 256 to 40,000 pulses per revolution (PPR)
  • 2 channel quadrature TTL squarewave outputs
  • Optional index (3rd channel)

See more info below

Configure the E3

E3 Product Description

Restriction of Hazardous Substances

The E3 is a high-resolution rotary encoder with a rugged glass-filled polymer enclosure, which utilizes either a 5-pin locking or standard connector. This optical incremental encoder is designed to easily mount to and dismount from an existing shaft to provide digital feedback information.

The internal components consist of a mylar disk mounted to a precision machined aluminum hub and an encoder module. The hub is available for diameters up to 1 in. The module contains a highly collimated solid-state light source and monolithic phased array sensor, which together provide a system extremely tolerant to mechanical misalignments.

The E3 is normally designed for applications of 10 feet or less. For applications requiring longer cable lengths, we recommend adding a PC4 / PC5 differential line driver or check out our E6 which has an optional differential output.

Attachment of the base to a surface may be accomplished by utilizing one of several machine screw bolt circle options. Positioning of the base to the centerline of a shaft is ensured by use of a centering tool. The cover is securely attached to the base with two 4-40 flat head screws to provide a resilient package protecting the internal components.

Connection to the E3 product is made through either a 5-pin locking or standard connector. The mating connectors are available from US Digital with several cable options and lengths.

Product Specifications

View here or download the specifications


Operating Temperature, CPR < 2000 -40 to 100 C
Operating Temperature, CPR ≥ 2000 -25 to 100 C
Electrostatic Discharge, IEC 61000-4-2 ± 4 kV
Vibration (10Hz to 2kHz, sinusoidal) 20 G
Shock (6 milliseconds, half-sine) 75 G


Max. Shaft Axial Play ±0.010 in.
Max. Shaft Runout 0.004 T.I.R. in.
Max. Acceleration 250000 rad/sec²
For CPR ≤ 2500:
Max. RPM (1)
Max. A/B Frequency
e.x. CPR=2500, Max. RPM=7200
e.x. CPR=100, Max. RPM=60000

minimum value of ((18 x 10^6) / CPR) and (60000)

For CPR = 3600, 4000, 4096, 5000:
Max. RPM (1)
Max. A/B Frequency

(21.6 x 10^6) / CPR

For CPR = 7200, 8000, 8192, 10000:
Max. RPM (1)
Max. A/B Frequency

(43.2 x 10^6) / CPR

Typical Product Weight 1.28 oz.
Codewheel Moment of Inertia 8.9 x 10^-5 for bore < 12mm
4.0 x 10^-4 for bore ≥ 12 mm
Hub Set Screw #3-48 or #4-48  
Hex Wrench Size 0.050 in.
Encoder Base Plate Thickness 0.135 in.
3 Mounting Screw Size #0-80  
3 Screw Bolt Circle Diameter (2) 0.823 ± 0.005 in.
2 Mounting Screw Size #2-56 or #4-40  
2 Screw Bolt Circle Diameter 0.750 ± 0.005 in.
2 Screw Bolt Circle Diameter 1.280 ± 0.005 in.
2 Screw Bolt Circle Diameter 1.812 ± 0.005 in.
Required Shaft Length (3)
  With E-option (2)
  With H-option
0.445 to 0.525
0.445 to 0.670
> 0.445
Index alignment to hub set screw 180 ± Typical degrees
Technical Bulletin TB1001 - Shaft and Bore Tolerances Download

(1) 60000 RPM is the maximum rpm due to mechanical considerations. The maximum RPM due to the module's maximum frequency response is dependent upon the module’s resolution (CPR).

(2) Only for shaft diameters < 0.472".

(3) Add 0.125" to all required shaft lengths when using M-option.


Hub Set Screw 2-3 in-lbs
Cover Screw 2-4 in-lbs
Base Mounting Screw (#0-80) 1-2 in-lbs
Base Mounting Screw (#2-56) 2-3 in-lbs
Base Mounting Screw (#4-40) 4-6 in-lbs
Adapter Plate Mounting Surface (#2-56 screws) 2-3 in-lbs
Adapter Plate Mounting Surface (#4-40 screws) 4-6 in-lbs
Module Mounting Screw 3.5-4 in-lbs


A leads B for clockwise shaft rotation, and B leads A for counterclockwise rotation viewed from the cover side of the encoder.


  • Specifications apply over the entire operating temperature range.
  • Typical values are specified at Vcc = 5.0Vdc and 25°C.
  • For complete details, see the EM1 and EM2 product pages.
Supply Voltage 4.5  5.0 5.5 V  
Supply Current   27 33 mA CPR < 1000, no load 
  54 62 mA CPR ≥ 1000 and < 3600, no load
  72 85 mA CPR ≥ 3600, no load
Low-level Output     0.5 V IOL = 8mA max., CPR < 3600
    0.5 mA IOL = 5mA max., CPR ≥ 3600
  0.05   mA no load, CPR < 3600
  0.25   mA no load, CPR ≥ 3600
High-level Output 2.0     V IOH = -8mA max., CPR < 3600
2.0     V IOH = -5mA max., CPR ≥ 3600
  4.8   V no load, CPR < 3600
  3.5   V no load, CPR ≥ 3600
Output Current Per Channel -8   8 mA CPR < 3600
-5   5 mA CPR ≥ 3600
Output Rise Time   110   nS CPR < 3600
  50   nS CPR ≥ 3600
Output Fall Time   35   nS CPR < 3600
  50   nS CPR ≥ 3600


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

Note: 5-pin single-ended mating connector is CON-C5 or CON-LC5


1. Centering Tool

The centering tool is only included with the -3 packaging option. It has to be ordered separately for other packaging options.

Part #: CTOOL - (Shaft Diameter)
Description: This reusable tool provides a simple method for accurately centering the E3 base onto the shaft in order to promote concentricity and thus, higher accuracy. It is recommended for the following situations:

  • When using mounting screws smaller than #4-40.
  • When the position of the mounting holes is in question.
  • When using the 3-hole mounting pattern.
  • When using the T-option transfer adhesive.

Instructions: When mounting encoder base, slide centering tool down shaft until it slips into centering hole of encoder base. Tighten mounting screws, then remove centering tool.

2. Hex Tool

Depending on the order packaging option, either a hex driver or hex wrench is included.

Part #: HEXD-050
Description: Hex driver, 0.050" flat-to-flat for #3-48 or #4-48 set screws. Only included with -B or -packaging options.

Part #: HEXW-050
Description: Hex wrench, 0.050" flat-to-flat for #3-48 or #4-48 set screws. Only included with -2 or -packaging options.

3. Spacer Tool

A spacer tool is included for all packaging options.

Part #: SPACER-E3S
Description: For shafts ≤ 0.394"

Part #: SPACER-E3L
Description: For shafts 12mm - 1"

4. Screws

Part #: SCREW-080-250-PH
Description: Pan Head, Philips #0-80 UNF x 1/4"
Use: Base Mounting
Quantity Required: 3
Screws are not included

Part #: SCREW-256-250-PH
Description: Pan Head, Philips #2-56 UNC x 1/4"
Use: Base Mounting
Quantity Required: 2
Screws are not included

Part #: SCREW-348-125-SS
Description: Socket Head Set Screw, 3-48 UNC x 1/8"
Use: Hub/Disk Mounting for 12mm - 1" Bore
Quantity Required: 2
Screws are included

Part #: SCREW-440-250-PH
Description: Pan Head, Philips #4-40 UNC x 1/4"
Use: Base Mounting
Quantity Required: 2
Screws are not included

Part #: SCREW-440-500-PH
Description: Pan Head, Phillips #4-40 UNC x 1/2"
Use: Module Mounting
Quantity Required: 2
Screws are included

Part #: SCREW-440-625-FH
Description: Flat Head, Phillips 4-40 UNC x 5/8"
Use: Cover Mounting
Quantity Required: 2
Screws are included

Part #: SCREW-448-063-SS
Description: Socket Head Set Screw, 4-48 UNC x 1/16"
Use: Hub/Disk Mounting for 5/16" - 10mm Bore
Quantity Required: 1
Screw is included

Part #: SCREW-448-125-SS
Description: Socket Head Set Screw, 4-48 UNC x 1/8"
Use: Hub/Disk Mounting for 2mm - 1/4" Bore
Quantity Required: 1
Screw is included


Title Date Description Download
E3 and E6 Packaging Option Changes - PCN 7357 2/21/2024 As part of our ongoing continuous improvement efforts, US Digital is implementing a change to the packaging options for our E3 and E6 encoders. We will now include a centering tool with all packaging options. We are implementing this change to ensure that the encoder is properly assembled using the tools as designed, as per our assembly instructions. A centering tool is needed to properly center the encoder base to the mounting surface. By including the centering tool, customers will no longer need to purchase them separately. Download
E3 Base Mold Update - PCN 6804 1/24/2019 As part of our ongoing continuous improvement efforts, and in order to enhance both function and appearance, multiple improvements are being incorporated into a plastic component redesign.The plastic base mounting holes and center hole counter-bore are increasing in size, and the four press-fit threaded inserts are being replaced with thread inserts that are over-molded into the base.With exception of the features outlined below, the new parts are dimensionally equivalent and will fit within the same envelope of the previous parts. Download
2" Hub/Disk Assembly Screw Change - PCN 6644 9/27/2018 As part of our ongoing continuous improvement efforts, the screws used in the assembly of the 2" hub/disk assembly, that is with a bore of 12mm and larger, will be changed from a black oxide to a zinc plated screw.The zinc plating improves corrosion resistance as well as alleviates any potential for oil residue.The plating change has no effect on form, fit or function of our hubdisk assembly. Download
Update to 1" and 2" Disks - PCN 6232 5/24/2018 This notice is to inform our customers of a minor disk design modification that is being implemented for standard 1" and 2" disks. This is a continuation of a change that was implemented for our index disks in 2015.We are revising the text on the disk, adding the US Digital logo and a line that is used internally by our manufacturing group.The change does not affect the quadrature or index tracks; therefore, it has no impact on form, fit or function. Download
Hub Set Screw Production Change - PCN 5367 7/20/2015 As part of our ongoing continuous improvement efforts, US Digital is implementing a change related to the production of our 5/16" (.313), 8mm (.315), 3/8" (.375), and 10mm (.394) HUBDISK assemblies. We are adding a low strength threadlocker to the set screw during our assembly process to assist in securing the set screw in the hub during transportation. This will aid in the set screw retention of these specific hub sizes; ensuring the retention is sufficient and avoid the potential of them backing out of the hub assembly during transit. This change does not affect form, fit or function. Download
Laser Marking - PCN 5253 6/17/2015 As part of our ongoing continuous improvement efforts, US Digital is changing the labeling/marking method for our E3, E6, H3, H6, S1, S2 and S6 products. 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
EM1 LED Die - PCN 1016 2/7/2013 As part of US Digital's continual assurance of supply strategy, we have qualified additional sources for our LED die used in our EM1 encoder module, which in turn impacts all of the following products:EM1, E2, E3, E5, E6, H1, H15, H3, H5, H6, HB5M, HB6M, HD25, PE, S1, S2, S5, S6, T5 and T6The device specification will remain the same, i.e. there will be no change to form, fit or function of the product(s) as specified by US Digital. The appropriate quality and reliability testing has been performed on representative products to ensure normal parametric distribution, consistent with US Digital's quality and reliability standards. Download

Additional Information

Product Notes

  • US Digital® warrants its products against defects in materials and workmanship for two years. See complete warranty for details.
  • Cables and connectors are not included and must be ordered separately.


Assembly Instructions


3D Model Downloads

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