S4T Miniature Optical Shaft Encoder

S4T Features

  • Small size
  • Low cost
  • High retention snap-in polarized connector
  • -20C to 100C operating temperature
  • 100 to 1,000 cycles per revolution (CPR)
  • 400 to 4,000 pulses per revolution (PPR)
  • 2-channel quadrature TTL square wave outputs

See more info below

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S4T Product Description

Restriction of Hazardous Substances

The S4T miniature optical shaft encoder is a non-contacting rotary to digital converter. The S4T contains an LED light source, monolithic photodetector, and mylar disk. The S4T encoder is available with shaft bushing or ball bearings for motion control applications or with shaft torque designed to feel like a potentiometer for front-panel manual interfaces. The encoder converts real-time shaft angle, speed, and direction into TTL-compatible quadrature outputs without index. It operates from a single +5VDC supply.

The S4T uses a high retention, 4 conductor snap-in polarized 1.25mm pitch connector. Mating cables and connectors (see the Cables/Connectors web page) are not included and are available separately.

Product Specifications

View here or download the specifications


Operating Temperature -20 to 100 C
Electrostatic Discharge, IEC 61000-4-2
Single-ended (-S version)
Differential (-D version) 

± 12
± 7 

Vibration (10Hz to 2kHz, sinusoidal) 20 G
Shock (6 milliseconds, half-sine) 75 G


Max. Acceleration 10000 rad/sec² 250000 rad/sec²
Max. Shaft Speed (1)
100 RPM 15000 RPM
Max. Shaft Torque 0.5 ±0.2 in-oz (D-option)
0.3 in-oz (N-option)
0.05 in-oz
Max. Shaft Loading 2 lbs. dynamic
20 lbs. static
1 lb.
Bearing Life > 1000000 revolutions L10 = (22/Fr)³ *
Where L10 = bearing life in millions of revs, and
Fr = radial shaft loading in pounds
Weight 0.48 oz. 0.43 oz.
Max. Shaft Runout 0.0015 in. T.I.R. 0.0015 in. T.I.R.
Max. Panel Nut Tightening Torque 20 in-lbs 20 in-lbs
Technical Bulletin TB1001 - Shaft and Bore Tolerances Download

* only valid with negligible axial shaft loading.

(1) The maximum speed due to electrical considerations is dependent on the CPR. See the E4T product page.



Symmetry, S 105 180 255 electrical degrees
Quadrature Delay, Q 30 90 150 electrical degrees

(1) B leads A for clockwise rotation, A leads B for counterclockwise rotation viewed from the shaft side of the encoder.


Supply Voltage 4.5 5.0 5.5 V  
Supply Current   25 30 mA CPR ≤ 500, no load
  34 42 mA CPR > 500, no load
Low-level Output     0.4 V CPR ≤ 500, IOL= 8 mA
CPR > 500, IOL= 5 mA
  0.035   V no load
High-level Output 2.4     V CPR ≤ 500, IOH= -8 mA
CPR > 500, IOH= -5 mA
  4.0   V no load
Output Rise Time   100   ns no load
Output Fall Time   50   ns no load


Supply Voltage 4.5 5.0 5.5 V  
Supply Current   27 32 mA CPR ≤ 500, no load
  36 44 mA CPR > 500, no load
Single-Ended Output Voltage High 4.75 5.0   V Min. @ 25mA load, Typ. @ no load
Single-Ended Output Voltage Low   0.25 0.60 V Typ. @ no load, Max. @ 4.5mA load
Differential Output Voltage 3.0 3.8   V RL = 100 ohm
Differential Output Rise/Fall Time     20 ns


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

(1) 4-pin single-ended mating connector is CON-MIC4
(2) 6-pin differential mating connector is CON-MIC6


Title Date Description Download
E4T and S4T Cover and Base Update - PCN 7192 3/3/2022 As part of our ongoing continuous improvement efforts, and to avoid any potential disruption to our supply chain, US Digital has decided to standardize our plastic material. Based on this, the E4T and S4T encoder cover and base will change from PBT (Polybutylene Terephthalate) to PC (polycarbonate). Download
Updated PCB for E4T and S4T - PCN 6466 1/29/2018 This notice is to inform our customers of a PCB design change that is being implemented for all the E4T and S4T product lines. The new PCBs will improve overall product performance and enhance robustness of these product lines. The new PCBs can be identified by their blue color (instead of black) and have two mounting holes that mate with the base plate instead of one hole and one slot. This change has no impact on form, fit or function for either the E4T or S4T. Download
E4T, S4T and E8T Laser Markings - PCN 6227 8/8/2017 This notification is to inform our customers of a change to product markings for the E4T, E8T, and S4T series of encoders. The new marking will be utilized across all three product lines. We are making this change to improve readability for our customers and to provide consistency across the product lines. Download

Additional Information

Product Notes

  • Cables and connectors are not included and must be ordered separately.
  • For ordering information please see the Compatible Cables / Connectors section above.



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