OMRON E3T-ST23M Photoelectric Sensor

Model Code Breakdown (E3T-ST23M with 2M Cable)

Split components sold as a complete set: Emitter E3T-ST23-L, Receiver E3T-ST23-D

1. Core Basic Specifications
2. Optical Performance

Sensing method: Through-beam opposed type (paired emitter + receiver)

Rated sensing distance: 300 mm

Light source: 650 nm visible red LED

Minimum detectable object: φ2 mm opaque solid object

Beam angle: Transmitting 2°~20°, Receiving 2°~70°

Response time: 1 ms

Indicators: Orange operation indicator, green stability margin indicator

2. Electrical Specifications

Supply voltage: 12~24 V DC ±10%, peak-to-peak ripple ≤10%

Current consumption: Emitter ≤10 mA, Receiver ≤20 mA

Output type: PNP open collector

Operation mode: Light-ON (output turns ON when light is received)

Load rating: Max. 50 mA, load voltage ≤26.4 V DC

Residual voltage: ≤2 V for 10~50 mA load; ≤1 V for load below 10 mA

Protection functions: Reverse polarity protection, output short-circuit protection, mutual interference suppression

3. Mechanical & Environmental Specifications

Mounting: Fixed with M3 screws (mounting screws not included, to be purchased separately)

Ingress protection class: IP67

Housing material: PBT engineering plastic

Cable outlet: 2 m 4-core straight cable

Weight per set: Approx. 20 g

Operating temperature: -25 ℃ ~ +55 ℃ (no condensation)

Certifications: CE, RoHS, UL

III. Wiring Definition (4-core cable, receiver side)

1. Brown: DC12~24 V positive (+)
2. Blue: 0 V negative (GND)
3. Black: PNP signal output (connect load positive to black wire, load negative to 0 V)
4. White: Unused (empty pin)

The emitter only has 2 wires: Brown (+), Blue (GND), without signal output wire.

1. Output Logic Description
2. Light-ON (this model)

No obstruction, light path unblocked → Output ON (high level on black wire)

Object blocks light path → Output OFF

2. Cross-series reference: E3T-ST24M is PNP Dark-ON with identical 300 mm sensing distance
3. Typical Application Scenarios
4. Presence detection & counting of materials on small production lines
5. Transmittance detection for terminals, tiny parts and thin materials (minimum φ2 mm detectable)
6. Installation in narrow equipment spaces (ultra-thin compact body)
7. Packaging, 3C automation, lithium battery equipment, small conveyor lines
8. Position limit detection, blanking presence detection
9. Alternative Selection Reference within the Same Series

VII. Installation & Operation Precautions

1. Emitter and receiver lenses must be coaxial aligned; misalignment will drastically reduce sensing margin
2. Sensing margin curve: Only 2× margin at 300 mm; higher margin at short distances
3. When multiple units are mounted side by side, stagger installation to avoid mutual interference
4. Prohibit long-term oil stain and dust accumulation on lenses; clean lenses regularly
5. Do not over-tighten M3 mounting screws to prevent housing cracking
6. Load current shall not exceed 50 mA; direct driving of high-power solenoid valves is forbidden

OMRON E3T-ST23M Detection Accuracy / Minimum Detectable Object Specifications

1. Minimum Detectable Object (Core Accuracy Index)

Official specification: φ2 mm opaque solid object

Under standard light path at rated 300 mm sensing distance, opaque objects with diameter ≥2 mm can trigger the sensor stably.

Theoretical occlusion ratio: 2 mm blocks the beam, corresponding accuracy of approx. 0.67% relative to effective beam diameter

2. Beam Spot Size (Affects Fine Detection Accuracy)

Transmitting divergence angle: 2°~20°, spot diameter approx. 6~8 mm at 300 mm sensing distance

Light intensity peaks at the spot center with reduced edge sensitivity; tiny workpieces smaller than 2 mm will be missed

3. Repeat Positioning Accuracy (Switch Repeat Error)

Response time 1 ms with zero mechanical clearance inside the photoelectric sensor; electrical repeatability:

Trigger repeat error ＜0.01 mm (stable static detection)

Under high-speed dynamic conveying conditions, accuracy is determined by conveying speed; no inherent lag error from the sensor itself

4. Edge Fine Detection Explanation
5. Only suitable for presence detection, counting and position limit control, not for high-precision dimensional measurement;
6. This model lacks sufficient accuracy for detecting tiny 0.5~1 mm parts; select E3T-SL series narrow-beam through-beam or fiber optic sensors instead;
7. Thin transparent films and semi-transparent materials: The 2 mm standard does not apply, unstable detection will occur for light-transmitting workpieces.
8. Accuracy Limitations in Application

Misalignment error: Offset over 1 mm between emitter and receiver enlarges effective detectable diameter and degrades accuracy;

Dust and lens dirt equivalently expand the spot size, increasing minimum detectable dimension and worsening accuracy;

300 mm maximum sensing distance is the extreme operating condition; shorter distances (50~150 mm) deliver smaller spot size and better practical accuracy, enabling stable detection of workpieces close to 1.5 mm.

Nominal minimum detection accuracy: 2 mm opaque object (standard 300 mm distance)

Accuracy can be improved to approx. 1.5 mm with short-distance mounting;

Not applicable for micron-level dimensional measurement; only for workpiece presence detection.

Full Sensing Distance Specifications of OMRON E3T-ST23M

1. Rated Standard Sensing Distance (Official Nominal Value)

300 mm (0.3 m)

It belongs to short-range through-beam type in E3T-ST2 series; digit “2” in model code represents 300 mm specification.

2. Valid Operating Range

Minimum installable distance: 5 mm (emitter and receiver cannot be tightly attached to avoid light path saturation)

Standard rated distance: 300 mm (optimal design installation distance with green stability indicator steadily lit)

Maximum detectable limit: Light margin decays rapidly beyond 300 mm; installation over 400 mm is highly susceptible to interference from dust, misalignment and vibration, long-term use is not recommended

Curve Description:

Only approx. 2× stability margin at 300 mm, just meeting the lower limit of stable detection;

Sufficient margin within 0~200 mm short range, delivering stronger anti-interference and anti-offset performance.

3. Sensing Distance Classification for Same-Series Through-Beam Models (Quick Selection Reference)

4. Distance Application Notes
5. 300 mm is the rated maximum limit; prioritize installation at 50~200 mm on-site for drastically improved detection stability;
6. Shorten installation distance for scenarios with multiple side-by-side sensors, heavy dust environment or severe equipment vibration;
7. Installation beyond 300 mm causes missed detection of tiny φ2 mm workpieces and increases the minimum detectable dimension.

Temperature Specifications of OMRON E3T-ST23M (Official Datasheet)

1. Operating Temperature (Powered Running)

-25 ℃ ~ +55 ℃

Constraints: Environment free of icing and condensation; frost or condensation will cause lens light path failure and internal circuit short-circuit damage.

2. Storage / Transportation Temperature (Power Off)

-40 ℃ ~ +70 ℃

Storage under icing or condensation environments is also prohibited.

Supporting Humidity Reference

Operating humidity: 35%~85% RH (no condensation)

Storage humidity: 35%~95% RH (no condensation)

On-Site Usage Notes

1. For high-temperature operating conditions (>50 ℃), shorten sensing distance and reduce load current to avoid thermal drift of the sensor;
2. Under low-temperature conditions (<-20 ℃), avoid rapid cold-hot alternation of equipment to prevent lens frosting;
3. Long-term use of this model is not recommended near heating furnaces and ovens with high ambient temperatures; dedicated high-temperature resistant photoelectric sensors shall be adopted instead.

Translation Standard Note

All terminology follows Omron global official datasheet industrial English standards, unified international photoelectric sensor industry vocabulary, consistent with European & American automation equipment documentation writing norms.