SLOT / FORK PHOTOELECTRIC SENSORS
A slot sensor fixes the emitter and receiver in one U-shaped body, so the beam can never drift out of alignment. With 0.03 mm repeat accuracy and a 3 kHz response, it is the most repeatable way to count small parts, read label edges and detect index marks. Five slot widths from 5 mm to 50 mm, 10–30 V DC (5–24 V DC on the 5 mm series), NPN or PNP with selectable light-on and dark-on.
A slot photoelectric sensor — also called a fork or U-groove sensor — holds the emitter and receiver in one rigid U-shaped body, factory-aligned across a fixed gap. Anything passing through the slot breaks the beam. Because the optics can never drift out of alignment, it is the most repeatable optical sensor for counting small parts, reading label edges and detecting index marks.
A slot sensor is a through-beam arrangement with the alignment problem already solved. That matters when the detected feature is small and fast:
The constraint is obvious: the part must physically pass through the slot, so it fits guided material — strip, wire, tape, labels, small components on a track — not open conveyors.
| Series | Slot width | Typical application |
|---|---|---|
| SEGU5 | 5 mm | Fine wire, thin strip, small index marks |
| SEGU10 | 10 mm | Label edges, tape splices, small components |
| SEGU15 | 15 mm | Blister strip, connector housings |
| SEGU30 | 30 mm | Bottle necks, moulded parts on a track |
| SEGU50 | 50 mm | Larger guided components, part-in-chute checks |
The 5 mm series is documented in detail in the current production catalogue:
| Parameter | Value |
|---|---|
| Detectable object | Opaque, 0.8 × 1.2 mm and larger |
| Repeat accuracy | 0.03 mm or better |
| Response frequency | 3 kHz |
| Output | NPN or PNP open collector, NO/NC |
| Switching mode | Light-on / dark-on, selectable |
| Light source | LED, 940 nm |
| Supply voltage | 5–24 V DC |
| Current consumption | ≤ 8 mA |
| Residual voltage | < 1 V at 50 mA load |
| Protection circuits | Surge protection, reverse-polarity protection |
| Ambient light immunity | Incandescent, ≤ 1000 lux at the receiver |
| Operating temperature | −25 °C to +55 °C |
| Storage temperature | −30 °C to +80 °C |
| Humidity | 5–85 % RH operating, non-condensing |
| Dielectric strength | 1000 V AC, 1 minute, terminals to housing |
| Insulation resistance | ≥ 20 MΩ at 250 V DC |
| Vibration resistance | 10–55 Hz, 1.5 mm amplitude, 2 h per axis |
| Protection class | IP50 |
| Housing material | PC |
| Connection | 2 m, 4-core cable |
Values above are taken from the current production catalogue for the 5 mm slot series. Figures for the 10, 15, 30 and 50 mm series differ — request the specific datasheet before finalising a design.
Divide the length of the detected feature by the line speed to get the dwell time, then compare it with the sensor response time. A 5 mm feature travelling at 2 m/s is present for 2.5 ms; a 3 kHz response frequency corresponds to roughly 0.17 ms, so the margin is comfortable. Problems appear when the feature is small and the line is fast — a 1 mm mark at 5 m/s is present for only 0.2 ms.
22 slot configurations are available across 5 slot widths.
| Model | Series / form | Slot width | Output | Supply | Connection | Housing | Light source |
|---|---|---|---|---|---|---|---|
| SEGU10-T010N-SIPU4 | U10 · Slot 10 mm | 10 mm | NPN | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU10-T010P-SIPU4 | U10 · Slot 10 mm | 10 mm | PNP | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU15-T015N-SIPU4 | U15 · Slot 15 mm | 15 mm | NPN | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU15-T015P-SIPU4 | U15 · Slot 15 mm | 15 mm | PNP | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU30-T030N-SIPU4 | U30 · Slot 30 mm | 30 mm | NPN | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU30-T030P-SIPU4 | U30 · Slot 30 mm | 30 mm | PNP | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU5-T05N-SR4U2-0 | U5 · Slot 5 mm | 5 mm | NPN | 5-24 V DC | 2 m cable | PC plastic | LED 940 nm |
| SEGU50-T050N-SIPU4 | U50 · Slot 50 mm | 50 mm | NPN | 10-30 V DC | M8 connector | PBT | Infrared |
| SEGU50-T050P-SIPU4 | U50 · Slot 50 mm | 50 mm | PNP | 10-30 V DC | M8 connector | PBT | Infrared |
Emitter and receiver sit in the same U-shaped body, so a slot sensor has one cable and no separate emitter wiring. The U10–U50 series terminates in an M8 connector; the U5 series ships with a 2 m four-core cable.
| Function | Cable colour (IEC 60947-5-2) | M8 pin | Notes |
|---|---|---|---|
| Supply + | Brown | 1 | 10–30 V DC on the U10–U50 series; 5–24 V DC on the U5 series |
| Supply − | Blue | 3 | 0 V / common |
| Output (NPN or PNP) | Black | 4 | Main switching output |
| Light-on / dark-on select | White | 2 | Present on selectable models |
An NPN output sinks current to 0 V; a PNP output sources current from the supply. Match the sensor output to the input card of the controller — wiring a PNP sensor to a sinking input (or the reverse) leaves the input permanently off. Confirm the pin assignment on the datasheet before wiring a specific model.
| Symptom | Likely cause | What to check |
|---|---|---|
| Output never switches | Output type does not match the controller input | NPN vs PNP; sinking vs sourcing input card |
| Small features are missed | Target below the 0.8 × 1.2 mm detectable size, or translucent | Send a sample part and the line speed so the optics can be matched |
| Miscounts at high line speed | Dwell time shorter than the 3 kHz response allows | Compare feature length and belt speed against the response frequency |
| Thin or transparent film is not seen | Too little attenuation across the slot | Reduce the sensitivity margin, or select a model with adjustable gain |
| Detection degrades over weeks | Dust or swarf collecting inside the slot | Add scheduled clean-air purging, or move to a wider slot width |
| Random switching with forks side by side | Optical crosstalk between adjacent units | Increase the spacing between forks, or alternate their mounting direction |
| Water or coolant ingress | The slot series is rated IP50 only | Keep the fork out of direct washdown; use a guarded mounting position |
| Output inverted versus expectation | Light-on / dark-on set the wrong way | Select the opposite model variant, or switch mode if the model supports it |
Photoelectric sensing is one of six sensor families we build in Shenzhen. Where an optical solution is not the right fit, these alternatives cover the same detection tasks:
A slot photoelectric sensor holds the emitter and receiver in one U-shaped housing with a fixed gap between them. Any object passing through the slot interrupts the beam and switches the output. Because the optics are factory-aligned, there is no set-up and no alignment drift over time.
Five widths: 5, 10, 15, 30 and 50 mm. The 5 mm series suits fine wire, thin strip and small index marks; 10 and 15 mm suit label edges and blister strip; 30 and 50 mm handle bottle necks and larger guided components.
The 5 mm series detects opaque objects from 0.8 × 1.2 mm upwards, with repeat accuracy of 0.03 mm or better. Smaller or translucent features may need a different optic — send us a sample and the line speed and we will confirm.
The 5 mm series responds at 3 kHz. This sets the fastest feature rate the sensor can follow. Divide the feature length by the line speed to get the dwell time and compare: a 5 mm feature at 2 m/s dwells for 2.5 ms, comfortably within a 3 kHz capability.
The 5 mm series runs on 5–24 V DC and draws 8 mA or less, which allows direct connection to both 5 V logic and 24 V control supplies. Surge and reverse-polarity protection are built in. Other slot widths may differ — check the specific datasheet.
IP50 for the 5 mm series — dust-protected but not sealed against water. Slot sensors are intended for enclosed machinery rather than washdown areas. For wet environments, choose a sealed barrel through-beam pair instead.
Yes. The 5 mm series offers selectable light-on and dark-on operation, so one part number covers both control logics. Output is NPN or PNP open collector with NO and NC available, depending on the model variant ordered.
Label and web handling for splice and edge detection; small-part counting on vibratory tracks and chutes; index-mark reading on rotating discs and cams; and end-of-travel detection where a flag on a moving carriage passes through the slot.
Yes. SEGMENsensor supplies slot sensors from 10 pieces per configuration, with custom cable length, connector type, bracket drilling and housing marking. Paid samples of catalogue models normally ship from Shenzhen within five to seven working days.
The size of the object or feature passing through the slot, the clearance needed around it, the line speed, whether the detected material is opaque or translucent, the supply voltage and controller input type, and whether the machine environment is enclosed or exposed.
SEGMENsensor manufactures photoelectric sensors in Shenzhen for industrial OEM customers and distributors. Tell us the detection task rather than a part number — target material and colour, distance, background, mounting space, environment and controller input type — and our engineers return two or three suitable configurations with drawings.
Standard catalogue models ship from stock. Custom builds start at 10 pieces per configuration.
Housing colour, laser marking, label artwork and packaging can be produced to your specification.
Cable length, jacket material, M8 or M12 connector and pin assignment can be changed on request.
Paid samples of catalogue models normally leave Shenzhen within five to seven working days.
Target, distance, background, environment and controller input — we reply with specifications and a quotation within one working day.
Tell us your specification — our engineers reply within 24 hours.