Professional Selection Guides & Technical Insights
Short answer: Pick through-beam (wenglor P1KE) for longest range and fastest counting: laser models see 10 m and detect parts down to 0.6 mm. Pick retro-reflective (P1KL) for 0.1–5 m where a reflector can be mounted. Pick diffuse (P1KH) for short, single-side jobs up to 150 mm when object color changes. Match the principle to distance, target and environment.
Wenglor sells hundreds of photoelectric models, but they all work on one of three sensing principles. That choice, more than any model number, decides how far the sensor sees, how small a part it can catch, and how it behaves in dust or glare. Get it right and the model almost picks itself; get it wrong and you'll chase false triggers and missed parts no matter what you order.
This guide uses three real wenglor series: P1KH (diffuse), P1KL (retro-reflective) and P1KE (through-beam). The numbers come from wenglor's published datasheets, so you can check them yourself.
A diffuse sensor keeps the emitter and receiver in one housing. The light bounces off the object itself, so you mount one device and you're done. No second unit, no reflector. That convenience is why diffuse is the default for presence detection under a metre.
The weakness is reflectivity. Black or matte surfaces absorb light, so a standard diffuse sensor loses range on dark parts, and a bright wall behind the object can trigger false signals. Wenglor's P1KH series sidesteps both problems with background suppression (BGS). Instead of measuring how much light comes back, it measures the angle the light returns at, so the switching point holds steady whatever the object's color, shape or surface. The P1KH002 is a red-light BGS sensor with a fixed 150 mm range; the P1KH008 is a 120 mm variant.
Use diffuse when the distance is short (roughly 150 mm or less), only one side is reachable, and the parts change color or finish between batches. Think part-present checks on a fixture, or feeding lines that mix dark and bright workpieces. Skip it when you need metres of range, or when the target is transparent. Glass and film let the light pass straight through.
A retro-reflective sensor also puts the emitter and receiver in one housing, but it aims the light at a reflector on the far side. The object breaks the beam on its way to the reflector. You still wire only one side, but the range jumps from millimetres to metres.
Wenglor's P1KL series is the middle of the road. The red-light P1KL001 reaches 5,000 mm (5 m) with a standard reflector. The P1KL006 swaps the red light for a fine class-1 laser. If you work with shiny parts there is one more model to know: the P1KL003 adds a polarization filter. On a mirror-finish part, light can bounce straight back to the sensor and make it think the beam is still clear. The filter blocks that reflection. Foil, polished metal, painted panels: specify the polarized model.
Use retro-reflective for ranges around 0.1–5 m where you can mount a reflector on the opposite side. It's also the cheapest reliable way to detect transparent objects like bottles and film. Two things to watch: keep the reflector clean, and keep it roughly aligned. Dust on the reflector shortens the range; a tilted reflector narrows the beam.
A through-beam pair splits the transmitter and receiver into two housings, mounted facing each other. The object is detected the moment it blocks the beam. It's the oldest principle and still the strongest on every metric that matters.
The P1KE series shows the spread. Red-light models like the P1KE005 reach 6,000 mm (6 m). The laser versions P1KE007, P1KE010 and P1KE013 reach 10,000 mm (10 m) and use laser class 1 (EN 60825-1), which is safe enough that no enclosure is required. The P1KE010 is a good reference for the rest of the family: 0.6 mm smallest detectable part, 4,500 Hz switching, 0.11 ms response, IP67/IP68 housing, IO-Link 1.1 for condition monitoring. It tolerates 10,000 lux of ambient light, so it works beside sunlit doors, and the light source is rated for 100,000 hours.
Through-beam also shrugs off dust and mist better than the others, because the light crosses the gap once. A dirty lens cuts the signal once instead of twice. And since detection is just "beam blocked or not", color, gloss and transparency don't matter. Glass, black rubber and mirror plate all block the beam the same way.
The cost is installation. You need two housings, power on both ends, and mounting space on both sides of the gap.
| Selection factor | Diffuse / BGS (P1KH) | Retro-reflective (P1KL) | Through-beam (P1KE) |
|---|---|---|---|
| Wenglor series | P1KH | P1KL | P1KE |
| Typical range (wenglor data) | ≤ 150 mm (P1KH002: 150 mm; P1KH008: 120 mm) | ≤ 5 m with standard reflector (P1KL001) | 6 m red light (P1KE005 etc.); 10 m laser class 1 (P1KE007/010/013) |
| Installation | One housing, one side | One housing + reflector on far side | Two housings, both sides, aligned |
| Minimum detectable part | Depends on object size and distance | Medium | Down to 0.6 mm (laser models) |
| Sensitive to object color? | No (BGS models) | No | No |
| Handles glossy/mirror targets? | Depends on geometry | Yes with polarization filter (P1KL003) | Yes |
| Handles transparent targets? | Poor | Yes | Yes |
| Dust / contamination tolerance | Low | Medium | Highest |
| Switching speed | Standard | Standard | Up to 4,500 Hz (P1KE010) |
| Typical jobs | Short-range presence, color-varying workpieces | Packaging lines, warehouse portals, medium-range detection | Long-range guarding, small-part counting, dusty environments |
Run through these questions in order. Each one removes a principle.
If two principles still fit after step 2, prefer retro-reflective. It gives you multi-metre range with one-side wiring at the lowest cost, and it handles transparent objects that diffuse sensors can't.
| Application | Recommended wenglor solution | Why |
|---|---|---|
| Part-present check on a fixture, under 150 mm, parts vary black to bright | P1KH BGS (e.g., P1KH002, 150 mm) | One-side mounting; switching point unaffected by color or surface |
| Object detection across a warehouse aisle, 2–5 m | P1KL retro-reflective (P1KL001) | One-side wiring, multi-metre range with a standard reflector |
| Counting shiny foil or metal parts on a packaging line | P1KL003 (polarization filter) | Polarized beam ignores mirror-like reflections that fool standard retro-reflective sensors |
| Counting small parts (down to ~0.6 mm) at high speed | P1KE laser through-beam (P1KE007/010/013) | 0.6 mm minimum part, 4,500 Hz, 0.11 ms response |
| Dusty environment, e.g., woodworking or cement handling, up to 6 m | P1KE red-light through-beam (P1KE005 etc.) | Single-pass beam resists contamination far better than reflected light |
| Detecting clear bottles or film web | P1KL retro-reflective | Transparent targets block the beam cleanly; diffuse sensors see through them |
Once the principle is settled, the last step is getting genuine parts with the right optical and electrical configuration. We source wenglor sensors from the manufacturers or their first-tier distributors, with original packaging and traceable paperwork. Send a part number and we'll quote it; send a photo of the old sensor or the machine nameplate and we'll work out the model. Single-piece orders are fine, and popular models can ship in 1–2 weeks from stock.
Diffuse sensors (P1KH) emit and receive from one housing and detect light reflected by the object. Short range, single-side mounting. Retro-reflective sensors (P1KL) also use one housing but bounce light off a reflector on the far side. Up to 5 m, still one-side wiring. Through-beam sensors (P1KE) split the emitter and receiver into two aligned housings and detect when the object blocks the beam. Longest range (up to 10 m), smallest detectable parts, highest speed.
For short distances, pick a P1KH background-suppression model. Its angle-measurement principle keeps the switching distance constant regardless of object color, so black parts are detected as reliably as white ones. For longer distances, through-beam (P1KE) is inherently color-independent, and retro-reflective (P1KL) works too because detection is based on blocking the beam, not on how reflective the object is.
Through-beam laser models reach 10,000 mm (10 m): P1KE007, P1KE010 and P1KE013. Red-light through-beam models reach 6,000 mm (6 m). Retro-reflective sensors reach 5,000 mm (5 m) with a standard reflector. Background-suppression diffuse sensors are built for short ranges around 120–150 mm.
Yes, with the polarized version. The P1KL003 adds a polarization filter that rejects the direct reflection from mirror-like surfaces, which would otherwise make a standard retro-reflective sensor miss the object. For shiny metal, foil or painted surfaces, specify the polarized model.
Ruilianxin Technology supplies genuine wenglor photoelectric sensors with original packaging and traceable documentation, quoting by part number worldwide. We support single-piece orders, consolidate multi-brand spare parts into one shipment, and help identify the correct model from photos or nameplates. Just send an inquiry.
Tell us the detection distance, the target material and the environment. The Ruilianxin technical team will confirm the right principle and model, then quote it by part number.
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