Through-beam is the most reliable photoelectric arrangement there is. The transmitter sits on one side of the gap and the receiver directly opposite; anything opaque that breaks the beam is detected. Because the receiver sees the emitter's light directly rather than a reflection, it gives the longest range and the strongest signal margin of any optical sensor.
Why through-beam is the most dependable choice
Retro-reflective and diffuse sensors rely on light returning from a reflector or the target itself, so a dirty lens, a dark product or an awkward surface angle all eat into the signal. Through-beam suffers none of that: the full emitted beam lands on the receiver, giving an excess gain so large that dust, mist and gradual lens contamination can build up substantially before detection is affected.
The trade-off is installation. You need power and mounting on both sides of the gap, and the two units must be aligned. Where those are acceptable, nothing beats it for reliability.
Key features
- Longest sensing range of any photoelectric type — well suited to wide conveyors and doorways.
- Highest excess gain — tolerates dust, mist and lens contamination.
- Detects any opaque object regardless of colour, finish or reflectivity.
- Unaffected by target surface angle, unlike diffuse sensing.
- Consistent trigger point — switching occurs at the beam edge, not at a reflectivity threshold.
- LED alignment indicator for straightforward commissioning.
Technical specifications
| Parameter | Value |
|---|---|
| Sensing method | Through beam — separate transmitter and receiver |
| Detection | Opaque objects of any colour or finish |
| Operating voltage | 10–30 V DC (230 V AC control unit version available) |
| Output | PNP or NPN, NO or NC |
| Frequency | 50 Hz |
| Status indication | LED on receiver for output and alignment |
| Housing | Corrosion-resistant industrial housing |
| Cable | 2 m standard (custom lengths on request) |
Typical applications
- Wide conveyors where the gap exceeds the range of a reflective sensor.
- Counting cartons, pallets and bags in dusty warehouse environments.
- Doorway and gate monitoring in material-handling areas.
- Detecting dark, matt or irregular products that reflect poorly.
How to order
Tell us the sensing gap, the target material, your supply voltage and the output type your controller needs. If you are replacing an existing sensor, a photograph of the body markings is usually enough for us to identify an equivalent. We will confirm the specification and quote — normally the same day.
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Frequently asked questions
How do I align a through-beam sensor?
Mount both units facing each other, power them up and watch the receiver's LED. Move the receiver slowly through the beam to find the centre of the detection zone rather than its edge, then lock it there. Aligning at the centre gives you margin for vibration and thermal movement in service.
What if I cannot get power to both sides of the machine?
Then use a retro-reflective sensor instead. It puts all the electronics on one side and needs only a passive reflector opposite, at the cost of some range and dust tolerance.
Will it detect a transparent bottle?
Not reliably — clear glass and PET pass most of the light through. For transparent containers we recommend a dedicated clear-object detection setup; tell us the container and line speed and we will advise.
Need a quote for the Through Beam Photoelectric Sensor?
Send us your application — target material, sensing distance, supply voltage and housing constraint. We will recommend a part, quote it, and ship from Mumbai.