Choosing a sensing component for a machine-safety or motion-control project often comes down to one question: are you detecting a blocked beam or a rotating shaft? That question separates the EMX Industries Thru-Beam Photometer Sensor from the Oak / Grigsby Rotary Encoder. The EMX is a thru-beam photoeye; the Oak / Grigsby is an encoder that reports shaft rotation as quadrature pulses. Here is how to pick between them.
Quick Verdict
If your priority is entrapment protection for doors, gates, and barriers, the EMX Industries Thru-Beam Photometer Sensor is the match. At $45.00, it is the more expensive of the two, but it comes as a complete photoeye kit. If you need rotary feedback, the Oak / Grigsby Rotary Encoder is the lower-priced pick at $16.95.
At a Glance
| Product | Price | Best For |
|---|---|---|
| EMX Industries Thru-Beam Photometer Sensor | $45.00 | Thru-beam safety detection |
| Oak / Grigsby Rotary Encoder | $16.95 | Incremental shaft position feedback |
Where EMX Wins
The EMX is the stronger choice for automated entrance safety. It is UL325 compliant and housed in an IP65-rated enclosure, so it is suited to both indoor and outdoor installations. The photoeye is designed to work with a wide variety of monitored operators and is also compatible with most non-monitored legacy products, giving it flexibility in retrofit situations. For an entrance that needs a safety input, this sensor is the focused solution.
Where Oak / Grigsby Wins
The Oak / Grigsby encoder wins for motion-control tasks that need rotational feedback. Its full quadrature output produces 512 total state changes per revolution, giving a control system a clear picture of direction and movement. A sealed sleeve bearing also makes it a durable option for a light industrial or bench setup. If your project is about measuring how far a shaft turns, this encoder is the practical pick.
Product Notes
EMX Industries Thru-Beam Photometer Sensor
If your entrance operator needs a monitored photoeye, this component is designed for exactly that job. The transmitter and receiver pair is housed in a compact enclosure with integrated sensor hoods and a removable lens sunshield, so the optics stay protected. The design focuses on minimizing fogging and false triggering, which makes alignment easier. A removable terminal block simplifies field wiring. One trade-off to keep in mind: this is a presence-detection device, not a rotation sensor, so it won't give you the position feedback a motion-control loop requires. For entrapment protection at an entrance, though, it is a strong, purpose-built option.
Oak / Grigsby Rotary Encoder
Motion-control projects that track shaft rotation will find this encoder a solid fit. It is a new-old-stock unit that outputs 128 pulses per revolution with a 2-bit gray code, and channel A leads channel B by 90 degrees during clockwise rotation. The 5V TTL-compatible interface is a plus for digital circuits. The 1/4-inch stainless steel shaft and sealed sleeve bearing offer a sturdy rotating assembly, and the package includes the mounting nut and internal tooth star lock washer. The main limitation is the 4-inch cable with bare wire ends: you will need to provide your own connector or terminate the leads yourself.
Final Choice by Use Case
Choose the EMX Industries Thru-Beam Photometer Sensor for automatic doors, gates, and barriers where a safety beam is the priority. Choose the Oak / Grigsby Rotary Encoder for bench projects, light automation, or any application where you need to measure how far a shaft has turned. If you are unsure, think about the physical quantity you are trying to sense: a blocked beam or a rotating shaft.
